Merge tag 'v1.9.1'2.0.0-alpha.0

Fixes for stmhal USB mass storage, lwIP bindings and VFS regressions

This release provides an important fix for the USB mass storage device in
the stmhal port by implementing the SCSI SYNCHRONIZE_CACHE command, which
is now require by some Operating Systems.  There are also fixes for the
lwIP bindings to improve non-blocking sockets and error codes.  The VFS has
some regressions fixed including the ability to statvfs the root.

All changes are listed below.

py core:
- modbuiltins: add core-provided version of input() function
- objstr: catch case of negative "maxsplit" arg to str.rsplit()
- persistentcode: allow to compile with complex numbers disabled
- objstr: allow to compile with obj-repr D, and unicode disabled
- modsys: allow to compile with obj-repr D and PY_ATTRTUPLE disabled
- provide mp_decode_uint_skip() to help reduce stack usage
- makeqstrdefs.py: make script run correctly with Python 2.6
- objstringio: if created from immutable object, follow copy on write policy

extmod:
- modlwip: connect: for non-blocking mode, return EINPROGRESS
- modlwip: fix error codes for duplicate calls to connect()
- modlwip: accept: fix error code for non-blocking mode
- vfs: allow to statvfs the root directory
- vfs: allow "buffering" and "encoding" args to VFS's open()
- modframebuf: fix signed/unsigned comparison pendantic warning

lib:
- libm: use isfinite instead of finitef, for C99 compatibility
- utils/interrupt_char: remove support for KBD_EXCEPTION disabled

tests:
- basics/string_rsplit: add tests for negative "maxsplit" argument
- float: convert "sys.exit()" to "raise SystemExit"
- float/builtin_float_minmax: PEP8 fixes
- basics: convert "sys.exit()" to "raise SystemExit"
- convert remaining "sys.exit()" to "raise SystemExit"

unix port:
- convert to use core-provided version of built-in import()
- Makefile: replace references to make with $(MAKE)

windows port:
- convert to use core-provided version of built-in import()

qemu-arm port:
- Makefile: adjust object-file lists to get correct dependencies
- enable micropython.mem_*() functions to allow more tests

stmhal port:
- boards: enable DAC for NUCLEO_F767ZI board
- add support for NUCLEO_F446RE board
- pass USB handler as parameter to allow more than one USB handler
- usb: use local USB handler variable in Start-of-Frame handler
- usb: make state for USB device private to top-level USB driver
- usbdev: for MSC implement SCSI SYNCHRONIZE_CACHE command
- convert from using stmhal's input() to core provided version

cc3200 port:
- convert from using stmhal's input() to core provided version

teensy port:
- convert from using stmhal's input() to core provided version

esp8266 port:
- Makefile: replace references to make with $(MAKE)
- Makefile: add clean-modules target
- convert from using stmhal's input() to core provided version

zephyr port:
- modusocket: getaddrinfo: Fix mp_obj_len() usage
- define MICROPY_PY_SYS_PLATFORM (to "zephyr")
- machine_pin: use native Zephyr types for Zephyr API calls

docs:
- machine.Pin: remove out_value() method
- machine.Pin: add on() and off() methods
- esp8266: consistently replace Pin.high/low methods with .on/off
- esp8266/quickref: polish Pin.on()/off() examples
- network: move confusingly-named cc3200 Server class to its reference
- uos: deconditionalize, remove minor port-specific details
- uos: move cc3200 port legacy VFS mounting functions to its ref doc
- machine: sort machine classes in logical order, not alphabetically
- network: first step to describe standard network class interface

examples:
- embedding: use core-provided KeyboardInterrupt object

30 files changed, 1324 insertions, 676 deletions

diff --git a/extmod/crypto-algorithms/sha256.c b/extmod/crypto-algorithms/sha256.c
index 82e5d9c7b..276611cfd 100644
--- a/extmod/crypto-algorithms/sha256.c
+++ b/extmod/crypto-algorithms/sha256.c
@@ -14,7 +14,6 @@
 
 /*************************** HEADER FILES ***************************/
 #include <stdlib.h>
-#include <memory.h>
 #include "sha256.h"
 
 /****************************** MACROS ******************************/
diff --git a/extmod/fsusermount.c b/extmod/fsusermount.c
deleted file mode 100644
index 5882aba99..000000000
--- a/extmod/fsusermount.c
+++ /dev/null
@@ -1,209 +0,0 @@
-/*
- * This file is part of the Micro Python project, http://micropython.org/
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2014 Damien P. George
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "py/mpconfig.h"
-#if MICROPY_FSUSERMOUNT
-#include <string.h>
-#include <errno.h>
-
-#include "py/nlr.h"
-#include "py/runtime.h"
-#include "py/mperrno.h"
-#include "lib/fatfs/ff.h"
-#include "extmod/fsusermount.h"
-
-fs_user_mount_t *fatfs_mount_mkfs(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args, bool mkfs) {
-    static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_readonly, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
-        { MP_QSTR_mkfs, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
-    };
-
-    // parse args
-    mp_obj_t device = pos_args[0];
-    mp_obj_t mount_point = pos_args[1];
-    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
-    mp_arg_parse_all(n_args - 2, pos_args + 2, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-
-    // get the mount point
-    mp_uint_t mnt_len;
-    const char *mnt_str = mp_obj_str_get_data(mount_point, &mnt_len);
-
-    if (device == mp_const_none) {
-        // umount
-        FRESULT res = FR_NO_FILESYSTEM;
-        for (size_t i = 0; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
-            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
-            if (vfs != NULL && !memcmp(mnt_str, vfs->str, mnt_len + 1)) {
-                res = f_mount(NULL, vfs->str, 0);
-                if (vfs->flags & FSUSER_FREE_OBJ) {
-                    m_del_obj(fs_user_mount_t, vfs);
-                }
-                MP_STATE_PORT(fs_user_mount)[i] = NULL;
-                break;
-            }
-        }
-        if (res != FR_OK) {
-            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't umount"));
-        }
-        return NULL;
-    } else {
-        // mount
-        size_t i = 0;
-        for (; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
-            if (MP_STATE_PORT(fs_user_mount)[i] == NULL) {
-                break;
-            }
-        }
-        if (i == MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount))) {
-            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "too many devices mounted"));
-        }
-
-        // create new object
-        fs_user_mount_t *vfs = m_new_obj(fs_user_mount_t);
-        vfs->str = mnt_str;
-        vfs->len = mnt_len;
-        vfs->flags = FSUSER_FREE_OBJ;
-
-        // load block protocol methods
-        mp_load_method(device, MP_QSTR_readblocks, vfs->readblocks);
-        mp_load_method_maybe(device, MP_QSTR_writeblocks, vfs->writeblocks);
-        mp_load_method_maybe(device, MP_QSTR_ioctl, vfs->u.ioctl);
-        if (vfs->u.ioctl[0] != MP_OBJ_NULL) {
-            // device supports new block protocol, so indicate it
-            vfs->flags |= FSUSER_HAVE_IOCTL;
-        } else {
-            // no ioctl method, so assume the device uses the old block protocol
-            mp_load_method_maybe(device, MP_QSTR_sync, vfs->u.old.sync);
-            mp_load_method(device, MP_QSTR_count, vfs->u.old.count);
-        }
-
-        // Read-only device indicated by writeblocks[0] == MP_OBJ_NULL.
-        // User can specify read-only device by:
-        //  1. readonly=True keyword argument
-        //  2. nonexistent writeblocks method (then writeblocks[0] == MP_OBJ_NULL already)
-        if (args[0].u_bool) {
-            vfs->writeblocks[0] = MP_OBJ_NULL;
-        }
-
-        // Register the vfs object so that it can be found by the FatFS driver using
-        // ff_get_ldnumber.  We don't register it any earlier than this point in case there
-        // is an exception, in which case there would remain a partially mounted device.
-        MP_STATE_PORT(fs_user_mount)[i] = vfs;
-
-        // mount the block device (if mkfs, only pre-mount)
-        FRESULT res = f_mount(&vfs->fatfs, vfs->str, !mkfs);
-        // check the result
-        if (res == FR_OK) {
-            if (mkfs) {
-                goto mkfs;
-            }
-        } else if (res == FR_NO_FILESYSTEM && args[1].u_bool) {
-mkfs:
-            res = f_mkfs(vfs->str, 1, 0);
-            if (res != FR_OK) {
-mkfs_error:
-                MP_STATE_PORT(fs_user_mount)[i] = NULL;
-                nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't mkfs"));
-            }
-            if (mkfs) {
-                // If requested to only mkfs, unmount pre-mounted device
-                res = f_mount(NULL, vfs->str, 0);
-                if (res != FR_OK) {
-                    goto mkfs_error;
-                }
-                MP_STATE_PORT(fs_user_mount)[i] = NULL;
-                return NULL;
-            }
-        } else {
-            MP_STATE_PORT(fs_user_mount)[i] = NULL;
-            nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't mount"));
-        }
-
-        /*
-        if (vfs->writeblocks[0] == MP_OBJ_NULL) {
-            printf("mounted read-only");
-        } else {
-            printf("mounted read-write");
-        }
-        DWORD nclst;
-        FATFS *fatfs;
-        f_getfree(vfs->str, &nclst, &fatfs);
-        printf(" on %s with %u bytes free\n", vfs->str, (uint)(nclst * fatfs->csize * 512));
-        */
-        return vfs;
-    }
-}
-
-STATIC mp_obj_t fatfs_mount(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    fatfs_mount_mkfs(n_args, pos_args, kw_args, false);
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_KW(fsuser_mount_obj, 2, fatfs_mount);
-
-mp_obj_t fatfs_umount(mp_obj_t bdev_or_path_in) {
-    size_t i = 0;
-    if (MP_OBJ_IS_STR(bdev_or_path_in)) {
-        mp_uint_t mnt_len;
-        const char *mnt_str = mp_obj_str_get_data(bdev_or_path_in, &mnt_len);
-        for (; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
-            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
-            if (vfs != NULL && !memcmp(mnt_str, vfs->str, mnt_len + 1)) {
-                break;
-            }
-        }
-    } else {
-        for (; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
-            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
-            if (vfs != NULL && bdev_or_path_in == vfs->readblocks[1]) {
-                break;
-            }
-        }
-    }
-
-    if (i == MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount))) {
-        mp_raise_OSError(MP_EINVAL);
-    }
-
-    fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
-    FRESULT res = f_mount(NULL, vfs->str, 0);
-    if (vfs->flags & FSUSER_FREE_OBJ) {
-        m_del_obj(fs_user_mount_t, vfs);
-    }
-    MP_STATE_PORT(fs_user_mount)[i] = NULL;
-    if (res != FR_OK) {
-        nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "can't umount"));
-    }
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_1(fsuser_umount_obj, fatfs_umount);
-
-STATIC mp_obj_t fatfs_mkfs(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    fatfs_mount_mkfs(n_args, pos_args, kw_args, true);
-    return mp_const_none;
-}
-MP_DEFINE_CONST_FUN_OBJ_KW(fsuser_mkfs_obj, 2, fatfs_mkfs);
-
-#endif // MICROPY_FSUSERMOUNT
diff --git a/extmod/machine_pulse.c b/extmod/machine_pulse.c
index b2a78d72e..5f837479d 100644
--- a/extmod/machine_pulse.c
+++ b/extmod/machine_pulse.c
@@ -34,7 +34,7 @@ mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t
     mp_uint_t start = mp_hal_ticks_us();
     while (mp_hal_pin_read(pin) != pulse_level) {
         if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout_us) {
-            return (mp_uint_t)-1;
+            return (mp_uint_t)-2;
         }
     }
     start = mp_hal_ticks_us();
@@ -57,9 +57,7 @@ STATIC mp_obj_t machine_time_pulse_us_(size_t n_args, const mp_obj_t *args) {
         timeout_us = mp_obj_get_int(args[2]);
     }
     mp_uint_t us = machine_time_pulse_us(pin, level, timeout_us);
-    if (us == (mp_uint_t)-1) {
-        mp_raise_OSError(MP_ETIMEDOUT);
-    }
+    // May return -1 or -2 in case of timeout
     return mp_obj_new_int(us);
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_pulse_us_obj, 2, 3, machine_time_pulse_us_);
diff --git a/extmod/machine_signal.c b/extmod/machine_signal.c
new file mode 100644
index 000000000..d08931296
--- /dev/null
+++ b/extmod/machine_signal.c
@@ -0,0 +1,183 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/mpconfig.h"
+#if MICROPY_PY_MACHINE
+
+#include <string.h>
+
+#include "py/obj.h"
+#include "py/runtime.h"
+#include "extmod/virtpin.h"
+#include "extmod/machine_signal.h"
+
+// Signal class
+
+typedef struct _machine_signal_t {
+    mp_obj_base_t base;
+    mp_obj_t pin;
+    bool invert;
+} machine_signal_t;
+
+STATIC mp_obj_t signal_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    mp_obj_t pin = args[0];
+    bool invert = false;
+
+    #if defined(MICROPY_PY_MACHINE_PIN_MAKE_NEW)
+    mp_pin_p_t *pin_p = NULL;
+
+    if (MP_OBJ_IS_OBJ(pin)) {
+        mp_obj_base_t *pin_base = (mp_obj_base_t*)MP_OBJ_TO_PTR(args[0]);
+        pin_p = (mp_pin_p_t*)pin_base->type->protocol;
+    }
+
+    if (pin_p == NULL) {
+        // If first argument isn't a Pin-like object, we filter out "invert"
+        // from keyword arguments and pass them all to the exported Pin
+        // constructor to create one.
+        mp_obj_t pin_args[n_args + n_kw * 2];
+        memcpy(pin_args, args, n_args * sizeof(mp_obj_t));
+        const mp_obj_t *src = args + n_args;
+        mp_obj_t *dst = pin_args + n_args;
+        mp_obj_t *sig_value = NULL;
+        for (size_t cnt = n_kw; cnt; cnt--) {
+            if (*src == MP_OBJ_NEW_QSTR(MP_QSTR_invert)) {
+                invert = mp_obj_is_true(src[1]);
+                n_kw--;
+            } else {
+                *dst++ = *src;
+                *dst++ = src[1];
+            }
+            if (*src == MP_OBJ_NEW_QSTR(MP_QSTR_value)) {
+                // Value is pertained to Signal, so we should invert
+                // it for Pin if needed, and we should do it only when
+                // inversion status is guaranteedly known.
+                sig_value = dst - 1;
+            }
+            src += 2;
+        }
+
+        if (invert && sig_value != NULL) {
+            *sig_value = mp_obj_is_true(*sig_value) ? MP_OBJ_NEW_SMALL_INT(0) : MP_OBJ_NEW_SMALL_INT(1);
+        }
+
+        // Here we pass NULL as a type, hoping that mp_pin_make_new()
+        // will just ignore it as set a concrete type. If not, we'd need
+        // to expose port's "default" pin type too.
+        pin = MICROPY_PY_MACHINE_PIN_MAKE_NEW(NULL, n_args, n_kw, pin_args);
+    }
+    else
+    #endif
+    // Otherwise there should be 1 or 2 args
+    {
+        if (n_args == 1) {
+            if (n_kw == 0) {
+            } else if (n_kw == 1 && args[1] == MP_OBJ_NEW_QSTR(MP_QSTR_invert)) {
+                invert = mp_obj_is_true(args[1]);
+            } else {
+                goto error;
+            }
+        } else {
+        error:
+            mp_raise_TypeError(NULL);
+        }
+    }
+
+    machine_signal_t *o = m_new_obj(machine_signal_t);
+    o->base.type = type;
+    o->pin = pin;
+    o->invert = invert;
+    return MP_OBJ_FROM_PTR(o);
+}
+
+STATIC mp_uint_t signal_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr_t arg, int *errcode) {
+    (void)errcode;
+    machine_signal_t *self = MP_OBJ_TO_PTR(self_in);
+
+    switch (request) {
+        case MP_PIN_READ: {
+            return mp_virtual_pin_read(self->pin) ^ self->invert;
+        }
+        case MP_PIN_WRITE: {
+            mp_virtual_pin_write(self->pin, arg ^ self->invert);
+            return 0;
+        }
+    }
+    return -1;
+}
+
+// fast method for getting/setting signal value
+STATIC mp_obj_t signal_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    mp_arg_check_num(n_args, n_kw, 0, 1, false);
+    if (n_args == 0) {
+        // get pin
+        return MP_OBJ_NEW_SMALL_INT(mp_virtual_pin_read(self_in));
+    } else {
+        // set pin
+        mp_virtual_pin_write(self_in, mp_obj_is_true(args[0]));
+        return mp_const_none;
+    }
+}
+
+STATIC mp_obj_t signal_value(size_t n_args, const mp_obj_t *args) {
+    return signal_call(args[0], n_args - 1, 0, args + 1);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(signal_value_obj, 1, 2, signal_value);
+
+STATIC mp_obj_t signal_on(mp_obj_t self_in) {
+    mp_virtual_pin_write(self_in, 1);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(signal_on_obj, signal_on);
+
+STATIC mp_obj_t signal_off(mp_obj_t self_in) {
+    mp_virtual_pin_write(self_in, 0);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(signal_off_obj, signal_off);
+
+STATIC const mp_rom_map_elem_t signal_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_value), MP_ROM_PTR(&signal_value_obj) },
+    { MP_ROM_QSTR(MP_QSTR_on), MP_ROM_PTR(&signal_on_obj) },
+    { MP_ROM_QSTR(MP_QSTR_off), MP_ROM_PTR(&signal_off_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(signal_locals_dict, signal_locals_dict_table);
+
+STATIC const mp_pin_p_t signal_pin_p = {
+    .ioctl = signal_ioctl,
+};
+
+const mp_obj_type_t machine_signal_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_Signal,
+    .make_new = signal_make_new,
+    .call = signal_call,
+    .protocol = &signal_pin_p,
+    .locals_dict = (void*)&signal_locals_dict,
+};
+
+#endif // MICROPY_PY_MACHINE
diff --git a/extmod/machine_signal.h b/extmod/machine_signal.h
new file mode 100644
index 000000000..7f88cbaa8
--- /dev/null
+++ b/extmod/machine_signal.h
@@ -0,0 +1,35 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Paul Sokolovsky
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+
+#ifndef __MICROPY_INCLUDED_EXTMOD_MACHINE_SIGNAL_H__
+#define __MICROPY_INCLUDED_EXTMOD_MACHINE_SIGNAL_H__
+
+#include "py/obj.h"
+
+extern const mp_obj_type_t machine_signal_type;
+
+#endif // __MICROPY_INCLUDED_EXTMOD_MACHINE_SIGNAL_H__
diff --git a/extmod/machine_spi.c b/extmod/machine_spi.c
index 6e7678498..a67d294ba 100644
--- a/extmod/machine_spi.c
+++ b/extmod/machine_spi.c
@@ -90,12 +90,6 @@ void mp_machine_soft_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint
         if (dest != NULL) {
             dest[i] = data_in;
         }
-
-        // Some ports need a regular callback, but probably we don't need
-        // to do this every byte, or even at all.
-        #ifdef MICROPY_EVENT_POLL_HOOK
-        MICROPY_EVENT_POLL_HOOK;
-        #endif
     }
 }
 
diff --git a/extmod/modbtree.c b/extmod/modbtree.c
index bb75845b1..127dd71a3 100644
--- a/extmod/modbtree.c
+++ b/extmod/modbtree.c
@@ -97,12 +97,8 @@ STATIC mp_obj_t btree_put(size_t n_args, const mp_obj_t *args) {
     (void)n_args;
     mp_obj_btree_t *self = MP_OBJ_TO_PTR(args[0]);
     DBT key, val;
-    // Different ports may have different type sizes
-    mp_uint_t v;
-    key.data = (void*)mp_obj_str_get_data(args[1], &v);
-    key.size = v;
-    val.data = (void*)mp_obj_str_get_data(args[2], &v);
-    val.size = v;
+    key.data = (void*)mp_obj_str_get_data(args[1], &key.size);
+    val.data = (void*)mp_obj_str_get_data(args[2], &val.size);
     return MP_OBJ_NEW_SMALL_INT(__bt_put(self->db, &key, &val, 0));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(btree_put_obj, 3, 4, btree_put);
@@ -110,10 +106,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(btree_put_obj, 3, 4, btree_put);
 STATIC mp_obj_t btree_get(size_t n_args, const mp_obj_t *args) {
     mp_obj_btree_t *self = MP_OBJ_TO_PTR(args[0]);
     DBT key, val;
-    // Different ports may have different type sizes
-    mp_uint_t v;
-    key.data = (void*)mp_obj_str_get_data(args[1], &v);
-    key.size = v;
+    key.data = (void*)mp_obj_str_get_data(args[1], &key.size);
     int res = __bt_get(self->db, &key, &val, 0);
     if (res == RET_SPECIAL) {
         if (n_args > 2) {
@@ -132,10 +125,7 @@ STATIC mp_obj_t btree_seq(size_t n_args, const mp_obj_t *args) {
     int flags = MP_OBJ_SMALL_INT_VALUE(args[1]);
     DBT key, val;
     if (n_args > 2) {
-        // Different ports may have different type sizes
-        mp_uint_t v;
-        key.data = (void*)mp_obj_str_get_data(args[2], &v);
-        key.size = v;
+        key.data = (void*)mp_obj_str_get_data(args[2], &key.size);
     }
 
     int res = __bt_seq(self->db, &key, &val, flags);
@@ -184,7 +174,8 @@ STATIC mp_obj_t btree_items(size_t n_args, const mp_obj_t *args) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(btree_items_obj, 1, 4, btree_items);
 
-STATIC mp_obj_t btree_getiter(mp_obj_t self_in) {
+STATIC mp_obj_t btree_getiter(mp_obj_t self_in, mp_obj_iter_buf_t *iter_buf) {
+    (void)iter_buf;
     mp_obj_btree_t *self = MP_OBJ_TO_PTR(self_in);
     if (self->next_flags != 0) {
         // If we're called immediately after keys(), values(), or items(),
@@ -205,14 +196,11 @@ STATIC mp_obj_t btree_iternext(mp_obj_t self_in) {
     mp_obj_btree_t *self = MP_OBJ_TO_PTR(self_in);
     DBT key, val;
     int res;
-    // Different ports may have different type sizes
-    mp_uint_t v;
     bool desc = self->flags & FLAG_DESC;
     if (self->start_key != MP_OBJ_NULL) {
         int flags = R_FIRST;
         if (self->start_key != mp_const_none) {
-            key.data = (void*)mp_obj_str_get_data(self->start_key, &v);
-            key.size = v;
+            key.data = (void*)mp_obj_str_get_data(self->start_key, &key.size);
             flags = R_CURSOR;
         } else if (desc) {
             flags = R_LAST;
@@ -230,8 +218,7 @@ STATIC mp_obj_t btree_iternext(mp_obj_t self_in) {
 
     if (self->end_key != mp_const_none) {
         DBT end_key;
-        end_key.data = (void*)mp_obj_str_get_data(self->end_key, &v);
-        end_key.size = v;
+        end_key.data = (void*)mp_obj_str_get_data(self->end_key, &end_key.size);
         BTREE *t = self->db->internal;
         int cmp = t->bt_cmp(&key, &end_key);
         if (desc) {
@@ -263,13 +250,10 @@ STATIC mp_obj_t btree_iternext(mp_obj_t self_in) {
 
 STATIC mp_obj_t btree_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
     mp_obj_btree_t *self = MP_OBJ_TO_PTR(self_in);
-    // Different ports may have different type sizes
-    mp_uint_t v;
     if (value == MP_OBJ_NULL) {
         // delete
         DBT key;
-        key.data = (void*)mp_obj_str_get_data(index, &v);
-        key.size = v;
+        key.data = (void*)mp_obj_str_get_data(index, &key.size);
         int res = __bt_delete(self->db, &key, 0);
         if (res == RET_SPECIAL) {
             nlr_raise(mp_obj_new_exception(&mp_type_KeyError));
@@ -279,8 +263,7 @@ STATIC mp_obj_t btree_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
     } else if (value == MP_OBJ_SENTINEL) {
         // load
         DBT key, val;
-        key.data = (void*)mp_obj_str_get_data(index, &v);
-        key.size = v;
+        key.data = (void*)mp_obj_str_get_data(index, &key.size);
         int res = __bt_get(self->db, &key, &val, 0);
         if (res == RET_SPECIAL) {
             nlr_raise(mp_obj_new_exception(&mp_type_KeyError));
@@ -290,10 +273,8 @@ STATIC mp_obj_t btree_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
     } else {
         // store
         DBT key, val;
-        key.data = (void*)mp_obj_str_get_data(index, &v);
-        key.size = v;
-        val.data = (void*)mp_obj_str_get_data(value, &v);
-        val.size = v;
+        key.data = (void*)mp_obj_str_get_data(index, &key.size);
+        val.data = (void*)mp_obj_str_get_data(value, &val.size);
         int res = __bt_put(self->db, &key, &val, 0);
         CHECK_ERROR(res);
         return mp_const_none;
@@ -304,10 +285,8 @@ STATIC mp_obj_t btree_binary_op(mp_uint_t op, mp_obj_t lhs_in, mp_obj_t rhs_in)
     mp_obj_btree_t *self = MP_OBJ_TO_PTR(lhs_in);
     switch (op) {
         case MP_BINARY_OP_IN: {
-            mp_uint_t v;
             DBT key, val;
-            key.data = (void*)mp_obj_str_get_data(rhs_in, &v);
-            key.size = v;
+            key.data = (void*)mp_obj_str_get_data(rhs_in, &key.size);
             int res = __bt_get(self->db, &key, &val, 0);
             CHECK_ERROR(res);
             return mp_obj_new_bool(res != RET_SPECIAL);
diff --git a/extmod/modframebuf.c b/extmod/modframebuf.c
index 22841102f..a07392675 100644
--- a/extmod/modframebuf.c
+++ b/extmod/modframebuf.c
@@ -53,6 +53,41 @@ typedef struct _mp_framebuf_p_t {
     fill_rect_t fill_rect;
 } mp_framebuf_p_t;
 
+// constants for formats
+#define FRAMEBUF_MVLSB    (0)
+#define FRAMEBUF_RGB565   (1)
+#define FRAMEBUF_GS4_HMSB (2)
+#define FRAMEBUF_MHLSB    (3)
+#define FRAMEBUF_MHMSB    (4)
+
+// Functions for MHLSB and MHMSB
+
+STATIC void mono_horiz_setpixel(const mp_obj_framebuf_t *fb, int x, int y, uint32_t color) {
+    size_t index = (x + y * fb->stride) >> 3;
+    int offset = fb->format == FRAMEBUF_MHMSB ? x & 0x07 : 7 - (x & 0x07);
+    ((uint8_t*)fb->buf)[index] = (((uint8_t*)fb->buf)[index] & ~(0x01 << offset)) | ((color != 0) << offset);
+}
+
+STATIC uint32_t mono_horiz_getpixel(const mp_obj_framebuf_t *fb, int x, int y) {
+    size_t index = (x + y * fb->stride) >> 3;
+    int offset = fb->format == FRAMEBUF_MHMSB ? x & 0x07 : 7 - (x & 0x07);
+    return (((uint8_t*)fb->buf)[index] >> (offset)) & 0x01;
+}
+
+STATIC void mono_horiz_fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, int h, uint32_t col) {
+    int reverse = fb->format == FRAMEBUF_MHMSB;
+    int advance = fb->stride >> 3;
+    while (w--) {
+        uint8_t *b = &((uint8_t*)fb->buf)[(x >> 3) + y * advance];
+        int offset = reverse ?  x & 7 : 7 - (x & 7);
+        for (int hh = h; hh; --hh) {
+            *b = (*b & ~(0x01 << offset)) | ((col != 0) << offset);
+            b += advance;
+        }
+        ++x;
+    }
+}
+
 // Functions for MVLSB format
 
 STATIC void mvlsb_setpixel(const mp_obj_framebuf_t *fb, int x, int y, uint32_t color) {
@@ -97,13 +132,63 @@ STATIC void rgb565_fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, i
     }
 }
 
-// constants for formats
-#define FRAMEBUF_MVLSB  (0)
-#define FRAMEBUF_RGB565 (1)
+// Functions for GS4_HMSB format
+
+STATIC void gs4_hmsb_setpixel(const mp_obj_framebuf_t *fb, int x, int y, uint32_t col) {
+    uint8_t *pixel = &((uint8_t*)fb->buf)[(x + y * fb->stride) >> 1];
+
+    if (x % 2) {
+        *pixel = ((uint8_t)col & 0x0f) | (*pixel & 0xf0);
+    } else {
+        *pixel = ((uint8_t)col << 4) | (*pixel & 0x0f);
+    }
+}
+
+STATIC uint32_t gs4_hmsb_getpixel(const mp_obj_framebuf_t *fb, int x, int y) {
+    if (x % 2) {
+        return ((uint8_t*)fb->buf)[(x + y * fb->stride) >> 1] & 0x0f;
+    }
+
+    return ((uint8_t*)fb->buf)[(x + y * fb->stride) >> 1] >> 4;
+}
+
+STATIC void gs4_hmsb_fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, int h, uint32_t col) {
+    col &= 0x0f;
+    uint8_t *pixel_pair = &((uint8_t*)fb->buf)[(x + y * fb->stride) >> 1];
+    uint8_t col_shifted_left = col << 4;
+    uint8_t colored_pixel_pair = col_shifted_left | col;
+    int pixel_count_till_next_line = (fb->stride - w) >> 1;
+    bool odd_x = (x % 2 == 1);
+
+    while (h--) {
+        int ww = w;
+
+        if (odd_x && ww > 0) {
+            *pixel_pair = (*pixel_pair & 0xf0) | col;
+            pixel_pair++;
+            ww--;
+        }
+
+        memset(pixel_pair, colored_pixel_pair, ww >> 1);
+        pixel_pair += ww >> 1;
+
+        if (ww % 2) {
+            *pixel_pair = col_shifted_left | (*pixel_pair & 0x0f);
+            if (!odd_x) {
+                pixel_pair++;
+            }
+        }
+
+        pixel_pair += pixel_count_till_next_line;
+    }
+}
 
 STATIC mp_framebuf_p_t formats[] = {
     [FRAMEBUF_MVLSB] = {mvlsb_setpixel, mvlsb_getpixel, mvlsb_fill_rect},
     [FRAMEBUF_RGB565] = {rgb565_setpixel, rgb565_getpixel, rgb565_fill_rect},
+    [FRAMEBUF_GS4_HMSB] = {gs4_hmsb_setpixel, gs4_hmsb_getpixel, gs4_hmsb_fill_rect},
+    [FRAMEBUF_MHLSB] = {mono_horiz_setpixel, mono_horiz_getpixel, mono_horiz_fill_rect},
+    [FRAMEBUF_MHMSB] = {mono_horiz_setpixel, mono_horiz_getpixel, mono_horiz_fill_rect},
 };
 
 static inline void setpixel(const mp_obj_framebuf_t *fb, int x, int y, uint32_t color) {
@@ -115,7 +200,7 @@ static inline uint32_t getpixel(const mp_obj_framebuf_t *fb, int x, int y) {
 }
 
 STATIC void fill_rect(const mp_obj_framebuf_t *fb, int x, int y, int w, int h, uint32_t col) {
-    if (x + w <= 0 || y + h <= 0 || y >= fb->height || x >= fb->width) {
+    if (h < 1 || w < 1 || x + w <= 0 || y + h <= 0 || y >= fb->height || x >= fb->width) {
         // No operation needed.
         return;
     }
@@ -152,6 +237,11 @@ STATIC mp_obj_t framebuf_make_new(const mp_obj_type_t *type, size_t n_args, size
     switch (o->format) {
         case FRAMEBUF_MVLSB:
         case FRAMEBUF_RGB565:
+        case FRAMEBUF_GS4_HMSB:
+            break;
+        case FRAMEBUF_MHLSB:
+        case FRAMEBUF_MHMSB:
+            o->stride = (o->stride + 7) & ~7;
             break;
         default:
             nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
@@ -302,9 +392,13 @@ STATIC mp_obj_t framebuf_line(size_t n_args, const mp_obj_t *args) {
     mp_int_t e = 2 * dy - dx;
     for (mp_int_t i = 0; i < dx; ++i) {
         if (steep) {
-            setpixel(self, y1, x1, col);
+            if (0 <= y1 && y1 < self->width && 0 <= x1 && x1 < self->height) {
+                setpixel(self, y1, x1, col);
+            }
         } else {
-            setpixel(self, x1, y1, col);
+            if (0 <= x1 && x1 < self->width && 0 <= y1 && y1 < self->height) {
+                setpixel(self, x1, y1, col);
+            }
         }
         while (e >= 0) {
             y1 += sy;
@@ -314,7 +408,9 @@ STATIC mp_obj_t framebuf_line(size_t n_args, const mp_obj_t *args) {
         e += 2 * dy;
     }
 
-    setpixel(self, x2, y2, col);
+    if (0 <= x2 && x2 < self->width && 0 <= y2 && y2 < self->height) {
+        setpixel(self, x2, y2, col);
+    }
 
     return mp_const_none;
 }
@@ -353,7 +449,7 @@ STATIC mp_obj_t framebuf_blit(size_t n_args, const mp_obj_t *args) {
         int cx1 = x1;
         for (int cx0 = x0; cx0 < x0end; ++cx0) {
             color = getpixel(source, cx1, y1);
-            if (key == -1 || color != (uint32_t)key) {
+            if (color != (uint32_t)key) {
                 setpixel(self, cx0, y0, color);
             }
             ++cx1;
@@ -483,7 +579,11 @@ STATIC const mp_rom_map_elem_t framebuf_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_FrameBuffer), MP_ROM_PTR(&mp_type_framebuf) },
     { MP_ROM_QSTR(MP_QSTR_FrameBuffer1), MP_ROM_PTR(&legacy_framebuffer1_obj) },
     { MP_ROM_QSTR(MP_QSTR_MVLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MVLSB) },
+    { MP_ROM_QSTR(MP_QSTR_MONO_VLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MVLSB) },
     { MP_ROM_QSTR(MP_QSTR_RGB565), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_RGB565) },
+    { MP_ROM_QSTR(MP_QSTR_GS4_HMSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_GS4_HMSB) },
+    { MP_ROM_QSTR(MP_QSTR_MONO_HLSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MHLSB) },
+    { MP_ROM_QSTR(MP_QSTR_MONO_HMSB), MP_OBJ_NEW_SMALL_INT(FRAMEBUF_MHMSB) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(framebuf_module_globals, framebuf_module_globals_table);
diff --git a/extmod/modlwip.c b/extmod/modlwip.c
index 9194fa5e4..79b750979 100644
--- a/extmod/modlwip.c
+++ b/extmod/modlwip.c
@@ -1,10 +1,11 @@
 /*
- * This file is part of the Micro Python project, http://micropython.org/
+ * This file is part of the MicroPython project, http://micropython.org/
  *
  * The MIT License (MIT)
  *
  * Copyright (c) 2013, 2014 Damien P. George
  * Copyright (c) 2015 Galen Hazelwood
+ * Copyright (c) 2015-2016 Paul Sokolovsky
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -35,7 +36,7 @@
 #include "py/mperrno.h"
 #include "py/mphal.h"
 
-#include "netutils.h"
+#include "lib/netutils/netutils.h"
 
 #include "lwip/init.h"
 #include "lwip/timers.h"
@@ -372,7 +373,7 @@ STATIC err_t _lwip_tcp_recv(void *arg, struct tcp_pcb *tcpb, struct pbuf *p, err
 }
 
 /*******************************************************************************/
-// Functions for socket send/recieve operations. Socket send/recv and friends call
+// Functions for socket send/receive operations. Socket send/recv and friends call
 // these to do the work.
 
 // Helper function for send/sendto to handle UDP packets.
@@ -731,7 +732,9 @@ STATIC mp_obj_t lwip_socket_accept(mp_obj_t self_in) {
 
     // accept incoming connection
     if (socket->incoming.connection == NULL) {
-        if (socket->timeout != -1) {
+        if (socket->timeout == 0) {
+            mp_raise_OSError(MP_EAGAIN);
+        } else if (socket->timeout != -1) {
             for (mp_uint_t retries = socket->timeout / 100; retries--;) {
                 mp_hal_delay_ms(100);
                 if (socket->incoming.connection != NULL) break;
@@ -799,12 +802,12 @@ STATIC mp_obj_t lwip_socket_connect(mp_obj_t self_in, mp_obj_t addr_in) {
         case MOD_NETWORK_SOCK_STREAM: {
             if (socket->state != STATE_NEW) {
                 if (socket->state == STATE_CONNECTED) {
-                    mp_raise_OSError(MP_EALREADY);
+                    mp_raise_OSError(MP_EISCONN);
                 } else {
-                    mp_raise_OSError(MP_EINPROGRESS);
+                    mp_raise_OSError(MP_EALREADY);
                 }
             }
-            // Register our recieve callback.
+            // Register our receive callback.
             tcp_recv(socket->pcb.tcp, _lwip_tcp_recv);
             socket->state = STATE_CONNECTING;
             err = tcp_connect(socket->pcb.tcp, &dest, port, _lwip_tcp_connected);
@@ -821,7 +824,7 @@ STATIC mp_obj_t lwip_socket_connect(mp_obj_t self_in, mp_obj_t addr_in) {
                     if (socket->state != STATE_CONNECTING) break;
                 }
                 if (socket->state == STATE_CONNECTING) {
-                    mp_raise_OSError(MP_ETIMEDOUT);
+                    mp_raise_OSError(MP_EINPROGRESS);
                 }
             } else {
                 while (socket->state == STATE_CONNECTING) {
@@ -1142,8 +1145,11 @@ STATIC mp_uint_t lwip_socket_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr_
             ret |= MP_STREAM_POLL_WR;
         }
 
-        if (flags & MP_STREAM_POLL_HUP && socket->state == STATE_PEER_CLOSED) {
-            ret |= MP_STREAM_POLL_HUP;
+        if (socket->state == STATE_PEER_CLOSED) {
+            // Peer-closed socket is both readable and writable: read will
+            // return EOF, write - error. Without this poll will hang on a
+            // socket which was closed by peer.
+            ret |= flags & (MP_STREAM_POLL_RD | MP_STREAM_POLL_WR);
         }
 
     } else {
@@ -1172,6 +1178,7 @@ STATIC const mp_map_elem_t lwip_socket_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_makefile), (mp_obj_t)&lwip_socket_makefile_obj },
 
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&mp_stream_read_obj },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_readinto), (mp_obj_t)&mp_stream_readinto_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_readline), (mp_obj_t)&mp_stream_unbuffered_readline_obj},
     { MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&mp_stream_write_obj },
 };
@@ -1261,9 +1268,13 @@ STATIC void lwip_getaddrinfo_cb(const char *name, ip_addr_t *ipaddr, void *arg)
 }
 
 // lwip.getaddrinfo
-STATIC mp_obj_t lwip_getaddrinfo(mp_obj_t host_in, mp_obj_t port_in) {
-    mp_uint_t hlen;
-    const char *host = mp_obj_str_get_data(host_in, &hlen);
+STATIC mp_obj_t lwip_getaddrinfo(size_t n_args, const mp_obj_t *args) {
+    if (n_args > 2) {
+        mp_warning("getaddrinfo constraints not supported");
+    }
+
+    mp_obj_t host_in = args[0], port_in = args[1];
+    const char *host = mp_obj_str_get_str(host_in);
     mp_int_t port = mp_obj_get_int(port_in);
 
     getaddrinfo_state_t state;
@@ -1298,7 +1309,7 @@ STATIC mp_obj_t lwip_getaddrinfo(mp_obj_t host_in, mp_obj_t port_in) {
     tuple->items[4] = netutils_format_inet_addr((uint8_t*)&state.ipaddr, port, NETUTILS_BIG);
     return mp_obj_new_list(1, (mp_obj_t*)&tuple);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(lwip_getaddrinfo_obj, lwip_getaddrinfo);
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(lwip_getaddrinfo_obj, 2, 6, lwip_getaddrinfo);
 
 // Debug functions
 
diff --git a/extmod/moductypes.c b/extmod/moductypes.c
index 44b36561f..641c1de64 100644
--- a/extmod/moductypes.c
+++ b/extmod/moductypes.c
@@ -360,7 +360,7 @@ STATIC void set_aligned(uint val_type, void *p, mp_int_t index, mp_obj_t val) {
         return;
     }
     #endif
-    mp_int_t v = mp_obj_get_int(val);
+    mp_int_t v = mp_obj_get_int_truncated(val);
     switch (val_type) {
         case UINT8:
             ((uint8_t*)p)[index] = (uint8_t)v; return;
diff --git a/extmod/modujson.c b/extmod/modujson.c
index ca4e6df10..bb2d45274 100644
--- a/extmod/modujson.c
+++ b/extmod/modujson.c
@@ -274,7 +274,7 @@ STATIC mp_obj_t mod_ujson_load(mp_obj_t stream_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_ujson_load_obj, mod_ujson_load);
 
 STATIC mp_obj_t mod_ujson_loads(mp_obj_t obj) {
-    mp_uint_t len;
+    size_t len;
     const char *buf = mp_obj_str_get_data(obj, &len);
     vstr_t vstr = {len, len, (char*)buf, true};
     mp_obj_stringio_t sio = {{&mp_type_stringio}, &vstr, 0};
diff --git a/extmod/modurandom.c b/extmod/modurandom.c
index 12e56741e..4b63dace4 100644
--- a/extmod/modurandom.c
+++ b/extmod/modurandom.c
@@ -74,7 +74,7 @@ STATIC uint32_t yasmarang_randbelow(uint32_t n) {
 STATIC mp_obj_t mod_urandom_getrandbits(mp_obj_t num_in) {
     int n = mp_obj_get_int(num_in);
     if (n > 32 || n == 0) {
-        nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+        mp_raise_ValueError(NULL);
     }
     uint32_t mask = ~0;
     // Beware of C undefined behavior when shifting by >= than bit size
@@ -102,7 +102,7 @@ STATIC mp_obj_t mod_urandom_randrange(size_t n_args, const mp_obj_t *args) {
         if (start > 0) {
             return mp_obj_new_int(yasmarang_randbelow(start));
         } else {
-            nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+            goto error;
         }
     } else {
         mp_int_t stop = mp_obj_get_int(args[1]);
@@ -111,7 +111,7 @@ STATIC mp_obj_t mod_urandom_randrange(size_t n_args, const mp_obj_t *args) {
             if (start < stop) {
                 return mp_obj_new_int(start + yasmarang_randbelow(stop - start));
             } else {
-                nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+                goto error;
             }
         } else {
             // range(start, stop, step)
@@ -122,15 +122,18 @@ STATIC mp_obj_t mod_urandom_randrange(size_t n_args, const mp_obj_t *args) {
             } else if (step < 0) {
                 n = (stop - start + step + 1) / step;
             } else {
-                nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+                goto error;
             }
             if (n > 0) {
                 return mp_obj_new_int(start + step * yasmarang_randbelow(n));
             } else {
-                nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+                goto error;
             }
         }
     }
+
+error:
+    mp_raise_ValueError(NULL);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_urandom_randrange_obj, 1, 3, mod_urandom_randrange);
 
@@ -140,7 +143,7 @@ STATIC mp_obj_t mod_urandom_randint(mp_obj_t a_in, mp_obj_t b_in) {
     if (a <= b) {
         return mp_obj_new_int(a + yasmarang_randbelow(b - a + 1));
     } else {
-        nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+        mp_raise_ValueError(NULL);
     }
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_urandom_randint_obj, mod_urandom_randint);
diff --git a/extmod/modure.c b/extmod/modure.c
index 6cd700763..817cf0ee9 100644
--- a/extmod/modure.c
+++ b/extmod/modure.c
@@ -96,7 +96,7 @@ STATIC mp_obj_t ure_exec(bool is_anchored, uint n_args, const mp_obj_t *args) {
     (void)n_args;
     mp_obj_re_t *self = MP_OBJ_TO_PTR(args[0]);
     Subject subj;
-    mp_uint_t len;
+    size_t len;
     subj.begin = mp_obj_str_get_data(args[1], &len);
     subj.end = subj.begin + len;
     int caps_num = (self->re.sub + 1) * 2;
@@ -128,7 +128,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(re_search_obj, 2, 4, re_search);
 STATIC mp_obj_t re_split(size_t n_args, const mp_obj_t *args) {
     mp_obj_re_t *self = MP_OBJ_TO_PTR(args[0]);
     Subject subj;
-    mp_uint_t len;
+    size_t len;
     subj.begin = mp_obj_str_get_data(args[1], &len);
     subj.end = subj.begin + len;
     int caps_num = (self->re.sub + 1) * 2;
diff --git a/extmod/moduselect.c b/extmod/moduselect.c
index 5cc72c69c..f51ee4f51 100644
--- a/extmod/moduselect.c
+++ b/extmod/moduselect.c
@@ -114,7 +114,7 @@ STATIC mp_uint_t poll_map_poll(mp_map_t *poll_map, mp_uint_t *rwx_num) {
 /// \function select(rlist, wlist, xlist[, timeout])
 STATIC mp_obj_t select_select(uint n_args, const mp_obj_t *args) {
     // get array data from tuple/list arguments
-    mp_uint_t rwx_len[3];
+    size_t rwx_len[3];
     mp_obj_t *r_array, *w_array, *x_array;
     mp_obj_get_array(args[0], &rwx_len[0], &r_array);
     mp_obj_get_array(args[1], &rwx_len[1], &w_array);
@@ -183,6 +183,11 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_select_select_obj, 3, 4, select_select);
 typedef struct _mp_obj_poll_t {
     mp_obj_base_t base;
     mp_map_t poll_map;
+    short iter_cnt;
+    short iter_idx;
+    int flags;
+    // callee-owned tuple
+    mp_obj_t ret_tuple;
 } mp_obj_poll_t;
 
 /// \method register(obj[, eventmask])
@@ -220,9 +225,7 @@ STATIC mp_obj_t poll_modify(mp_obj_t self_in, mp_obj_t obj_in, mp_obj_t eventmas
 }
 MP_DEFINE_CONST_FUN_OBJ_3(poll_modify_obj, poll_modify);
 
-/// \method poll([timeout])
-/// Timeout is in milliseconds.
-STATIC mp_obj_t poll_poll(uint n_args, const mp_obj_t *args) {
+STATIC mp_uint_t poll_poll_internal(uint n_args, const mp_obj_t *args) {
     mp_obj_poll_t *self = args[0];
 
     // work out timeout (its given already in ms)
@@ -240,48 +243,109 @@ STATIC mp_obj_t poll_poll(uint n_args, const mp_obj_t *args) {
         }
     }
 
+    self->flags = flags;
+
     mp_uint_t start_tick = mp_hal_ticks_ms();
+    mp_uint_t n_ready;
     for (;;) {
         // poll the objects
-        mp_uint_t n_ready = poll_map_poll(&self->poll_map, NULL);
-
+        n_ready = poll_map_poll(&self->poll_map, NULL);
         if (n_ready > 0 || (timeout != -1 && mp_hal_ticks_ms() - start_tick >= timeout)) {
-            // one or more objects are ready, or we had a timeout
-            mp_obj_list_t *ret_list = mp_obj_new_list(n_ready, NULL);
-            n_ready = 0;
-            for (mp_uint_t i = 0; i < self->poll_map.alloc; ++i) {
-                if (!MP_MAP_SLOT_IS_FILLED(&self->poll_map, i)) {
-                    continue;
-                }
-                poll_obj_t *poll_obj = (poll_obj_t*)self->poll_map.table[i].value;
-                if (poll_obj->flags_ret != 0) {
-                    mp_obj_t tuple[2] = {poll_obj->obj, MP_OBJ_NEW_SMALL_INT(poll_obj->flags_ret)};
-                    ret_list->items[n_ready++] = mp_obj_new_tuple(2, tuple);
-                    if (flags & FLAG_ONESHOT) {
-                        // Don't poll next time, until new event flags will be set explicitly
-                        poll_obj->flags = 0;
-                    }
-                }
-            }
-            return ret_list;
+            break;
         }
         MICROPY_EVENT_POLL_HOOK
     }
+
+    return n_ready;
+}
+
+STATIC mp_obj_t poll_poll(uint n_args, const mp_obj_t *args) {
+    mp_obj_poll_t *self = args[0];
+    mp_uint_t n_ready = poll_poll_internal(n_args, args);
+
+    // one or more objects are ready, or we had a timeout
+    mp_obj_list_t *ret_list = mp_obj_new_list(n_ready, NULL);
+    n_ready = 0;
+    for (mp_uint_t i = 0; i < self->poll_map.alloc; ++i) {
+        if (!MP_MAP_SLOT_IS_FILLED(&self->poll_map, i)) {
+            continue;
+        }
+        poll_obj_t *poll_obj = (poll_obj_t*)self->poll_map.table[i].value;
+        if (poll_obj->flags_ret != 0) {
+            mp_obj_t tuple[2] = {poll_obj->obj, MP_OBJ_NEW_SMALL_INT(poll_obj->flags_ret)};
+            ret_list->items[n_ready++] = mp_obj_new_tuple(2, tuple);
+            if (self->flags & FLAG_ONESHOT) {
+                // Don't poll next time, until new event flags will be set explicitly
+                poll_obj->flags = 0;
+            }
+        }
+    }
+    return ret_list;
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_poll_obj, 1, 3, poll_poll);
 
-STATIC const mp_map_elem_t poll_locals_dict_table[] = {
-    { MP_OBJ_NEW_QSTR(MP_QSTR_register), (mp_obj_t)&poll_register_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_unregister), (mp_obj_t)&poll_unregister_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_modify), (mp_obj_t)&poll_modify_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_poll), (mp_obj_t)&poll_poll_obj },
+STATIC mp_obj_t poll_ipoll(size_t n_args, const mp_obj_t *args) {
+    mp_obj_poll_t *self = MP_OBJ_TO_PTR(args[0]);
+
+    if (self->ret_tuple == MP_OBJ_NULL) {
+        self->ret_tuple = mp_obj_new_tuple(2, NULL);
+    }
+
+    int n_ready = poll_poll_internal(n_args, args);
+    self->iter_cnt = n_ready;
+    self->iter_idx = 0;
+
+    return args[0];
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(poll_ipoll_obj, 1, 3, poll_ipoll);
+
+STATIC mp_obj_t poll_iternext(mp_obj_t self_in) {
+    mp_obj_poll_t *self = MP_OBJ_TO_PTR(self_in);
+
+    if (self->iter_cnt == 0) {
+        return MP_OBJ_STOP_ITERATION;
+    }
+
+    self->iter_cnt--;
+
+    for (mp_uint_t i = self->iter_idx; i < self->poll_map.alloc; ++i) {
+        self->iter_idx++;
+        if (!MP_MAP_SLOT_IS_FILLED(&self->poll_map, i)) {
+            continue;
+        }
+        poll_obj_t *poll_obj = (poll_obj_t*)self->poll_map.table[i].value;
+        if (poll_obj->flags_ret != 0) {
+            mp_obj_tuple_t *t = MP_OBJ_TO_PTR(self->ret_tuple);
+            t->items[0] = poll_obj->obj;
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(poll_obj->flags_ret);
+            if (self->flags & FLAG_ONESHOT) {
+                // Don't poll next time, until new event flags will be set explicitly
+                poll_obj->flags = 0;
+            }
+            return MP_OBJ_FROM_PTR(t);
+        }
+    }
+
+    assert(!"inconsistent number of poll active entries");
+    self->iter_cnt = 0;
+    return MP_OBJ_STOP_ITERATION;
+}
+
+STATIC const mp_rom_map_elem_t poll_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_register), MP_ROM_PTR(&poll_register_obj) },
+    { MP_ROM_QSTR(MP_QSTR_unregister), MP_ROM_PTR(&poll_unregister_obj) },
+    { MP_ROM_QSTR(MP_QSTR_modify), MP_ROM_PTR(&poll_modify_obj) },
+    { MP_ROM_QSTR(MP_QSTR_poll), MP_ROM_PTR(&poll_poll_obj) },
+    { MP_ROM_QSTR(MP_QSTR_ipoll), MP_ROM_PTR(&poll_ipoll_obj) },
 };
 STATIC MP_DEFINE_CONST_DICT(poll_locals_dict, poll_locals_dict_table);
 
 STATIC const mp_obj_type_t mp_type_poll = {
     { &mp_type_type },
     .name = MP_QSTR_poll,
-    .locals_dict = (mp_obj_t)&poll_locals_dict,
+    .getiter = mp_identity_getiter,
+    .iternext = poll_iternext,
+    .locals_dict = (void*)&poll_locals_dict,
 };
 
 /// \function poll()
@@ -289,18 +353,20 @@ STATIC mp_obj_t select_poll(void) {
     mp_obj_poll_t *poll = m_new_obj(mp_obj_poll_t);
     poll->base.type = &mp_type_poll;
     mp_map_init(&poll->poll_map, 0);
+    poll->iter_cnt = 0;
+    poll->ret_tuple = MP_OBJ_NULL;
     return poll;
 }
 MP_DEFINE_CONST_FUN_OBJ_0(mp_select_poll_obj, select_poll);
 
-STATIC const mp_map_elem_t mp_module_select_globals_table[] = {
-    { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_uselect) },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_select), (mp_obj_t)&mp_select_select_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_poll), (mp_obj_t)&mp_select_poll_obj },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_POLLIN), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_RD) },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_POLLOUT), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_WR) },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_POLLERR), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_ERR) },
-    { MP_OBJ_NEW_QSTR(MP_QSTR_POLLHUP), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_HUP) },
+STATIC const mp_rom_map_elem_t mp_module_select_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_uselect) },
+    { MP_ROM_QSTR(MP_QSTR_select), MP_ROM_PTR(&mp_select_select_obj) },
+    { MP_ROM_QSTR(MP_QSTR_poll), MP_ROM_PTR(&mp_select_poll_obj) },
+    { MP_ROM_QSTR(MP_QSTR_POLLIN), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_RD) },
+    { MP_ROM_QSTR(MP_QSTR_POLLOUT), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_WR) },
+    { MP_ROM_QSTR(MP_QSTR_POLLERR), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_ERR) },
+    { MP_ROM_QSTR(MP_QSTR_POLLHUP), MP_OBJ_NEW_SMALL_INT(MP_STREAM_POLL_HUP) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(mp_module_select_globals, mp_module_select_globals_table);
diff --git a/extmod/modussl_mbedtls.c b/extmod/modussl_mbedtls.c
index 291d4bb0c..35b470a83 100644
--- a/extmod/modussl_mbedtls.c
+++ b/extmod/modussl_mbedtls.c
@@ -156,13 +156,13 @@ STATIC mp_obj_ssl_socket_t *socket_new(mp_obj_t sock, struct ssl_args *args) {
     mbedtls_ssl_set_bio(&o->ssl, &o->sock, _mbedtls_ssl_send, _mbedtls_ssl_recv, NULL);
 
     if (args->key.u_obj != MP_OBJ_NULL) {
-        mp_uint_t key_len;
+        size_t key_len;
         const byte *key = (const byte*)mp_obj_str_get_data(args->key.u_obj, &key_len);
         // len should include terminating null
         ret = mbedtls_pk_parse_key(&o->pkey, key, key_len + 1, NULL, 0);
         assert(ret == 0);
 
-        mp_uint_t cert_len;
+        size_t cert_len;
         const byte *cert = (const byte*)mp_obj_str_get_data(args->cert.u_obj, &cert_len);
         // len should include terminating null
         ret = mbedtls_x509_crt_parse(&o->cert, cert, cert_len + 1);
diff --git a/extmod/modutimeq.c b/extmod/modutimeq.c
index 26ccb5182..e54415b28 100644
--- a/extmod/modutimeq.c
+++ b/extmod/modutimeq.c
@@ -4,7 +4,7 @@
  * The MIT License (MIT)
  *
  * Copyright (c) 2014 Damien P. George
- * Copyright (c) 2016 Paul Sokolovsky
+ * Copyright (c) 2016-2017 Paul Sokolovsky
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -43,6 +43,7 @@
 
 struct qentry {
     mp_uint_t time;
+    mp_uint_t id;
     mp_obj_t callback;
     mp_obj_t args;
 };
@@ -54,6 +55,7 @@ typedef struct _mp_obj_utimeq_t {
     struct qentry items[];
 } mp_obj_utimeq_t;
 
+STATIC mp_uint_t utimeq_id;
 
 STATIC mp_obj_utimeq_t *get_heap(mp_obj_t heap_in) {
     return MP_OBJ_TO_PTR(heap_in);
@@ -63,6 +65,11 @@ STATIC bool time_less_than(struct qentry *item, struct qentry *parent) {
     mp_uint_t item_tm = item->time;
     mp_uint_t parent_tm = parent->time;
     mp_uint_t res = parent_tm - item_tm;
+    if (res == 0) {
+        // TODO: This actually should use the same "ring" logic
+        // as for time, to avoid artifacts when id's overflow.
+        return item->id < parent->id;
+    }
     if ((mp_int_t)res < 0) {
         res += MODULO;
     }
@@ -125,6 +132,7 @@ STATIC mp_obj_t mod_utimeq_heappush(size_t n_args, const mp_obj_t *args) {
     }
     mp_uint_t l = heap->len;
     heap->items[l].time = MP_OBJ_SMALL_INT_VALUE(args[1]);
+    heap->items[l].id = utimeq_id++;
     heap->items[l].callback = args[2];
     heap->items[l].args = args[3];
     heap_siftdown(heap, 0, heap->len);
@@ -158,6 +166,17 @@ STATIC mp_obj_t mod_utimeq_heappop(mp_obj_t heap_in, mp_obj_t list_ref) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(mod_utimeq_heappop_obj, mod_utimeq_heappop);
 
+STATIC mp_obj_t mod_utimeq_peektime(mp_obj_t heap_in) {
+    mp_obj_utimeq_t *heap = get_heap(heap_in);
+    if (heap->len == 0) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_IndexError, "empty heap"));
+    }
+
+    struct qentry *item = &heap->items[0];
+    return MP_OBJ_NEW_SMALL_INT(item->time);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_utimeq_peektime_obj, mod_utimeq_peektime);
+
 #if DEBUG
 STATIC mp_obj_t mod_utimeq_dump(mp_obj_t heap_in) {
     mp_obj_utimeq_t *heap = get_heap(heap_in);
@@ -182,6 +201,7 @@ STATIC mp_obj_t utimeq_unary_op(mp_uint_t op, mp_obj_t self_in) {
 STATIC const mp_rom_map_elem_t utimeq_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_push), MP_ROM_PTR(&mod_utimeq_heappush_obj) },
     { MP_ROM_QSTR(MP_QSTR_pop), MP_ROM_PTR(&mod_utimeq_heappop_obj) },
+    { MP_ROM_QSTR(MP_QSTR_peektime), MP_ROM_PTR(&mod_utimeq_peektime_obj) },
     #if DEBUG
     { MP_ROM_QSTR(MP_QSTR_dump), MP_ROM_PTR(&mod_utimeq_dump_obj) },
     #endif
diff --git a/extmod/modwebrepl.c b/extmod/modwebrepl.c
index 571acabfe..ec965587e 100644
--- a/extmod/modwebrepl.c
+++ b/extmod/modwebrepl.c
@@ -308,7 +308,7 @@ STATIC mp_obj_t webrepl_close(mp_obj_t self_in) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(webrepl_close_obj, webrepl_close);
 
 STATIC mp_obj_t webrepl_set_password(mp_obj_t passwd_in) {
-    mp_uint_t len;
+    size_t len;
     const char *passwd = mp_obj_str_get_data(passwd_in, &len);
     if (len > sizeof(webrepl_passwd) - 1) {
         mp_raise_ValueError("");
diff --git a/extmod/modwebsocket.c b/extmod/modwebsocket.c
index 8200ea708..9e17d6a6d 100644
--- a/extmod/modwebsocket.c
+++ b/extmod/modwebsocket.c
@@ -132,7 +132,7 @@ STATIC mp_uint_t websocket_read(mp_obj_t self_in, void *buf, mp_uint_t size, int
 
                 self->buf_pos = 0;
                 self->to_recv = to_recv;
-                self->msg_sz = sz; // May be overriden by FRAME_OPT
+                self->msg_sz = sz; // May be overridden by FRAME_OPT
                 if (to_recv != 0) {
                     self->state = FRAME_OPT;
                 } else {
diff --git a/extmod/utime_mphal.c b/extmod/utime_mphal.c
index f447b3a68..e99ba46ce 100644
--- a/extmod/utime_mphal.c
+++ b/extmod/utime_mphal.c
@@ -37,13 +37,11 @@
 #include "extmod/utime_mphal.h"
 
 STATIC mp_obj_t time_sleep(mp_obj_t seconds_o) {
-    MP_THREAD_GIL_EXIT();
     #if MICROPY_PY_BUILTINS_FLOAT
     mp_hal_delay_ms(1000 * mp_obj_get_float(seconds_o));
     #else
     mp_hal_delay_ms(1000 * mp_obj_get_int(seconds_o));
     #endif
-    MP_THREAD_GIL_ENTER();
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_utime_sleep_obj, time_sleep);
@@ -51,9 +49,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_utime_sleep_obj, time_sleep);
 STATIC mp_obj_t time_sleep_ms(mp_obj_t arg) {
     mp_int_t ms = mp_obj_get_int(arg);
     if (ms > 0) {
-        MP_THREAD_GIL_EXIT();
         mp_hal_delay_ms(ms);
-        MP_THREAD_GIL_ENTER();
     }
     return mp_const_none;
 }
@@ -62,9 +58,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_utime_sleep_ms_obj, time_sleep_ms);
 STATIC mp_obj_t time_sleep_us(mp_obj_t arg) {
     mp_int_t us = mp_obj_get_int(arg);
     if (us > 0) {
-        MP_THREAD_GIL_EXIT();
         mp_hal_delay_us(us);
-        MP_THREAD_GIL_ENTER();
     }
     return mp_const_none;
 }
diff --git a/extmod/vfs.c b/extmod/vfs.c
new file mode 100644
index 000000000..3bdce80db
--- /dev/null
+++ b/extmod/vfs.c
@@ -0,0 +1,457 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include "py/runtime0.h"
+#include "py/runtime.h"
+#include "py/objstr.h"
+#include "py/mperrno.h"
+#include "extmod/vfs.h"
+
+#if MICROPY_VFS
+
+#if MICROPY_VFS_FAT
+#include "extmod/vfs_fat.h"
+#endif
+
+// path is the path to lookup and *path_out holds the path within the VFS
+// object (starts with / if an absolute path).
+// Returns MP_VFS_ROOT for root dir (and then path_out is undefined) and
+// MP_VFS_NONE for path not found.
+mp_vfs_mount_t *mp_vfs_lookup_path(const char *path, const char **path_out) {
+    if (*path == '/' || MP_STATE_VM(vfs_cur) == MP_VFS_ROOT) {
+        // an absolute path, or the current volume is root, so search root dir
+        bool is_abs = 0;
+        if (*path == '/') {
+            ++path;
+            is_abs = 1;
+        }
+        if (*path == '\0') {
+            // path is "" or "/" so return virtual root
+            return MP_VFS_ROOT;
+        }
+        for (mp_vfs_mount_t *vfs = MP_STATE_VM(vfs_mount_table); vfs != NULL; vfs = vfs->next) {
+            size_t len = vfs->len - 1;
+            if (len == 0) {
+                *path_out = path - is_abs;
+                return vfs;
+            }
+            if (strncmp(path, vfs->str + 1, len) == 0) {
+                if (path[len] == '/') {
+                    *path_out = path + len;
+                    return vfs;
+                } else if (path[len] == '\0') {
+                    *path_out = "/";
+                    return vfs;
+                }
+            }
+        }
+
+        // if we get here then there's nothing mounted on /
+
+        if (is_abs) {
+            // path began with / and was not found
+            return MP_VFS_NONE;
+        }
+    }
+
+    // a relative path within a mounted device
+    *path_out = path;
+    return MP_STATE_VM(vfs_cur);
+}
+
+// Version of mp_vfs_lookup_path that takes and returns uPy string objects.
+STATIC mp_vfs_mount_t *lookup_path(mp_obj_t path_in, mp_obj_t *path_out) {
+    const char *path = mp_obj_str_get_str(path_in);
+    const char *p_out;
+    mp_vfs_mount_t *vfs = mp_vfs_lookup_path(path, &p_out);
+    if (vfs != MP_VFS_NONE && vfs != MP_VFS_ROOT) {
+        *path_out = mp_obj_new_str_of_type(mp_obj_get_type(path_in),
+            (const byte*)p_out, strlen(p_out));
+    }
+    return vfs;
+}
+
+STATIC mp_obj_t mp_vfs_proxy_call(mp_vfs_mount_t *vfs, qstr meth_name, size_t n_args, const mp_obj_t *args) {
+    if (vfs == MP_VFS_NONE) {
+        // mount point not found
+        mp_raise_OSError(MP_ENODEV);
+    }
+    if (vfs == MP_VFS_ROOT) {
+        // can't do operation on root dir
+        mp_raise_OSError(MP_EPERM);
+    }
+    mp_obj_t meth[n_args + 2];
+    mp_load_method(vfs->obj, meth_name, meth);
+    if (args != NULL) {
+        memcpy(meth + 2, args, n_args * sizeof(*args));
+    }
+    return mp_call_method_n_kw(n_args, 0, meth);
+}
+
+mp_import_stat_t mp_vfs_import_stat(const char *path) {
+    const char *path_out;
+    mp_vfs_mount_t *vfs = mp_vfs_lookup_path(path, &path_out);
+    if (vfs == MP_VFS_NONE || vfs == MP_VFS_ROOT) {
+        return MP_IMPORT_STAT_NO_EXIST;
+    }
+    #if MICROPY_VFS_FAT
+    // fast paths for known VFS types
+    if (mp_obj_get_type(vfs->obj) == &mp_fat_vfs_type) {
+        return fat_vfs_import_stat(MP_OBJ_TO_PTR(vfs->obj), path_out);
+    }
+    #endif
+    // TODO delegate to vfs.stat() method
+    return MP_IMPORT_STAT_NO_EXIST;
+}
+
+mp_obj_t mp_vfs_mount(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_readonly, ARG_mkfs };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_readonly, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_false} },
+        { MP_QSTR_mkfs, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_false} },
+    };
+
+    // parse args
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args - 2, pos_args + 2, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    // get the mount point
+    size_t mnt_len;
+    const char *mnt_str = mp_obj_str_get_data(pos_args[1], &mnt_len);
+
+    // see if we need to auto-detect and create the filesystem
+    mp_obj_t vfs_obj = pos_args[0];
+    mp_obj_t dest[2];
+    mp_load_method_maybe(vfs_obj, MP_QSTR_mount, dest);
+    if (dest[0] == MP_OBJ_NULL) {
+        // Input object has no mount method, assume it's a block device and try to
+        // auto-detect the filesystem and create the corresponding VFS entity.
+        // (At the moment we only support FAT filesystems.)
+        #if MICROPY_VFS_FAT
+        vfs_obj = mp_fat_vfs_type.make_new(&mp_fat_vfs_type, 1, 0, &vfs_obj);
+        #endif
+    }
+
+    // create new object
+    mp_vfs_mount_t *vfs = m_new_obj(mp_vfs_mount_t);
+    vfs->str = mnt_str;
+    vfs->len = mnt_len;
+    vfs->obj = vfs_obj;
+    vfs->next = NULL;
+
+    // call the underlying object to do any mounting operation
+    mp_vfs_proxy_call(vfs, MP_QSTR_mount, 2, (mp_obj_t*)&args);
+
+    // check that the destination mount point is unused
+    const char *path_out;
+    mp_vfs_mount_t *existing_mount = mp_vfs_lookup_path(mp_obj_str_get_str(pos_args[1]), &path_out);
+    if (existing_mount != MP_VFS_NONE && existing_mount != MP_VFS_ROOT) {
+        if (vfs->len != 1 && existing_mount->len == 1) {
+            // if root dir is mounted, still allow to mount something within a subdir of root
+        } else {
+            // mount point in use
+            mp_raise_OSError(MP_EPERM);
+        }
+    }
+
+    // insert the vfs into the mount table
+    mp_vfs_mount_t **vfsp = &MP_STATE_VM(vfs_mount_table);
+    while (*vfsp != NULL) {
+        if ((*vfsp)->len == 1) {
+            // make sure anything mounted at the root stays at the end of the list
+            vfs->next = *vfsp;
+            break;
+        }
+        vfsp = &(*vfsp)->next;
+    }
+    *vfsp = vfs;
+
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(mp_vfs_mount_obj, 2, mp_vfs_mount);
+
+mp_obj_t mp_vfs_umount(mp_obj_t mnt_in) {
+    // remove vfs from the mount table
+    mp_vfs_mount_t *vfs = NULL;
+    size_t mnt_len;
+    const char *mnt_str = NULL;
+    if (MP_OBJ_IS_STR(mnt_in)) {
+        mnt_str = mp_obj_str_get_data(mnt_in, &mnt_len);
+    }
+    for (mp_vfs_mount_t **vfsp = &MP_STATE_VM(vfs_mount_table); *vfsp != NULL; vfsp = &(*vfsp)->next) {
+        if ((mnt_str != NULL && !memcmp(mnt_str, (*vfsp)->str, mnt_len + 1)) || (*vfsp)->obj == mnt_in) {
+            vfs = *vfsp;
+            *vfsp = (*vfsp)->next;
+            break;
+        }
+    }
+
+    if (vfs == NULL) {
+        mp_raise_OSError(MP_EINVAL);
+    }
+
+    // if we unmounted the current device then set current to root
+    if (MP_STATE_VM(vfs_cur) == vfs) {
+        MP_STATE_VM(vfs_cur) = MP_VFS_ROOT;
+    }
+
+    // call the underlying object to do any unmounting operation
+    mp_vfs_proxy_call(vfs, MP_QSTR_umount, 0, NULL);
+
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_umount_obj, mp_vfs_umount);
+
+// Note: buffering and encoding args are currently ignored
+mp_obj_t mp_vfs_open(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_file, ARG_mode, ARG_encoding };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_mode, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_QSTR(MP_QSTR_r)} },
+        { MP_QSTR_buffering, MP_ARG_INT, {.u_int = -1} },
+        { MP_QSTR_encoding, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+    };
+
+    // parse args
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    mp_vfs_mount_t *vfs = lookup_path((mp_obj_t)args[ARG_file].u_rom_obj, &args[ARG_file].u_obj);
+    return mp_vfs_proxy_call(vfs, MP_QSTR_open, 2, (mp_obj_t*)&args);
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(mp_vfs_open_obj, 0, mp_vfs_open);
+
+mp_obj_t mp_vfs_chdir(mp_obj_t path_in) {
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+    MP_STATE_VM(vfs_cur) = vfs;
+    if (vfs == MP_VFS_ROOT) {
+        // If we change to the root dir and a VFS is mounted at the root then
+        // we must change that VFS's current dir to the root dir so that any
+        // subsequent relative paths begin at the root of that VFS.
+        for (vfs = MP_STATE_VM(vfs_mount_table); vfs != NULL; vfs = vfs->next) {
+            if (vfs->len == 1) {
+                mp_obj_t root = mp_obj_new_str("/", 1, false);
+                mp_vfs_proxy_call(vfs, MP_QSTR_chdir, 1, &root);
+                break;
+            }
+        }
+    } else {
+        mp_vfs_proxy_call(vfs, MP_QSTR_chdir, 1, &path_out);
+    }
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_chdir_obj, mp_vfs_chdir);
+
+mp_obj_t mp_vfs_getcwd(void) {
+    if (MP_STATE_VM(vfs_cur) == MP_VFS_ROOT) {
+        return MP_OBJ_NEW_QSTR(MP_QSTR__slash_);
+    }
+    mp_obj_t cwd_o = mp_vfs_proxy_call(MP_STATE_VM(vfs_cur), MP_QSTR_getcwd, 0, NULL);
+    if (MP_STATE_VM(vfs_cur)->len == 1) {
+        // don't prepend "/" for vfs mounted at root
+        return cwd_o;
+    }
+    const char *cwd = mp_obj_str_get_str(cwd_o);
+    vstr_t vstr;
+    vstr_init(&vstr, MP_STATE_VM(vfs_cur)->len + strlen(cwd) + 1);
+    vstr_add_strn(&vstr, MP_STATE_VM(vfs_cur)->str, MP_STATE_VM(vfs_cur)->len);
+    if (!(cwd[0] == '/' && cwd[1] == 0)) {
+        vstr_add_str(&vstr, cwd);
+    }
+    return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
+}
+MP_DEFINE_CONST_FUN_OBJ_0(mp_vfs_getcwd_obj, mp_vfs_getcwd);
+
+typedef struct _mp_vfs_ilistdir_it_t {
+    mp_obj_base_t base;
+    mp_fun_1_t iternext;
+    union {
+        mp_vfs_mount_t *vfs;
+        mp_obj_t iter;
+    } cur;
+    bool is_str;
+    bool is_iter;
+} mp_vfs_ilistdir_it_t;
+
+STATIC mp_obj_t mp_vfs_ilistdir_it_iternext(mp_obj_t self_in) {
+    mp_vfs_ilistdir_it_t *self = MP_OBJ_TO_PTR(self_in);
+    if (self->is_iter) {
+        // continue delegating to root dir
+        return mp_iternext(self->cur.iter);
+    } else if (self->cur.vfs == NULL) {
+        // finished iterating mount points and no root dir is mounted
+        return MP_OBJ_STOP_ITERATION;
+    } else {
+        // continue iterating mount points
+        mp_vfs_mount_t *vfs = self->cur.vfs;
+        self->cur.vfs = vfs->next;
+        if (vfs->len == 1) {
+            // vfs is mounted at root dir, delegate to it
+            mp_obj_t root = mp_obj_new_str("/", 1, false);
+            self->is_iter = true;
+            self->cur.iter = mp_vfs_proxy_call(vfs, MP_QSTR_ilistdir, 1, &root);
+            return mp_iternext(self->cur.iter);
+        } else {
+            // a mounted directory
+            mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(3, NULL));
+            t->items[0] = mp_obj_new_str_of_type(
+                self->is_str ? &mp_type_str : &mp_type_bytes,
+                (const byte*)vfs->str + 1, vfs->len - 1);
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(MP_S_IFDIR);
+            t->items[2] = MP_OBJ_NEW_SMALL_INT(0); // no inode number
+            return MP_OBJ_FROM_PTR(t);
+        }
+    }
+}
+
+mp_obj_t mp_vfs_ilistdir(size_t n_args, const mp_obj_t *args) {
+    mp_obj_t path_in;
+    if (n_args == 1) {
+        path_in = args[0];
+    } else {
+        path_in = MP_OBJ_NEW_QSTR(MP_QSTR_);
+    }
+
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+
+    if (vfs == MP_VFS_ROOT) {
+        // list the root directory
+        mp_vfs_ilistdir_it_t *iter = m_new_obj(mp_vfs_ilistdir_it_t);
+        iter->base.type = &mp_type_polymorph_iter;
+        iter->iternext = mp_vfs_ilistdir_it_iternext;
+        iter->cur.vfs = MP_STATE_VM(vfs_mount_table);
+        iter->is_str = mp_obj_get_type(path_in) == &mp_type_str;
+        iter->is_iter = false;
+        return MP_OBJ_FROM_PTR(iter);
+    }
+
+    return mp_vfs_proxy_call(vfs, MP_QSTR_ilistdir, 1, &path_out);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_vfs_ilistdir_obj, 0, 1, mp_vfs_ilistdir);
+
+mp_obj_t mp_vfs_listdir(size_t n_args, const mp_obj_t *args) {
+    mp_obj_t iter = mp_vfs_ilistdir(n_args, args);
+    mp_obj_t dir_list = mp_obj_new_list(0, NULL);
+    mp_obj_t next;
+    while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
+        mp_obj_t *items;
+        mp_obj_get_array_fixed_n(next, 3, &items);
+        mp_obj_list_append(dir_list, items[0]);
+    }
+    return dir_list;
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_vfs_listdir_obj, 0, 1, mp_vfs_listdir);
+
+mp_obj_t mp_vfs_mkdir(mp_obj_t path_in) {
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+    if (vfs == MP_VFS_ROOT || (vfs != MP_VFS_NONE && !strcmp(mp_obj_str_get_str(path_out), "/"))) {
+        mp_raise_OSError(MP_EEXIST);
+    }
+    return mp_vfs_proxy_call(vfs, MP_QSTR_mkdir, 1, &path_out);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_mkdir_obj, mp_vfs_mkdir);
+
+mp_obj_t mp_vfs_remove(mp_obj_t path_in) {
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+    return mp_vfs_proxy_call(vfs, MP_QSTR_remove, 1, &path_out);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_remove_obj, mp_vfs_remove);
+
+mp_obj_t mp_vfs_rename(mp_obj_t old_path_in, mp_obj_t new_path_in) {
+    mp_obj_t args[2];
+    mp_vfs_mount_t *old_vfs = lookup_path(old_path_in, &args[0]);
+    mp_vfs_mount_t *new_vfs = lookup_path(new_path_in, &args[1]);
+    if (old_vfs != new_vfs) {
+        // can't rename across filesystems
+        mp_raise_OSError(MP_EPERM);
+    }
+    return mp_vfs_proxy_call(old_vfs, MP_QSTR_rename, 2, args);
+}
+MP_DEFINE_CONST_FUN_OBJ_2(mp_vfs_rename_obj, mp_vfs_rename);
+
+mp_obj_t mp_vfs_rmdir(mp_obj_t path_in) {
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+    return mp_vfs_proxy_call(vfs, MP_QSTR_rmdir, 1, &path_out);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_rmdir_obj, mp_vfs_rmdir);
+
+mp_obj_t mp_vfs_stat(mp_obj_t path_in) {
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+    if (vfs == MP_VFS_ROOT) {
+        mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
+        t->items[0] = MP_OBJ_NEW_SMALL_INT(MP_S_IFDIR); // st_mode
+        for (int i = 1; i <= 9; ++i) {
+            t->items[i] = MP_OBJ_NEW_SMALL_INT(0); // dev, nlink, uid, gid, size, atime, mtime, ctime
+        }
+        return MP_OBJ_FROM_PTR(t);
+    }
+    return mp_vfs_proxy_call(vfs, MP_QSTR_stat, 1, &path_out);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_stat_obj, mp_vfs_stat);
+
+mp_obj_t mp_vfs_statvfs(mp_obj_t path_in) {
+    mp_obj_t path_out;
+    mp_vfs_mount_t *vfs = lookup_path(path_in, &path_out);
+    if (vfs == MP_VFS_ROOT) {
+        // statvfs called on the root directory, see if there's anything mounted there
+        for (vfs = MP_STATE_VM(vfs_mount_table); vfs != NULL; vfs = vfs->next) {
+            if (vfs->len == 1) {
+                break;
+            }
+        }
+
+        // If there's nothing mounted at root then return a mostly-empty tuple
+        if (vfs == NULL) {
+            mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
+
+            // fill in: bsize, frsize, blocks, bfree, bavail, files, ffree, favail, flags
+            for (int i = 0; i <= 8; ++i) {
+                t->items[i] = MP_OBJ_NEW_SMALL_INT(0);
+            }
+
+            // Put something sensible in f_namemax
+            t->items[9] = MP_OBJ_NEW_SMALL_INT(MICROPY_ALLOC_PATH_MAX);
+
+            return MP_OBJ_FROM_PTR(t);
+        }
+
+        // VFS mounted at root so delegate the call to it
+        path_out = MP_OBJ_NEW_QSTR(MP_QSTR__slash_);
+    }
+    return mp_vfs_proxy_call(vfs, MP_QSTR_statvfs, 1, &path_out);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_statvfs_obj, mp_vfs_statvfs);
+
+#endif // MICROPY_VFS
diff --git a/extmod/vfs.h b/extmod/vfs.h
new file mode 100644
index 000000000..edaeb5349
--- /dev/null
+++ b/extmod/vfs.h
@@ -0,0 +1,86 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef MICROPY_INCLUDED_EXTMOD_VFS_H
+#define MICROPY_INCLUDED_EXTMOD_VFS_H
+
+#include "py/lexer.h"
+#include "py/obj.h"
+
+// return values of mp_vfs_lookup_path
+// ROOT is 0 so that the default current directory is the root directory
+#define MP_VFS_NONE ((mp_vfs_mount_t*)1)
+#define MP_VFS_ROOT ((mp_vfs_mount_t*)0)
+
+// MicroPython's port-standardized versions of stat constants
+#define MP_S_IFDIR (0x4000)
+#define MP_S_IFREG (0x8000)
+
+// constants for block protocol ioctl
+#define BP_IOCTL_INIT           (1)
+#define BP_IOCTL_DEINIT         (2)
+#define BP_IOCTL_SYNC           (3)
+#define BP_IOCTL_SEC_COUNT      (4)
+#define BP_IOCTL_SEC_SIZE       (5)
+
+typedef struct _mp_vfs_mount_t {
+    const char *str; // mount point with leading /
+    size_t len;
+    mp_obj_t obj;
+    struct _mp_vfs_mount_t *next;
+} mp_vfs_mount_t;
+
+mp_vfs_mount_t *mp_vfs_lookup_path(const char *path, const char **path_out);
+mp_import_stat_t mp_vfs_import_stat(const char *path);
+mp_obj_t mp_vfs_mount(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args);
+mp_obj_t mp_vfs_umount(mp_obj_t mnt_in);
+mp_obj_t mp_vfs_open(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args);
+mp_obj_t mp_vfs_chdir(mp_obj_t path_in);
+mp_obj_t mp_vfs_getcwd(void);
+mp_obj_t mp_vfs_ilistdir(size_t n_args, const mp_obj_t *args);
+mp_obj_t mp_vfs_listdir(size_t n_args, const mp_obj_t *args);
+mp_obj_t mp_vfs_mkdir(mp_obj_t path_in);
+mp_obj_t mp_vfs_remove(mp_obj_t path_in);
+mp_obj_t mp_vfs_rename(mp_obj_t old_path_in, mp_obj_t new_path_in);
+mp_obj_t mp_vfs_rmdir(mp_obj_t path_in);
+mp_obj_t mp_vfs_stat(mp_obj_t path_in);
+mp_obj_t mp_vfs_statvfs(mp_obj_t path_in);
+
+MP_DECLARE_CONST_FUN_OBJ_KW(mp_vfs_mount_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_umount_obj);
+MP_DECLARE_CONST_FUN_OBJ_KW(mp_vfs_open_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_chdir_obj);
+MP_DECLARE_CONST_FUN_OBJ_0(mp_vfs_getcwd_obj);
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_vfs_ilistdir_obj);
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_vfs_listdir_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_mkdir_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_remove_obj);
+MP_DECLARE_CONST_FUN_OBJ_2(mp_vfs_rename_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_rmdir_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_stat_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mp_vfs_statvfs_obj);
+
+#endif // MICROPY_INCLUDED_EXTMOD_VFS_H
diff --git a/extmod/vfs_fat.c b/extmod/vfs_fat.c
index 0043b77bd..0ec3fe6d2 100644
--- a/extmod/vfs_fat.c
+++ b/extmod/vfs_fat.c
@@ -28,40 +28,71 @@
 #include "py/mpconfig.h"
 #if MICROPY_VFS_FAT
 
+#if !MICROPY_VFS
+#error "with MICROPY_VFS_FAT enabled, must also enable MICROPY_VFS"
+#endif
+
 #include <string.h>
 #include "py/nlr.h"
 #include "py/runtime.h"
 #include "py/mperrno.h"
-#include "lib/fatfs/ff.h"
-#include "lib/fatfs/diskio.h"
-#include "extmod/vfs_fat_file.h"
-#include "extmod/fsusermount.h"
-#include "timeutils.h"
+#include "lib/oofatfs/ff.h"
+#include "extmod/vfs_fat.h"
+#include "lib/timeutils/timeutils.h"
+
+#if _MAX_SS == _MIN_SS
+#define SECSIZE(fs) (_MIN_SS)
+#else
+#define SECSIZE(fs) ((fs)->ssize)
+#endif
 
 #define mp_obj_fat_vfs_t fs_user_mount_t
 
 STATIC mp_obj_t fat_vfs_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
-    mp_arg_check_num(n_args, n_kw, 2, 2, false);
-    mp_obj_fat_vfs_t *vfs = fatfs_mount_mkfs(n_args, args, (mp_map_t*)&mp_const_empty_map, false);
+    mp_arg_check_num(n_args, n_kw, 1, 1, false);
+
+    // create new object
+    fs_user_mount_t *vfs = m_new_obj(fs_user_mount_t);
     vfs->base.type = type;
+    vfs->flags = FSUSER_FREE_OBJ;
+    vfs->fatfs.drv = vfs;
+
+    // load block protocol methods
+    mp_load_method(args[0], MP_QSTR_readblocks, vfs->readblocks);
+    mp_load_method_maybe(args[0], MP_QSTR_writeblocks, vfs->writeblocks);
+    mp_load_method_maybe(args[0], MP_QSTR_ioctl, vfs->u.ioctl);
+    if (vfs->u.ioctl[0] != MP_OBJ_NULL) {
+        // device supports new block protocol, so indicate it
+        vfs->flags |= FSUSER_HAVE_IOCTL;
+    } else {
+        // no ioctl method, so assume the device uses the old block protocol
+        mp_load_method_maybe(args[0], MP_QSTR_sync, vfs->u.old.sync);
+        mp_load_method(args[0], MP_QSTR_count, vfs->u.old.count);
+    }
+
     return MP_OBJ_FROM_PTR(vfs);
 }
 
 STATIC mp_obj_t fat_vfs_mkfs(mp_obj_t bdev_in) {
-    mp_obj_t args[] = {bdev_in, MP_OBJ_NEW_QSTR(MP_QSTR_mkfs)};
-    fatfs_mount_mkfs(2, args, (mp_map_t*)&mp_const_empty_map, true);
+    // create new object
+    fs_user_mount_t *vfs = MP_OBJ_TO_PTR(fat_vfs_make_new(&mp_fat_vfs_type, 1, 0, &bdev_in));
+
+    // make the filesystem
+    uint8_t working_buf[_MAX_SS];
+    FRESULT res = f_mkfs(&vfs->fatfs, FM_FAT | FM_SFD, 0, working_buf, sizeof(working_buf));
+    if (res != FR_OK) {
+        mp_raise_OSError(fresult_to_errno_table[res]);
+    }
+
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(fat_vfs_mkfs_fun_obj, fat_vfs_mkfs);
 STATIC MP_DEFINE_CONST_STATICMETHOD_OBJ(fat_vfs_mkfs_obj, MP_ROM_PTR(&fat_vfs_mkfs_fun_obj));
 
-STATIC mp_obj_t fat_vfs_open(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
-    // Skip self
-    return fatfs_builtin_open(n_args - 1, args + 1, kwargs);
-}
-MP_DEFINE_CONST_FUN_OBJ_KW(fat_vfs_open_obj, 2, fat_vfs_open);
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(fat_vfs_open_obj, fatfs_builtin_open_self);
 
-STATIC mp_obj_t fat_vfs_listdir_func(size_t n_args, const mp_obj_t *args) {
+STATIC mp_obj_t fat_vfs_ilistdir_func(size_t n_args, const mp_obj_t *args) {
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(args[0]);
     bool is_str_type = true;
     const char *path;
     if (n_args == 2) {
@@ -73,19 +104,16 @@ STATIC mp_obj_t fat_vfs_listdir_func(size_t n_args, const mp_obj_t *args) {
         path = "";
     }
 
-    return fat_vfs_listdir(path, is_str_type);
+    return fat_vfs_ilistdir2(self, path, is_str_type);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(fat_vfs_listdir_obj, 1, 2, fat_vfs_listdir_func);
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(fat_vfs_ilistdir_obj, 1, 2, fat_vfs_ilistdir_func);
 
-STATIC mp_obj_t fat_vfs_remove_internal(mp_obj_t path_in, mp_int_t attr) {
+STATIC mp_obj_t fat_vfs_remove_internal(mp_obj_t vfs_in, mp_obj_t path_in, mp_int_t attr) {
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
     const char *path = mp_obj_str_get_str(path_in);
 
     FILINFO fno;
-#if _USE_LFN
-    fno.lfname = NULL;
-    fno.lfsize = 0;
-#endif
-    FRESULT res = f_stat(path, &fno);
+    FRESULT res = f_stat(&self->fatfs, path, &fno);
 
     if (res != FR_OK) {
         mp_raise_OSError(fresult_to_errno_table[res]);
@@ -93,7 +121,7 @@ STATIC mp_obj_t fat_vfs_remove_internal(mp_obj_t path_in, mp_int_t attr) {
 
     // check if path is a file or directory
     if ((fno.fattrib & AM_DIR) == attr) {
-        res = f_unlink(path);
+        res = f_unlink(&self->fatfs, path);
 
         if (res != FR_OK) {
             mp_raise_OSError(fresult_to_errno_table[res]);
@@ -105,27 +133,25 @@ STATIC mp_obj_t fat_vfs_remove_internal(mp_obj_t path_in, mp_int_t attr) {
 }
 
 STATIC mp_obj_t fat_vfs_remove(mp_obj_t vfs_in, mp_obj_t path_in) {
-    (void)vfs_in;
-    return fat_vfs_remove_internal(path_in, 0); // 0 == file attribute
+    return fat_vfs_remove_internal(vfs_in, path_in, 0); // 0 == file attribute
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_remove_obj, fat_vfs_remove);
 
 STATIC mp_obj_t fat_vfs_rmdir(mp_obj_t vfs_in, mp_obj_t path_in) {
-    (void) vfs_in;
-    return fat_vfs_remove_internal(path_in, AM_DIR);
+    return fat_vfs_remove_internal(vfs_in, path_in, AM_DIR);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_rmdir_obj, fat_vfs_rmdir);
 
 STATIC mp_obj_t fat_vfs_rename(mp_obj_t vfs_in, mp_obj_t path_in, mp_obj_t path_out) {
-    (void)vfs_in;
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
     const char *old_path = mp_obj_str_get_str(path_in);
     const char *new_path = mp_obj_str_get_str(path_out);
-    FRESULT res = f_rename(old_path, new_path);
+    FRESULT res = f_rename(&self->fatfs, old_path, new_path);
     if (res == FR_EXIST) {
         // if new_path exists then try removing it (but only if it's a file)
-        fat_vfs_remove_internal(path_out, 0); // 0 == file attribute
+        fat_vfs_remove_internal(vfs_in, path_out, 0); // 0 == file attribute
         // try to rename again
-        res = f_rename(old_path, new_path);
+        res = f_rename(&self->fatfs, old_path, new_path);
     }
     if (res == FR_OK) {
         return mp_const_none;
@@ -137,9 +163,9 @@ STATIC mp_obj_t fat_vfs_rename(mp_obj_t vfs_in, mp_obj_t path_in, mp_obj_t path_
 STATIC MP_DEFINE_CONST_FUN_OBJ_3(fat_vfs_rename_obj, fat_vfs_rename);
 
 STATIC mp_obj_t fat_vfs_mkdir(mp_obj_t vfs_in, mp_obj_t path_o) {
-    (void)vfs_in;
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
     const char *path = mp_obj_str_get_str(path_o);
-    FRESULT res = f_mkdir(path);
+    FRESULT res = f_mkdir(&self->fatfs, path);
     if (res == FR_OK) {
         return mp_const_none;
     } else {
@@ -150,15 +176,11 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_mkdir_obj, fat_vfs_mkdir);
 
 /// Change current directory.
 STATIC mp_obj_t fat_vfs_chdir(mp_obj_t vfs_in, mp_obj_t path_in) {
-    (void)vfs_in;
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
     const char *path;
     path = mp_obj_str_get_str(path_in);
 
-    FRESULT res = f_chdrive(path);
-
-    if (res == FR_OK) {
-        res = f_chdir(path);
-    }
+    FRESULT res = f_chdir(&self->fatfs, path);
 
     if (res != FR_OK) {
         mp_raise_OSError(fresult_to_errno_table[res]);
@@ -170,71 +192,31 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_chdir_obj, fat_vfs_chdir);
 
 /// Get the current directory.
 STATIC mp_obj_t fat_vfs_getcwd(mp_obj_t vfs_in) {
-    (void)vfs_in;
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
     char buf[MICROPY_ALLOC_PATH_MAX + 1];
-    FRESULT res = f_getcwd(buf, sizeof buf);
-
+    FRESULT res = f_getcwd(&self->fatfs, buf, sizeof(buf));
     if (res != FR_OK) {
         mp_raise_OSError(fresult_to_errno_table[res]);
     }
-
     return mp_obj_new_str(buf, strlen(buf), false);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(fat_vfs_getcwd_obj, fat_vfs_getcwd);
 
-// Checks for path equality, ignoring trailing slashes:
-//   path_equal(/, /) -> true
-// second argument must be in canonical form (meaning no trailing slash, unless it's just /)
-STATIC bool path_equal(const char *path, const char *path_canonical) {
-    while (*path_canonical != '\0' && *path == *path_canonical) {
-        ++path;
-        ++path_canonical;
-    }
-    if (*path_canonical != '\0') {
-        return false;
-    }
-    while (*path == '/') {
-        ++path;
-    }
-    return *path == '\0';
-}
-
 /// \function stat(path)
 /// Get the status of a file or directory.
 STATIC mp_obj_t fat_vfs_stat(mp_obj_t vfs_in, mp_obj_t path_in) {
-    (void)vfs_in;
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
     const char *path = mp_obj_str_get_str(path_in);
 
     FILINFO fno;
-#if _USE_LFN
-    fno.lfname = NULL;
-    fno.lfsize = 0;
-#endif
-    FRESULT res;
-
-    if (path_equal(path, "/")) {
+    if (path[0] == 0 || (path[0] == '/' && path[1] == 0)) {
         // stat root directory
         fno.fsize = 0;
         fno.fdate = 0x2821; // Jan 1, 2000
         fno.ftime = 0;
         fno.fattrib = AM_DIR;
     } else {
-        res = FR_NO_PATH;
-        for (size_t i = 0; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
-            fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
-            if (vfs != NULL && path_equal(path, vfs->str)) {
-                // stat mounted device directory
-                fno.fsize = 0;
-                fno.fdate = 0x2821; // Jan 1, 2000
-                fno.ftime = 0;
-                fno.fattrib = AM_DIR;
-                res = FR_OK;
-            }
-        }
-        if (res == FR_NO_PATH) {
-            // stat normal file
-            res = f_stat(path, &fno);
-        }
+        FRESULT res = f_stat(&self->fatfs, path, &fno);
         if (res != FR_OK) {
             mp_raise_OSError(fresult_to_errno_table[res]);
         }
@@ -243,9 +225,9 @@ STATIC mp_obj_t fat_vfs_stat(mp_obj_t vfs_in, mp_obj_t path_in) {
     mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
     mp_int_t mode = 0;
     if (fno.fattrib & AM_DIR) {
-        mode |= 0x4000; // stat.S_IFDIR
+        mode |= MP_S_IFDIR;
     } else {
-        mode |= 0x8000; // stat.S_IFREG
+        mode |= MP_S_IFREG;
     }
     mp_int_t seconds = timeutils_seconds_since_2000(
         1980 + ((fno.fdate >> 9) & 0x7f),
@@ -272,25 +254,21 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_stat_obj, fat_vfs_stat);
 
 // Get the status of a VFS.
 STATIC mp_obj_t fat_vfs_statvfs(mp_obj_t vfs_in, mp_obj_t path_in) {
-    (void)vfs_in;
-    const char *path = mp_obj_str_get_str(path_in);
+    mp_obj_fat_vfs_t *self = MP_OBJ_TO_PTR(vfs_in);
+    (void)path_in;
 
-    FATFS *fatfs;
     DWORD nclst;
-    FRESULT res = f_getfree(path, &nclst, &fatfs);
+    FATFS *fatfs = &self->fatfs;
+    FRESULT res = f_getfree(fatfs, &nclst);
     if (FR_OK != res) {
         mp_raise_OSError(fresult_to_errno_table[res]);
     }
 
     mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
 
-    #if _MIN_SS != _MAX_SS
-        t->items[0] = MP_OBJ_NEW_SMALL_INT(fatfs->csize * fatfs->ssize); // f_bsize
-    #else
-        t->items[0] = MP_OBJ_NEW_SMALL_INT(fatfs->csize * _MIN_SS); // f_bsize
-    #endif
+    t->items[0] = MP_OBJ_NEW_SMALL_INT(fatfs->csize * SECSIZE(fatfs)); // f_bsize
     t->items[1] = t->items[0]; // f_frsize
-    t->items[2] = MP_OBJ_NEW_SMALL_INT((fatfs->n_fatent - 2) * fatfs->csize); // f_blocks
+    t->items[2] = MP_OBJ_NEW_SMALL_INT((fatfs->n_fatent - 2)); // f_blocks
     t->items[3] = MP_OBJ_NEW_SMALL_INT(nclst); // f_bfree
     t->items[4] = t->items[3]; // f_bavail
     t->items[5] = MP_OBJ_NEW_SMALL_INT(0); // f_files
@@ -303,17 +281,47 @@ STATIC mp_obj_t fat_vfs_statvfs(mp_obj_t vfs_in, mp_obj_t path_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(fat_vfs_statvfs_obj, fat_vfs_statvfs);
 
-// Unmount the filesystem
-STATIC mp_obj_t fat_vfs_umount(mp_obj_t vfs_in) {
-    fatfs_umount(((fs_user_mount_t *)vfs_in)->readblocks[1]);
+STATIC mp_obj_t vfs_fat_mount(mp_obj_t self_in, mp_obj_t readonly, mp_obj_t mkfs) {
+    fs_user_mount_t *self = MP_OBJ_TO_PTR(self_in);
+
+    // Read-only device indicated by writeblocks[0] == MP_OBJ_NULL.
+    // User can specify read-only device by:
+    //  1. readonly=True keyword argument
+    //  2. nonexistent writeblocks method (then writeblocks[0] == MP_OBJ_NULL already)
+    if (mp_obj_is_true(readonly)) {
+        self->writeblocks[0] = MP_OBJ_NULL;
+    }
+
+    // mount the block device
+    FRESULT res = f_mount(&self->fatfs);
+
+    // check if we need to make the filesystem
+    if (res == FR_NO_FILESYSTEM && mp_obj_is_true(mkfs)) {
+        uint8_t working_buf[_MAX_SS];
+        res = f_mkfs(&self->fatfs, FM_FAT | FM_SFD, 0, working_buf, sizeof(working_buf));
+    }
+    if (res != FR_OK) {
+        mp_raise_OSError(fresult_to_errno_table[res]);
+    }
+
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(vfs_fat_mount_obj, vfs_fat_mount);
+
+STATIC mp_obj_t vfs_fat_umount(mp_obj_t self_in) {
+    fs_user_mount_t *self = MP_OBJ_TO_PTR(self_in);
+    FRESULT res = f_umount(&self->fatfs);
+    if (res != FR_OK) {
+        mp_raise_OSError(fresult_to_errno_table[res]);
+    }
     return mp_const_none;
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(fat_vfs_umount_obj, fat_vfs_umount);
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(fat_vfs_umount_obj, vfs_fat_umount);
 
 STATIC const mp_rom_map_elem_t fat_vfs_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_mkfs), MP_ROM_PTR(&fat_vfs_mkfs_obj) },
     { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&fat_vfs_open_obj) },
-    { MP_ROM_QSTR(MP_QSTR_listdir), MP_ROM_PTR(&fat_vfs_listdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_ilistdir), MP_ROM_PTR(&fat_vfs_ilistdir_obj) },
     { MP_ROM_QSTR(MP_QSTR_mkdir), MP_ROM_PTR(&fat_vfs_mkdir_obj) },
     { MP_ROM_QSTR(MP_QSTR_rmdir), MP_ROM_PTR(&fat_vfs_rmdir_obj) },
     { MP_ROM_QSTR(MP_QSTR_chdir), MP_ROM_PTR(&fat_vfs_chdir_obj) },
@@ -322,6 +330,7 @@ STATIC const mp_rom_map_elem_t fat_vfs_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_rename), MP_ROM_PTR(&fat_vfs_rename_obj) },
     { MP_ROM_QSTR(MP_QSTR_stat), MP_ROM_PTR(&fat_vfs_stat_obj) },
     { MP_ROM_QSTR(MP_QSTR_statvfs), MP_ROM_PTR(&fat_vfs_statvfs_obj) },
+    { MP_ROM_QSTR(MP_QSTR_mount), MP_ROM_PTR(&vfs_fat_mount_obj) },
     { MP_ROM_QSTR(MP_QSTR_umount), MP_ROM_PTR(&fat_vfs_umount_obj) },
 };
 STATIC MP_DEFINE_CONST_DICT(fat_vfs_locals_dict, fat_vfs_locals_dict_table);
diff --git a/extmod/fsusermount.h b/extmod/vfs_fat.h
index abfd2d4e3..90d66443e 100644
--- a/extmod/fsusermount.h
+++ b/extmod/vfs_fat.h
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2014 Damien P. George
+ * Copyright (c) 2013, 2014 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -24,12 +24,12 @@
  * THE SOFTWARE.
  */
 
-
-#ifndef __MICROPY_INCLUDED_EXTMOD_FSUSERMOUNT_H__
-#define __MICROPY_INCLUDED_EXTMOD_FSUSERMOUNT_H__
-
-#include "lib/fatfs/ff.h"
+#ifndef __MICROPY_INCLUDED_EXTMOD_VFS_FAT_H__
+#define __MICROPY_INCLUDED_EXTMOD_VFS_FAT_H__
+#include "py/lexer.h"
 #include "py/obj.h"
+#include "lib/oofatfs/ff.h"
+#include "extmod/vfs.h"
 
 // these are the values for fs_user_mount_t.flags
 #define FSUSER_NATIVE        (0x0001) // readblocks[2]/writeblocks[2] contain native func
@@ -38,17 +38,8 @@
 // Device is write-able over USB and read-only to MicroPython.
 #define FSUSER_USB_WRITEABLE (0x0008)
 
-// constants for block protocol ioctl
-#define BP_IOCTL_INIT           (1)
-#define BP_IOCTL_DEINIT         (2)
-#define BP_IOCTL_SYNC           (3)
-#define BP_IOCTL_SEC_COUNT      (4)
-#define BP_IOCTL_SEC_SIZE       (5)
-
 typedef struct _fs_user_mount_t {
     mp_obj_base_t base;
-    const char *str;
-    uint16_t len; // length of str
     uint16_t flags;
     mp_obj_t readblocks[4];
     mp_obj_t writeblocks[4];
@@ -63,11 +54,17 @@ typedef struct _fs_user_mount_t {
     FATFS fatfs;
 } fs_user_mount_t;
 
-fs_user_mount_t *fatfs_mount_mkfs(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args, bool mkfs);
-mp_obj_t fatfs_umount(mp_obj_t bdev_or_path_in);
+extern const byte fresult_to_errno_table[20];
+extern const mp_obj_type_t mp_fat_vfs_type;
+
+mp_import_stat_t fat_vfs_import_stat(struct _fs_user_mount_t *vfs, const char *path);
+mp_obj_t fatfs_builtin_open_self(mp_obj_t self_in, mp_obj_t path, mp_obj_t mode);
+MP_DECLARE_CONST_FUN_OBJ_KW(mp_builtin_open_obj);
+
+mp_obj_t fat_vfs_ilistdir2(struct _fs_user_mount_t *vfs, const char *path, bool is_str_type);
 
 MP_DECLARE_CONST_FUN_OBJ_KW(fsuser_mount_obj);
 MP_DECLARE_CONST_FUN_OBJ_1(fsuser_umount_obj);
 MP_DECLARE_CONST_FUN_OBJ_KW(fsuser_mkfs_obj);
 
-#endif  // __MICROPY_INCLUDED_EXTMOD_FSUSERMOUNT_H__
+#endif  // __MICROPY_INCLUDED_EXTMOD_VFS_FAT_H__
diff --git a/extmod/vfs_fat_diskio.c b/extmod/vfs_fat_diskio.c
index 4d776f6b4..282599ffc 100644
--- a/extmod/vfs_fat_diskio.c
+++ b/extmod/vfs_fat_diskio.c
@@ -28,7 +28,7 @@
  */
 
 #include "py/mpconfig.h"
-#if MICROPY_FSUSERMOUNT
+#if MICROPY_VFS && MICROPY_VFS_FAT
 
 #include <stdint.h>
 #include <stdio.h>
@@ -36,9 +36,9 @@
 #include "py/mphal.h"
 
 #include "py/runtime.h"
-#include "lib/fatfs/ff.h"        /* FatFs lower layer API */
-#include "lib/fatfs/diskio.h"    /* FatFs lower layer API */
-#include "extmod/fsusermount.h"
+#include "lib/oofatfs/ff.h"
+#include "lib/oofatfs/diskio.h"
+#include "extmod/vfs_fat.h"
 
 #if _MAX_SS == _MIN_SS
 #define SECSIZE(fs) (_MIN_SS)
@@ -46,20 +46,18 @@
 #define SECSIZE(fs) ((fs)->ssize)
 #endif
 
-STATIC fs_user_mount_t *disk_get_device(uint id) {
-    if (id < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount))) {
-        return MP_STATE_PORT(fs_user_mount)[id];
-    } else {
-        return NULL;
-    }
+typedef void *bdev_t;
+STATIC fs_user_mount_t *disk_get_device(void *bdev) {
+    return (fs_user_mount_t*)bdev;
 }
 
 /*-----------------------------------------------------------------------*/
 /* Initialize a Drive                                                    */
 /*-----------------------------------------------------------------------*/
 
+STATIC
 DSTATUS disk_initialize (
-    BYTE pdrv                /* Physical drive nmuber (0..) */
+    bdev_t pdrv              /* Physical drive nmuber (0..) */
 )
 {
     fs_user_mount_t *vfs = disk_get_device(pdrv);
@@ -89,8 +87,9 @@ DSTATUS disk_initialize (
 /* Get Disk Status                                                       */
 /*-----------------------------------------------------------------------*/
 
+STATIC
 DSTATUS disk_status (
-    BYTE pdrv        /* Physical drive number (0..) */
+    bdev_t pdrv      /* Physical drive nmuber (0..) */
 )
 {
     fs_user_mount_t *vfs = disk_get_device(pdrv);
@@ -113,7 +112,7 @@ DSTATUS disk_status (
 /*-----------------------------------------------------------------------*/
 
 DRESULT disk_read (
-    BYTE pdrv,        /* Physical drive number (0..) */
+    bdev_t pdrv,      /* Physical drive nmuber (0..) */
     BYTE *buff,        /* Data buffer to store read data */
     DWORD sector,    /* Sector address (LBA) */
     UINT count        /* Number of sectors to read (1..128) */
@@ -143,9 +142,8 @@ DRESULT disk_read (
 /* Write Sector(s)                                                       */
 /*-----------------------------------------------------------------------*/
 
-#if _USE_WRITE
 DRESULT disk_write (
-    BYTE pdrv,            /* Physical drive nmuber (0..) */
+    bdev_t pdrv,          /* Physical drive nmuber (0..) */
     const BYTE *buff,    /* Data to be written */
     DWORD sector,        /* Sector address (LBA) */
     UINT count            /* Number of sectors to write (1..128) */
@@ -175,16 +173,14 @@ DRESULT disk_write (
 
     return RES_OK;
 }
-#endif
 
 
 /*-----------------------------------------------------------------------*/
 /* Miscellaneous Functions                                               */
 /*-----------------------------------------------------------------------*/
 
-#if _USE_IOCTL
 DRESULT disk_ioctl (
-    BYTE pdrv,        /* Physical drive nmuber (0..) */
+    bdev_t pdrv,      /* Physical drive nmuber (0..) */
     BYTE cmd,        /* Control code */
     void *buff        /* Buffer to send/receive control data */
 )
@@ -221,6 +217,10 @@ DRESULT disk_ioctl (
                 } else {
                     *((WORD*)buff) = mp_obj_get_int(ret);
                 }
+                #if _MAX_SS != _MIN_SS
+                // need to store ssize because we use it in disk_read/disk_write
+                vfs->fatfs.ssize = *((WORD*)buff);
+                #endif
                 return RES_OK;
             }
 
@@ -228,6 +228,14 @@ DRESULT disk_ioctl (
                 *((DWORD*)buff) = 1; // erase block size in units of sector size
                 return RES_OK;
 
+            case IOCTL_INIT:
+                *((DSTATUS*)buff) = disk_initialize(pdrv);
+                return RES_OK;
+
+            case IOCTL_STATUS:
+                *((DSTATUS*)buff) = disk_status(pdrv);
+                return RES_OK;
+
             default:
                 return RES_PARERR;
         }
@@ -248,17 +256,28 @@ DRESULT disk_ioctl (
 
             case GET_SECTOR_SIZE:
                 *((WORD*)buff) = 512; // old protocol had fixed sector size
+                #if _MAX_SS != _MIN_SS
+                // need to store ssize because we use it in disk_read/disk_write
+                vfs->fatfs.ssize = 512;
+                #endif
                 return RES_OK;
 
             case GET_BLOCK_SIZE:
                 *((DWORD*)buff) = 1; // erase block size in units of sector size
                 return RES_OK;
 
+            case IOCTL_INIT:
+                *((DSTATUS*)buff) = disk_initialize(pdrv);
+                return RES_OK;
+
+            case IOCTL_STATUS:
+                *((DSTATUS*)buff) = disk_status(pdrv);
+                return RES_OK;
+
             default:
                 return RES_PARERR;
         }
     }
 }
-#endif
 
-#endif // MICROPY_FSUSERMOUNT
+#endif // MICROPY_VFS && MICROPY_VFS_FAT
diff --git a/extmod/vfs_fat_ffconf.c b/extmod/vfs_fat_ffconf.c
deleted file mode 100644
index f8935af75..000000000
--- a/extmod/vfs_fat_ffconf.c
+++ /dev/null
@@ -1,82 +0,0 @@
-/*
- * This file is part of the Micro Python project, http://micropython.org/
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2013, 2014 Damien P. George
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "py/mpconfig.h"
-#if MICROPY_FSUSERMOUNT
-
-#include <string.h>
-
-#include "py/mpstate.h"
-#include "lib/fatfs/ff.h"
-#include "lib/fatfs/ffconf.h"
-#include "lib/fatfs/diskio.h"
-#include "extmod/fsusermount.h"
-
-STATIC bool check_path(const TCHAR **path, const char *mount_point_str, mp_uint_t mount_point_len) {
-    if (strncmp(*path, mount_point_str, mount_point_len) == 0) {
-        if ((*path)[mount_point_len] == '/') {
-            *path += mount_point_len;
-            return true;
-        } else if ((*path)[mount_point_len] == '\0') {
-            *path = "/";
-            return true;
-        }
-    }
-    return false;
-}
-
-// "path" is the path to lookup; will advance this pointer beyond the volume name.
-// Returns logical drive number (-1 means invalid path).
-int ff_get_ldnumber (const TCHAR **path) {
-    if (!(*path)) {
-        return -1;
-    }
-
-    if (**path != '/') {
-        #if _FS_RPATH
-        return ff_CurrVol;
-        #else
-        return -1;
-        #endif
-    }
-
-    for (size_t i = 0; i < MP_ARRAY_SIZE(MP_STATE_PORT(fs_user_mount)); ++i) {
-        fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[i];
-        if (vfs != NULL && check_path(path, vfs->str, vfs->len)) {
-            return i;
-        }
-    }
-
-    return -1;
-}
-
-void ff_get_volname(BYTE vol, TCHAR **dest) {
-    fs_user_mount_t *vfs = MP_STATE_PORT(fs_user_mount)[vol];
-    memcpy(*dest, vfs->str, vfs->len);
-    *dest += vfs->len;
-}
-
-#endif // MICROPY_FSUSERMOUNT
diff --git a/extmod/vfs_fat_file.c b/extmod/vfs_fat_file.c
index ef57225a9..9c166e163 100644
--- a/extmod/vfs_fat_file.c
+++ b/extmod/vfs_fat_file.c
@@ -24,11 +24,10 @@
  * THE SOFTWARE.
  */
 
-#include "extmod/vfs_fat_file.h"
+#include "py/mpconfig.h"
+#if MICROPY_VFS && MICROPY_VFS_FAT
 
-// *_ADHOC part is for cc3200 port which doesn't use general uPy
-// infrastructure and instead duplicates code. TODO: Resolve.
-#if MICROPY_FSUSERMOUNT || MICROPY_FSUSERMOUNT_ADHOC
+#include "extmod/vfs_fat_file.h"
 
 #include <stdio.h>
 #include <errno.h>
@@ -37,7 +36,8 @@
 #include "py/runtime.h"
 #include "py/stream.h"
 #include "py/mperrno.h"
-#include "lib/fatfs/ff.h"
+#include "lib/oofatfs/ff.h"
+#include "extmod/vfs_fat.h"
 
 // this table converts from FRESULT to POSIX errno
 const byte fresult_to_errno_table[20] = {
@@ -99,7 +99,7 @@ STATIC mp_uint_t file_obj_write(mp_obj_t self_in, const void *buf, mp_uint_t siz
 STATIC mp_obj_t file_obj_close(mp_obj_t self_in) {
     pyb_file_obj_t *self = MP_OBJ_TO_PTR(self_in);
     // if fs==NULL then the file is closed and in that case this method is a no-op
-    if (self->fp.fs != NULL) {
+    if (self->fp.obj.fs != NULL) {
         FRESULT res = f_close(&self->fp);
         if (res != FR_OK) {
             mp_raise_OSError(fresult_to_errno_table[res]);
@@ -165,7 +165,7 @@ STATIC const mp_arg_t file_open_args[] = {
 };
 #define FILE_OPEN_NUM_ARGS MP_ARRAY_SIZE(file_open_args)
 
-STATIC mp_obj_t file_open(const mp_obj_type_t *type, mp_arg_val_t *args) {
+STATIC mp_obj_t file_open(fs_user_mount_t *vfs, const mp_obj_type_t *type, mp_arg_val_t *args) {
     int mode = 0;
     const char *mode_s = mp_obj_str_get_str(args[1].u_obj);
     // TODO make sure only one of r, w, x, a, and b, t are specified
@@ -201,7 +201,8 @@ STATIC mp_obj_t file_open(const mp_obj_type_t *type, mp_arg_val_t *args) {
     o->base.type = type;
 
     const char *fname = mp_obj_str_get_str(args[0].u_obj);
-    FRESULT res = f_open(&o->fp, fname, mode);
+    assert(vfs != NULL);
+    FRESULT res = f_open(&vfs->fatfs, &o->fp, fname, mode);
     if (res != FR_OK) {
         m_del_obj(pyb_file_obj_t, o);
         mp_raise_OSError(fresult_to_errno_table[res]);
@@ -218,7 +219,7 @@ STATIC mp_obj_t file_open(const mp_obj_type_t *type, mp_arg_val_t *args) {
 STATIC mp_obj_t file_obj_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     mp_arg_val_t arg_vals[FILE_OPEN_NUM_ARGS];
     mp_arg_parse_all_kw_array(n_args, n_kw, args, FILE_OPEN_NUM_ARGS, file_open_args, arg_vals);
-    return file_open(type, arg_vals);
+    return file_open(NULL, type, arg_vals);
 }
 
 // TODO gc hook to close the file if not already closed
@@ -252,7 +253,7 @@ const mp_obj_type_t mp_type_fileio = {
     .name = MP_QSTR_FileIO,
     .print = file_obj_print,
     .make_new = file_obj_make_new,
-    .getiter = mp_identity,
+    .getiter = mp_identity_getiter,
     .iternext = mp_stream_unbuffered_iter,
     .protocol = &fileio_stream_p,
     .locals_dict = (mp_obj_dict_t*)&rawfile_locals_dict,
@@ -271,18 +272,21 @@ const mp_obj_type_t mp_type_textio = {
     .name = MP_QSTR_TextIOWrapper,
     .print = file_obj_print,
     .make_new = file_obj_make_new,
-    .getiter = mp_identity,
+    .getiter = mp_identity_getiter,
     .iternext = mp_stream_unbuffered_iter,
     .protocol = &textio_stream_p,
     .locals_dict = (mp_obj_dict_t*)&rawfile_locals_dict,
 };
 
 // Factory function for I/O stream classes
-mp_obj_t fatfs_builtin_open(mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
+mp_obj_t fatfs_builtin_open_self(mp_obj_t self_in, mp_obj_t path, mp_obj_t mode) {
     // TODO: analyze buffering args and instantiate appropriate type
+    fs_user_mount_t *self = MP_OBJ_TO_PTR(self_in);
     mp_arg_val_t arg_vals[FILE_OPEN_NUM_ARGS];
-    mp_arg_parse_all(n_args, args, kwargs, FILE_OPEN_NUM_ARGS, file_open_args, arg_vals);
-    return file_open(&mp_type_textio, arg_vals);
+    arg_vals[0].u_obj = path;
+    arg_vals[1].u_obj = mode;
+    arg_vals[2].u_obj = mp_const_none;
+    return file_open(self, &mp_type_textio, arg_vals);
 }
 
-#endif // MICROPY_FSUSERMOUNT
+#endif // MICROPY_VFS && MICROPY_VFS_FAT
diff --git a/extmod/vfs_fat_file.h b/extmod/vfs_fat_file.h
index 5dc627986..96efe9a7c 100644
--- a/extmod/vfs_fat_file.h
+++ b/extmod/vfs_fat_file.h
@@ -27,18 +27,15 @@
 #ifndef __MICROPY_INCLUDED_EXTMOD_VFS_FAT_FILE_H__
 #define __MICROPY_INCLUDED_EXTMOD_VFS_FAT_FILE_H__
 
-#include "lib/fatfs/ff.h"
 #include "py/mpconfig.h"
-#include "py/obj.h"
 
-#if MICROPY_FSUSERMOUNT || MICROPY_FSUSERMOUNT_ADHOC
+#if MICROPY_VFS && MICROPY_VFS_FAT
 
-extern const byte fresult_to_errno_table[20];
+#include "lib/oofatfs/ff.h"
+#include "py/obj.h"
 
-#if MICROPY_VFS_FAT
 #define mp_type_fileio fatfs_type_fileio
 #define mp_type_textio fatfs_type_textio
-#endif
 
 extern const mp_obj_type_t mp_type_fileio;
 extern const mp_obj_type_t mp_type_textio;
@@ -48,11 +45,6 @@ typedef struct _pyb_file_obj_t {
     FIL fp;
 } pyb_file_obj_t;
 
-mp_obj_t fatfs_builtin_open(mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kwargs);
-MP_DECLARE_CONST_FUN_OBJ_KW(mp_builtin_open_obj);
-
-mp_obj_t fat_vfs_listdir(const char *path, bool is_str_type);
-
-#endif  // MICROPY_FSUSERMOUNT || MICROPY_FSUSERMOUNT_ADHOC
+#endif  // MICROPY_VFS && MICROPY_VFS_FAT
 
 #endif  // __MICROPY_INCLUDED_EXTMOD_VFS_FAT_FILE_H__
diff --git a/extmod/vfs_fat_misc.c b/extmod/vfs_fat_misc.c
index d3507a85f..7c16db7e5 100644
--- a/extmod/vfs_fat_misc.c
+++ b/extmod/vfs_fat_misc.c
@@ -25,86 +25,77 @@
  */
 
 #include "py/mpconfig.h"
-// *_ADHOC part is for cc3200 port which doesn't use general uPy
-// infrastructure and instead duplicates code. TODO: Resolve.
-#if MICROPY_VFS_FAT || MICROPY_FSUSERMOUNT || MICROPY_FSUSERMOUNT_ADHOC
+#if MICROPY_VFS_FAT
 
 #include <string.h>
 #include "py/nlr.h"
 #include "py/runtime.h"
-#include "lib/fatfs/ff.h"
-#include "lib/fatfs/diskio.h"
-#include "extmod/vfs_fat_file.h"
-#include "extmod/fsusermount.h"
+#include "lib/oofatfs/ff.h"
+#include "extmod/vfs_fat.h"
 #include "py/lexer.h"
 
-#if _USE_LFN
-STATIC char lfn[_MAX_LFN + 1];   /* Buffer to store the LFN */
-#endif
+typedef struct _mp_vfs_fat_ilistdir_it_t {
+    mp_obj_base_t base;
+    mp_fun_1_t iternext;
+    bool is_str;
+    FF_DIR dir;
+} mp_vfs_fat_ilistdir_it_t;
 
-// TODO: actually, the core function should be ilistdir()
-mp_obj_t fat_vfs_listdir(const char *path, bool is_str_type) {
-    FRESULT res;
-    FILINFO fno;
-    DIR dir;
-#if _USE_LFN
-    fno.lfname = lfn;
-    fno.lfsize = sizeof lfn;
-#endif
-
-    res = f_opendir(&dir, path);                       /* Open the directory */
-    if (res != FR_OK) {
-        mp_raise_OSError(fresult_to_errno_table[res]);
-    }
-
-    mp_obj_t dir_list = mp_obj_new_list(0, NULL);
+STATIC mp_obj_t mp_vfs_fat_ilistdir_it_iternext(mp_obj_t self_in) {
+    mp_vfs_fat_ilistdir_it_t *self = MP_OBJ_TO_PTR(self_in);
 
     for (;;) {
-        res = f_readdir(&dir, &fno);                   /* Read a directory item */
-        if (res != FR_OK || fno.fname[0] == 0) break;  /* Break on error or end of dir */
-        if (fno.fname[0] == '.' && fno.fname[1] == 0) continue;             /* Ignore . entry */
-        if (fno.fname[0] == '.' && fno.fname[1] == '.' && fno.fname[2] == 0) continue;             /* Ignore .. entry */
-
-#if _USE_LFN
-        char *fn = *fno.lfname ? fno.lfname : fno.fname;
-#else
+        FILINFO fno;
+        FRESULT res = f_readdir(&self->dir, &fno);
         char *fn = fno.fname;
-#endif
+        if (res != FR_OK || fn[0] == 0) {
+            // stop on error or end of dir
+            break;
+        }
+
+        // Note that FatFS already filters . and .., so we don't need to
 
-        /*
+        // make 3-tuple with info about this entry
+        mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(3, NULL));
+        if (self->is_str) {
+            t->items[0] = mp_obj_new_str(fn, strlen(fn), false);
+        } else {
+            t->items[0] = mp_obj_new_bytes((const byte*)fn, strlen(fn));
+        }
         if (fno.fattrib & AM_DIR) {
             // dir
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(MP_S_IFDIR);
         } else {
             // file
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(MP_S_IFREG);
         }
-        */
-
-        // make a string object for this entry
-        mp_obj_t entry_o;
-        if (is_str_type) {
-            entry_o = mp_obj_new_str(fn, strlen(fn), false);
-        } else {
-            entry_o = mp_obj_new_bytes((const byte*)fn, strlen(fn));
-        }
+        t->items[2] = MP_OBJ_NEW_SMALL_INT(0); // no inode number
 
-        // add the entry to the list
-        mp_obj_list_append(dir_list, entry_o);
+        return MP_OBJ_FROM_PTR(t);
     }
 
-    f_closedir(&dir);
+    // ignore error because we may be closing a second time
+    f_closedir(&self->dir);
 
-    return dir_list;
+    return MP_OBJ_STOP_ITERATION;
 }
 
-mp_import_stat_t fat_vfs_import_stat(const char *path);
+mp_obj_t fat_vfs_ilistdir2(fs_user_mount_t *vfs, const char *path, bool is_str_type) {
+    mp_vfs_fat_ilistdir_it_t *iter = m_new_obj(mp_vfs_fat_ilistdir_it_t);
+    iter->base.type = &mp_type_polymorph_iter;
+    iter->iternext = mp_vfs_fat_ilistdir_it_iternext;
+    iter->is_str = is_str_type;
+    FRESULT res = f_opendir(&vfs->fatfs, &iter->dir, path);
+    if (res != FR_OK) {
+        mp_raise_OSError(fresult_to_errno_table[res]);
+    }
+    return MP_OBJ_FROM_PTR(iter);
+}
 
-mp_import_stat_t fat_vfs_import_stat(const char *path) {
+mp_import_stat_t fat_vfs_import_stat(fs_user_mount_t *vfs, const char *path) {
     FILINFO fno;
-#if _USE_LFN
-    fno.lfname = NULL;
-    fno.lfsize = 0;
-#endif
-    FRESULT res = f_stat(path, &fno);
+    assert(vfs != NULL);
+    FRESULT res = f_stat(&vfs->fatfs, path, &fno);
     if (res == FR_OK) {
         if ((fno.fattrib & AM_DIR) != 0) {
             return MP_IMPORT_STAT_DIR;
diff --git a/extmod/vfs_fat_reader.c b/extmod/vfs_reader.c
index 7a00f18de..891098aa1 100644
--- a/extmod/vfs_fat_reader.c
+++ b/extmod/vfs_reader.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2013-2016 Damien P. George
+ * Copyright (c) 2013-2017 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -25,64 +25,63 @@
  */
 
 #include <stdio.h>
-#include <assert.h>
+#include <string.h>
 
-#include "py/mperrno.h"
+#include "py/runtime.h"
+#include "py/stream.h"
 #include "py/reader.h"
+#include "extmod/vfs.h"
 
-#if MICROPY_READER_FATFS
+#if MICROPY_READER_VFS
 
-#include "lib/fatfs/ff.h"
-#include "extmod/vfs_fat_file.h"
-
-typedef struct _mp_reader_fatfs_t {
-    FIL fp;
+typedef struct _mp_reader_vfs_t {
+    mp_obj_t file;
     uint16_t len;
     uint16_t pos;
-    byte buf[20];
-} mp_reader_fatfs_t;
+    byte buf[24];
+} mp_reader_vfs_t;
 
-STATIC mp_uint_t mp_reader_fatfs_readbyte(void *data) {
-    mp_reader_fatfs_t *reader = (mp_reader_fatfs_t*)data;
+STATIC mp_uint_t mp_reader_vfs_readbyte(void *data) {
+    mp_reader_vfs_t *reader = (mp_reader_vfs_t*)data;
     if (reader->pos >= reader->len) {
         if (reader->len < sizeof(reader->buf)) {
             return MP_READER_EOF;
         } else {
-            UINT n;
-            f_read(&reader->fp, reader->buf, sizeof(reader->buf), &n);
-            if (n == 0) {
+            int errcode;
+            reader->len = mp_stream_rw(reader->file, reader->buf, sizeof(reader->buf),
+                &errcode, MP_STREAM_RW_READ | MP_STREAM_RW_ONCE);
+            if (errcode != 0) {
+                // TODO handle errors properly
+                return MP_READER_EOF;
+            }
+            if (reader->len == 0) {
                 return MP_READER_EOF;
             }
-            reader->len = n;
             reader->pos = 0;
         }
     }
     return reader->buf[reader->pos++];
 }
 
-STATIC void mp_reader_fatfs_close(void *data) {
-    mp_reader_fatfs_t *reader = (mp_reader_fatfs_t*)data;
-    f_close(&reader->fp);
-    m_del_obj(mp_reader_fatfs_t, reader);
+STATIC void mp_reader_vfs_close(void *data) {
+    mp_reader_vfs_t *reader = (mp_reader_vfs_t*)data;
+    mp_stream_close(reader->file);
+    m_del_obj(mp_reader_vfs_t, reader);
 }
 
-int mp_reader_new_file(mp_reader_t *reader, const char *filename) {
-    mp_reader_fatfs_t *rf = m_new_obj_maybe(mp_reader_fatfs_t);
-    if (rf == NULL) {
-        return MP_ENOMEM;
-    }
-    FRESULT res = f_open(&rf->fp, filename, FA_READ);
-    if (res != FR_OK) {
-        return fresult_to_errno_table[res];
+void mp_reader_new_file(mp_reader_t *reader, const char *filename) {
+    mp_reader_vfs_t *rf = m_new_obj(mp_reader_vfs_t);
+    mp_obj_t arg = mp_obj_new_str(filename, strlen(filename), false);
+    rf->file = mp_vfs_open(1, &arg, (mp_map_t*)&mp_const_empty_map);
+    int errcode;
+    rf->len = mp_stream_rw(rf->file, rf->buf, sizeof(rf->buf), &errcode, MP_STREAM_RW_READ | MP_STREAM_RW_ONCE);
+    if (errcode != 0) {
+        mp_raise_OSError(errcode);
     }
-    UINT n;
-    f_read(&rf->fp, rf->buf, sizeof(rf->buf), &n);
-    rf->len = n;
     rf->pos = 0;
     reader->data = rf;
-    reader->readbyte = mp_reader_fatfs_readbyte;
-    reader->close = mp_reader_fatfs_close;
-    return 0; // success
+    reader->readbyte = mp_reader_vfs_readbyte;
+    reader->close = mp_reader_vfs_close;
 }
 
-#endif
+#endif // MICROPY_READER_VFS
diff --git a/extmod/virtpin.h b/extmod/virtpin.h
index 3821f9dec..041010350 100644
--- a/extmod/virtpin.h
+++ b/extmod/virtpin.h
@@ -38,3 +38,6 @@ typedef struct _mp_pin_p_t {
 
 int mp_virtual_pin_read(mp_obj_t pin);
 void mp_virtual_pin_write(mp_obj_t pin, int value);
+
+// If a port exposes a Pin object, it's constructor should be like this
+mp_obj_t mp_pin_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args);