atmel-samd: Introduce a nvm module for non-volatile byte-level memory access. (#203)

* atmel-samd: Introduce a nvm module for non-volatile byte-level memory access.

This allows for persisting small configuration values even when the file system
is read-only from CircuitPython.

Fixes #160

* Review feedback:
* Add tests.
* Fix non-zero index.
* Fix len()

32 files changed, 575 insertions, 25 deletions

diff --git a/atmel-samd/Makefile b/atmel-samd/Makefile
index 913461261..5476a91e9 100644
--- a/atmel-samd/Makefile
+++ b/atmel-samd/Makefile
@@ -252,6 +252,8 @@ SRC_COMMON_HAL = \
 	microcontroller/__init__.c \
 	microcontroller/Pin.c \
 	neopixel_write/__init__.c \
+	nvm/__init__.c \
+	nvm/ByteArray.c \
 	os/__init__.c \
 	pulseio/__init__.c \
 	pulseio/PulseIn.c \
diff --git a/atmel-samd/boards/arduino_zero/mpconfigboard.h b/atmel-samd/boards/arduino_zero/mpconfigboard.h
index dd4ec88d3..149963840 100644
--- a/atmel-samd/boards/arduino_zero/mpconfigboard.h
+++ b/atmel-samd/boards/arduino_zero/mpconfigboard.h
@@ -12,4 +12,6 @@
 
 #include "internal_flash.h"
 
+#define CIRCUITPY_INTERNAL_NVM_SIZE 0
+
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
diff --git a/atmel-samd/boards/circuitplayground_express/mpconfigboard.h b/atmel-samd/boards/circuitplayground_express/mpconfigboard.h
index 9499d25a2..f9ff05084 100644
--- a/atmel-samd/boards/circuitplayground_express/mpconfigboard.h
+++ b/atmel-samd/boards/circuitplayground_express/mpconfigboard.h
@@ -25,7 +25,11 @@
 
 #include "spi_flash.h"
 
-#define BOARD_FLASH_SIZE (0x00040000 - 0x2000)
+// If you change this, then make sure to update the linker scripts as well to
+// make sure you don't overwrite code.
+#define CIRCUITPY_INTERNAL_NVM_SIZE 256
+
+#define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - CIRCUITPY_INTERNAL_NVM_SIZE)
 
 #include "flash_S25FL216K.h"
 #include "flash_GD25Q16C.h"
diff --git a/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h b/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h
index f1b9dfcbe..2a2d21dd3 100644
--- a/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h
+++ b/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.h
@@ -11,4 +11,6 @@
 
 #include "internal_flash.h"
 
+#define CIRCUITPY_INTERNAL_NVM_SIZE 0
+
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
diff --git a/atmel-samd/boards/feather_m0_basic/mpconfigboard.h b/atmel-samd/boards/feather_m0_basic/mpconfigboard.h
index ff6088c3a..a8a8247fa 100644
--- a/atmel-samd/boards/feather_m0_basic/mpconfigboard.h
+++ b/atmel-samd/boards/feather_m0_basic/mpconfigboard.h
@@ -11,4 +11,6 @@
 
 #include "internal_flash.h"
 
+#define CIRCUITPY_INTERNAL_NVM_SIZE 0
+
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
diff --git a/atmel-samd/boards/feather_m0_express/mpconfigboard.h b/atmel-samd/boards/feather_m0_express/mpconfigboard.h
index 929a8c0f3..896a04dd8 100644
--- a/atmel-samd/boards/feather_m0_express/mpconfigboard.h
+++ b/atmel-samd/boards/feather_m0_express/mpconfigboard.h
@@ -23,7 +23,11 @@
 
 #include "spi_flash.h"
 
-#define BOARD_FLASH_SIZE (0x00040000 - 0x2000)
+// If you change this, then make sure to update the linker scripts as well to
+// make sure you don't overwrite code.
+#define CIRCUITPY_INTERNAL_NVM_SIZE 256
+
+#define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - CIRCUITPY_INTERNAL_NVM_SIZE)
 
 #include "flash_S25FL216K.h"
 #include "flash_GD25Q16C.h"
diff --git a/atmel-samd/boards/gemma_m0/mpconfigboard.h b/atmel-samd/boards/gemma_m0/mpconfigboard.h
index ae1aa24a1..8988c9a63 100644
--- a/atmel-samd/boards/gemma_m0/mpconfigboard.h
+++ b/atmel-samd/boards/gemma_m0/mpconfigboard.h
@@ -11,6 +11,8 @@
 #define MICROPY_PORT_A        (PORT_PA00 | PORT_PA01 | PORT_PA24 | PORT_PA25)
 #define MICROPY_PORT_B        (0)
 
+#define CIRCUITPY_INTERNAL_NVM_SIZE 0
+
 #include "internal_flash.h"
 
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
diff --git a/atmel-samd/boards/metro_m0_express/mpconfigboard.h b/atmel-samd/boards/metro_m0_express/mpconfigboard.h
index 9bb9a2f79..cbc28dc78 100644
--- a/atmel-samd/boards/metro_m0_express/mpconfigboard.h
+++ b/atmel-samd/boards/metro_m0_express/mpconfigboard.h
@@ -25,7 +25,11 @@
 
 #include "spi_flash.h"
 
-#define BOARD_FLASH_SIZE (0x00040000 - 0x2000)
+// If you change this, then make sure to update the linker scripts as well to
+// make sure you don't overwrite code.
+#define CIRCUITPY_INTERNAL_NVM_SIZE 256
+
+#define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - CIRCUITPY_INTERNAL_NVM_SIZE)
 
 #include "flash_S25FL216K.h"
 #include "flash_GD25Q16C.h"
diff --git a/atmel-samd/boards/samd21x18-bootloader-crystalless.ld b/atmel-samd/boards/samd21x18-bootloader-crystalless.ld
index 96527ab7e..56ae5feb4 100644
--- a/atmel-samd/boards/samd21x18-bootloader-crystalless.ld
+++ b/atmel-samd/boards/samd21x18-bootloader-crystalless.ld
@@ -5,8 +5,8 @@
 /* Specify the memory areas */
 MEMORY
 {
-    /* Leave 8KiB for the bootloader, 256b for persistent config (clock), and 64k for the flash file system. */
-    FLASH (rx) : ORIGIN = 0x00000000+0x2000, LENGTH = 0x00040000 - 0x2000 - 0x100 - 0x010000
+    /* Leave 8KiB for the bootloader, 256b for persistent config (clock), 64k for the flash file system and 256b for the user config. */
+    FLASH (rx) : ORIGIN = 0x00000000+0x2000, LENGTH = 0x00040000 - 0x2000 - 0x100 - 0x010000 - 0x100
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
 }
 
diff --git a/atmel-samd/boards/samd21x18-bootloader-external-flash-crystalless.ld b/atmel-samd/boards/samd21x18-bootloader-external-flash-crystalless.ld
index a6be02f90..1c0424747 100644
--- a/atmel-samd/boards/samd21x18-bootloader-external-flash-crystalless.ld
+++ b/atmel-samd/boards/samd21x18-bootloader-external-flash-crystalless.ld
@@ -5,7 +5,8 @@
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx) : ORIGIN = 0x00000000 + 0x2000, LENGTH = 0x00040000 - 0x2000 - 0x100 /* Leave 8KiB for the bootloader and 256b for config. */
+    /* Leave 8KiB for the bootloader, 256b for internal config and 256b for user config. */
+    FLASH (rx) : ORIGIN = 0x00000000 + 0x2000, LENGTH = 0x00040000 - 0x2000 - 0x100 - 0x100
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
 }
 
diff --git a/atmel-samd/boards/samd21x18-bootloader-external-flash.ld b/atmel-samd/boards/samd21x18-bootloader-external-flash.ld
index bb1d3fdc4..4346c170c 100644
--- a/atmel-samd/boards/samd21x18-bootloader-external-flash.ld
+++ b/atmel-samd/boards/samd21x18-bootloader-external-flash.ld
@@ -5,7 +5,7 @@
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx) : ORIGIN = 0x00000000 + 0x2000, LENGTH = 0x00040000 - 0x2000 /* Leave 8KiB for the bootloader. */
+    FLASH (rx) : ORIGIN = 0x00000000 + 0x2000, LENGTH = 0x00040000 - 0x2000 - 0x100 /* Leave 8KiB for the bootloader and 256b for user config. */
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
 }
 
diff --git a/atmel-samd/boards/samd21x18-bootloader.ld b/atmel-samd/boards/samd21x18-bootloader.ld
index 0ea475ede..13a3f75c1 100644
--- a/atmel-samd/boards/samd21x18-bootloader.ld
+++ b/atmel-samd/boards/samd21x18-bootloader.ld
@@ -5,7 +5,7 @@
 /* Specify the memory areas */
 MEMORY
 {
-    /* Leave 8KiB for the bootloader and 64k for the flash file system. */
+    /* Leave 8KiB for the bootloader, and 64k for the flash file system. */
     FLASH (rx) : ORIGIN = 0x00000000+0x2000, LENGTH = 0x00040000 - 0x2000 - 0x010000
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
 }
diff --git a/atmel-samd/boards/samd21x18-external-flash.ld b/atmel-samd/boards/samd21x18-external-flash.ld
index 90cb6160a..f5797cf6f 100644
--- a/atmel-samd/boards/samd21x18-external-flash.ld
+++ b/atmel-samd/boards/samd21x18-external-flash.ld
@@ -5,7 +5,8 @@
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00040000 - 0x100 /* 256 KiB but leave 256b for config */
+    /* 256 KiB but leave 256b for internal config and 256b for user config (protected eeprom) */
+    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00040000 - 0x100 - 0x100
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
 }
 
diff --git a/atmel-samd/boards/samd21x18.ld b/atmel-samd/boards/samd21x18.ld
index 98a24a811..a68094758 100644
--- a/atmel-samd/boards/samd21x18.ld
+++ b/atmel-samd/boards/samd21x18.ld
@@ -5,7 +5,8 @@
 /* Specify the memory areas */
 MEMORY
 {
-    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00040000 - 0x100 - 0x010000 /* Leave 256b for config and 64k for the flash file system. */
+    /* Leave 256b for internal config, 64k for the flash file system and 256b for user config. */
+    FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00040000 - 0x100 - 0x010000
     RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x008000 /* 32 KiB */
 }
 
diff --git a/atmel-samd/boards/trinket_m0/mpconfigboard.h b/atmel-samd/boards/trinket_m0/mpconfigboard.h
index 7bb4f14cf..8fc70f22d 100644
--- a/atmel-samd/boards/trinket_m0/mpconfigboard.h
+++ b/atmel-samd/boards/trinket_m0/mpconfigboard.h
@@ -12,4 +12,6 @@
 
 #include "internal_flash.h"
 
+#define CIRCUITPY_INTERNAL_NVM_SIZE 0
+
 #define BOARD_FLASH_SIZE (0x00040000 - 0x2000 - 0x010000)
diff --git a/atmel-samd/common-hal/microcontroller/__init__.c b/atmel-samd/common-hal/microcontroller/__init__.c
index 12a530f68..50e8cdcef 100644
--- a/atmel-samd/common-hal/microcontroller/__init__.c
+++ b/atmel-samd/common-hal/microcontroller/__init__.c
@@ -25,9 +25,12 @@
  */
 
 #include "py/mphal.h"
+#include "py/obj.h"
 
 #include "samd21_pins.h"
 
+#include "shared-bindings/nvm/ByteArray.h"
+
 void common_hal_mcu_delay_us(uint32_t delay) {
     mp_hal_delay_us(delay);
 }
@@ -47,6 +50,17 @@ void common_hal_mcu_enable_interrupts(void) {
     cpu_irq_restore(irq_flags);
 }
 
+// NVM is only available on Express boards for now.
+#if CIRCUITPY_INTERNAL_NVM_SIZE > 0
+nvm_bytearray_obj_t common_hal_mcu_nvm_obj = {
+    .base = {
+        .type = &nvm_bytearray_type,
+    },
+    .len = NVMCTRL_ROW_SIZE,
+    .start_address = (uint8_t*) (FLASH_SIZE - NVMCTRL_ROW_SIZE)
+};
+#endif
+
 // This maps MCU pin names to pin objects.
 STATIC const mp_map_elem_t mcu_pin_global_dict_table[] = {
 // Pins in datasheet order.
diff --git a/atmel-samd/common-hal/nvm/ByteArray.c b/atmel-samd/common-hal/nvm/ByteArray.c
new file mode 100644
index 000000000..165634b83
--- /dev/null
+++ b/atmel-samd/common-hal/nvm/ByteArray.c
@@ -0,0 +1,88 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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 "common-hal/nvm/ByteArray.h"
+
+#include "asf/sam0/drivers/nvm/nvm.h"
+
+#include <stdint.h>
+#include <string.h>
+
+uint32_t common_hal_nvm_bytearray_get_length(nvm_bytearray_obj_t *self) {
+    return self->len;
+}
+
+bool common_hal_nvm_bytearray_set_bytes(nvm_bytearray_obj_t *self,
+    uint32_t start_index, uint8_t* values, uint32_t len) {
+    uint32_t total_written = 0;
+    for (uint32_t i = 0; i < self->len / NVMCTRL_ROW_SIZE; i++) {
+        uint32_t row_start = NVMCTRL_ROW_SIZE * i;
+        if (row_start + NVMCTRL_ROW_SIZE < start_index || start_index + len < row_start) {
+            continue;
+        }
+        uint8_t temp_row[NVMCTRL_ROW_SIZE];
+        memcpy(temp_row,
+               self->start_address + row_start,
+               NVMCTRL_ROW_SIZE);
+        enum status_code error_code;
+        do {
+            error_code = nvm_erase_row((uint32_t) self->start_address + row_start);
+        } while (error_code == STATUS_BUSY);
+        if (error_code != STATUS_OK) {
+            return false;
+        }
+        uint32_t data_start = 0;
+        if (start_index > row_start) {
+            data_start = start_index - row_start;
+        }
+        uint32_t data_len = len;
+        uint32_t data_remaining = data_len - total_written;
+        uint32_t row_remaining = NVMCTRL_ROW_SIZE - data_start;
+        if (data_remaining > row_remaining) {
+            data_len = row_remaining;
+        }
+        memcpy(temp_row + data_start,
+               values + total_written,
+               data_len);
+        for (int page = 0; page < NVMCTRL_ROW_SIZE / NVMCTRL_PAGE_SIZE; page++) {
+            do {
+                error_code = nvm_write_buffer((uint32_t) self->start_address + row_start + page * NVMCTRL_PAGE_SIZE,
+                                              temp_row + page * NVMCTRL_PAGE_SIZE,
+                                              NVMCTRL_PAGE_SIZE);
+            } while (error_code == STATUS_BUSY);
+            if (error_code != STATUS_OK) {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+// NVM memory is memory mapped so reading it is easy.
+void common_hal_nvm_bytearray_get_bytes(nvm_bytearray_obj_t *self,
+    uint32_t start_index, uint32_t len, uint8_t* values) {
+    memcpy(values, self->start_address + start_index, len);
+}
diff --git a/atmel-samd/common-hal/nvm/ByteArray.h b/atmel-samd/common-hal/nvm/ByteArray.h
new file mode 100644
index 000000000..cd23c894d
--- /dev/null
+++ b/atmel-samd/common-hal/nvm/ByteArray.h
@@ -0,0 +1,38 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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_ATMEL_SAMD_COMMON_HAL_NVM_BYTEARRAY_H__
+#define __MICROPY_INCLUDED_ATMEL_SAMD_COMMON_HAL_NVM_BYTEARRAY_H__
+
+#include "py/obj.h"
+
+typedef struct {
+    mp_obj_base_t base;
+    uint8_t* start_address;
+    uint32_t len;
+} nvm_bytearray_obj_t;
+
+#endif // __MICROPY_INCLUDED_ATMEL_SAMD_COMMON_HAL_NVM_BYTEARRAY_H__
diff --git a/atmel-samd/common-hal/nvm/__init__.c b/atmel-samd/common-hal/nvm/__init__.c
new file mode 100644
index 000000000..1b702a158
--- /dev/null
+++ b/atmel-samd/common-hal/nvm/__init__.c
@@ -0,0 +1 @@
+// No nvm module functions.
diff --git a/atmel-samd/internal_flash.c b/atmel-samd/internal_flash.c
index 1ff1cabcf..23b1153b3 100644
--- a/atmel-samd/internal_flash.c
+++ b/atmel-samd/internal_flash.c
@@ -40,12 +40,6 @@
 
 #include "rgb_led_status.h"
 
-#define TOTAL_INTERNAL_FLASH_SIZE 0x010000
-
-#define INTERNAL_FLASH_MEM_SEG1_START_ADDR (0x00040000 - TOTAL_INTERNAL_FLASH_SIZE)
-#define INTERNAL_FLASH_PART1_START_BLOCK (0x1)
-#define INTERNAL_FLASH_PART1_NUM_BLOCKS (TOTAL_INTERNAL_FLASH_SIZE / FILESYSTEM_BLOCK_SIZE)
-
 void internal_flash_init(void) {
     // Activity LED for flash writes.
     #ifdef MICROPY_HW_LED_MSC
@@ -120,7 +114,6 @@ static int32_t convert_block_to_flash_addr(uint32_t block) {
 }
 
 bool internal_flash_read_block(uint8_t *dest, uint32_t block) {
-    //printf("RD %u\n", block);
     if (block == 0) {
         // fake the MBR so we can decide on our own partition table
 
diff --git a/atmel-samd/internal_flash.h b/atmel-samd/internal_flash.h
index 52ae4c9f1..e8b4d7ae0 100644
--- a/atmel-samd/internal_flash.h
+++ b/atmel-samd/internal_flash.h
@@ -32,6 +32,12 @@
 
 #define FLASH_ROOT_POINTERS
 
+#define TOTAL_INTERNAL_FLASH_SIZE 0x010000
+
+#define INTERNAL_FLASH_MEM_SEG1_START_ADDR (0x00040000 - TOTAL_INTERNAL_FLASH_SIZE - CIRCUITPY_INTERNAL_NVM_SIZE)
+#define INTERNAL_FLASH_PART1_START_BLOCK (0x1)
+#define INTERNAL_FLASH_PART1_NUM_BLOCKS (TOTAL_INTERNAL_FLASH_SIZE / FILESYSTEM_BLOCK_SIZE)
+
 #define INTERNAL_FLASH_SYSTICK_MASK    (0x1ff) // 512ms
 #define INTERNAL_FLASH_IDLE_TICK(tick) (((tick) & INTERNAL_FLASH_SYSTICK_MASK) == 2)
 
diff --git a/atmel-samd/main.c b/atmel-samd/main.c
index b3cfa69fd..76a98dc60 100644
--- a/atmel-samd/main.c
+++ b/atmel-samd/main.c
@@ -34,13 +34,6 @@
 #include "common-hal/pulseio/PWMOut.h"
 #include "common-hal/usb_hid/__init__.h"
 
-#ifdef EXPRESS_BOARD
-#include "common-hal/touchio/TouchIn.h"
-#define INTERNAL_CIRCUITPY_CONFIG_START_ADDR (0x00040000 - 0x100)
-#else
-#define INTERNAL_CIRCUITPY_CONFIG_START_ADDR (0x00040000 - 0x010000 - 0x100)
-#endif
-
 #include "autoreload.h"
 #include "flash_api.h"
 #include "mpconfigboard.h"
@@ -48,6 +41,13 @@
 #include "shared_dma.h"
 #include "tick.h"
 
+#ifdef EXPRESS_BOARD
+#include "common-hal/touchio/TouchIn.h"
+#define INTERNAL_CIRCUITPY_CONFIG_START_ADDR (0x00040000 - 0x100 - CIRCUITPY_INTERNAL_NVM_SIZE)
+#else
+#define INTERNAL_CIRCUITPY_CONFIG_START_ADDR (0x00040000 - 0x010000 - 0x100 - CIRCUITPY_INTERNAL_NVM_SIZE)
+#endif
+
 fs_user_mount_t fs_user_mount_flash;
 mp_vfs_mount_t mp_vfs_mount_flash;
 
@@ -568,6 +568,35 @@ safe_mode_t samd21_init(void) {
         return USER_SAFE_MODE;
     }
 
+    #if CIRCUITPY_INTERNAL_NVM_SIZE > 0
+    // Upgrade the nvm flash to include one sector for eeprom emulation.
+    struct nvm_fusebits fuses;
+    if (nvm_get_fuses(&fuses) == STATUS_OK &&
+            fuses.eeprom_size == NVM_EEPROM_EMULATOR_SIZE_0) {
+        #ifdef INTERNAL_FLASH_FS
+        // Shift the internal file system up one row.
+        for (uint8_t row = 0; row < TOTAL_INTERNAL_FLASH_SIZE / NVMCTRL_ROW_SIZE; row++) {
+            uint32_t new_row_address = INTERNAL_FLASH_MEM_SEG1_START_ADDR + row * NVMCTRL_ROW_SIZE;
+            nvm_erase_row(new_row_address);
+            nvm_write_buffer(new_row_address,
+                             (uint8_t*) (new_row_address + CIRCUITPY_INTERNAL_EEPROM_SIZE),
+                             NVMCTRL_ROW_SIZE);
+        }
+        #endif
+        uint32_t nvm_size = CIRCUITPY_INTERNAL_NVM_SIZE;
+        uint8_t enum_value = 6;
+        while (nvm_size > 256 && enum_value != 255) {
+            nvm_size /= 2;
+            enum_value -= 1;
+        }
+        if (enum_value != 255 && nvm_size == 256) {
+            // Mark the last section as eeprom now.
+            fuses.eeprom_size = (enum nvm_eeprom_emulator_size) enum_value;
+            nvm_set_fuses(&fuses);
+        }
+    }
+    #endif
+
     return NO_SAFE_MODE;
 }
 
diff --git a/atmel-samd/mpconfigport.h b/atmel-samd/mpconfigport.h
index 0059ea976..ba6b54d49 100644
--- a/atmel-samd/mpconfigport.h
+++ b/atmel-samd/mpconfigport.h
@@ -147,6 +147,7 @@ extern const struct _mp_obj_module_t os_module;
 extern const struct _mp_obj_module_t random_module;
 extern const struct _mp_obj_module_t storage_module;
 extern const struct _mp_obj_module_t time_module;
+extern const struct _mp_obj_module_t cpy_nvm_module;
 extern const struct _mp_obj_module_t neopixel_write_module;
 extern const struct _mp_obj_module_t uheap_module;
 extern const struct _mp_obj_module_t ustack_module;
@@ -174,6 +175,7 @@ extern const struct _mp_obj_module_t usb_hid_module;
     #define EXTRA_BUILTIN_MODULES \
         { MP_OBJ_NEW_QSTR(MP_QSTR_audioio), (mp_obj_t)&audioio_module }, \
         { MP_OBJ_NEW_QSTR(MP_QSTR_audiobusio), (mp_obj_t)&audiobusio_module }, \
+        { MP_OBJ_NEW_QSTR(MP_QSTR_nvm), (mp_obj_t)&cpy_nvm_module }, \
         { MP_OBJ_NEW_QSTR(MP_QSTR_pulseio), (mp_obj_t)&pulseio_module }, \
         { MP_OBJ_NEW_QSTR(MP_QSTR_bitbangio), (mp_obj_t)&bitbangio_module }
     #define EXPRESS_BOARD
diff --git a/shared-bindings/microcontroller/__init__.c b/shared-bindings/microcontroller/__init__.c
index fbe359ed9..56d363eed 100644
--- a/shared-bindings/microcontroller/__init__.c
+++ b/shared-bindings/microcontroller/__init__.c
@@ -90,6 +90,12 @@ STATIC mp_obj_t mcu_enable_interrupts(void) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(mcu_enable_interrupts_obj, mcu_enable_interrupts);
 
+//| .. attribute:: nvm
+//|
+//|   Available non-volatile memory. Its a `nvm.ByteArray` when available or
+//|   ``None`` otherwise.
+//|
+
 //| :mod:`microcontroller.pin` --- Microcontroller pin names
 //| --------------------------------------------------------
 //|
@@ -109,7 +115,12 @@ STATIC const mp_rom_map_elem_t mcu_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_delay_us), MP_ROM_PTR(&mcu_delay_us_obj) },
     { MP_ROM_QSTR(MP_QSTR_disable_interrupts), MP_ROM_PTR(&mcu_disable_interrupts_obj) },
     { MP_ROM_QSTR(MP_QSTR_enable_interrupts), MP_ROM_PTR(&mcu_enable_interrupts_obj) },
-    { MP_ROM_QSTR(MP_QSTR_Pin),   MP_ROM_PTR(&mcu_pin_type) },
+    #if CIRCUITPY_INTERNAL_NVM_SIZE > 0
+    { MP_ROM_QSTR(MP_QSTR_nvm),  &common_hal_mcu_nvm_obj },
+    #else
+    { MP_ROM_QSTR(MP_QSTR_nvm),  &mp_const_none_obj },
+    #endif
+    { MP_ROM_QSTR(MP_QSTR_Pin),  MP_ROM_PTR(&mcu_pin_type) },
     { MP_ROM_QSTR(MP_QSTR_pin),  MP_ROM_PTR(&mcu_pin_module) },
 };
 
diff --git a/shared-bindings/microcontroller/__init__.h b/shared-bindings/microcontroller/__init__.h
index 8c0b071ec..52aabf9b8 100644
--- a/shared-bindings/microcontroller/__init__.h
+++ b/shared-bindings/microcontroller/__init__.h
@@ -27,6 +27,7 @@
 #ifndef __MICROPY_INCLUDED_SHARED_BINDINGS_MICROCONTROLLER___INIT___H__
 #define __MICROPY_INCLUDED_SHARED_BINDINGS_MICROCONTROLLER___INIT___H__
 
+#include "py/mpconfig.h"
 #include "py/obj.h"
 
 extern void common_hal_mcu_delay_us(uint32_t);
@@ -36,4 +37,11 @@ extern void common_hal_mcu_enable_interrupts(void);
 
 extern const mp_obj_dict_t mcu_pin_globals;
 
+#if CIRCUITPY_INTERNAL_NVM_SIZE > 0
+
+#include "common-hal/nvm/ByteArray.h"
+extern const nvm_bytearray_obj_t common_hal_mcu_nvm_obj;
+
+#endif
+
 #endif  // __MICROPY_INCLUDED_SHARED_BINDINGS_MICROCONTROLLER___INIT___H__
diff --git a/shared-bindings/nvm/ByteArray.c b/shared-bindings/nvm/ByteArray.c
new file mode 100644
index 000000000..0ba511a77
--- /dev/null
+++ b/shared-bindings/nvm/ByteArray.c
@@ -0,0 +1,159 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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/binary.h"
+#include "py/objproperty.h"
+#include "py/runtime.h"
+#include "py/runtime0.h"
+#include "shared-bindings/nvm/ByteArray.h"
+
+//| .. currentmodule:: nvm
+//|
+//| :class:`ByteArray` -- Presents a stretch of non-volatile memory as a bytearray.
+//| ================================================================================
+//|
+//| Non-volatile memory is available as a byte array that persists over reloads
+//| and power cycles.
+//|
+//| Usage::
+//|
+//|    import microcontroller
+//|    microcontroller.nvm[0] = 0xcc
+//|
+
+//| .. class:: ByteArray()
+//|
+//|   Not currently dynamically supported. Access one through `microcontroller.nvm`.
+//|
+STATIC mp_obj_t nvm_bytearray_make_new(const mp_obj_type_t *type,
+        mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
+    return mp_const_none;
+}
+
+//|   .. method:: __len__()
+//|
+//|     Return the length. This is used by (`len`)
+//|
+STATIC mp_obj_t nvm_bytearray_unary_op(mp_uint_t op, mp_obj_t self_in) {
+    nvm_bytearray_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    uint16_t len = common_hal_nvm_bytearray_get_length(self);
+    switch (op) {
+        case MP_UNARY_OP_BOOL: return mp_obj_new_bool(len != 0);
+        case MP_UNARY_OP_LEN: return MP_OBJ_NEW_SMALL_INT(len);
+        default: return MP_OBJ_NULL; // op not supported
+    }
+}
+
+STATIC const mp_rom_map_elem_t nvm_bytearray_locals_dict_table[] = {
+};
+
+STATIC MP_DEFINE_CONST_DICT(nvm_bytearray_locals_dict, nvm_bytearray_locals_dict_table);
+
+STATIC mp_obj_t nvm_bytearray_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_obj_t value) {
+    if (value == MP_OBJ_NULL) {
+        // delete item
+        // slice deletion
+        return MP_OBJ_NULL; // op not supported
+    } else {
+        nvm_bytearray_obj_t *self = MP_OBJ_TO_PTR(self_in);
+        if (0) {
+#if MICROPY_PY_BUILTINS_SLICE
+        } else if (MP_OBJ_IS_TYPE(index_in, &mp_type_slice)) {
+            mp_bound_slice_t slice;
+            if (!mp_seq_get_fast_slice_indexes(common_hal_nvm_bytearray_get_length(self), index_in, &slice)) {
+                mp_raise_NotImplementedError("only slices with step=1 (aka None) are supported");
+            }
+            if (value != MP_OBJ_SENTINEL) {
+                #if MICROPY_PY_ARRAY_SLICE_ASSIGN
+                // Assign
+                size_t src_len = slice.stop - slice.start;
+                uint8_t* src_items;
+                if (MP_OBJ_IS_TYPE(value, &mp_type_array) ||
+                        MP_OBJ_IS_TYPE(value, &mp_type_bytearray) ||
+                        MP_OBJ_IS_TYPE(value, &mp_type_memoryview) ||
+                        MP_OBJ_IS_TYPE(value, &mp_type_bytes)) {
+                    mp_buffer_info_t bufinfo;
+                    mp_get_buffer_raise(value, &bufinfo, MP_BUFFER_READ);
+                    if (bufinfo.len != src_len) {
+                        mp_raise_ValueError("Slice and value different lengths.");
+                    }
+                    src_len = bufinfo.len;
+                    src_items = bufinfo.buf;
+                    if (1 != mp_binary_get_size('@', bufinfo.typecode, NULL)) {
+                        mp_raise_ValueError("Array values should be single bytes.");
+                    }
+                } else {
+                    mp_raise_NotImplementedError("array/bytes required on right side");
+                }
+
+                if (!common_hal_nvm_bytearray_set_bytes(self, slice.start, src_items, src_len)) {
+                    mp_raise_RuntimeError("Unable to write to nvm.");
+                }
+                return mp_const_none;
+                #else
+                return MP_OBJ_NULL; // op not supported
+                #endif
+            } else {
+                // Read slice.
+                size_t len = slice.stop - slice.start;
+                uint8_t *items = m_new(uint8_t, len);
+                common_hal_nvm_bytearray_get_bytes(self, slice.start, len, items);
+                return mp_obj_new_bytearray_by_ref(len, items);
+            }
+#endif
+        } else {
+            // Single index rather than slice.
+            size_t index = mp_get_index(self->base.type, self->len, index_in, false);
+            if (value == MP_OBJ_SENTINEL) {
+                // load
+                uint8_t value_out;
+                common_hal_nvm_bytearray_get_bytes(self, index, 1, &value_out);
+                return MP_OBJ_NEW_SMALL_INT(value_out);
+            } else {
+                // store
+                mp_int_t byte_value = mp_obj_get_int(value);
+                if (byte_value > 0xff || byte_value < 0) {
+                    mp_raise_ValueError("Bytes must be between 0 and 255.");
+                }
+                uint8_t short_value = byte_value;
+                if (!common_hal_nvm_bytearray_set_bytes(self, index, &short_value, 1)) {
+                    mp_raise_RuntimeError("Unable to write to nvm.");
+                }
+                return mp_const_none;
+            }
+        }
+    }
+}
+
+const mp_obj_type_t nvm_bytearray_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_ByteArray,
+    .make_new = nvm_bytearray_make_new,
+    .subscr = nvm_bytearray_subscr,
+    .unary_op = nvm_bytearray_unary_op,
+    .print = NULL,
+    .locals_dict = (mp_obj_t)&nvm_bytearray_locals_dict,
+};
diff --git a/shared-bindings/nvm/ByteArray.h b/shared-bindings/nvm/ByteArray.h
new file mode 100644
index 000000000..43d942c23
--- /dev/null
+++ b/shared-bindings/nvm/ByteArray.h
@@ -0,0 +1,43 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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_SHARED_BINDINGS_NVM_BYTEARRAY_H__
+#define __MICROPY_INCLUDED_SHARED_BINDINGS_NVM_BYTEARRAY_H__
+
+#include "common-hal/nvm/ByteArray.h"
+
+const mp_obj_type_t nvm_bytearray_type;
+
+uint32_t common_hal_nvm_bytearray_get_length(nvm_bytearray_obj_t *self);
+
+bool common_hal_nvm_bytearray_set_bytes(nvm_bytearray_obj_t *self,
+    uint32_t start_index, uint8_t* values, uint32_t len);
+// len and values are intentionally swapped to signify values is an output and
+// also leverage the compiler to validate uses are expected.
+void common_hal_nvm_bytearray_get_bytes(nvm_bytearray_obj_t *self,
+    uint32_t start_index, uint32_t len, uint8_t* values);
+
+#endif  // __MICROPY_INCLUDED_SHARED_BINDINGS_NVM_BYTEARRAY_H__
diff --git a/shared-bindings/nvm/__init__.c b/shared-bindings/nvm/__init__.c
new file mode 100644
index 000000000..8caf33ffb
--- /dev/null
+++ b/shared-bindings/nvm/__init__.c
@@ -0,0 +1,62 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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/obj.h"
+#include "py/mphal.h"
+#include "py/runtime.h"
+
+#include "shared-bindings/nvm/__init__.h"
+#include "shared-bindings/nvm/ByteArray.h"
+
+//| :mod:`nvm` --- Non-volatile memory
+//| ===========================================================
+//|
+//| .. module:: nvm
+//|   :synopsis: Non-volatile memory
+//|   :platform: SAMD21
+//|
+//| The `nvm` module allows you to store whatever raw bytes you wish in a
+//| reserved section non-volatile memory.
+//|
+
+//| Libraries
+//|
+//| .. toctree::
+//|     :maxdepth: 3
+//|
+//|     ByteArray
+STATIC const mp_rom_map_elem_t nvm_module_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_nvm) },
+    { MP_ROM_QSTR(MP_QSTR_ByteArray),   MP_ROM_PTR(&nvm_bytearray_type) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(nvm_module_globals, nvm_module_globals_table);
+
+// cpy prefix is used to prevent collision with nvm_module global in ASF.
+const mp_obj_module_t cpy_nvm_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&nvm_module_globals,
+};
diff --git a/shared-bindings/nvm/__init__.h b/shared-bindings/nvm/__init__.h
new file mode 100644
index 000000000..9e1799974
--- /dev/null
+++ b/shared-bindings/nvm/__init__.h
@@ -0,0 +1,30 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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 SHARED_BINDINGS_NVM_H
+#define SHARED_BINDINGS_NVM_H
+
+#endif  // SHARED_BINDINGS_NVM_H
diff --git a/tests/circuitpython/nvm_not_present.py b/tests/circuitpython/nvm_not_present.py
new file mode 100644
index 000000000..141e60b01
--- /dev/null
+++ b/tests/circuitpython/nvm_not_present.py
@@ -0,0 +1,6 @@
+import skip_if
+skip_if.board_not_in("gemma_m0", "trinket_m0")
+
+import microcontroller
+
+assert(microcontroller.nvm == None)
diff --git a/tests/circuitpython/nvm_present.py b/tests/circuitpython/nvm_present.py
new file mode 100644
index 000000000..a2cf3a22c
--- /dev/null
+++ b/tests/circuitpython/nvm_present.py
@@ -0,0 +1,22 @@
+import skip_if
+skip_if.board_not_in("metro_m0_express", "feather_m0_express", "circuitplayground_express")
+
+import microcontroller
+import random
+nvm = microcontroller.nvm
+
+len(nvm)
+
+single = random.randint(0, 255)
+nvm[1] = single
+assert(nvm[1] == single)
+
+nvm[0] = single
+assert(nvm[0] == single)
+
+b = bytearray()
+for i in range(10):
+    b.append(random.randint(0, 255))
+
+microcontroller.nvm[10:20] = b
+assert(microcontroller.nvm[10:20] == b)
diff --git a/tests/skip_if.py b/tests/skip_if.py
index f6d22b4c1..7b1e06871 100644
--- a/tests/skip_if.py
+++ b/tests/skip_if.py
@@ -52,6 +52,17 @@ def board_in(*board):
     if test_env.board in board:
         skip()
 
+def board_not_in(*board):
+    try:
+        import test_env
+    except ImportError:
+        class Env:
+            def __init__(self, board):
+                self.board = board
+        test_env = Env("unknown")
+    if test_env.board not in board:
+        skip()
+
 def no_cpython_compat():
     try:
         try: