Merge remote-tracking branch 'origin/master' into nrf-pdm-audioin

21 files changed, 991 insertions, 788 deletions

diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index 9da2c498d..fad127514 100755
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -95,8 +95,7 @@ ifeq ($(DEBUG), 1)
   CFLAGS += -fno-inline -fno-ipa-sra
 else
   CFLAGS += -Os -DNDEBUG
-  # TODO: Test with -flto
-  ### CFLAGS += -flto
+  CFLAGS += -flto -flto-partition=none
 endif
 
 
diff --git a/ports/nrf/boards/make-pins.py b/ports/nrf/boards/make-pins.py
deleted file mode 100644
index d1cfd5b70..000000000
--- a/ports/nrf/boards/make-pins.py
+++ /dev/null
@@ -1,208 +0,0 @@
-#!/usr/bin/env python
-"""Creates the pin file for the nRF5."""
-
-from __future__ import print_function
-
-import argparse
-import sys
-import csv
-
-
-def parse_port_pin(name_str):
-    """Parses a string and returns a (port-num, pin-num) tuple."""
-    if len(name_str) < 4:
-        raise ValueError("Expecting pin name to be at least 5 charcters.")
-    if name_str[0] != 'P':
-        raise ValueError("Expecting pin name to start with P")
-    if name_str[1] not in ('0', '1'):
-        raise ValueError("Expecting pin port to be in 0 or 1")
-    port = ord(name_str[1]) - ord('0')
-    pin_str = name_str[3:]
-    if not pin_str.isdigit():
-        raise ValueError("Expecting numeric pin number.")
-    return (port, int(pin_str))
-
-
-class Pin(object):
-    """Holds the information associated with a pin."""
-
-    def __init__(self, port, pin):
-        self.port = port
-        self.pin = pin
-        self.adc_channel = '0'
-        self.board_pin = False
-
-    def cpu_pin_name(self):
-        return 'P{:d}_{:02d}'.format(self.port, self.pin)
-
-    def is_board_pin(self):
-        return self.board_pin
-
-    def set_is_board_pin(self):
-        self.board_pin = True
-
-    def parse_adc(self, adc_str):
-        if (adc_str[:3] != 'AIN'):
-            return
-        self.adc_channel = 'SAADC_CH_PSELP_PSELP_AnalogInput%d' % int(adc_str[3])
-
-    def print(self):
-        print('const pin_obj_t pin_{:s} = PIN({:s}, {:d}, {:d}, {:s});'.format(
-            self.cpu_pin_name(), self.cpu_pin_name(),
-            self.port, self.pin, self.adc_channel))
-
-    def print_header(self, hdr_file):
-        hdr_file.write('extern const pin_obj_t pin_{:s};\n'.
-                       format(self.cpu_pin_name()))
-
-
-class NamedPin(object):
-
-    def __init__(self, name, pin):
-        self._name = name
-        self._pin = pin
-
-    def pin(self):
-        return self._pin
-
-    def name(self):
-        return self._name
-
-
-class Pins(object):
-
-    def __init__(self):
-        self.cpu_pins = []    # list of NamedPin objects
-        self.board_pins = []  # list of NamedPin objects
-
-    def find_pin(self, port_num, pin_num):
-        for named_pin in self.cpu_pins:
-            pin = named_pin.pin()
-            if pin.port == port_num and pin.pin == pin_num:
-                return pin
-
-    def parse_af_file(self, filename):
-        with open(filename, 'r') as csvfile:
-            rows = csv.reader(csvfile)
-            for row in rows:
-                try:
-                    (port_num, pin_num) = parse_port_pin(row[0])
-                except:
-                    continue
-                pin = Pin(port_num, pin_num)
-                if len(row) > 1:
-                    pin.parse_adc(row[1])
-                self.cpu_pins.append(NamedPin(pin.cpu_pin_name(), pin))
-
-    def parse_board_file(self, filename):
-        with open(filename, 'r') as csvfile:
-            rows = csv.reader(csvfile)
-            for row in rows:
-                try:
-                    (port_num, pin_num) = parse_port_pin(row[1])
-                except:
-                    continue
-                pin = self.find_pin(port_num, pin_num)
-                if pin:
-                    pin.set_is_board_pin()
-                    self.board_pins.append(NamedPin(row[0], pin))
-
-    def print_named(self, label, named_pins):
-        print('')
-        print('STATIC const mp_rom_map_elem_t {:s}_table[] = {{'.format(label))
-        for named_pin in named_pins:
-            pin = named_pin.pin()
-            if pin.is_board_pin():
-                print('  {{ MP_ROM_QSTR(MP_QSTR_{:s}), MP_ROM_PTR(&pin_{:s}) }},'.format(named_pin.name(),  pin.cpu_pin_name()))
-        print('};')
-        print('MP_DEFINE_CONST_DICT({:s}, {:s}_table);'.format(label, label))
-
-    def print(self):
-        for named_pin in self.cpu_pins:
-            pin = named_pin.pin()
-            if pin.is_board_pin():
-                pin.print()
-        self.print_named('mcu_pin_globals', self.cpu_pins)
-        self.print_named('board_module_globals', self.board_pins)
-
-    def print_header(self, hdr_filename):
-        with open(hdr_filename, 'wt') as hdr_file:
-            for named_pin in self.cpu_pins:
-                pin = named_pin.pin()
-                if pin.is_board_pin():
-                    pin.print_header(hdr_file)
-
-    def print_qstr(self, qstr_filename):
-        with open(qstr_filename, 'wt') as qstr_file:
-            qstr_set = set([])
-            for named_pin in self.cpu_pins:
-                pin = named_pin.pin()
-                if pin.is_board_pin():
-                    qstr_set |= set([named_pin.name()])
-            for named_pin in self.board_pins:
-                qstr_set |= set([named_pin.name()])
-            for qstr in sorted(qstr_set):
-                print('Q({})'.format(qstr), file=qstr_file)
-
-
-def main():
-    parser = argparse.ArgumentParser(
-        prog="make-pins.py",
-        usage="%(prog)s [options] [command]",
-        description="Generate board specific pin file"
-    )
-    parser.add_argument(
-        "-a", "--af",
-        dest="af_filename",
-        help="Specifies the alternate function file for the chip",
-        default="nrf_af.csv"
-    )
-    parser.add_argument(
-        "-b", "--board",
-        dest="board_filename",
-        help="Specifies the board file",
-    )
-    parser.add_argument(
-        "-p", "--prefix",
-        dest="prefix_filename",
-        help="Specifies beginning portion of generated pins file",
-        default="nrf52_prefix.c"
-    )
-    parser.add_argument(
-        "-q", "--qstr",
-        dest="qstr_filename",
-        help="Specifies name of generated qstr header file",
-        default="build/pins_qstr.h"
-    )
-    parser.add_argument(
-        "-r", "--hdr",
-        dest="hdr_filename",
-        help="Specifies name of generated pin header file",
-        default="build/pins.h"
-    )
-    args = parser.parse_args(sys.argv[1:])
-
-    pins = Pins()
-
-    print('// This file was automatically generated by make-pins.py')
-    print('//')
-    if args.af_filename:
-        print('// --af {:s}'.format(args.af_filename))
-        pins.parse_af_file(args.af_filename)
-
-    if args.board_filename:
-        print('// --board {:s}'.format(args.board_filename))
-        pins.parse_board_file(args.board_filename)
-
-    if args.prefix_filename:
-        print('// --prefix {:s}'.format(args.prefix_filename))
-        print('')
-        with open(args.prefix_filename, 'r') as prefix_file:
-            print(prefix_file.read())
-    pins.print()
-    pins.print_header(args.hdr_filename)
-    pins.print_qstr(args.qstr_filename)
-
-
-if __name__ == "__main__":
-    main()
diff --git a/ports/nrf/common-hal/bleio/Adapter.c b/ports/nrf/common-hal/bleio/Adapter.c
index 9d0912930..936dfcb9b 100644
--- a/ports/nrf/common-hal/bleio/Adapter.c
+++ b/ports/nrf/common-hal/bleio/Adapter.c
@@ -34,10 +34,11 @@
 #include "nrfx_power.h"
 #include "nrf_nvic.h"
 #include "nrf_sdm.h"
+#include "py/objstr.h"
 #include "py/runtime.h"
-#include "shared-bindings/bleio/Adapter.h"
-
 #include "supervisor/usb.h"
+#include "shared-bindings/bleio/Adapter.h"
+#include "shared-bindings/bleio/Address.h"
 
 STATIC void softdevice_assert_handler(uint32_t id, uint32_t pc, uint32_t info) {
     mp_raise_msg_varg(&mp_type_AssertionError,
@@ -132,20 +133,42 @@ bool common_hal_bleio_adapter_get_enabled(void) {
     return is_enabled;
 }
 
-void common_hal_bleio_adapter_get_address(bleio_address_obj_t *address) {
-    ble_gap_addr_t local_address;
+void get_address(ble_gap_addr_t *address) {
     uint32_t err_code;
 
     common_hal_bleio_adapter_set_enabled(true);
-    err_code = sd_ble_gap_addr_get(&local_address);
+    err_code = sd_ble_gap_addr_get(address);
 
     if (err_code != NRF_SUCCESS) {
         mp_raise_OSError_msg(translate("Failed to get local address"));
     }
+}
+
+bleio_address_obj_t *common_hal_bleio_adapter_get_address(void) {
+    common_hal_bleio_adapter_set_enabled(true);
+
+    ble_gap_addr_t local_address;
+    get_address(&local_address);
+
+    bleio_address_obj_t *address = m_new_obj(bleio_address_obj_t);
+    address->base.type = &bleio_address_type;
+
+    common_hal_bleio_address_construct(address, local_address.addr, local_address.addr_type);
+    return address;
+}
+
+mp_obj_t common_hal_bleio_adapter_get_default_name(void) {
+   common_hal_bleio_adapter_set_enabled(true);
+
+    ble_gap_addr_t local_address;
+    get_address(&local_address);
+
+    char name[] = { 'C', 'I', 'R', 'C', 'U', 'I', 'T', 'P', 'Y', 0, 0, 0, 0 };
 
-    address->type = local_address.addr_type;
+    name[sizeof(name) - 4] = nibble_to_hex_lower[local_address.addr[1] >> 4 & 0xf];
+    name[sizeof(name) - 3] = nibble_to_hex_lower[local_address.addr[1] & 0xf];
+    name[sizeof(name) - 2] = nibble_to_hex_lower[local_address.addr[0] >> 4 & 0xf];
+    name[sizeof(name) - 1] = nibble_to_hex_lower[local_address.addr[0] & 0xf];
 
-    mp_buffer_info_t buf_info;
-    mp_get_buffer_raise(address, &buf_info, MP_BUFFER_READ);
-    memcpy(address->bytes, buf_info.buf, NUM_BLEIO_ADDRESS_BYTES);
+    return mp_obj_new_str(name, sizeof(name));
 }
diff --git a/ports/nrf/common-hal/bleio/Attribute.c b/ports/nrf/common-hal/bleio/Attribute.c
new file mode 100644
index 000000000..fd1e7538d
--- /dev/null
+++ b/ports/nrf/common-hal/bleio/Attribute.c
@@ -0,0 +1,60 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Dan Halbert 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 "shared-bindings/bleio/Attribute.h"
+
+// Convert a bleio security mode to a ble_gap_conn_sec_mode_t setting.
+void bleio_attribute_gatts_set_security_mode(ble_gap_conn_sec_mode_t *perm, bleio_attribute_security_mode_t security_mode) {
+    switch (security_mode) {
+        case SECURITY_MODE_NO_ACCESS:
+            BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(perm);
+            break;
+
+        case SECURITY_MODE_OPEN:
+            BLE_GAP_CONN_SEC_MODE_SET_OPEN(perm);
+            break;
+
+        case SECURITY_MODE_ENC_NO_MITM:
+            BLE_GAP_CONN_SEC_MODE_SET_ENC_NO_MITM(perm);
+            break;
+
+        case SECURITY_MODE_ENC_WITH_MITM:
+            BLE_GAP_CONN_SEC_MODE_SET_ENC_WITH_MITM(perm);
+            break;
+
+        case SECURITY_MODE_LESC_ENC_WITH_MITM:
+            BLE_GAP_CONN_SEC_MODE_SET_LESC_ENC_WITH_MITM(perm);
+            break;
+
+        case SECURITY_MODE_SIGNED_NO_MITM:
+            BLE_GAP_CONN_SEC_MODE_SET_SIGNED_NO_MITM(perm);
+            break;
+
+        case SECURITY_MODE_SIGNED_WITH_MITM:
+            BLE_GAP_CONN_SEC_MODE_SET_SIGNED_WITH_MITM(perm);
+            break;
+    }
+}
diff --git a/ports/nrf/common-hal/bleio/Attribute.h b/ports/nrf/common-hal/bleio/Attribute.h
new file mode 100644
index 000000000..44c2fdfa1
--- /dev/null
+++ b/ports/nrf/common-hal/bleio/Attribute.h
@@ -0,0 +1,32 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Dan Halbert 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_NRF_COMMON_HAL_BLEIO_ATTRIBUTE_H
+#define MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_ATTRIBUTE_H
+
+// Nothing yet.
+
+#endif // MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_ATTRIBUTE_H
diff --git a/ports/nrf/common-hal/bleio/Central.c b/ports/nrf/common-hal/bleio/Central.c
index d90737411..d771437d6 100644
--- a/ports/nrf/common-hal/bleio/Central.c
+++ b/ports/nrf/common-hal/bleio/Central.c
@@ -34,217 +34,9 @@
 #include "nrf_soc.h"
 #include "py/objstr.h"
 #include "py/runtime.h"
+#include "shared-bindings/bleio/__init__.h"
 #include "shared-bindings/bleio/Adapter.h"
-#include "shared-bindings/bleio/Characteristic.h"
 #include "shared-bindings/bleio/Central.h"
-#include "shared-bindings/bleio/Descriptor.h"
-#include "shared-bindings/bleio/Service.h"
-#include "shared-bindings/bleio/UUID.h"
-
-static bleio_service_obj_t *m_char_discovery_service;
-static bleio_characteristic_obj_t *m_desc_discovery_characteristic;
-
-static volatile bool m_discovery_in_process;
-static volatile bool m_discovery_successful;
-
-// service_uuid may be NULL, to discover all services.
-STATIC bool discover_next_services(bleio_central_obj_t *self, uint16_t start_handle, ble_uuid_t *service_uuid) {
-    m_discovery_successful = false;
-    m_discovery_in_process = true;
-
-    uint32_t err_code = sd_ble_gattc_primary_services_discover(self->conn_handle, start_handle, service_uuid);
-
-    if (err_code != NRF_SUCCESS) {
-        mp_raise_OSError_msg(translate("Failed to discover services"));
-    }
-
-    // Wait for a discovery event.
-    while (m_discovery_in_process) {
-        MICROPY_VM_HOOK_LOOP;
-    }
-    return m_discovery_successful;
-}
-
-STATIC bool discover_next_characteristics(bleio_central_obj_t *self, bleio_service_obj_t *service, uint16_t start_handle) {
-    m_char_discovery_service = service;
-
-    ble_gattc_handle_range_t handle_range;
-    handle_range.start_handle = start_handle;
-    handle_range.end_handle = service->end_handle;
-
-    m_discovery_successful = false;
-    m_discovery_in_process = true;
-
-    uint32_t err_code = sd_ble_gattc_characteristics_discover(self->conn_handle, &handle_range);
-    if (err_code != NRF_SUCCESS) {
-        return false;
-    }
-
-    // Wait for a discovery event.
-    while (m_discovery_in_process) {
-        MICROPY_VM_HOOK_LOOP;
-    }
-    return m_discovery_successful;
-}
-
-STATIC bool discover_next_descriptors(bleio_central_obj_t *self, bleio_characteristic_obj_t *characteristic, uint16_t start_handle, uint16_t end_handle) {
-    m_desc_discovery_characteristic = characteristic;
-
-    ble_gattc_handle_range_t handle_range;
-    handle_range.start_handle = start_handle;
-    handle_range.end_handle = end_handle;
-
-    m_discovery_successful = false;
-    m_discovery_in_process = true;
-
-    uint32_t err_code = sd_ble_gattc_descriptors_discover(self->conn_handle, &handle_range);
-    if (err_code != NRF_SUCCESS) {
-        return false;
-    }
-
-    // Wait for a discovery event.
-    while (m_discovery_in_process) {
-        MICROPY_VM_HOOK_LOOP;
-    }
-    return m_discovery_successful;
-}
-
-STATIC void on_primary_srv_discovery_rsp(ble_gattc_evt_prim_srvc_disc_rsp_t *response, bleio_central_obj_t *central) {
-    for (size_t i = 0; i < response->count; ++i) {
-        ble_gattc_service_t *gattc_service = &response->services[i];
-
-        bleio_service_obj_t *service = m_new_obj(bleio_service_obj_t);
-        service->base.type = &bleio_service_type;
-
-        // Initialize several fields at once.
-        common_hal_bleio_service_construct(service, NULL, mp_obj_new_list(0, NULL), false);
-
-        service->device = MP_OBJ_FROM_PTR(central);
-        service->start_handle = gattc_service->handle_range.start_handle;
-        service->end_handle = gattc_service->handle_range.end_handle;
-        service->handle = gattc_service->handle_range.start_handle;
-
-        if (gattc_service->uuid.type != BLE_UUID_TYPE_UNKNOWN) {
-            // Known service UUID.
-            bleio_uuid_obj_t *uuid = m_new_obj(bleio_uuid_obj_t);
-            uuid->base.type = &bleio_uuid_type;
-            bleio_uuid_construct_from_nrf_ble_uuid(uuid, &gattc_service->uuid);
-            service->uuid = uuid;
-            service->device = MP_OBJ_FROM_PTR(central);
-        } else {
-            // The discovery response contained a 128-bit UUID that has not yet been registered with the
-            // softdevice via sd_ble_uuid_vs_add(). We need to fetch the 128-bit value and register it.
-            // For now, just set the UUID to NULL.
-            service->uuid = NULL;
-        }
-
-        mp_obj_list_append(central->service_list, service);
-    }
-
-    if (response->count > 0) {
-        m_discovery_successful = true;
-    }
-    m_discovery_in_process = false;
-}
-
-STATIC void on_char_discovery_rsp(ble_gattc_evt_char_disc_rsp_t *response, bleio_central_obj_t *central) {
-    for (size_t i = 0; i < response->count; ++i) {
-        ble_gattc_char_t *gattc_char = &response->chars[i];
-
-        bleio_characteristic_obj_t *characteristic = m_new_obj(bleio_characteristic_obj_t);
-        characteristic->base.type = &bleio_characteristic_type;
-
-        characteristic->descriptor_list = mp_obj_new_list(0, NULL);
-
-        bleio_uuid_obj_t *uuid = NULL;
-
-        if (gattc_char->uuid.type != BLE_UUID_TYPE_UNKNOWN) {
-            // Known characteristic UUID.
-            uuid = m_new_obj(bleio_uuid_obj_t);
-            uuid->base.type = &bleio_uuid_type;
-            bleio_uuid_construct_from_nrf_ble_uuid(uuid, &gattc_char->uuid);
-        } else {
-            // The discovery response contained a 128-bit UUID that has not yet been registered with the
-            // softdevice via sd_ble_uuid_vs_add(). We need to fetch the 128-bit value and register it.
-            // For now, just leave the UUID as NULL.
-        }
-
-        bleio_characteristic_properties_t props;
-
-        props.broadcast = gattc_char->char_props.broadcast;
-        props.indicate = gattc_char->char_props.indicate;
-        props.notify = gattc_char->char_props.notify;
-        props.read = gattc_char->char_props.read;
-        props.write = gattc_char->char_props.write;
-        props.write_no_response = gattc_char->char_props.write_wo_resp;
-
-        // Call common_hal_bleio_characteristic_construct() to initalize some fields and set up evt handler.
-        common_hal_bleio_characteristic_construct(characteristic, uuid, props, mp_obj_new_list(0, NULL));
-        characteristic->handle = gattc_char->handle_value;
-        characteristic->service = m_char_discovery_service;
-
-        mp_obj_list_append(m_char_discovery_service->characteristic_list, MP_OBJ_FROM_PTR(characteristic));
-    }
-
-    if (response->count > 0) {
-        m_discovery_successful = true;
-    }
-    m_discovery_in_process = false;
-}
-
-STATIC void on_desc_discovery_rsp(ble_gattc_evt_desc_disc_rsp_t *response, bleio_central_obj_t *central) {
-    for (size_t i = 0; i < response->count; ++i) {
-        ble_gattc_desc_t *gattc_desc = &response->descs[i];
-
-        // Remember handles for certain well-known descriptors.
-        switch (gattc_desc->uuid.uuid) {
-            case DESCRIPTOR_UUID_CLIENT_CHARACTERISTIC_CONFIGURATION:
-                m_desc_discovery_characteristic->cccd_handle = gattc_desc->handle;
-                break;
-
-            case DESCRIPTOR_UUID_SERVER_CHARACTERISTIC_CONFIGURATION:
-                m_desc_discovery_characteristic->sccd_handle = gattc_desc->handle;
-                break;
-
-            case DESCRIPTOR_UUID_CHARACTERISTIC_USER_DESCRIPTION:
-                m_desc_discovery_characteristic->user_desc_handle = gattc_desc->handle;
-                break;
-
-            default:
-                // TODO: sd_ble_gattc_descriptors_discover() can return things that are not descriptors,
-                // so ignore those.
-                // https://devzone.nordicsemi.com/f/nordic-q-a/49500/sd_ble_gattc_descriptors_discover-is-returning-attributes-that-are-not-descriptors
-                break;
-        }
-
-        bleio_descriptor_obj_t *descriptor = m_new_obj(bleio_descriptor_obj_t);
-        descriptor->base.type = &bleio_descriptor_type;
-
-        bleio_uuid_obj_t *uuid = NULL;
-
-        if (gattc_desc->uuid.type != BLE_UUID_TYPE_UNKNOWN) {
-            // Known descriptor UUID.
-            uuid = m_new_obj(bleio_uuid_obj_t);
-            uuid->base.type = &bleio_uuid_type;
-            bleio_uuid_construct_from_nrf_ble_uuid(uuid, &gattc_desc->uuid);
-        } else {
-            // The discovery response contained a 128-bit UUID that has not yet been registered with the
-            // softdevice via sd_ble_uuid_vs_add(). We need to fetch the 128-bit value and register it.
-            // For now, just leave the UUID as NULL.
-        }
-
-        common_hal_bleio_descriptor_construct(descriptor, uuid);
-        descriptor->handle = gattc_desc->handle;
-        descriptor->characteristic = m_desc_discovery_characteristic;
-
-        mp_obj_list_append(m_desc_discovery_characteristic->descriptor_list, MP_OBJ_FROM_PTR(descriptor));
-    }
-
-    if (response->count > 0) {
-        m_discovery_successful = true;
-    }
-    m_discovery_in_process = false;
-}
 
 STATIC void central_on_ble_evt(ble_evt_t *ble_evt, void *central_in) {
     bleio_central_obj_t *central = (bleio_central_obj_t*)central_in;
@@ -262,20 +54,6 @@ STATIC void central_on_ble_evt(ble_evt_t *ble_evt, void *central_in) {
 
         case BLE_GAP_EVT_DISCONNECTED:
             central->conn_handle = BLE_CONN_HANDLE_INVALID;
-            m_discovery_successful = false;
-            m_discovery_in_process = false;
-            break;
-
-        case BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP:
-            on_primary_srv_discovery_rsp(&ble_evt->evt.gattc_evt.params.prim_srvc_disc_rsp, central);
-            break;
-
-        case BLE_GATTC_EVT_CHAR_DISC_RSP:
-            on_char_discovery_rsp(&ble_evt->evt.gattc_evt.params.char_disc_rsp, central);
-            break;
-
-        case BLE_GATTC_EVT_DESC_DISC_RSP:
-            on_desc_discovery_rsp(&ble_evt->evt.gattc_evt.params.desc_disc_rsp, central);
             break;
 
         case BLE_GAP_EVT_SEC_PARAMS_REQUEST:
@@ -288,7 +66,6 @@ STATIC void central_on_ble_evt(ble_evt_t *ble_evt, void *central_in) {
             sd_ble_gap_conn_param_update(central->conn_handle, &request->conn_params);
             break;
         }
-
         default:
             // For debugging.
             // mp_printf(&mp_plat_print, "Unhandled central event: 0x%04x\n", ble_evt->header.evt_id);
@@ -299,12 +76,11 @@ STATIC void central_on_ble_evt(ble_evt_t *ble_evt, void *central_in) {
 void common_hal_bleio_central_construct(bleio_central_obj_t *self) {
     common_hal_bleio_adapter_set_enabled(true);
 
-    self->service_list = mp_obj_new_list(0, NULL);
-    self->gatt_role = GATT_ROLE_CLIENT;
+    self->remote_services_list = mp_obj_new_list(0, NULL);
     self->conn_handle = BLE_CONN_HANDLE_INVALID;
 }
 
-void common_hal_bleio_central_connect(bleio_central_obj_t *self, bleio_address_obj_t *address, mp_float_t timeout, mp_obj_t service_uuids) {
+void common_hal_bleio_central_connect(bleio_central_obj_t *self, bleio_address_obj_t *address, mp_float_t timeout) {
     common_hal_bleio_adapter_set_enabled(true);
     ble_drv_add_event_handler(central_on_ble_evt, self);
 
@@ -345,109 +121,6 @@ void common_hal_bleio_central_connect(bleio_central_obj_t *self, bleio_address_o
     if (self->conn_handle == BLE_CONN_HANDLE_INVALID) {
         mp_raise_OSError_msg(translate("Failed to connect: timeout"));
     }
-
-    // Connection successful.
-    // Now discover services on the remote peripheral.
-
-    if (service_uuids == mp_const_none) {
-
-        // List of service UUID's not given, so discover all available services.
-
-        uint16_t next_service_start_handle = BLE_GATT_HANDLE_START;
-
-        while (discover_next_services(self, next_service_start_handle, MP_OBJ_NULL)) {
-            // discover_next_services() appends to service_list.
-
-            // Get the most recently discovered service, and then ask for services
-            // whose handles start after the last attribute handle inside that service.
-            const bleio_service_obj_t *service =
-                MP_OBJ_TO_PTR(self->service_list->items[self->service_list->len - 1]);
-            next_service_start_handle = service->end_handle + 1;
-        }
-    } else {
-        mp_obj_iter_buf_t iter_buf;
-        mp_obj_t iterable = mp_getiter(service_uuids, &iter_buf);
-        mp_obj_t uuid_obj;
-        while ((uuid_obj = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
-            if (!MP_OBJ_IS_TYPE(uuid_obj, &bleio_uuid_type)) {
-                mp_raise_ValueError(translate("non-UUID found in service_uuids"));
-            }
-            bleio_uuid_obj_t *uuid = MP_OBJ_TO_PTR(uuid_obj);
-
-            ble_uuid_t nrf_uuid;
-            bleio_uuid_convert_to_nrf_ble_uuid(uuid, &nrf_uuid);
-
-            // Service might or might not be discovered; that's ok. Caller has to check
-            // Central.remote_services to find out.
-            // We only need to call this once for each service to discover.
-            discover_next_services(self, BLE_GATT_HANDLE_START, &nrf_uuid);
-        }
-    }
-
-
-    for (size_t service_idx = 0; service_idx < self->service_list->len; ++service_idx) {
-        bleio_service_obj_t *service = MP_OBJ_TO_PTR(self->service_list->items[service_idx]);
-
-        // Skip the service if it had an unknown (unregistered) UUID.
-        if (service->uuid == NULL) {
-            continue;
-        }
-
-        uint16_t next_char_start_handle = service->start_handle;
-
-        // Stop when we go past the end of the range of handles for this service or
-        // discovery call returns nothing.
-        // discover_next_characteristics() appends to the characteristic_list.
-        while (next_char_start_handle <= service->end_handle &&
-               discover_next_characteristics(self, service, next_char_start_handle)) {
-
-
-            // Get the most recently discovered characteristic, and then ask for characteristics
-            // whose handles start after the last attribute handle inside that characteristic.
-            const bleio_characteristic_obj_t *characteristic =
-                MP_OBJ_TO_PTR(service->characteristic_list->items[service->characteristic_list->len - 1]);
-            next_char_start_handle = characteristic->handle + 1;
-        }
-
-        // Got characteristics for this service. Now discover descriptors for each characteristic.
-        size_t char_list_len = service->characteristic_list->len;
-        for (size_t char_idx = 0; char_idx < char_list_len; ++char_idx) {
-            bleio_characteristic_obj_t *characteristic =
-                MP_OBJ_TO_PTR(service->characteristic_list->items[char_idx]);
-            const bool last_characteristic = char_idx == char_list_len - 1;
-            bleio_characteristic_obj_t *next_characteristic = last_characteristic
-                ? NULL
-                : MP_OBJ_TO_PTR(service->characteristic_list->items[char_idx + 1]);
-
-            // Skip the characteristic if it had an unknown (unregistered) UUID.
-            if (characteristic->uuid == NULL) {
-                continue;
-            }
-
-            uint16_t next_desc_start_handle = characteristic->handle + 1;
-
-            // Don't run past the end of this service or the beginning of the next characteristic.
-            uint16_t next_desc_end_handle = next_characteristic == NULL
-                ? service->end_handle
-                : next_characteristic->handle - 1;
-
-            // Stop when we go past the end of the range of handles for this service or
-            // discovery call returns nothing.
-            // discover_next_descriptors() appends to the descriptor_list.
-            while (next_desc_start_handle <= service->end_handle &&
-                   next_desc_start_handle < next_desc_end_handle &&
-                   discover_next_descriptors(self, characteristic,
-                                             next_desc_start_handle, next_desc_end_handle)) {
-
-                // Get the most recently discovered descriptor, and then ask for descriptors
-                // whose handles start after that descriptor's handle.
-                const bleio_descriptor_obj_t *descriptor =
-                    MP_OBJ_TO_PTR(characteristic->descriptor_list->items[characteristic->descriptor_list->len - 1]);
-                next_desc_start_handle = descriptor->handle + 1;
-            }
-        }
-
-    }
 }
 
 void common_hal_bleio_central_disconnect(bleio_central_obj_t *self) {
@@ -458,6 +131,15 @@ bool common_hal_bleio_central_get_connected(bleio_central_obj_t *self) {
     return self->conn_handle != BLE_CONN_HANDLE_INVALID;
 }
 
+mp_obj_tuple_t *common_hal_bleio_central_discover_remote_services(bleio_central_obj_t *self, mp_obj_t service_uuids_whitelist) {
+    common_hal_bleio_device_discover_remote_services(MP_OBJ_FROM_PTR(self), service_uuids_whitelist);
+    // Convert to a tuple and then clear the list so the callee will take ownership.
+    mp_obj_tuple_t *services_tuple = mp_obj_new_tuple(self->remote_services_list->len,
+                                                      self->remote_services_list->items);
+    mp_obj_list_clear(self->remote_services_list);
+    return services_tuple;
+}
+
 mp_obj_list_t *common_hal_bleio_central_get_remote_services(bleio_central_obj_t *self) {
-    return self->service_list;
+    return self->remote_services_list;
 }
diff --git a/ports/nrf/common-hal/bleio/Central.h b/ports/nrf/common-hal/bleio/Central.h
index ac1670088..b7a9050b8 100644
--- a/ports/nrf/common-hal/bleio/Central.h
+++ b/ports/nrf/common-hal/bleio/Central.h
@@ -31,15 +31,14 @@
 #include <stdbool.h>
 
 #include "py/objlist.h"
-#include "shared-module/bleio/__init__.h"
 #include "shared-module/bleio/Address.h"
 
 typedef struct {
     mp_obj_base_t base;
-    gatt_role_t gatt_role;
     volatile bool waiting_to_connect;
     volatile uint16_t conn_handle;
-    mp_obj_list_t *service_list;
+    // Services discovered after connecting to a remote peripheral.
+    mp_obj_list_t *remote_services_list;
 } bleio_central_obj_t;
 
 #endif // MICROPY_INCLUDED_SHARED_MODULE_BLEIO_CENTRAL_H
diff --git a/ports/nrf/common-hal/bleio/Characteristic.c b/ports/nrf/common-hal/bleio/Characteristic.c
index 17417a5e6..f8b6ce06c 100644
--- a/ports/nrf/common-hal/bleio/Characteristic.c
+++ b/ports/nrf/common-hal/bleio/Characteristic.c
@@ -25,29 +25,23 @@
  * THE SOFTWARE.
  */
 
-#include <string.h>
-#include <stdio.h>
-
-#include "ble_drv.h"
-#include "ble_gatts.h"
-#include "nrf_soc.h"
-
 #include "py/runtime.h"
-#include "common-hal/bleio/__init__.h"
-#include "common-hal/bleio/Characteristic.h"
 
-STATIC volatile bleio_characteristic_obj_t *m_read_characteristic;
+#include "shared-bindings/bleio/__init__.h"
+#include "shared-bindings/bleio/Characteristic.h"
+#include "shared-bindings/bleio/Descriptor.h"
+#include "shared-bindings/bleio/Service.h"
 
-STATIC uint16_t get_cccd(bleio_characteristic_obj_t *characteristic) {
-    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(characteristic->service->device);
+static volatile bleio_characteristic_obj_t *m_read_characteristic;
+
+STATIC uint16_t characteristic_get_cccd(uint16_t cccd_handle, uint16_t conn_handle) {
     uint16_t cccd;
     ble_gatts_value_t value = {
         .p_value = (uint8_t*) &cccd,
         .len = 2,
     };
 
-    const uint32_t err_code = sd_ble_gatts_value_get(conn_handle, characteristic->cccd_handle, &value);
-
+    const uint32_t err_code = sd_ble_gatts_value_get(conn_handle, cccd_handle, &value);
 
     if (err_code == BLE_ERROR_GATTS_SYS_ATTR_MISSING) {
         // CCCD is not set, so say that neither Notify nor Indicate is enabled.
@@ -59,64 +53,39 @@ STATIC uint16_t get_cccd(bleio_characteristic_obj_t *characteristic) {
     return cccd;
 }
 
-STATIC void gatts_read(bleio_characteristic_obj_t *characteristic) {
-    // This might be BLE_CONN_HANDLE_INVALID if we're not connected, but that's OK, because
-    // we can still read and write the local value.
-    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(characteristic->service->device);
-
-    mp_buffer_info_t bufinfo;
-    ble_gatts_value_t gatts_value = {
-        .p_value = NULL,
-        .len = 0,
-    };
-
-    // Read once to find out what size buffer we need, then read again to fill buffer.
-
-    uint32_t err_code = sd_ble_gatts_value_get(conn_handle, characteristic->handle, &gatts_value);
-    if (err_code == NRF_SUCCESS) {
-        characteristic->value_data = mp_obj_new_bytearray_of_zeros(gatts_value.len);
-        mp_get_buffer_raise(characteristic->value_data, &bufinfo, MP_BUFFER_WRITE);
-        gatts_value.p_value = bufinfo.buf;
-
-        // Read again, with the correct size of buffer.
-        err_code = sd_ble_gatts_value_get(conn_handle, characteristic->handle, &gatts_value);
-    }
-
-    if (err_code != NRF_SUCCESS) {
-        mp_raise_OSError_msg_varg(translate("Failed to read gatts value, err 0x%04x"), err_code);
-    }
-}
-
+STATIC void characteristic_on_gattc_read_rsp_evt(ble_evt_t *ble_evt, void *param) {
+    switch (ble_evt->header.evt_id) {
 
-STATIC void gatts_write(bleio_characteristic_obj_t *characteristic, mp_buffer_info_t *bufinfo) {
-    // This might be BLE_CONN_HANDLE_INVALID if we're not conected, but that's OK, because
-    // we can still read and write the local value.
-    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(characteristic->service->device);
+        // More events may be handled later, so keep this as a switch.
 
-    ble_gatts_value_t gatts_value = {
-        .p_value = bufinfo->buf,
-        .len = bufinfo->len,
-    };
+        case BLE_GATTC_EVT_READ_RSP: {
+            ble_gattc_evt_read_rsp_t *response = &ble_evt->evt.gattc_evt.params.read_rsp;
+            if (m_read_characteristic) {
+                m_read_characteristic->value = mp_obj_new_bytearray(response->len, response->data);
+            }
+            // Indicate to busy-wait loop that we've read the attribute value.
+            m_read_characteristic = NULL;
+            break;
+        }
 
-    const uint32_t err_code = sd_ble_gatts_value_set(conn_handle, characteristic->handle, &gatts_value);
-    if (err_code != NRF_SUCCESS) {
-        mp_raise_OSError_msg_varg(translate("Failed to write gatts value, err 0x%04x"), err_code);
+        default:
+            // For debugging.
+            // mp_printf(&mp_plat_print, "Unhandled characteristic event: 0x%04x\n", ble_evt->header.evt_id);
+            break;
     }
 }
 
-STATIC void gatts_notify_indicate(bleio_characteristic_obj_t *characteristic, mp_buffer_info_t *bufinfo, uint16_t hvx_type) {
+STATIC void characteristic_gatts_notify_indicate(uint16_t handle, uint16_t conn_handle, mp_buffer_info_t *bufinfo, uint16_t hvx_type) {
     uint16_t hvx_len = bufinfo->len;
 
     ble_gatts_hvx_params_t hvx_params = {
-        .handle = characteristic->handle,
+        .handle = handle,
         .type = hvx_type,
         .offset = 0,
         .p_len = &hvx_len,
         .p_data = bufinfo->buf,
     };
 
-    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(characteristic->service->device);
-
     while (1) {
         const uint32_t err_code = sd_ble_gatts_hvx(conn_handle, &hvx_params);
         if (err_code == NRF_SUCCESS) {
@@ -132,21 +101,17 @@ STATIC void gatts_notify_indicate(bleio_characteristic_obj_t *characteristic, mp
         // Some real error has occurred.
         mp_raise_OSError_msg_varg(translate("Failed to notify or indicate attribute value, err 0x%04x"), err_code);
     }
-
-}
-
-STATIC void check_connected(uint16_t conn_handle) {
-    if (conn_handle == BLE_CONN_HANDLE_INVALID) {
-        mp_raise_OSError_msg(translate("Not connected"));
-    }
 }
 
-STATIC void gattc_read(bleio_characteristic_obj_t *characteristic) {
+STATIC void characteristic_gattc_read(bleio_characteristic_obj_t *characteristic) {
     const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(characteristic->service->device);
-    check_connected(conn_handle);
+    common_hal_bleio_check_connected(conn_handle);
 
+    // Set to NULL in event loop after event.
     m_read_characteristic = characteristic;
 
+    ble_drv_add_event_handler(characteristic_on_gattc_read_rsp_evt, characteristic);
+
     const uint32_t err_code = sd_ble_gattc_read(conn_handle, characteristic->handle, 0);
     if (err_code != NRF_SUCCESS) {
         mp_raise_OSError_msg_varg(translate("Failed to read attribute value, err 0x%04x"), err_code);
@@ -155,126 +120,102 @@ STATIC void gattc_read(bleio_characteristic_obj_t *characteristic) {
     while (m_read_characteristic != NULL) {
         MICROPY_VM_HOOK_LOOP;
     }
-}
-
-STATIC void gattc_write(bleio_characteristic_obj_t *characteristic, mp_buffer_info_t *bufinfo) {
-    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(characteristic->service->device);
-    check_connected(conn_handle);
-
-    ble_gattc_write_params_t write_params = {
-        .write_op = characteristic->props.write_no_response ? BLE_GATT_OP_WRITE_CMD : BLE_GATT_OP_WRITE_REQ,
-        .handle = characteristic->handle,
-        .p_value = bufinfo->buf,
-        .len = bufinfo->len,
-    };
-
-    while (1) {
-        uint32_t err_code = sd_ble_gattc_write(conn_handle, &write_params);
-        if (err_code == NRF_SUCCESS) {
-            break;
-        }
-
-        // Write with response will return NRF_ERROR_BUSY if the response has not been received.
-        // Write without reponse will return NRF_ERROR_RESOURCES if too many writes are pending.
-        if (err_code == NRF_ERROR_BUSY || err_code == NRF_ERROR_RESOURCES) {
-            // We could wait for an event indicating the write is complete, but just retrying is easier.
-            MICROPY_VM_HOOK_LOOP;
-            continue;
-        }
-
-        // Some real error occurred.
-        mp_raise_OSError_msg_varg(translate("Failed to write attribute value, err 0x%04x"), err_code);
-    }
 
+    ble_drv_remove_event_handler(characteristic_on_gattc_read_rsp_evt, characteristic);
 }
 
-STATIC void characteristic_on_ble_evt(ble_evt_t *ble_evt, void *param) {
-    switch (ble_evt->header.evt_id) {
-
-        // More events may be handled later, so keep this as a switch.
-
-        case BLE_GATTC_EVT_READ_RSP: {
-            ble_gattc_evt_read_rsp_t *response = &ble_evt->evt.gattc_evt.params.read_rsp;
-            m_read_characteristic->value_data = mp_obj_new_bytearray(response->len, response->data);
-            // Indicate to busy-wait loop that we've read the characteristic.
-            m_read_characteristic = NULL;
-            break;
-        }
-
-            // For debugging.
-        default:
-            // mp_printf(&mp_plat_print, "Unhandled characteristic event: 0x%04x\n", ble_evt->header.evt_id);
-            break;
-    }
-
-}
-
-void common_hal_bleio_characteristic_construct(bleio_characteristic_obj_t *self, bleio_uuid_obj_t *uuid, bleio_characteristic_properties_t props, mp_obj_list_t *descriptor_list) {
-    self->service = mp_const_none;
+void common_hal_bleio_characteristic_construct(bleio_characteristic_obj_t *self, bleio_uuid_obj_t *uuid, bleio_characteristic_properties_t props, bleio_attribute_security_mode_t read_perm, bleio_attribute_security_mode_t write_perm, mp_int_t max_length, bool fixed_length, mp_obj_list_t *descriptor_list) {
+    self->service = MP_OBJ_NULL;
     self->uuid = uuid;
-    self->value_data = mp_const_none;
+    self->value = mp_const_empty_bytes;
+    self->handle = BLE_GATT_HANDLE_INVALID;
     self->props = props;
+    self->read_perm = read_perm;
+    self->write_perm = write_perm;
     self->descriptor_list = descriptor_list;
-    self->handle = BLE_GATT_HANDLE_INVALID;
 
-    ble_drv_add_event_handler(characteristic_on_ble_evt, self);
+    const mp_int_t max_length_max = fixed_length ? BLE_GATTS_FIX_ATTR_LEN_MAX : BLE_GATTS_VAR_ATTR_LEN_MAX;
+    if (max_length < 0 || max_length > max_length_max) {
+        mp_raise_ValueError_varg(translate("max_length must be 0-%d when fixed_length is %s"),
+                                 max_length_max, fixed_length ? "True" : "False");
+    }
+    self->max_length = max_length;
+    self->fixed_length = fixed_length;
+
+    for (size_t descriptor_idx = 0; descriptor_idx < descriptor_list->len; ++descriptor_idx) {
+        bleio_descriptor_obj_t *descriptor =
+            MP_OBJ_TO_PTR(descriptor_list->items[descriptor_idx]);
+        descriptor->characteristic = self;
+    }
 }
 
 mp_obj_list_t *common_hal_bleio_characteristic_get_descriptor_list(bleio_characteristic_obj_t *self) {
     return self->descriptor_list;
 }
 
+bleio_service_obj_t *common_hal_bleio_characteristic_get_service(bleio_characteristic_obj_t *self) {
+    return self->service;
+}
+
 mp_obj_t common_hal_bleio_characteristic_get_value(bleio_characteristic_obj_t *self) {
-    switch (common_hal_bleio_device_get_gatt_role(self->service->device)) {
-    case GATT_ROLE_CLIENT:
-        gattc_read(self);
-        break;
-
-    case GATT_ROLE_SERVER:
-        gatts_read(self);
-        break;
-
-    default:
-        mp_raise_RuntimeError(translate("bad GATT role"));
-        break;
+    // Do GATT operations only if this characteristic has been added to a registered service.
+    if (self->handle != BLE_GATT_HANDLE_INVALID) {
+        uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(self->service->device);
+        if (common_hal_bleio_service_get_is_remote(self->service)) {
+            // self->value is set by evt handler.
+            characteristic_gattc_read(self);
+        } else {
+            self->value = common_hal_bleio_gatts_read(self->handle, conn_handle);
+        }
     }
 
-    return self->value_data;
+    return self->value;
 }
 
 void common_hal_bleio_characteristic_set_value(bleio_characteristic_obj_t *self, mp_buffer_info_t *bufinfo) {
-    bool sent = false;
-    uint16_t cccd = 0;
+    // Do GATT operations only if this characteristic has been added to a registered service.
+    if (self->handle != BLE_GATT_HANDLE_INVALID) {
+        uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(self->service->device);
+
+        if (common_hal_bleio_service_get_is_remote(self->service)) {
+            // Last argument is true if write-no-reponse desired.
+            common_hal_bleio_gattc_write(self->handle, conn_handle, bufinfo,
+                                         (self->props & CHAR_PROP_WRITE_NO_RESPONSE));
+        } else {
+            if (self->fixed_length && bufinfo->len != self->max_length) {
+                mp_raise_ValueError(translate("Value length  required fixed length"));
+            }
+            if (bufinfo->len > self->max_length) {
+                mp_raise_ValueError(translate("Value length > max_length"));
+            }
+
+            bool sent = false;
+            uint16_t cccd = 0;
 
-    switch (common_hal_bleio_device_get_gatt_role(self->service->device)) {
-        case GATT_ROLE_SERVER:
-            if (self->props.notify || self->props.indicate) {
-                cccd = get_cccd(self);
+            const bool notify = self->props & CHAR_PROP_NOTIFY;
+            const bool indicate = self->props & CHAR_PROP_INDICATE;
+            if (notify | indicate) {
+                cccd = characteristic_get_cccd(self->cccd_handle, conn_handle);
             }
+
             // It's possible that both notify and indicate are set.
-            if (self->props.notify && (cccd & BLE_GATT_HVX_NOTIFICATION)) {
-                gatts_notify_indicate(self, bufinfo, BLE_GATT_HVX_NOTIFICATION);
+            if (notify && (cccd & BLE_GATT_HVX_NOTIFICATION)) {
+                characteristic_gatts_notify_indicate(self->handle, conn_handle, bufinfo, BLE_GATT_HVX_NOTIFICATION);
                 sent = true;
             }
-            if (self->props.indicate && (cccd & BLE_GATT_HVX_INDICATION)) {
-                gatts_notify_indicate(self, bufinfo, BLE_GATT_HVX_INDICATION);
+            if (indicate && (cccd & BLE_GATT_HVX_INDICATION)) {
+                characteristic_gatts_notify_indicate(self->handle, conn_handle, bufinfo, BLE_GATT_HVX_INDICATION);
                 sent = true;
             }
+
             if (!sent) {
-                gatts_write(self, bufinfo);
+                common_hal_bleio_gatts_write(self->handle, conn_handle, bufinfo);
             }
-            break;
-
-        case GATT_ROLE_CLIENT:
-            gattc_write(self, bufinfo);
-            break;
-
-        default:
-            mp_raise_RuntimeError(translate("bad GATT role"));
-            break;
+        }
     }
-}
 
+    self->value = mp_obj_new_bytes(bufinfo->buf, bufinfo->len);
+}
 
 bleio_uuid_obj_t *common_hal_bleio_characteristic_get_uuid(bleio_characteristic_obj_t *self) {
     return self->uuid;
@@ -289,18 +230,17 @@ void common_hal_bleio_characteristic_set_cccd(bleio_characteristic_obj_t *self,
         mp_raise_ValueError(translate("No CCCD for this Characteristic"));
     }
 
-    if (common_hal_bleio_device_get_gatt_role(self->service->device) != GATT_ROLE_CLIENT) {
-        mp_raise_ValueError(translate("Can't set CCCD for local Characteristic"));
+    if (!common_hal_bleio_service_get_is_remote(self->service)) {
+        mp_raise_ValueError(translate("Can't set CCCD on local Characteristic"));
     }
 
+    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(self->service->device);
+    common_hal_bleio_check_connected(conn_handle);
+
     uint16_t cccd_value =
         (notify ? BLE_GATT_HVX_NOTIFICATION : 0) |
         (indicate ? BLE_GATT_HVX_INDICATION : 0);
 
-    const uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(self->service->device);
-    check_connected(conn_handle);
-
-
     ble_gattc_write_params_t write_params = {
         .write_op = BLE_GATT_OP_WRITE_REQ,
         .handle = self->cccd_handle,
diff --git a/ports/nrf/common-hal/bleio/Characteristic.h b/ports/nrf/common-hal/bleio/Characteristic.h
index 7cb227596..fb6a4c6ce 100644
--- a/ports/nrf/common-hal/bleio/Characteristic.h
+++ b/ports/nrf/common-hal/bleio/Characteristic.h
@@ -28,17 +28,23 @@
 #ifndef MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_CHARACTERISTIC_H
 #define MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_CHARACTERISTIC_H
 
+#include "shared-bindings/bleio/Attribute.h"
+#include "shared-module/bleio/Characteristic.h"
 #include "common-hal/bleio/Service.h"
 #include "common-hal/bleio/UUID.h"
-#include "shared-module/bleio/Characteristic.h"
 
 typedef struct {
     mp_obj_base_t base;
+    // Will be MP_OBJ_NULL before being assigned to a Service.
     bleio_service_obj_t *service;
     bleio_uuid_obj_t *uuid;
-    volatile mp_obj_t value_data;
+    mp_obj_t value;
+    uint16_t max_length;
+    bool fixed_length;
     uint16_t handle;
     bleio_characteristic_properties_t props;
+    bleio_attribute_security_mode_t read_perm;
+    bleio_attribute_security_mode_t write_perm;
     mp_obj_list_t *descriptor_list;
     uint16_t user_desc_handle;
     uint16_t cccd_handle;
diff --git a/ports/nrf/common-hal/bleio/CharacteristicBuffer.c b/ports/nrf/common-hal/bleio/CharacteristicBuffer.c
index 59eaaf02b..a6d834d7d 100644
--- a/ports/nrf/common-hal/bleio/CharacteristicBuffer.c
+++ b/ports/nrf/common-hal/bleio/CharacteristicBuffer.c
@@ -37,7 +37,7 @@
 
 #include "tick.h"
 
-#include "common-hal/bleio/__init__.h"
+#include "shared-bindings/bleio/__init__.h"
 #include "common-hal/bleio/CharacteristicBuffer.h"
 
 STATIC void write_to_ringbuf(bleio_characteristic_buffer_obj_t *self, uint8_t *data, uint16_t len) {
diff --git a/ports/nrf/common-hal/bleio/Descriptor.c b/ports/nrf/common-hal/bleio/Descriptor.c
index 005af6eaa..2a2019277 100644
--- a/ports/nrf/common-hal/bleio/Descriptor.c
+++ b/ports/nrf/common-hal/bleio/Descriptor.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Dan Halbert for Adafruit Industries
+ * Copyright (c) 2019 Dan Halbert for Adafruit Industries
  * Copyright (c) 2018 Artur Pacholec
  * Copyright (c) 2016 Glenn Ruben Bakke
  *
@@ -26,17 +26,116 @@
  * THE SOFTWARE.
  */
 
-#include "common-hal/bleio/Descriptor.h"
+#include "py/runtime.h"
+
+#include "shared-bindings/bleio/__init__.h"
+#include "shared-bindings/bleio/Descriptor.h"
+#include "shared-bindings/bleio/Service.h"
 #include "shared-bindings/bleio/UUID.h"
 
-void common_hal_bleio_descriptor_construct(bleio_descriptor_obj_t *self, bleio_uuid_obj_t *uuid) {
+static volatile bleio_descriptor_obj_t *m_read_descriptor;
+
+void common_hal_bleio_descriptor_construct(bleio_descriptor_obj_t *self, bleio_uuid_obj_t *uuid, bleio_attribute_security_mode_t read_perm, bleio_attribute_security_mode_t write_perm, mp_int_t max_length, bool fixed_length) {
+    self->characteristic = MP_OBJ_NULL;
     self->uuid = uuid;
-}
+    self->value = mp_const_empty_bytes;
+    self->handle = BLE_GATT_HANDLE_INVALID;
+    self->read_perm = read_perm;
+    self->write_perm = write_perm;
 
-mp_int_t common_hal_bleio_descriptor_get_handle(bleio_descriptor_obj_t *self) {
-    return self->handle;
+    const mp_int_t max_length_max = fixed_length ? BLE_GATTS_FIX_ATTR_LEN_MAX : BLE_GATTS_VAR_ATTR_LEN_MAX;
+    if (max_length < 0 || max_length > max_length_max) {
+        mp_raise_ValueError_varg(translate("max_length must be 0-%d when fixed_length is %s"),
+                                 max_length_max, fixed_length ? "True" : "False");
+    }
+    self->max_length = max_length;
+    self->fixed_length = fixed_length;
 }
 
 bleio_uuid_obj_t *common_hal_bleio_descriptor_get_uuid(bleio_descriptor_obj_t *self) {
     return self->uuid;
 }
+
+bleio_characteristic_obj_t *common_hal_bleio_descriptor_get_characteristic(bleio_descriptor_obj_t *self) {
+    return self->characteristic;
+}
+
+STATIC void descriptor_on_gattc_read_rsp_evt(ble_evt_t *ble_evt, void *param) {
+    switch (ble_evt->header.evt_id) {
+
+        // More events may be handled later, so keep this as a switch.
+
+        case BLE_GATTC_EVT_READ_RSP: {
+            ble_gattc_evt_read_rsp_t *response = &ble_evt->evt.gattc_evt.params.read_rsp;
+            if (m_read_descriptor) {
+                m_read_descriptor->value = mp_obj_new_bytearray(response->len, response->data);
+            }
+            // Indicate to busy-wait loop that we've read the attribute value.
+            m_read_descriptor = NULL;
+            break;
+        }
+
+        default:
+            // For debugging.
+            // mp_printf(&mp_plat_print, "Unhandled descriptor event: 0x%04x\n", ble_evt->header.evt_id);
+            break;
+    }
+}
+
+STATIC void descriptor_gattc_read(bleio_descriptor_obj_t *descriptor) {
+    const uint16_t conn_handle =
+        common_hal_bleio_device_get_conn_handle(descriptor->characteristic->service->device);
+    common_hal_bleio_check_connected(conn_handle);
+
+    // Set to NULL in event loop after event.
+    m_read_descriptor = descriptor;
+
+    ble_drv_add_event_handler(descriptor_on_gattc_read_rsp_evt, descriptor);
+
+    const uint32_t err_code = sd_ble_gattc_read(conn_handle, descriptor->handle, 0);
+    if (err_code != NRF_SUCCESS) {
+        mp_raise_OSError_msg_varg(translate("Failed to read attribute value, err 0x%04x"), err_code);
+    }
+
+    while (m_read_descriptor != NULL) {
+        MICROPY_VM_HOOK_LOOP;
+    }
+
+    ble_drv_remove_event_handler(descriptor_on_gattc_read_rsp_evt, descriptor);
+}
+
+mp_obj_t common_hal_bleio_descriptor_get_value(bleio_descriptor_obj_t *self) {
+    // Do GATT operations only if this descriptor has been registered
+    if (self->handle != BLE_GATT_HANDLE_INVALID) {
+        if (common_hal_bleio_service_get_is_remote(self->characteristic->service)) {
+            descriptor_gattc_read(self);
+        } else {
+            self->value = common_hal_bleio_gatts_read(
+                self->handle, common_hal_bleio_device_get_conn_handle(self->characteristic->service->device));
+        }
+    }
+
+    return self->value;
+}
+
+void common_hal_bleio_descriptor_set_value(bleio_descriptor_obj_t *self, mp_buffer_info_t *bufinfo) {
+    // Do GATT operations only if this descriptor has been registered.
+    if (self->handle != BLE_GATT_HANDLE_INVALID) {
+        uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(self->characteristic->service->device);
+        if (common_hal_bleio_service_get_is_remote(self->characteristic->service)) {
+            // false means WRITE_REQ, not write-no-response
+            common_hal_bleio_gattc_write(self->handle, conn_handle, bufinfo, false);
+        } else {
+            if (self->fixed_length && bufinfo->len != self->max_length) {
+                mp_raise_ValueError(translate("Value length != required fixed length"));
+            }
+            if (bufinfo->len > self->max_length) {
+                mp_raise_ValueError(translate("Value length > max_length"));
+            }
+
+            common_hal_bleio_gatts_write(self->handle, conn_handle, bufinfo);
+        }
+    }
+
+    self->value = mp_obj_new_bytes(bufinfo->buf, bufinfo->len);
+}
diff --git a/ports/nrf/common-hal/bleio/Descriptor.h b/ports/nrf/common-hal/bleio/Descriptor.h
index b7af6a42f..6db4d7be3 100644
--- a/ports/nrf/common-hal/bleio/Descriptor.h
+++ b/ports/nrf/common-hal/bleio/Descriptor.h
@@ -30,14 +30,21 @@
 #define MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_DESCRIPTOR_H
 
 #include "py/obj.h"
-#include "common-hal/bleio/Characteristic.h"
+
+#include "shared-bindings/bleio/Characteristic.h"
 #include "common-hal/bleio/UUID.h"
 
 typedef struct {
     mp_obj_base_t base;
-    uint16_t handle;
+    // Will be MP_OBJ_NULL before being assigned to a Characteristic.
     bleio_characteristic_obj_t *characteristic;
     bleio_uuid_obj_t *uuid;
+    mp_obj_t value;
+    uint16_t max_length;
+    bool fixed_length;
+    uint16_t handle;
+    bleio_attribute_security_mode_t read_perm;
+    bleio_attribute_security_mode_t write_perm;
 } bleio_descriptor_obj_t;
 
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_DESCRIPTOR_H
diff --git a/ports/nrf/common-hal/bleio/Peripheral.c b/ports/nrf/common-hal/bleio/Peripheral.c
index 608bd1342..ed35516fc 100644
--- a/ports/nrf/common-hal/bleio/Peripheral.c
+++ b/ports/nrf/common-hal/bleio/Peripheral.c
@@ -36,12 +36,12 @@
 #include "py/objlist.h"
 #include "py/objstr.h"
 #include "py/runtime.h"
+#include "shared-bindings/bleio/__init__.h"
 #include "shared-bindings/bleio/Adapter.h"
 #include "shared-bindings/bleio/Characteristic.h"
 #include "shared-bindings/bleio/Peripheral.h"
 #include "shared-bindings/bleio/Service.h"
 #include "shared-bindings/bleio/UUID.h"
-#include "common-hal/bleio/Service.h"
 
 #define BLE_MIN_CONN_INTERVAL        MSEC_TO_UNITS(15, UNIT_0_625_MS)
 #define BLE_MAX_CONN_INTERVAL        MSEC_TO_UNITS(300, UNIT_0_625_MS)
@@ -52,6 +52,19 @@
 #define BLE_ADV_AD_TYPE_FIELD_SIZE  1
 #define BLE_AD_TYPE_FLAGS_DATA_SIZE 1
 
+static const ble_gap_sec_params_t pairing_sec_params = {
+    .bond = 0,  // TODO: add bonding
+    .mitm = 0,
+    .lesc = 0,
+    .keypress = 0,
+    .oob = 0,
+    .io_caps = BLE_GAP_IO_CAPS_NONE,
+    .min_key_size = 7,
+    .max_key_size = 16,
+    .kdist_own    = { .enc = 1, .id = 1},
+    .kdist_peer   = { .enc = 1, .id = 1},
+};
+
 STATIC void check_data_fit(size_t data_len) {
     if (data_len > BLE_GAP_ADV_SET_DATA_SIZE_MAX) {
         mp_raise_ValueError(translate("Data too large for advertisement packet"));
@@ -61,6 +74,9 @@ STATIC void check_data_fit(size_t data_len) {
 STATIC void peripheral_on_ble_evt(ble_evt_t *ble_evt, void *self_in) {
     bleio_peripheral_obj_t *self = (bleio_peripheral_obj_t*)self_in;
 
+    // For debugging.
+    // mp_printf(&mp_plat_print, "Peripheral event: 0x%04x\n", ble_evt->header.evt_id);
+
     switch (ble_evt->header.evt_id) {
         case BLE_GAP_EVT_CONNECTED: {
             // Central has connected.
@@ -89,10 +105,6 @@ STATIC void peripheral_on_ble_evt(ble_evt_t *ble_evt, void *self_in) {
             // Someday may handle timeouts or limit reached.
             break;
 
-        case BLE_GAP_EVT_SEC_PARAMS_REQUEST:
-            sd_ble_gap_sec_params_reply(self->conn_handle, BLE_GAP_SEC_STATUS_PAIRING_NOT_SUPP, NULL, NULL);
-            break;
-
         case BLE_GAP_EVT_CONN_PARAM_UPDATE_REQUEST: {
             ble_gap_evt_conn_param_update_request_t *request =
                 &ble_evt->evt.gap_evt.params.conn_param_update_request;
@@ -113,6 +125,47 @@ STATIC void peripheral_on_ble_evt(ble_evt_t *ble_evt, void *self_in) {
             sd_ble_gatts_sys_attr_set(self->conn_handle, NULL, 0, 0);
             break;
 
+        case BLE_GAP_EVT_SEC_PARAMS_REQUEST:
+            sd_ble_gap_sec_params_reply(self->conn_handle, BLE_GAP_SEC_STATUS_SUCCESS, &pairing_sec_params, NULL);
+            break;
+
+        case BLE_GAP_EVT_LESC_DHKEY_REQUEST:
+            // TODO for LESC pairing:
+            // sd_ble_gap_lesc_dhkey_reply(...);
+            break;
+
+        case BLE_GAP_EVT_AUTH_STATUS: {
+            // Pairing process completed
+            ble_gap_evt_auth_status_t* status = &ble_evt->evt.gap_evt.params.auth_status;
+            if (BLE_GAP_SEC_STATUS_SUCCESS == status->auth_status) {
+                // mp_printf(&mp_plat_print, "Pairing succeeded, status: 0x%04x\n", status->auth_status);
+                self->pair_status = PAIR_PAIRED;
+            } else {
+                // mp_printf(&mp_plat_print, "Pairing failed, status: 0x%04x\n", status->auth_status);
+                self->pair_status = PAIR_NOT_PAIRED;
+            }
+            break;
+        }
+
+        case BLE_GAP_EVT_CONN_SEC_UPDATE: {
+            ble_gap_conn_sec_t* conn_sec = &ble_evt->evt.gap_evt.params.conn_sec_update.conn_sec;
+            if (conn_sec->sec_mode.sm <= 1 && conn_sec->sec_mode.lv <= 1) {
+                // Security setup did not succeed:
+                // mode 0, level 0 means no access
+                // mode 1, level 1 means open link
+                // mode >=1 and/or level >=1 means encryption is set up
+                self->pair_status = PAIR_NOT_PAIRED;
+            } else {
+                // TODO: see Bluefruit lib
+                // if ( !bond_load_cccd(_role, _conn_hdl, _ediv) ) {
+                //    sd_ble_gatts_sys_attr_set(_conn_hdl, NULL, 0, 0);
+                // }
+                self->pair_status = PAIR_PAIRED;
+            }
+            break;
+        }
+
+
         default:
             // For debugging.
             // mp_printf(&mp_plat_print, "Unhandled peripheral event: 0x%04x\n", ble_evt->header.evt_id);
@@ -120,20 +173,22 @@ STATIC void peripheral_on_ble_evt(ble_evt_t *ble_evt, void *self_in) {
     }
 }
 
-void common_hal_bleio_peripheral_construct(bleio_peripheral_obj_t *self, mp_obj_list_t *service_list, mp_obj_t name) {
+void common_hal_bleio_peripheral_construct(bleio_peripheral_obj_t *self, mp_obj_list_t *services_list, mp_obj_t name) {
     common_hal_bleio_adapter_set_enabled(true);
 
-    self->service_list = service_list;
+    self->services_list = services_list;
+    // Used only for discovery when acting as a client.
+    self->remote_services_list = mp_obj_new_list(0, NULL);
     self->name = name;
 
-    self->gatt_role = GATT_ROLE_SERVER;
     self->conn_handle = BLE_CONN_HANDLE_INVALID;
     self->adv_handle = BLE_GAP_ADV_SET_HANDLE_NOT_SET;
+    self->pair_status = PAIR_NOT_PAIRED;
 
     // Add all the services.
 
-    for (size_t service_idx = 0; service_idx < service_list->len; ++service_idx) {
-        bleio_service_obj_t *service = MP_OBJ_TO_PTR(service_list->items[service_idx]);
+    for (size_t service_idx = 0; service_idx < services_list->len; ++service_idx) {
+        bleio_service_obj_t *service = MP_OBJ_TO_PTR(services_list->items[service_idx]);
 
         service->device = MP_OBJ_FROM_PTR(self);
 
@@ -156,8 +211,8 @@ void common_hal_bleio_peripheral_construct(bleio_peripheral_obj_t *self, mp_obj_
 }
 
 
-mp_obj_list_t *common_hal_bleio_peripheral_get_service_list(bleio_peripheral_obj_t *self) {
-    return self->service_list;
+mp_obj_list_t *common_hal_bleio_peripheral_get_services(bleio_peripheral_obj_t *self) {
+    return self->services_list;
 }
 
 bool common_hal_bleio_peripheral_get_connected(bleio_peripheral_obj_t *self) {
@@ -247,3 +302,30 @@ void common_hal_bleio_peripheral_stop_advertising(bleio_peripheral_obj_t *self)
 void common_hal_bleio_peripheral_disconnect(bleio_peripheral_obj_t *self) {
     sd_ble_gap_disconnect(self->conn_handle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
 }
+
+mp_obj_tuple_t *common_hal_bleio_peripheral_discover_remote_services(bleio_peripheral_obj_t *self, mp_obj_t service_uuids_whitelist) {
+    common_hal_bleio_device_discover_remote_services(MP_OBJ_FROM_PTR(self), service_uuids_whitelist);
+    // Convert to a tuple and then clear the list so the callee will take ownership.
+    mp_obj_tuple_t *services_tuple = mp_obj_new_tuple(self->remote_services_list->len,
+                                                      self->remote_services_list->items);
+    mp_obj_list_clear(self->remote_services_list);
+    return services_tuple;
+}
+
+void common_hal_bleio_peripheral_pair(bleio_peripheral_obj_t *self) {
+    self->pair_status = PAIR_WAITING;
+
+    uint32_t err_code = sd_ble_gap_authenticate(self->conn_handle, &pairing_sec_params);
+
+    if (err_code != NRF_SUCCESS) {
+        mp_raise_OSError_msg_varg(translate("Failed to start pairing, error 0x%04x"), err_code);
+    }
+
+    while (self->pair_status == PAIR_WAITING) {
+        MICROPY_VM_HOOK_LOOP;
+    }
+
+    if (self->pair_status == PAIR_NOT_PAIRED) {
+        mp_raise_OSError_msg(translate("Failed to pair"));
+    }
+}
diff --git a/ports/nrf/common-hal/bleio/Peripheral.h b/ports/nrf/common-hal/bleio/Peripheral.h
index 2a1251715..e75a1641a 100644
--- a/ports/nrf/common-hal/bleio/Peripheral.h
+++ b/ports/nrf/common-hal/bleio/Peripheral.h
@@ -35,22 +35,29 @@
 #include "py/obj.h"
 #include "py/objlist.h"
 
-#include "shared-module/bleio/__init__.h"
 #include "shared-module/bleio/Address.h"
 
+typedef enum {
+    PAIR_NOT_PAIRED,
+    PAIR_WAITING,
+    PAIR_PAIRED,
+} pair_status_t;
+
 typedef struct {
     mp_obj_base_t base;
     mp_obj_t name;
-    gatt_role_t gatt_role;
     volatile uint16_t conn_handle;
-    mp_obj_list_t *service_list;
+    // Services provided by this peripheral.
+    mp_obj_list_t *services_list;
+    // Remote services discovered when this peripheral is acting as a client.
+    mp_obj_list_t *remote_services_list;
     // The advertising data and scan response buffers are held by us, not by the SD, so we must
     // maintain them and not change it. If we need to change the contents during advertising,
     // there are tricks to get the SD to notice (see DevZone - TBS).
     uint8_t* advertising_data;
     uint8_t* scan_response_data;
     uint8_t adv_handle;
-
+    pair_status_t pair_status;
 } bleio_peripheral_obj_t;
 
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_PERIPHERAL_H
diff --git a/ports/nrf/common-hal/bleio/Service.c b/ports/nrf/common-hal/bleio/Service.c
index b6fcde827..a7a3a6db0 100644
--- a/ports/nrf/common-hal/bleio/Service.c
+++ b/ports/nrf/common-hal/bleio/Service.c
@@ -29,8 +29,8 @@
 #include "ble.h"
 #include "py/runtime.h"
 #include "common-hal/bleio/__init__.h"
-#include "common-hal/bleio/Characteristic.h"
 #include "shared-bindings/bleio/Characteristic.h"
+#include "shared-bindings/bleio/Descriptor.h"
 #include "shared-bindings/bleio/Service.h"
 #include "shared-bindings/bleio/Adapter.h"
 
@@ -39,6 +39,7 @@ void common_hal_bleio_service_construct(bleio_service_obj_t *self, bleio_uuid_ob
     self->handle = 0xFFFF;
     self->uuid = uuid;
     self->characteristic_list = characteristic_list;
+    self->is_remote = false;
     self->is_secondary = is_secondary;
 
     for (size_t characteristic_idx = 0; characteristic_idx < characteristic_list->len; ++characteristic_idx) {
@@ -46,7 +47,6 @@ void common_hal_bleio_service_construct(bleio_service_obj_t *self, bleio_uuid_ob
             MP_OBJ_TO_PTR(characteristic_list->items[characteristic_idx]);
         characteristic->service = self;
     }
-
 }
 
 bleio_uuid_obj_t *common_hal_bleio_service_get_uuid(bleio_service_obj_t *self) {
@@ -57,6 +57,10 @@ mp_obj_list_t *common_hal_bleio_service_get_characteristic_list(bleio_service_ob
     return self->characteristic_list;
 }
 
+bool common_hal_bleio_service_get_is_remote(bleio_service_obj_t *self) {
+    return self->is_remote;
+}
+
 bool common_hal_bleio_service_get_is_secondary(bleio_service_obj_t *self) {
     return self->is_secondary;
 }
@@ -68,13 +72,17 @@ void common_hal_bleio_service_add_all_characteristics(bleio_service_obj_t *self)
         bleio_characteristic_obj_t *characteristic =
             MP_OBJ_TO_PTR(self->characteristic_list->items[characteristic_idx]);
 
+        if (characteristic->handle != BLE_GATT_HANDLE_INVALID) {
+            mp_raise_ValueError(translate("Characteristic already in use by another Service."));
+        }
+
         ble_gatts_char_md_t char_md = {
-            .char_props.broadcast      = characteristic->props.broadcast,
-            .char_props.read           = characteristic->props.read,
-            .char_props.write_wo_resp  = characteristic->props.write_no_response,
-            .char_props.write          = characteristic->props.write,
-            .char_props.notify         = characteristic->props.notify,
-            .char_props.indicate       = characteristic->props.indicate,
+            .char_props.broadcast      = (characteristic->props & CHAR_PROP_BROADCAST) ? 1 : 0,
+            .char_props.read           = (characteristic->props & CHAR_PROP_READ) ? 1 : 0,
+            .char_props.write_wo_resp  = (characteristic->props & CHAR_PROP_WRITE_NO_RESPONSE) ? 1 : 0,
+            .char_props.write          = (characteristic->props & CHAR_PROP_WRITE) ? 1 : 0,
+            .char_props.notify         = (characteristic->props & CHAR_PROP_NOTIFY) ? 1 : 0,
+            .char_props.indicate       = (characteristic->props & CHAR_PROP_INDICATE) ? 1 : 0,
         };
 
         ble_gatts_attr_md_t cccd_md = {
@@ -88,39 +96,74 @@ void common_hal_bleio_service_add_all_characteristics(bleio_service_obj_t *self)
             char_md.p_cccd_md = &cccd_md;
         }
 
-        ble_uuid_t uuid;
-        bleio_uuid_convert_to_nrf_ble_uuid(characteristic->uuid, &uuid);
+        ble_uuid_t char_uuid;
+        bleio_uuid_convert_to_nrf_ble_uuid(characteristic->uuid, &char_uuid);
 
-        ble_gatts_attr_md_t attr_md = {
+        ble_gatts_attr_md_t char_attr_md = {
             .vloc = BLE_GATTS_VLOC_STACK,
-            .vlen = 1,
+            .vlen = !characteristic->fixed_length,
         };
 
-        BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);
-        BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
+        BLE_GAP_CONN_SEC_MODE_SET_OPEN(&char_attr_md.read_perm);
+        BLE_GAP_CONN_SEC_MODE_SET_OPEN(&char_attr_md.write_perm);
+
+        mp_buffer_info_t char_value_bufinfo;
+        mp_get_buffer_raise(characteristic->value, &char_value_bufinfo, MP_BUFFER_READ);
 
-        ble_gatts_attr_t attr_char_value = {
-            .p_uuid = &uuid,
-            .p_attr_md = &attr_md,
-            .init_len = sizeof(uint8_t),
-            .max_len = GATT_MAX_DATA_LENGTH,
+        ble_gatts_attr_t char_attr = {
+            .p_uuid = &char_uuid,
+            .p_attr_md = &char_attr_md,
+            .init_len = char_value_bufinfo.len,
+            .p_value = char_value_bufinfo.buf,
+            .init_offs = 0,
+            .max_len = characteristic->max_length,
         };
 
-        ble_gatts_char_handles_t handles;
+        ble_gatts_char_handles_t char_handles;
 
         uint32_t err_code;
-        err_code = sd_ble_gatts_characteristic_add(self->handle, &char_md, &attr_char_value, &handles);
+        err_code = sd_ble_gatts_characteristic_add(self->handle, &char_md, &char_attr, &char_handles);
         if (err_code != NRF_SUCCESS) {
             mp_raise_OSError_msg_varg(translate("Failed to add characteristic, err 0x%04x"), err_code);
         }
 
-        if (characteristic->handle != BLE_GATT_HANDLE_INVALID) {
-            mp_raise_ValueError(translate("Characteristic already in use by another Service."));
-        }
+        characteristic->user_desc_handle = char_handles.user_desc_handle;
+        characteristic->cccd_handle = char_handles.cccd_handle;
+        characteristic->sccd_handle = char_handles.sccd_handle;
+        characteristic->handle = char_handles.value_handle;
 
-        characteristic->user_desc_handle = handles.user_desc_handle;
-        characteristic->cccd_handle = handles.cccd_handle;
-        characteristic->sccd_handle = handles.sccd_handle;
-        characteristic->handle = handles.value_handle;
-    }
+        // Add the descriptors for this characteristic.
+        for (size_t descriptor_idx = 0; descriptor_idx < characteristic->descriptor_list->len; ++descriptor_idx) {
+            bleio_descriptor_obj_t *descriptor =
+                MP_OBJ_TO_PTR(characteristic->descriptor_list->items[descriptor_idx]);
+
+            ble_uuid_t desc_uuid;
+            bleio_uuid_convert_to_nrf_ble_uuid(descriptor->uuid, &desc_uuid);
+
+            ble_gatts_attr_md_t desc_attr_md = {
+                // Data passed is not in a permanent location and should be copied.
+                .vloc = BLE_GATTS_VLOC_STACK,
+                .vlen = !descriptor->fixed_length,
+            };
+
+            BLE_GAP_CONN_SEC_MODE_SET_OPEN(&desc_attr_md.read_perm);
+            BLE_GAP_CONN_SEC_MODE_SET_OPEN(&desc_attr_md.write_perm);
+
+            mp_buffer_info_t desc_value_bufinfo;
+            mp_get_buffer_raise(descriptor->value, &desc_value_bufinfo, MP_BUFFER_READ);
+
+            ble_gatts_attr_t desc_attr = {
+                .p_uuid = &desc_uuid,
+                .p_attr_md = &desc_attr_md,
+                .init_len = desc_value_bufinfo.len,
+                .p_value = desc_value_bufinfo.buf,
+                .init_offs = 0,
+                .max_len = descriptor->max_length,
+            };
+
+            err_code = sd_ble_gatts_descriptor_add(characteristic->handle, &desc_attr, &descriptor->handle);
+
+        } // loop over descriptors
+
+    } // loop over characteristics
 }
diff --git a/ports/nrf/common-hal/bleio/Service.h b/ports/nrf/common-hal/bleio/Service.h
index 583593fb8..03ac2bca8 100644
--- a/ports/nrf/common-hal/bleio/Service.h
+++ b/ports/nrf/common-hal/bleio/Service.h
@@ -35,6 +35,8 @@ typedef struct {
     mp_obj_base_t base;
     // Handle for this service.
     uint16_t handle;
+    // True if created during discovery.
+    bool is_remote;
     bool is_secondary;
     bleio_uuid_obj_t *uuid;
     // May be a Peripheral, Central, etc.
diff --git a/ports/nrf/common-hal/bleio/__init__.c b/ports/nrf/common-hal/bleio/__init__.c
index 2dba5780c..2e26ac07d 100644
--- a/ports/nrf/common-hal/bleio/__init__.c
+++ b/ports/nrf/common-hal/bleio/__init__.c
@@ -26,12 +26,24 @@
  * THE SOFTWARE.
  */
 
+#include "py/runtime.h"
 #include "shared-bindings/bleio/__init__.h"
 #include "shared-bindings/bleio/Adapter.h"
 #include "shared-bindings/bleio/Central.h"
+#include "shared-bindings/bleio/Characteristic.h"
+#include "shared-bindings/bleio/Descriptor.h"
 #include "shared-bindings/bleio/Peripheral.h"
+#include "shared-bindings/bleio/Service.h"
+#include "shared-bindings/bleio/UUID.h"
+
 #include "common-hal/bleio/__init__.h"
 
+static volatile bool m_discovery_in_process;
+static volatile bool m_discovery_successful;
+
+static bleio_service_obj_t *m_char_discovery_service;
+static bleio_characteristic_obj_t *m_desc_discovery_characteristic;
+
 // Turn off BLE on a reset or reload.
 void bleio_reset() {
     if (common_hal_bleio_adapter_get_enabled()) {
@@ -47,13 +59,9 @@ const super_adapter_obj_t common_hal_bleio_adapter_obj = {
     },
 };
 
-gatt_role_t common_hal_bleio_device_get_gatt_role(mp_obj_t device) {
-    if (MP_OBJ_IS_TYPE(device, &bleio_peripheral_type)) {
-        return ((bleio_peripheral_obj_t*) MP_OBJ_TO_PTR(device))->gatt_role;
-    } else if (MP_OBJ_IS_TYPE(device, &bleio_central_type)) {
-        return ((bleio_central_obj_t*) MP_OBJ_TO_PTR(device))->gatt_role;
-    } else {
-        return GATT_ROLE_NONE;
+void common_hal_bleio_check_connected(uint16_t conn_handle) {
+    if (conn_handle == BLE_CONN_HANDLE_INVALID) {
+        mp_raise_OSError_msg(translate("Not connected"));
     }
 }
 
@@ -63,6 +71,433 @@ uint16_t common_hal_bleio_device_get_conn_handle(mp_obj_t device) {
     } else if (MP_OBJ_IS_TYPE(device, &bleio_central_type)) {
         return ((bleio_central_obj_t*) MP_OBJ_TO_PTR(device))->conn_handle;
     } else {
-        return 0;
+        return BLE_CONN_HANDLE_INVALID;
+    }
+}
+
+mp_obj_list_t *common_hal_bleio_device_get_remote_services_list(mp_obj_t device) {
+    if (MP_OBJ_IS_TYPE(device, &bleio_peripheral_type)) {
+        return ((bleio_peripheral_obj_t*) MP_OBJ_TO_PTR(device))->remote_services_list;
+    } else if (MP_OBJ_IS_TYPE(device, &bleio_central_type)) {
+        return ((bleio_central_obj_t*) MP_OBJ_TO_PTR(device))->remote_services_list;
+    } else {
+        return NULL;
+    }
+}
+
+// service_uuid may be NULL, to discover all services.
+STATIC bool discover_next_services(mp_obj_t device, uint16_t start_handle, ble_uuid_t *service_uuid) {
+    m_discovery_successful = false;
+    m_discovery_in_process = true;
+
+    uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(device);
+    uint32_t err_code = sd_ble_gattc_primary_services_discover(conn_handle, start_handle, service_uuid);
+
+    if (err_code != NRF_SUCCESS) {
+        mp_raise_OSError_msg(translate("Failed to discover services"));
+    }
+
+    // Wait for a discovery event.
+    while (m_discovery_in_process) {
+        MICROPY_VM_HOOK_LOOP;
+    }
+    return m_discovery_successful;
+}
+
+STATIC bool discover_next_characteristics(mp_obj_t device, bleio_service_obj_t *service, uint16_t start_handle) {
+    m_char_discovery_service = service;
+
+    ble_gattc_handle_range_t handle_range;
+    handle_range.start_handle = start_handle;
+    handle_range.end_handle = service->end_handle;
+
+    m_discovery_successful = false;
+    m_discovery_in_process = true;
+
+    uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(device);
+    uint32_t err_code = sd_ble_gattc_characteristics_discover(conn_handle, &handle_range);
+    if (err_code != NRF_SUCCESS) {
+        return false;
+    }
+
+    // Wait for a discovery event.
+    while (m_discovery_in_process) {
+        MICROPY_VM_HOOK_LOOP;
+    }
+    return m_discovery_successful;
+}
+
+STATIC bool discover_next_descriptors(mp_obj_t device, bleio_characteristic_obj_t *characteristic, uint16_t start_handle, uint16_t end_handle) {
+    m_desc_discovery_characteristic = characteristic;
+
+    ble_gattc_handle_range_t handle_range;
+    handle_range.start_handle = start_handle;
+    handle_range.end_handle = end_handle;
+
+    m_discovery_successful = false;
+    m_discovery_in_process = true;
+
+    uint16_t conn_handle = common_hal_bleio_device_get_conn_handle(device);
+    uint32_t err_code = sd_ble_gattc_descriptors_discover(conn_handle, &handle_range);
+    if (err_code != NRF_SUCCESS) {
+        return false;
     }
+
+    // Wait for a discovery event.
+    while (m_discovery_in_process) {
+        MICROPY_VM_HOOK_LOOP;
+    }
+    return m_discovery_successful;
+}
+
+STATIC void on_primary_srv_discovery_rsp(ble_gattc_evt_prim_srvc_disc_rsp_t *response, mp_obj_t device) {
+    for (size_t i = 0; i < response->count; ++i) {
+        ble_gattc_service_t *gattc_service = &response->services[i];
+
+        bleio_service_obj_t *service = m_new_obj(bleio_service_obj_t);
+        service->base.type = &bleio_service_type;
+
+        // Initialize several fields at once.
+        common_hal_bleio_service_construct(service, NULL, mp_obj_new_list(0, NULL), false);
+
+        service->device = device;
+        service->is_remote = true;
+        service->start_handle = gattc_service->handle_range.start_handle;
+        service->end_handle = gattc_service->handle_range.end_handle;
+        service->handle = gattc_service->handle_range.start_handle;
+
+        if (gattc_service->uuid.type != BLE_UUID_TYPE_UNKNOWN) {
+            // Known service UUID.
+            bleio_uuid_obj_t *uuid = m_new_obj(bleio_uuid_obj_t);
+            uuid->base.type = &bleio_uuid_type;
+            bleio_uuid_construct_from_nrf_ble_uuid(uuid, &gattc_service->uuid);
+            service->uuid = uuid;
+        } else {
+            // The discovery response contained a 128-bit UUID that has not yet been registered with the
+            // softdevice via sd_ble_uuid_vs_add(). We need to fetch the 128-bit value and register it.
+            // For now, just set the UUID to NULL.
+            service->uuid = NULL;
+        }
+
+        mp_obj_list_append(common_hal_bleio_device_get_remote_services_list(device), service);
+    }
+
+    if (response->count > 0) {
+        m_discovery_successful = true;
+    }
+    m_discovery_in_process = false;
+}
+
+STATIC void on_char_discovery_rsp(ble_gattc_evt_char_disc_rsp_t *response, mp_obj_t device) {
+    for (size_t i = 0; i < response->count; ++i) {
+        ble_gattc_char_t *gattc_char = &response->chars[i];
+
+        bleio_characteristic_obj_t *characteristic = m_new_obj(bleio_characteristic_obj_t);
+        characteristic->base.type = &bleio_characteristic_type;
+
+        bleio_uuid_obj_t *uuid = NULL;
+
+        if (gattc_char->uuid.type != BLE_UUID_TYPE_UNKNOWN) {
+            // Known characteristic UUID.
+            uuid = m_new_obj(bleio_uuid_obj_t);
+            uuid->base.type = &bleio_uuid_type;
+            bleio_uuid_construct_from_nrf_ble_uuid(uuid, &gattc_char->uuid);
+        } else {
+            // The discovery response contained a 128-bit UUID that has not yet been registered with the
+            // softdevice via sd_ble_uuid_vs_add(). We need to fetch the 128-bit value and register it.
+            // For now, just leave the UUID as NULL.
+        }
+
+        bleio_characteristic_properties_t props =
+            (gattc_char->char_props.broadcast ? CHAR_PROP_BROADCAST : 0) |
+            (gattc_char->char_props.indicate ? CHAR_PROP_INDICATE : 0) |
+            (gattc_char->char_props.notify ? CHAR_PROP_NOTIFY : 0) |
+            (gattc_char->char_props.read ? CHAR_PROP_READ : 0) |
+            (gattc_char->char_props.write ? CHAR_PROP_WRITE : 0) |
+            (gattc_char->char_props.write_wo_resp ? CHAR_PROP_WRITE_NO_RESPONSE : 0);
+
+        // Call common_hal_bleio_characteristic_construct() to initalize some fields and set up evt handler.
+        common_hal_bleio_characteristic_construct(
+            characteristic, uuid, props, SECURITY_MODE_OPEN, SECURITY_MODE_OPEN,
+            GATT_MAX_DATA_LENGTH, false,   // max_length, fixed_length: values may not matter for gattc
+            mp_obj_new_list(0, NULL));
+        characteristic->handle = gattc_char->handle_value;
+        characteristic->service = m_char_discovery_service;
+
+        mp_obj_list_append(m_char_discovery_service->characteristic_list, MP_OBJ_FROM_PTR(characteristic));
+    }
+
+    if (response->count > 0) {
+        m_discovery_successful = true;
+    }
+    m_discovery_in_process = false;
+}
+
+STATIC void on_desc_discovery_rsp(ble_gattc_evt_desc_disc_rsp_t *response, mp_obj_t device) {
+    for (size_t i = 0; i < response->count; ++i) {
+        ble_gattc_desc_t *gattc_desc = &response->descs[i];
+
+        // Remember handles for certain well-known descriptors.
+        switch (gattc_desc->uuid.uuid) {
+            case BLE_UUID_DESCRIPTOR_CLIENT_CHAR_CONFIG:
+                m_desc_discovery_characteristic->cccd_handle = gattc_desc->handle;
+                break;
+
+            case BLE_UUID_DESCRIPTOR_SERVER_CHAR_CONFIG:
+                m_desc_discovery_characteristic->sccd_handle = gattc_desc->handle;
+                break;
+
+            case BLE_UUID_DESCRIPTOR_CHAR_USER_DESC:
+                m_desc_discovery_characteristic->user_desc_handle = gattc_desc->handle;
+                break;
+
+            default:
+                // TODO: sd_ble_gattc_descriptors_discover() can return things that are not descriptors,
+                // so ignore those.
+                // https://devzone.nordicsemi.com/f/nordic-q-a/49500/sd_ble_gattc_descriptors_discover-is-returning-attributes-that-are-not-descriptors
+                break;
+        }
+
+        bleio_descriptor_obj_t *descriptor = m_new_obj(bleio_descriptor_obj_t);
+        descriptor->base.type = &bleio_descriptor_type;
+
+        bleio_uuid_obj_t *uuid = NULL;
+
+        if (gattc_desc->uuid.type != BLE_UUID_TYPE_UNKNOWN) {
+            // Known descriptor UUID.
+            uuid = m_new_obj(bleio_uuid_obj_t);
+            uuid->base.type = &bleio_uuid_type;
+            bleio_uuid_construct_from_nrf_ble_uuid(uuid, &gattc_desc->uuid);
+        } else {
+            // The discovery response contained a 128-bit UUID that has not yet been registered with the
+            // softdevice via sd_ble_uuid_vs_add(). We need to fetch the 128-bit value and register it.
+            // For now, just leave the UUID as NULL.
+        }
+
+        common_hal_bleio_descriptor_construct(descriptor, uuid, SECURITY_MODE_OPEN, SECURITY_MODE_OPEN,
+                                              GATT_MAX_DATA_LENGTH, false);
+        descriptor->handle = gattc_desc->handle;
+        descriptor->characteristic = m_desc_discovery_characteristic;
+
+        mp_obj_list_append(m_desc_discovery_characteristic->descriptor_list, MP_OBJ_FROM_PTR(descriptor));
+    }
+
+    if (response->count > 0) {
+        m_discovery_successful = true;
+    }
+    m_discovery_in_process = false;
+}
+
+STATIC void discovery_on_ble_evt(ble_evt_t *ble_evt, mp_obj_t device) {
+    switch (ble_evt->header.evt_id) {
+        case BLE_GAP_EVT_DISCONNECTED:
+            m_discovery_successful = false;
+            m_discovery_in_process = false;
+            break;
+
+        case BLE_GATTC_EVT_PRIM_SRVC_DISC_RSP:
+            on_primary_srv_discovery_rsp(&ble_evt->evt.gattc_evt.params.prim_srvc_disc_rsp, device);
+            break;
+
+        case BLE_GATTC_EVT_CHAR_DISC_RSP:
+            on_char_discovery_rsp(&ble_evt->evt.gattc_evt.params.char_disc_rsp, device);
+            break;
+
+        case BLE_GATTC_EVT_DESC_DISC_RSP:
+            on_desc_discovery_rsp(&ble_evt->evt.gattc_evt.params.desc_disc_rsp, device);
+            break;
+
+        default:
+            // For debugging.
+            // mp_printf(&mp_plat_print, "Unhandled discovery event: 0x%04x\n", ble_evt->header.evt_id);
+            break;
+    }
+}
+
+
+void common_hal_bleio_device_discover_remote_services(mp_obj_t device, mp_obj_t service_uuids_whitelist) {
+    mp_obj_list_t *remote_services_list = common_hal_bleio_device_get_remote_services_list(device);
+
+    ble_drv_add_event_handler(discovery_on_ble_evt, device);
+
+    // Start over with an empty list.
+    mp_obj_list_clear(MP_OBJ_FROM_PTR(common_hal_bleio_device_get_remote_services_list(device)));
+
+    if (service_uuids_whitelist == mp_const_none) {
+        // List of service UUID's not given, so discover all available services.
+
+        uint16_t next_service_start_handle = BLE_GATT_HANDLE_START;
+
+        while (discover_next_services(device, next_service_start_handle, MP_OBJ_NULL)) {
+            // discover_next_services() appends to remote_services_list.
+
+            // Get the most recently discovered service, and then ask for services
+            // whose handles start after the last attribute handle inside that service.
+            const bleio_service_obj_t *service =
+                MP_OBJ_TO_PTR(remote_services_list->items[remote_services_list->len - 1]);
+            next_service_start_handle = service->end_handle + 1;
+        }
+    } else {
+        mp_obj_iter_buf_t iter_buf;
+        mp_obj_t iterable = mp_getiter(service_uuids_whitelist, &iter_buf);
+        mp_obj_t uuid_obj;
+        while ((uuid_obj = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
+            if (!MP_OBJ_IS_TYPE(uuid_obj, &bleio_uuid_type)) {
+                mp_raise_ValueError(translate("non-UUID found in service_uuids_whitelist"));
+            }
+            bleio_uuid_obj_t *uuid = MP_OBJ_TO_PTR(uuid_obj);
+
+            ble_uuid_t nrf_uuid;
+            bleio_uuid_convert_to_nrf_ble_uuid(uuid, &nrf_uuid);
+
+            // Service might or might not be discovered; that's ok. Caller has to check
+            // Central.remote_services to find out.
+            // We only need to call this once for each service to discover.
+            discover_next_services(device, BLE_GATT_HANDLE_START, &nrf_uuid);
+        }
+    }
+
+
+    for (size_t service_idx = 0; service_idx < remote_services_list->len; ++service_idx) {
+        bleio_service_obj_t *service = MP_OBJ_TO_PTR(remote_services_list->items[service_idx]);
+
+        // Skip the service if it had an unknown (unregistered) UUID.
+        if (service->uuid == NULL) {
+            continue;
+        }
+
+        uint16_t next_char_start_handle = service->start_handle;
+
+        // Stop when we go past the end of the range of handles for this service or
+        // discovery call returns nothing.
+        // discover_next_characteristics() appends to the characteristic_list.
+        while (next_char_start_handle <= service->end_handle &&
+               discover_next_characteristics(device, service, next_char_start_handle)) {
+
+
+            // Get the most recently discovered characteristic, and then ask for characteristics
+            // whose handles start after the last attribute handle inside that characteristic.
+            const bleio_characteristic_obj_t *characteristic =
+                MP_OBJ_TO_PTR(service->characteristic_list->items[service->characteristic_list->len - 1]);
+            next_char_start_handle = characteristic->handle + 1;
+        }
+
+        // Got characteristics for this service. Now discover descriptors for each characteristic.
+        size_t char_list_len = service->characteristic_list->len;
+        for (size_t char_idx = 0; char_idx < char_list_len; ++char_idx) {
+            bleio_characteristic_obj_t *characteristic =
+                MP_OBJ_TO_PTR(service->characteristic_list->items[char_idx]);
+            const bool last_characteristic = char_idx == char_list_len - 1;
+            bleio_characteristic_obj_t *next_characteristic = last_characteristic
+                ? NULL
+                : MP_OBJ_TO_PTR(service->characteristic_list->items[char_idx + 1]);
+
+            // Skip the characteristic if it had an unknown (unregistered) UUID.
+            if (characteristic->uuid == NULL) {
+                continue;
+            }
+
+            uint16_t next_desc_start_handle = characteristic->handle + 1;
+
+            // Don't run past the end of this service or the beginning of the next characteristic.
+            uint16_t next_desc_end_handle = next_characteristic == NULL
+                ? service->end_handle
+                : next_characteristic->handle - 1;
+
+            // Stop when we go past the end of the range of handles for this service or
+            // discovery call returns nothing.
+            // discover_next_descriptors() appends to the descriptor_list.
+            while (next_desc_start_handle <= service->end_handle &&
+                   next_desc_start_handle < next_desc_end_handle &&
+                   discover_next_descriptors(device, characteristic,
+                                             next_desc_start_handle, next_desc_end_handle)) {
+
+                // Get the most recently discovered descriptor, and then ask for descriptors
+                // whose handles start after that descriptor's handle.
+                const bleio_descriptor_obj_t *descriptor =
+                    MP_OBJ_TO_PTR(characteristic->descriptor_list->items[characteristic->descriptor_list->len - 1]);
+                next_desc_start_handle = descriptor->handle + 1;
+            }
+        }
+    }
+
+    // This event handler is no longer needed.
+    ble_drv_remove_event_handler(discovery_on_ble_evt, device);
+
+}
+
+// GATTS read of a Characteristic or Descriptor.
+mp_obj_t common_hal_bleio_gatts_read(uint16_t handle, uint16_t conn_handle) {
+    // conn_handle might be BLE_CONN_HANDLE_INVALID if we're not connected, but that's OK, because
+    // we can still read and write the local value.
+
+    mp_buffer_info_t bufinfo;
+    ble_gatts_value_t gatts_value = {
+        .p_value = NULL,
+        .len = 0,
+    };
+
+    // Read once to find out what size buffer we need, then read again to fill buffer.
+
+    mp_obj_t value = mp_const_none;
+    uint32_t err_code = sd_ble_gatts_value_get(conn_handle, handle, &gatts_value);
+    if (err_code == NRF_SUCCESS) {
+        value = mp_obj_new_bytearray_of_zeros(gatts_value.len);
+        mp_get_buffer_raise(value, &bufinfo, MP_BUFFER_WRITE);
+        gatts_value.p_value = bufinfo.buf;
+
+        // Read again, with the correct size of buffer.
+        err_code = sd_ble_gatts_value_get(conn_handle, handle, &gatts_value);
+    }
+
+    if (err_code != NRF_SUCCESS) {
+        mp_raise_OSError_msg_varg(translate("Failed to read gatts value, err 0x%04x"), err_code);
+    }
+
+    return value;
+}
+
+void common_hal_bleio_gatts_write(uint16_t handle, uint16_t conn_handle, mp_buffer_info_t *bufinfo) {
+    // conn_handle might be BLE_CONN_HANDLE_INVALID if we're not connected, but that's OK, because
+    // we can still read and write the local value.
+
+    ble_gatts_value_t gatts_value = {
+        .p_value = bufinfo->buf,
+        .len = bufinfo->len,
+    };
+
+    const uint32_t err_code = sd_ble_gatts_value_set(conn_handle, handle, &gatts_value);
+    if (err_code != NRF_SUCCESS) {
+        mp_raise_OSError_msg_varg(translate("Failed to write gatts value, err 0x%04x"), err_code);
+    }
+}
+
+void common_hal_bleio_gattc_write(uint16_t handle, uint16_t conn_handle, mp_buffer_info_t *bufinfo, bool write_no_response) {
+    common_hal_bleio_check_connected(conn_handle);
+
+    ble_gattc_write_params_t write_params = {
+        .write_op = write_no_response ? BLE_GATT_OP_WRITE_CMD: BLE_GATT_OP_WRITE_REQ,
+        .handle = handle,
+        .p_value = bufinfo->buf,
+        .len = bufinfo->len,
+    };
+
+    while (1) {
+        uint32_t err_code = sd_ble_gattc_write(conn_handle, &write_params);
+        if (err_code == NRF_SUCCESS) {
+            break;
+        }
+
+        // Write with response will return NRF_ERROR_BUSY if the response has not been received.
+        // Write without reponse will return NRF_ERROR_RESOURCES if too many writes are pending.
+        if (err_code == NRF_ERROR_BUSY || err_code == NRF_ERROR_RESOURCES) {
+            // We could wait for an event indicating the write is complete, but just retrying is easier.
+            MICROPY_VM_HOOK_LOOP;
+            continue;
+        }
+
+        // Some real error occurred.
+        mp_raise_OSError_msg_varg(translate("Failed to write attribute value, err 0x%04x"), err_code);
+    }
+
 }
diff --git a/ports/nrf/common-hal/bleio/__init__.h b/ports/nrf/common-hal/bleio/__init__.h
index 0c46b631f..c0bba3799 100644
--- a/ports/nrf/common-hal/bleio/__init__.h
+++ b/ports/nrf/common-hal/bleio/__init__.h
@@ -27,16 +27,10 @@
 #ifndef MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_INIT_H
 #define MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_INIT_H
 
-#include "shared-bindings/bleio/__init__.h"
-#include "shared-bindings/bleio/Adapter.h"
-
-#include "shared-module/bleio/__init__.h"
+void bleio_reset(void);
 
 // We assume variable length data.
 // 20 bytes max (23 - 3).
 #define GATT_MAX_DATA_LENGTH (BLE_GATT_ATT_MTU_DEFAULT - 3)
 
-gatt_role_t common_hal_bleio_device_get_gatt_role(mp_obj_t device);
-uint16_t common_hal_bleio_device_get_conn_handle(mp_obj_t device);
-
 #endif // MICROPY_INCLUDED_NRF_COMMON_HAL_BLEIO_INIT_H
diff --git a/ports/nrf/device/nrf52/startup_nrf52840.c b/ports/nrf/device/nrf52/startup_nrf52840.c
index 30634a1b5..8e1c36012 100644
--- a/ports/nrf/device/nrf52/startup_nrf52840.c
+++ b/ports/nrf/device/nrf52/startup_nrf52840.c
@@ -116,7 +116,7 @@ void CRYPTOCELL_IRQHandler       (void) __attribute__ ((weak, alias("Default_Han
 void SPIM3_IRQHandler            (void) __attribute__ ((weak, alias("Default_Handler")));
 void PWM3_IRQHandler             (void) __attribute__ ((weak, alias("Default_Handler")));
 
-const func __Vectors[] __attribute__ ((section(".isr_vector"))) = {
+const func __Vectors[] __attribute__ ((used, section(".isr_vector"))) = {
     (func)&_estack,
     Reset_Handler,
     NMI_Handler,
diff --git a/ports/nrf/nrfx_config.h b/ports/nrf/nrfx_config.h
index a2b48065d..8fa6721e2 100644
--- a/ports/nrf/nrfx_config.h
+++ b/ports/nrf/nrfx_config.h
@@ -78,6 +78,7 @@
 // TIMERS
 #define NRFX_TIMER_ENABLED 1
 // Don't enable TIMER0: it's used by the SoftDevice.
+#define NRFX_TIMER0_ENABLED 0
 #define NRFX_TIMER1_ENABLED 1
 #define NRFX_TIMER2_ENABLED 1
 
diff --git a/ports/nrf/peripherals/nrf/timers.c b/ports/nrf/peripherals/nrf/timers.c
index 7f7a003d3..88f3dd468 100644
--- a/ports/nrf/peripherals/nrf/timers.c
+++ b/ports/nrf/peripherals/nrf/timers.c
@@ -36,7 +36,7 @@
 
 STATIC nrfx_timer_t nrfx_timers[] = {
 #if NRFX_CHECK(NRFX_TIMER0_ENABLED)
-    // Note that TIMER0 is reserved for use by the SoftDevice, so it should not usually be enabled.
+    #error NRFX_TIMER0_ENABLED should not be on: TIMER0 is used by the SoftDevice
     NRFX_TIMER_INSTANCE(0),
 #endif
 #if NRFX_CHECK(NRFX_TIMER1_ENABLED)