extmod/modbluetooth_nimble: Move nimble specific code, factor nimble.mk.

Move extmod/modbluetooth_nimble.* to extmod/nimble.  And move common
Makefile lines to extmod/nimble/nimble.mk (which was previously only used
by stm32).  This allows (upcoming) btstack to follow a similar structure.

Work done in collaboration with Jim Mussared aka @jimmo.

1 files changed, 833 insertions, 0 deletions

diff --git a/extmod/nimble/modbluetooth_nimble.c b/extmod/nimble/modbluetooth_nimble.c
new file mode 100644
index 000000000..f7602c35f
--- /dev/null
+++ b/extmod/nimble/modbluetooth_nimble.c
@@ -0,0 +1,833 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Damien P. George
+ * Copyright (c) 2019 Jim Mussared
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/runtime.h"
+#include "py/mperrno.h"
+#include "py/mphal.h"
+
+#if MICROPY_PY_BLUETOOTH && MICROPY_BLUETOOTH_NIMBLE
+
+#include "extmod/nimble/modbluetooth_nimble.h"
+#include "extmod/modbluetooth.h"
+
+#include "host/ble_hs.h"
+#include "host/util/util.h"
+#include "nimble/ble.h"
+#include "nimble/nimble_port.h"
+#include "services/gap/ble_svc_gap.h"
+
+#ifndef MICROPY_PY_BLUETOOTH_DEFAULT_NAME
+#define MICROPY_PY_BLUETOOTH_DEFAULT_NAME "PYBD"
+#endif
+
+#define DEBUG_EVENT_printf(...) //printf(__VA_ARGS__)
+
+STATIC int8_t ble_hs_err_to_errno_table[] = {
+    [BLE_HS_EAGAIN] = MP_EAGAIN,
+    [BLE_HS_EALREADY] = MP_EALREADY,
+    [BLE_HS_EINVAL] = MP_EINVAL,
+    [BLE_HS_EMSGSIZE] = MP_EIO,
+    [BLE_HS_ENOENT] = MP_ENOENT,
+    [BLE_HS_ENOMEM] = MP_ENOMEM,
+    [BLE_HS_ENOTCONN] = MP_ENOTCONN,
+    [BLE_HS_ENOTSUP] = MP_EOPNOTSUPP,
+    [BLE_HS_EAPP] = MP_EIO,
+    [BLE_HS_EBADDATA] = MP_EIO,
+    [BLE_HS_EOS] = MP_EIO,
+    [BLE_HS_ECONTROLLER] = MP_EIO,
+    [BLE_HS_ETIMEOUT] = MP_ETIMEDOUT,
+    [BLE_HS_EDONE] = MP_EIO,               // TODO: Maybe should be MP_EISCONN (connect uses this for "already connected").
+    [BLE_HS_EBUSY] = MP_EBUSY,
+    [BLE_HS_EREJECT] = MP_EIO,
+    [BLE_HS_EUNKNOWN] = MP_EIO,
+    [BLE_HS_EROLE] = MP_EIO,
+    [BLE_HS_ETIMEOUT_HCI] = MP_EIO,
+    [BLE_HS_ENOMEM_EVT] = MP_EIO,
+    [BLE_HS_ENOADDR] = MP_EIO,
+    [BLE_HS_ENOTSYNCED] = MP_EIO,
+    [BLE_HS_EAUTHEN] = MP_EIO,
+    [BLE_HS_EAUTHOR] = MP_EIO,
+    [BLE_HS_EENCRYPT] = MP_EIO,
+    [BLE_HS_EENCRYPT_KEY_SZ] = MP_EIO,
+    [BLE_HS_ESTORE_CAP] = MP_EIO,
+    [BLE_HS_ESTORE_FAIL] = MP_EIO,
+    [BLE_HS_EPREEMPTED] = MP_EIO,
+    [BLE_HS_EDISABLED] = MP_EIO,
+};
+
+STATIC int ble_hs_err_to_errno(int err) {
+    if (0 <= err && err < MP_ARRAY_SIZE(ble_hs_err_to_errno_table)) {
+        return ble_hs_err_to_errno_table[err];
+    } else {
+        return MP_EIO;
+    }
+}
+
+// Note: modbluetooth UUIDs store their data in LE.
+STATIC ble_uuid_t *create_nimble_uuid(const mp_obj_bluetooth_uuid_t *uuid) {
+    if (uuid->type == MP_BLUETOOTH_UUID_TYPE_16) {
+        ble_uuid16_t *result = m_new(ble_uuid16_t, 1);
+        result->u.type = BLE_UUID_TYPE_16;
+        result->value = (uuid->data[1] << 8) | uuid->data[0];
+        return (ble_uuid_t *)result;
+    } else if (uuid->type == MP_BLUETOOTH_UUID_TYPE_32) {
+        ble_uuid32_t *result = m_new(ble_uuid32_t, 1);
+        result->u.type = BLE_UUID_TYPE_32;
+        result->value = (uuid->data[1] << 24) | (uuid->data[1] << 16) | (uuid->data[1] << 8) | uuid->data[0];
+        return (ble_uuid_t *)result;
+    } else if (uuid->type == MP_BLUETOOTH_UUID_TYPE_128) {
+        ble_uuid128_t *result = m_new(ble_uuid128_t, 1);
+        result->u.type = BLE_UUID_TYPE_128;
+        memcpy(result->value, uuid->data, 16);
+        return (ble_uuid_t *)result;
+    } else {
+        return NULL;
+    }
+}
+
+#if MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
+
+STATIC mp_obj_bluetooth_uuid_t create_mp_uuid(const ble_uuid_any_t *uuid) {
+    mp_obj_bluetooth_uuid_t result;
+    switch (uuid->u.type) {
+        case BLE_UUID_TYPE_16:
+            result.type = MP_BLUETOOTH_UUID_TYPE_16;
+            result.data[0] = uuid->u16.value & 0xff;
+            result.data[1] = (uuid->u16.value >> 8) & 0xff;
+            break;
+        case BLE_UUID_TYPE_32:
+            result.type = MP_BLUETOOTH_UUID_TYPE_32;
+            result.data[0] = uuid->u32.value & 0xff;
+            result.data[1] = (uuid->u32.value >> 8) & 0xff;
+            result.data[2] = (uuid->u32.value >> 16) & 0xff;
+            result.data[3] = (uuid->u32.value >> 24) & 0xff;
+            break;
+        case BLE_UUID_TYPE_128:
+            result.type = MP_BLUETOOTH_UUID_TYPE_128;
+            memcpy(result.data, uuid->u128.value, 16);
+            break;
+        default:
+            assert(false);
+    }
+    return result;
+}
+
+// modbluetooth (and the layers above it) work in BE for addresses, Nimble works in LE.
+STATIC void reverse_addr_byte_order(uint8_t *addr_out, const uint8_t *addr_in) {
+    for (int i = 0; i < 6; ++i) {
+        addr_out[i] = addr_in[5 - i];
+    }
+}
+
+STATIC ble_addr_t create_nimble_addr(uint8_t addr_type, const uint8_t *addr) {
+    ble_addr_t addr_nimble;
+    addr_nimble.type = addr_type;
+    // Incoming addr is from modbluetooth (BE), so copy and convert to LE for Nimble.
+    reverse_addr_byte_order(addr_nimble.val, addr);
+    return addr_nimble;
+}
+
+#endif // MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
+
+typedef struct {
+    // Pointer to heap-allocated data.
+    uint8_t *data;
+    // Allocated size of data.
+    size_t data_alloc;
+    // Current bytes in use.
+    size_t data_len;
+    // Whether new writes append or replace existing data (default false).
+    bool append;
+} gatts_db_entry_t;
+
+volatile int mp_bluetooth_nimble_ble_state = MP_BLUETOOTH_NIMBLE_BLE_STATE_OFF;
+
+STATIC void reset_cb(int reason) {
+    (void)reason;
+}
+
+STATIC void sync_cb(void) {
+    int rc;
+    ble_addr_t addr;
+
+    rc = ble_hs_util_ensure_addr(0); // prefer public address
+    if (rc != 0) {
+        // https://mynewt.apache.org/latest/tutorials/ble/eddystone.html#configure-the-nimble-stack-with-an-address
+        #if MICROPY_PY_BLUETOOTH_RANDOM_ADDR
+        rc = ble_hs_id_gen_rnd(1, &addr);
+        assert(rc == 0);
+        rc = ble_hs_id_set_rnd(addr.val);
+        assert(rc == 0);
+        #else
+        uint8_t addr_be[6];
+        mp_hal_get_mac(MP_HAL_MAC_BDADDR, addr_be);
+        reverse_addr_byte_order(addr.val, addr_be);
+        // ble_hs_id_set_pub(addr.val);
+        rc = ble_hs_id_set_rnd(addr.val);
+        assert(rc == 0);
+        #endif
+
+        rc = ble_hs_util_ensure_addr(0); // prefer public address
+        assert(rc == 0);
+    }
+
+    if (MP_BLUETOOTH_MAX_ATTR_SIZE > 20) {
+        rc = ble_att_set_preferred_mtu(MP_BLUETOOTH_MAX_ATTR_SIZE + 3);
+        assert(rc == 0);
+    }
+
+    ble_svc_gap_device_name_set(MICROPY_PY_BLUETOOTH_DEFAULT_NAME);
+
+    mp_bluetooth_nimble_ble_state = MP_BLUETOOTH_NIMBLE_BLE_STATE_ACTIVE;
+}
+
+STATIC void create_gatts_db_entry(uint16_t handle) {
+    mp_map_elem_t *elem = mp_map_lookup(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, MP_OBJ_NEW_SMALL_INT(handle), MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
+    gatts_db_entry_t *entry = m_new(gatts_db_entry_t, 1);
+    entry->data = m_new(uint8_t, MP_BLUETOOTH_MAX_ATTR_SIZE);
+    entry->data_alloc = MP_BLUETOOTH_MAX_ATTR_SIZE;
+    entry->data_len = 0;
+    entry->append = false;
+    elem->value = MP_OBJ_FROM_PTR(entry);
+}
+
+STATIC void gatts_register_cb(struct ble_gatt_register_ctxt *ctxt, void *arg) {
+    switch (ctxt->op) {
+        case BLE_GATT_REGISTER_OP_SVC:
+            // Called when a service is successfully registered.
+            DEBUG_EVENT_printf("gatts_register_cb: svc uuid=%p handle=%d\n", &ctxt->svc.svc_def->uuid, ctxt->svc.handle);
+            break;
+
+        case BLE_GATT_REGISTER_OP_CHR:
+            // Called when a characteristic is successfully registered.
+            DEBUG_EVENT_printf("gatts_register_cb: chr uuid=%p def_handle=%d val_handle=%d\n", &ctxt->chr.chr_def->uuid, ctxt->chr.def_handle, ctxt->chr.val_handle);
+
+            // Note: We will get this event for the default GAP Service, meaning that we allocate storage for the
+            // "device name" and "appearance" characteristics, even though we never see the reads for them.
+            // TODO: Possibly check if the service UUID is 0x1801 and ignore?
+
+            // Allocate the gatts_db storage for this characteristic.
+            // Although this function is a callback, it's called synchronously from ble_hs_sched_start/ble_gatts_start, so safe to allocate.
+            create_gatts_db_entry(ctxt->chr.val_handle);
+            break;
+
+        case BLE_GATT_REGISTER_OP_DSC:
+            // Called when a descriptor is successfully registered.
+            // Note: This is event is not called for the CCCD.
+            DEBUG_EVENT_printf("gatts_register_cb: dsc uuid=%p handle=%d\n", &ctxt->dsc.dsc_def->uuid, ctxt->dsc.handle);
+
+            // See above, safe to alloc.
+            create_gatts_db_entry(ctxt->dsc.handle);
+
+            // Unlike characteristics, we have to manually provide a way to get the handle back to the register method.
+            *((uint16_t *)ctxt->dsc.dsc_def->arg) = ctxt->dsc.handle;
+            break;
+
+        default:
+            DEBUG_EVENT_printf("gatts_register_cb: unknown op %d\n", ctxt->op);
+            break;
+    }
+}
+
+STATIC int gap_event_cb(struct ble_gap_event *event, void *arg) {
+    DEBUG_EVENT_printf("gap_event_cb: type=%d\n", event->type);
+    struct ble_gap_conn_desc desc;
+    uint8_t addr[6] = {0};
+
+    switch (event->type) {
+        case BLE_GAP_EVENT_CONNECT:
+            if (event->connect.status == 0) {
+                // Connection established.
+                ble_gap_conn_find(event->connect.conn_handle, &desc);
+                reverse_addr_byte_order(addr, desc.peer_id_addr.val);
+                mp_bluetooth_gap_on_connected_disconnected(MP_BLUETOOTH_IRQ_CENTRAL_CONNECT, event->connect.conn_handle, desc.peer_id_addr.type, addr);
+            } else {
+                // Connection failed.
+                mp_bluetooth_gap_on_connected_disconnected(MP_BLUETOOTH_IRQ_CENTRAL_DISCONNECT, event->connect.conn_handle, 0xff, addr);
+            }
+            break;
+
+        case BLE_GAP_EVENT_DISCONNECT:
+            // Disconnect.
+            reverse_addr_byte_order(addr, event->disconnect.conn.peer_id_addr.val);
+            mp_bluetooth_gap_on_connected_disconnected(MP_BLUETOOTH_IRQ_CENTRAL_DISCONNECT, event->disconnect.conn.conn_handle, event->disconnect.conn.peer_id_addr.type, addr);
+            break;
+    }
+
+    return 0;
+}
+
+int mp_bluetooth_init(void) {
+    // Clean up if necessary.
+    mp_bluetooth_deinit();
+
+    ble_hs_cfg.reset_cb = reset_cb;
+    ble_hs_cfg.sync_cb = sync_cb;
+    ble_hs_cfg.gatts_register_cb = gatts_register_cb;
+    ble_hs_cfg.store_status_cb = ble_store_util_status_rr;
+
+    MP_STATE_PORT(bluetooth_nimble_root_pointers) = m_new0(mp_bluetooth_nimble_root_pointers_t, 1);
+    MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db = m_new(mp_map_t, 1);
+
+    mp_bluetooth_nimble_ble_state = MP_BLUETOOTH_NIMBLE_BLE_STATE_STARTING;
+
+    mp_bluetooth_nimble_port_preinit();
+    nimble_port_init();
+    mp_bluetooth_nimble_port_postinit();
+
+    // By default, just register the default gap service.
+    ble_svc_gap_init();
+
+    mp_bluetooth_nimble_port_start();
+
+    // Wait for sync callback
+    while (mp_bluetooth_nimble_ble_state != MP_BLUETOOTH_NIMBLE_BLE_STATE_ACTIVE) {
+        MICROPY_EVENT_POLL_HOOK
+    }
+
+    return 0;
+}
+
+// Called when the host stop procedure has completed.
+STATIC void ble_hs_shutdown_stop_cb(int status, void *arg) {
+    mp_bluetooth_nimble_ble_state = MP_BLUETOOTH_NIMBLE_BLE_STATE_OFF;
+}
+
+STATIC struct ble_hs_stop_listener ble_hs_shutdown_stop_listener;
+
+void mp_bluetooth_deinit(void) {
+    if (mp_bluetooth_nimble_ble_state == MP_BLUETOOTH_NIMBLE_BLE_STATE_OFF) {
+        return;
+    }
+
+    mp_bluetooth_gap_advertise_stop();
+    #if MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
+    mp_bluetooth_gap_scan_stop();
+    #endif
+
+    ble_hs_stop(&ble_hs_shutdown_stop_listener, ble_hs_shutdown_stop_cb, NULL);
+
+    while (mp_bluetooth_nimble_ble_state != MP_BLUETOOTH_NIMBLE_BLE_STATE_OFF) {
+        MICROPY_EVENT_POLL_HOOK
+    }
+
+    mp_bluetooth_nimble_port_deinit();
+
+    MP_STATE_PORT(bluetooth_nimble_root_pointers) = NULL;
+}
+
+bool mp_bluetooth_is_enabled(void) {
+    return mp_bluetooth_nimble_ble_state == MP_BLUETOOTH_NIMBLE_BLE_STATE_ACTIVE;
+}
+
+void mp_bluetooth_get_device_addr(uint8_t *addr) {
+    #if MICROPY_PY_BLUETOOTH_RANDOM_ADDR
+    ble_hs_id_copy_addr(BLE_ADDR_RANDOM, addr, NULL);
+    #else
+    mp_hal_get_mac(MP_HAL_MAC_BDADDR, addr);
+    #endif
+}
+
+int mp_bluetooth_gap_advertise_start(bool connectable, int32_t interval_us, const uint8_t *adv_data, size_t adv_data_len, const uint8_t *sr_data, size_t sr_data_len) {
+    int ret;
+
+    mp_bluetooth_gap_advertise_stop();
+
+    if (adv_data) {
+        ret = ble_gap_adv_set_data(adv_data, adv_data_len);
+        if (ret != 0) {
+            return ble_hs_err_to_errno(ret);
+        }
+    }
+
+    if (sr_data) {
+        ret = ble_gap_adv_rsp_set_data(sr_data, sr_data_len);
+        if (ret != 0) {
+            return ble_hs_err_to_errno(ret);
+        }
+    }
+
+    struct ble_gap_adv_params adv_params = {
+        .conn_mode = connectable ? BLE_GAP_CONN_MODE_UND : BLE_GAP_CONN_MODE_NON,
+        .disc_mode = BLE_GAP_DISC_MODE_GEN,
+        .itvl_min = interval_us / BLE_HCI_ADV_ITVL, // convert to 625us units.
+        .itvl_max = interval_us / BLE_HCI_ADV_ITVL,
+        .channel_map = 7, // all 3 channels.
+    };
+
+    ret = ble_gap_adv_start(BLE_OWN_ADDR_PUBLIC, NULL, BLE_HS_FOREVER, &adv_params, gap_event_cb, NULL);
+    if (ret == 0) {
+        return 0;
+    }
+    ret = ble_gap_adv_start(BLE_OWN_ADDR_RPA_PUBLIC_DEFAULT, NULL, BLE_HS_FOREVER, &adv_params, gap_event_cb, NULL);
+    if (ret == 0) {
+        return 0;
+    }
+    ret = ble_gap_adv_start(BLE_OWN_ADDR_RPA_RANDOM_DEFAULT, NULL, BLE_HS_FOREVER, &adv_params, gap_event_cb, NULL);
+    if (ret == 0) {
+        return 0;
+    }
+    ret = ble_gap_adv_start(BLE_OWN_ADDR_RANDOM, NULL, BLE_HS_FOREVER, &adv_params, gap_event_cb, NULL);
+    if (ret == 0) {
+        return 0;
+    }
+    DEBUG_EVENT_printf("ble_gap_adv_start: %d\n", ret);
+
+    return ble_hs_err_to_errno(ret);
+}
+
+void mp_bluetooth_gap_advertise_stop(void) {
+    if (ble_gap_adv_active()) {
+        ble_gap_adv_stop();
+    }
+}
+
+static int characteristic_access_cb(uint16_t conn_handle, uint16_t value_handle, struct ble_gatt_access_ctxt *ctxt, void *arg) {
+    DEBUG_EVENT_printf("characteristic_access_cb: conn_handle=%u value_handle=%u op=%u\n", conn_handle, value_handle, ctxt->op);
+    mp_map_elem_t *elem;
+    gatts_db_entry_t *entry;
+    switch (ctxt->op) {
+        case BLE_GATT_ACCESS_OP_READ_CHR:
+        case BLE_GATT_ACCESS_OP_READ_DSC:
+            #if MICROPY_PY_BLUETOOTH_GATTS_ON_READ_CALLBACK
+            // Allow Python code to override (by using gatts_write), or deny (by returning false) the read.
+            if (!mp_bluetooth_gatts_on_read_request(conn_handle, value_handle)) {
+                return BLE_ATT_ERR_READ_NOT_PERMITTED;
+            }
+            #endif
+
+            elem = mp_map_lookup(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, MP_OBJ_NEW_SMALL_INT(value_handle), MP_MAP_LOOKUP);
+            if (!elem) {
+                return BLE_ATT_ERR_ATTR_NOT_FOUND;
+            }
+            entry = MP_OBJ_TO_PTR(elem->value);
+
+            os_mbuf_append(ctxt->om, entry->data, entry->data_len);
+
+            return 0;
+        case BLE_GATT_ACCESS_OP_WRITE_CHR:
+        case BLE_GATT_ACCESS_OP_WRITE_DSC:
+            elem = mp_map_lookup(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, MP_OBJ_NEW_SMALL_INT(value_handle), MP_MAP_LOOKUP);
+            if (!elem) {
+                return BLE_ATT_ERR_ATTR_NOT_FOUND;
+            }
+            entry = MP_OBJ_TO_PTR(elem->value);
+
+            size_t offset = 0;
+            if (entry->append) {
+                offset = entry->data_len;
+            }
+            entry->data_len = MIN(entry->data_alloc, OS_MBUF_PKTLEN(ctxt->om) + offset);
+            os_mbuf_copydata(ctxt->om, 0, entry->data_len - offset, entry->data + offset);
+
+            mp_bluetooth_gatts_on_write(conn_handle, value_handle);
+
+            return 0;
+    }
+    return BLE_ATT_ERR_UNLIKELY;
+}
+
+int mp_bluetooth_gatts_register_service_begin(bool append) {
+    int ret = ble_gatts_reset();
+    if (ret != 0) {
+        return ble_hs_err_to_errno(ret);
+    }
+
+    // Reset the gatt characteristic value db.
+    mp_map_init(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, 0);
+
+    // By default, just register the default gap service.
+    ble_svc_gap_init();
+
+    if (!append) {
+        // Unref any previous service definitions.
+        for (int i = 0; i < MP_STATE_PORT(bluetooth_nimble_root_pointers)->n_services; ++i) {
+            MP_STATE_PORT(bluetooth_nimble_root_pointers)->services[i] = NULL;
+        }
+        MP_STATE_PORT(bluetooth_nimble_root_pointers)->n_services = 0;
+    }
+
+    return 0;
+}
+
+int mp_bluetooth_gatts_register_service_end() {
+    int ret = ble_gatts_start();
+    if (ret != 0) {
+        return ble_hs_err_to_errno(ret);
+    }
+
+    return 0;
+}
+
+int mp_bluetooth_gatts_register_service(mp_obj_bluetooth_uuid_t *service_uuid, mp_obj_bluetooth_uuid_t **characteristic_uuids, uint8_t *characteristic_flags, mp_obj_bluetooth_uuid_t **descriptor_uuids, uint8_t *descriptor_flags, uint8_t *num_descriptors, uint16_t *handles, size_t num_characteristics) {
+    if (MP_STATE_PORT(bluetooth_nimble_root_pointers)->n_services == MP_BLUETOOTH_NIMBLE_MAX_SERVICES) {
+        return MP_E2BIG;
+    }
+    size_t handle_index = 0;
+    size_t descriptor_index = 0;
+
+    struct ble_gatt_chr_def *characteristics = m_new(struct ble_gatt_chr_def, num_characteristics + 1);
+    for (size_t i = 0; i < num_characteristics; ++i) {
+        characteristics[i].uuid = create_nimble_uuid(characteristic_uuids[i]);
+        characteristics[i].access_cb = characteristic_access_cb;
+        characteristics[i].arg = NULL;
+        characteristics[i].flags = characteristic_flags[i];
+        characteristics[i].min_key_size = 0;
+        characteristics[i].val_handle = &handles[handle_index];
+        ++handle_index;
+
+        if (num_descriptors[i] == 0) {
+            characteristics[i].descriptors = NULL;
+        } else {
+            struct ble_gatt_dsc_def *descriptors = m_new(struct ble_gatt_dsc_def, num_descriptors[i] + 1);
+
+            for (size_t j = 0; j < num_descriptors[i]; ++j) {
+                descriptors[j].uuid = create_nimble_uuid(descriptor_uuids[descriptor_index]);
+                descriptors[j].access_cb = characteristic_access_cb;
+                descriptors[j].att_flags = descriptor_flags[descriptor_index];
+                descriptors[j].min_key_size = 0;
+                // Unlike characteristic, Nimble doesn't provide an automatic way to remember the handle, so use the arg.
+                descriptors[j].arg = &handles[handle_index];
+                ++descriptor_index;
+                ++handle_index;
+            }
+            descriptors[num_descriptors[i]].uuid = NULL; // no more descriptors
+
+            characteristics[i].descriptors = descriptors;
+        }
+    }
+    characteristics[num_characteristics].uuid = NULL; // no more characteristics
+
+    struct ble_gatt_svc_def *service = m_new(struct ble_gatt_svc_def, 2);
+    service[0].type = BLE_GATT_SVC_TYPE_PRIMARY;
+    service[0].uuid = create_nimble_uuid(service_uuid);
+    service[0].includes = NULL;
+    service[0].characteristics = characteristics;
+    service[1].type = 0; // no more services
+
+    MP_STATE_PORT(bluetooth_nimble_root_pointers)->services[MP_STATE_PORT(bluetooth_nimble_root_pointers)->n_services++] = service;
+
+    // Note: advertising must be stopped for gatts registration to work
+
+    int ret = ble_gatts_count_cfg(service);
+    if (ret != 0) {
+        return ble_hs_err_to_errno(ret);
+    }
+
+    ret = ble_gatts_add_svcs(service);
+    if (ret != 0) {
+        return ble_hs_err_to_errno(ret);
+    }
+
+    return 0;
+}
+
+int mp_bluetooth_gap_disconnect(uint16_t conn_handle) {
+    return ble_hs_err_to_errno(ble_gap_terminate(conn_handle, BLE_ERR_REM_USER_CONN_TERM));
+}
+
+int mp_bluetooth_gatts_read(uint16_t value_handle, uint8_t **value, size_t *value_len) {
+    mp_map_elem_t *elem = mp_map_lookup(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, MP_OBJ_NEW_SMALL_INT(value_handle), MP_MAP_LOOKUP);
+    if (!elem) {
+        return MP_EINVAL;
+    }
+    gatts_db_entry_t *entry = MP_OBJ_TO_PTR(elem->value);
+    *value = entry->data;
+    *value_len = entry->data_len;
+    if (entry->append) {
+        entry->data_len = 0;
+    }
+    return 0;
+}
+
+int mp_bluetooth_gatts_write(uint16_t value_handle, const uint8_t *value, size_t value_len) {
+    mp_map_elem_t *elem = mp_map_lookup(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, MP_OBJ_NEW_SMALL_INT(value_handle), MP_MAP_LOOKUP);
+    if (!elem) {
+        return MP_EINVAL;
+    }
+    gatts_db_entry_t *entry = MP_OBJ_TO_PTR(elem->value);
+    if (value_len > entry->data_alloc) {
+        entry->data = m_new(uint8_t, value_len);
+        entry->data_alloc = value_len;
+    }
+
+    memcpy(entry->data, value, value_len);
+    entry->data_len = value_len;
+    return 0;
+}
+
+// TODO: Could use ble_gatts_chr_updated to send to all subscribed centrals.
+
+int mp_bluetooth_gatts_notify(uint16_t conn_handle, uint16_t value_handle) {
+    // Confusingly, notify/notify_custom/indicate are "gattc" function (even though they're used by peripherals (i.e. gatt servers)).
+    // See https://www.mail-archive.com/dev@mynewt.apache.org/msg01293.html
+    return ble_hs_err_to_errno(ble_gattc_notify(conn_handle, value_handle));
+}
+
+int mp_bluetooth_gatts_notify_send(uint16_t conn_handle, uint16_t value_handle, const uint8_t *value, size_t *value_len) {
+    struct os_mbuf *om = ble_hs_mbuf_from_flat(value, *value_len);
+    if (om == NULL) {
+        return -1;
+    }
+    // TODO: check that notify_custom takes ownership of om, if not os_mbuf_free_chain(om).
+    return ble_hs_err_to_errno(ble_gattc_notify_custom(conn_handle, value_handle, om));
+}
+
+int mp_bluetooth_gatts_indicate(uint16_t conn_handle, uint16_t value_handle) {
+    return ble_hs_err_to_errno(ble_gattc_indicate(conn_handle, value_handle));
+}
+
+int mp_bluetooth_gatts_set_buffer(uint16_t value_handle, size_t len, bool append) {
+    mp_map_elem_t *elem = mp_map_lookup(MP_STATE_PORT(bluetooth_nimble_root_pointers)->gatts_db, MP_OBJ_NEW_SMALL_INT(value_handle), MP_MAP_LOOKUP);
+    if (!elem) {
+        return MP_EINVAL;
+    }
+    gatts_db_entry_t *entry = MP_OBJ_TO_PTR(elem->value);
+    entry->data = m_renew(uint8_t, entry->data, entry->data_alloc, len);
+    entry->data_alloc = len;
+    entry->data_len = 0;
+    entry->append = append;
+    return 0;
+}
+
+#if MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
+
+STATIC void gattc_on_data_available(uint16_t event, uint16_t conn_handle, uint16_t value_handle, const struct os_mbuf *om) {
+    MICROPY_PY_BLUETOOTH_ENTER
+    size_t len = OS_MBUF_PKTLEN(om);
+    len = mp_bluetooth_gattc_on_data_available_start(event, conn_handle, value_handle, len);
+    while (len > 0 && om != NULL) {
+        size_t n = MIN(om->om_len, len);
+        mp_bluetooth_gattc_on_data_available_chunk(OS_MBUF_DATA(om, const uint8_t *), n);
+        len -= n;
+        om = SLIST_NEXT(om, om_next);
+    }
+    mp_bluetooth_gattc_on_data_available_end();
+    MICROPY_PY_BLUETOOTH_EXIT
+}
+
+STATIC int gap_scan_cb(struct ble_gap_event *event, void *arg) {
+    DEBUG_EVENT_printf("gap_scan_cb: event=%d type=%d\n", event->type, event->type == BLE_GAP_EVENT_DISC ? event->disc.event_type : -1);
+
+    if (event->type == BLE_GAP_EVENT_DISC_COMPLETE) {
+        mp_bluetooth_gap_on_scan_complete();
+        return 0;
+    }
+
+    if (event->type != BLE_GAP_EVENT_DISC) {
+        return 0;
+    }
+
+    if (event->disc.event_type == BLE_HCI_ADV_RPT_EVTYPE_ADV_IND || event->disc.event_type == BLE_HCI_ADV_RPT_EVTYPE_NONCONN_IND) {
+        bool connectable = event->disc.event_type == BLE_HCI_ADV_RPT_EVTYPE_ADV_IND;
+        uint8_t addr[6];
+        reverse_addr_byte_order(addr, event->disc.addr.val);
+        mp_bluetooth_gap_on_scan_result(event->disc.addr.type, addr, connectable, event->disc.rssi, event->disc.data, event->disc.length_data);
+    } else if (event->disc.event_type == BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP) {
+        // TODO
+    } else if (event->disc.event_type == BLE_HCI_ADV_RPT_EVTYPE_SCAN_IND) {
+        // TODO
+    }
+
+    return 0;
+}
+
+int mp_bluetooth_gap_scan_start(int32_t duration_ms, int32_t interval_us, int32_t window_us) {
+    if (duration_ms == 0) {
+        duration_ms = BLE_HS_FOREVER;
+    }
+    struct ble_gap_disc_params discover_params = {
+        .itvl = MAX(BLE_HCI_SCAN_ITVL_MIN, MIN(BLE_HCI_SCAN_ITVL_MAX, interval_us / BLE_HCI_SCAN_ITVL)),
+        .window = MAX(BLE_HCI_SCAN_WINDOW_MIN, MIN(BLE_HCI_SCAN_WINDOW_MAX, window_us / BLE_HCI_SCAN_ITVL)),
+        .filter_policy = BLE_HCI_CONN_FILT_NO_WL,
+        .limited = 0,
+        .passive = 1,  // TODO: Handle BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP in gap_scan_cb above.
+        .filter_duplicates = 0,
+    };
+    int err = ble_gap_disc(BLE_OWN_ADDR_PUBLIC, duration_ms, &discover_params, gap_scan_cb, NULL);
+    return ble_hs_err_to_errno(err);
+}
+
+int mp_bluetooth_gap_scan_stop(void) {
+    if (!ble_gap_disc_active()) {
+        return 0;
+    }
+    int err = ble_gap_disc_cancel();
+    if (err == 0) {
+        mp_bluetooth_gap_on_scan_complete();
+        return 0;
+    }
+    return ble_hs_err_to_errno(err);
+}
+
+// Central role: GAP events for a connected peripheral.
+STATIC int peripheral_gap_event_cb(struct ble_gap_event *event, void *arg) {
+    DEBUG_EVENT_printf("peripheral_gap_event_cb: event=%d\n", event->type);
+    struct ble_gap_conn_desc desc;
+    uint8_t addr[6] = {0};
+
+    switch (event->type) {
+        case BLE_GAP_EVENT_CONNECT:
+            if (event->connect.status == 0) {
+                // Connection established.
+                ble_gap_conn_find(event->connect.conn_handle, &desc);
+                reverse_addr_byte_order(addr, desc.peer_id_addr.val);
+                mp_bluetooth_gap_on_connected_disconnected(MP_BLUETOOTH_IRQ_PERIPHERAL_CONNECT, event->connect.conn_handle, desc.peer_id_addr.type, addr);
+            } else {
+                // Connection failed.
+                mp_bluetooth_gap_on_connected_disconnected(MP_BLUETOOTH_IRQ_PERIPHERAL_DISCONNECT, event->connect.conn_handle, 0xff, addr);
+            }
+            break;
+
+        case BLE_GAP_EVENT_DISCONNECT:
+            // Disconnect.
+            reverse_addr_byte_order(addr, event->disconnect.conn.peer_id_addr.val);
+            mp_bluetooth_gap_on_connected_disconnected(MP_BLUETOOTH_IRQ_PERIPHERAL_DISCONNECT, event->disconnect.conn.conn_handle, event->disconnect.conn.peer_id_addr.type, addr);
+
+            break;
+
+        case BLE_GAP_EVENT_NOTIFY_RX: {
+            uint16_t ev = event->notify_rx.indication == 0 ? MP_BLUETOOTH_IRQ_GATTC_NOTIFY : MP_BLUETOOTH_IRQ_GATTC_INDICATE;
+            gattc_on_data_available(ev, event->notify_rx.conn_handle, event->notify_rx.attr_handle, event->notify_rx.om);
+            break;
+        }
+
+        case BLE_GAP_EVENT_CONN_UPDATE:
+            // TODO
+            break;
+
+        case BLE_GAP_EVENT_CONN_UPDATE_REQ:
+            // TODO
+            break;
+
+        default:
+            break;
+    }
+    return 0;
+}
+
+int mp_bluetooth_gap_peripheral_connect(uint8_t addr_type, const uint8_t *addr, int32_t duration_ms) {
+    if (ble_gap_disc_active()) {
+        mp_bluetooth_gap_scan_stop();
+    }
+
+    // TODO: This is the same as ble_gap_conn_params_dflt (i.e. passing NULL).
+    STATIC const struct ble_gap_conn_params params = {
+        .scan_itvl = 0x0010,
+        .scan_window = 0x0010,
+        .itvl_min = BLE_GAP_INITIAL_CONN_ITVL_MIN,
+        .itvl_max = BLE_GAP_INITIAL_CONN_ITVL_MAX,
+        .latency = BLE_GAP_INITIAL_CONN_LATENCY,
+        .supervision_timeout = BLE_GAP_INITIAL_SUPERVISION_TIMEOUT,
+        .min_ce_len = BLE_GAP_INITIAL_CONN_MIN_CE_LEN,
+        .max_ce_len = BLE_GAP_INITIAL_CONN_MAX_CE_LEN,
+    };
+
+    ble_addr_t addr_nimble = create_nimble_addr(addr_type, addr);
+    int err = ble_gap_connect(BLE_OWN_ADDR_PUBLIC, &addr_nimble, duration_ms, &params, &peripheral_gap_event_cb, NULL);
+    return ble_hs_err_to_errno(err);
+}
+
+STATIC int peripheral_discover_service_cb(uint16_t conn_handle, const struct ble_gatt_error *error, const struct ble_gatt_svc *service, void *arg) {
+    DEBUG_EVENT_printf("peripheral_discover_service_cb: conn_handle=%d status=%d start_handle=%d\n", conn_handle, error->status, service ? service->start_handle : -1);
+    if (error->status == 0) {
+        mp_obj_bluetooth_uuid_t service_uuid = create_mp_uuid(&service->uuid);
+        mp_bluetooth_gattc_on_primary_service_result(conn_handle, service->start_handle, service->end_handle, &service_uuid);
+    }
+    return 0;
+}
+
+int mp_bluetooth_gattc_discover_primary_services(uint16_t conn_handle) {
+    int err = ble_gattc_disc_all_svcs(conn_handle, &peripheral_discover_service_cb, NULL);
+    return ble_hs_err_to_errno(err);
+}
+
+STATIC int ble_gatt_characteristic_cb(uint16_t conn_handle, const struct ble_gatt_error *error, const struct ble_gatt_chr *characteristic, void *arg) {
+    DEBUG_EVENT_printf("ble_gatt_characteristic_cb: conn_handle=%d status=%d def_handle=%d val_handle=%d\n", conn_handle, error->status, characteristic ? characteristic->def_handle : -1, characteristic ? characteristic->val_handle : -1);
+    if (error->status == 0) {
+        mp_obj_bluetooth_uuid_t characteristic_uuid = create_mp_uuid(&characteristic->uuid);
+        mp_bluetooth_gattc_on_characteristic_result(conn_handle, characteristic->def_handle, characteristic->val_handle, characteristic->properties, &characteristic_uuid);
+    }
+    return 0;
+}
+
+int mp_bluetooth_gattc_discover_characteristics(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle) {
+    int err = ble_gattc_disc_all_chrs(conn_handle, start_handle, end_handle, &ble_gatt_characteristic_cb, NULL);
+    return ble_hs_err_to_errno(err);
+}
+
+STATIC int ble_gatt_descriptor_cb(uint16_t conn_handle, const struct ble_gatt_error *error, uint16_t characteristic_val_handle, const struct ble_gatt_dsc *descriptor, void *arg) {
+    DEBUG_EVENT_printf("ble_gatt_descriptor_cb: conn_handle=%d status=%d chr_handle=%d dsc_handle=%d\n", conn_handle, error->status, characteristic_val_handle, descriptor ? descriptor->handle : -1);
+    if (error->status == 0) {
+        mp_obj_bluetooth_uuid_t descriptor_uuid = create_mp_uuid(&descriptor->uuid);
+        mp_bluetooth_gattc_on_descriptor_result(conn_handle, descriptor->handle, &descriptor_uuid);
+    }
+    return 0;
+}
+
+int mp_bluetooth_gattc_discover_descriptors(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle) {
+    int err = ble_gattc_disc_all_dscs(conn_handle, start_handle, end_handle, &ble_gatt_descriptor_cb, NULL);
+    return ble_hs_err_to_errno(err);
+}
+
+STATIC int ble_gatt_attr_read_cb(uint16_t conn_handle, const struct ble_gatt_error *error, struct ble_gatt_attr *attr, void *arg) {
+    DEBUG_EVENT_printf("ble_gatt_attr_read_cb: conn_handle=%d status=%d handle=%d\n", conn_handle, error->status, attr ? attr->handle : -1);
+    // TODO: Maybe send NULL if error->status non-zero.
+    if (error->status == 0) {
+        gattc_on_data_available(MP_BLUETOOTH_IRQ_GATTC_READ_RESULT, conn_handle, attr->handle, attr->om);
+    }
+    return 0;
+}
+
+// Initiate read of a value from the remote peripheral.
+int mp_bluetooth_gattc_read(uint16_t conn_handle, uint16_t value_handle) {
+    int err = ble_gattc_read(conn_handle, value_handle, &ble_gatt_attr_read_cb, NULL);
+    return ble_hs_err_to_errno(err);
+}
+
+STATIC int ble_gatt_attr_write_cb(uint16_t conn_handle, const struct ble_gatt_error *error, struct ble_gatt_attr *attr, void *arg) {
+    DEBUG_EVENT_printf("ble_gatt_attr_write_cb: conn_handle=%d status=%d handle=%d\n", conn_handle, error->status, attr ? attr->handle : -1);
+    mp_bluetooth_gattc_on_write_status(conn_handle, attr->handle, error->status);
+    return 0;
+}
+
+// Write the value to the remote peripheral.
+int mp_bluetooth_gattc_write(uint16_t conn_handle, uint16_t value_handle, const uint8_t *value, size_t *value_len, unsigned int mode) {
+    int err;
+    if (mode == MP_BLUETOOTH_WRITE_MODE_NO_RESPONSE) {
+        err = ble_gattc_write_no_rsp_flat(conn_handle, value_handle, value, *value_len);
+    } else if (mode == MP_BLUETOOTH_WRITE_MODE_WITH_RESPONSE) {
+        err = ble_gattc_write_flat(conn_handle, value_handle, value, *value_len, &ble_gatt_attr_write_cb, NULL);
+    } else {
+        err = BLE_HS_EINVAL;
+    }
+    return ble_hs_err_to_errno(err);
+}
+
+#endif // MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
+
+#endif // MICROPY_PY_BLUETOOTH && MICROPY_BLUETOOTH_NIMBLE