ble.py

# This example finds and connects to a BLE temperature sensor (e.g. the one in ble_temperature.py).

import bluetooth
import random
import struct
import time
import micropython

from ble_advertising import decode_services, decode_name

from micropython import const

_IRQ_CENTRAL_CONNECT = const(1)
_IRQ_CENTRAL_DISCONNECT = const(2)
_IRQ_GATTS_WRITE = const(3)
_IRQ_GATTS_READ_REQUEST = const(4)
_IRQ_SCAN_RESULT = const(5)
_IRQ_SCAN_DONE = const(6)
_IRQ_PERIPHERAL_CONNECT = const(7)
_IRQ_PERIPHERAL_DISCONNECT = const(8)
_IRQ_GATTC_SERVICE_RESULT = const(9)
_IRQ_GATTC_SERVICE_DONE = const(10)
_IRQ_GATTC_CHARACTERISTIC_RESULT = const(11)
_IRQ_GATTC_CHARACTERISTIC_DONE = const(12)
_IRQ_GATTC_DESCRIPTOR_RESULT = const(13)
_IRQ_GATTC_DESCRIPTOR_DONE = const(14)
_IRQ_GATTC_READ_RESULT = const(15)
_IRQ_GATTC_READ_DONE = const(16)
_IRQ_GATTC_WRITE_DONE = const(17)
_IRQ_GATTC_NOTIFY = const(18)
_IRQ_GATTC_INDICATE = const(19)

_ADV_IND = const(0x00)
_ADV_DIRECT_IND = const(0x01)
_ADV_SCAN_IND = const(0x02)
_ADV_NONCONN_IND = const(0x03)

# org.bluetooth.service.environmental_sensing
_ENV_SENSE_UUID = bluetooth.UUID(0x181A)
# org.bluetooth.characteristic.temperature
_TEMP_UUID = bluetooth.UUID(0x2A6E)
_TEMP_CHAR = (
    _TEMP_UUID,
    bluetooth.FLAG_READ | bluetooth.FLAG_NOTIFY,
)
_ENV_SENSE_SERVICE = (
    _ENV_SENSE_UUID,
    (_TEMP_CHAR,),
)

# org.bluetooth.characteristic.gap.appearance.xml
_ADV_APPEARANCE_GENERIC_THERMOMETER = const(768)


class BLETemperatureCentral:
    def __init__(self, ble):
        self._ble = ble
        self._ble.active(True)
        self._ble.irq(self._irq)

        self._reset()

    def _reset(self):
        # Cached name and address from a successful scan.
        self._name = None
        self._addr_type = None
        self._addr = None

        # Cached value (if we have one)
        self._value = None

        # Callbacks for completion of various operations.
        # These reset back to None after being invoked.
        self._scan_callback = None
        self._conn_callback = None
        self._read_callback = None

        # Persistent callback for when new data is notified from the device.
        self._notify_callback = None

        # Connected device.
        self._conn_handle = None
        self._start_handle = None
        self._end_handle = None
        self._value_handle = None

    def _irq(self, event, data):
        if event == _IRQ_SCAN_RESULT:
            addr_type, addr, adv_type, rssi, adv_data = data
            if adv_type in (_ADV_IND, _ADV_DIRECT_IND) and _ENV_SENSE_UUID in decode_services(
                adv_data
            ):
                # Found a potential device, remember it and stop scanning.
                self._addr_type = addr_type
                self._addr = bytes(
                    addr
                )  # Note: addr buffer is owned by caller so need to copy it.
                self._name = decode_name(adv_data) or "?"
                self._ble.gap_scan(None)

        elif event == _IRQ_SCAN_DONE:
            if self._scan_callback:
                if self._addr:
                    # Found a device during the scan (and the scan was explicitly stopped).
                    self._scan_callback(self._addr_type, self._addr, self._name)
                    self._scan_callback = None
                else:
                    # Scan timed out.
                    self._scan_callback(None, None, None)

        elif event == _IRQ_PERIPHERAL_CONNECT:
            # Connect successful.
            conn_handle, addr_type, addr = data
            if addr_type == self._addr_type and addr == self._addr:
                self._conn_handle = conn_handle
                self._ble.gattc_discover_services(self._conn_handle)

        elif event == _IRQ_PERIPHERAL_DISCONNECT:
            # Disconnect (either initiated by us or the remote end).
            conn_handle, _, _ = data
            if conn_handle == self._conn_handle:
                # If it was initiated by us, it'll already be reset.
                self._reset()

        elif event == _IRQ_GATTC_SERVICE_RESULT:
            # Connected device returned a service.
            conn_handle, start_handle, end_handle, uuid = data
            if conn_handle == self._conn_handle and uuid == _ENV_SENSE_UUID:
                self._start_handle, self._end_handle = start_handle, end_handle

        elif event == _IRQ_GATTC_SERVICE_DONE:
            # Service query complete.
            if self._start_handle and self._end_handle:
                self._ble.gattc_discover_characteristics(
                    self._conn_handle, self._start_handle, self._end_handle
                )
            else:
                print("Failed to find environmental sensing service.")

        elif event == _IRQ_GATTC_CHARACTERISTIC_RESULT:
            # Connected device returned a characteristic.
            conn_handle, def_handle, value_handle, properties, uuid = data
            if conn_handle == self._conn_handle and uuid == _TEMP_UUID:
                self._value_handle = value_handle

        elif event == _IRQ_GATTC_CHARACTERISTIC_DONE:
            # Characteristic query complete.
            if self._value_handle:
                # We've finished connecting and discovering device, fire the connect callback.
                if self._conn_callback:
                    self._conn_callback()
            else:
                print("Failed to find temperature characteristic.")

        elif event == _IRQ_GATTC_READ_RESULT:
            # A read completed successfully.
            conn_handle, value_handle, char_data = data
            if conn_handle == self._conn_handle and value_handle == self._value_handle:
                self._update_value(char_data)
                if self._read_callback:
                    self._read_callback(self._value)
                    self._read_callback = None

        elif event == _IRQ_GATTC_READ_DONE:
            # Read completed (no-op).
            conn_handle, value_handle, status = data

        elif event == _IRQ_GATTC_NOTIFY:
            # The ble_temperature.py demo periodically notifies its value.
            conn_handle, value_handle, notify_data = data
            if conn_handle == self._conn_handle and value_handle == self._value_handle:
                self._update_value(notify_data)
                if self._notify_callback:
                    self._notify_callback(self._value)

    # Returns true if we've successfully connected and discovered characteristics.
    def is_connected(self):
        return self._conn_handle is not None and self._value_handle is not None

    # Find a device advertising the environmental sensor service.
    def scan(self, callback=None):
        self._addr_type = None
        self._addr = None
        self._scan_callback = callback
        self._ble.gap_scan(2000, 30000, 30000)

    # Connect to the specified device (otherwise use cached address from a scan).
    def connect(self, addr_type=None, addr=None, callback=None):
        self._addr_type = addr_type or self._addr_type
        self._addr = addr or self._addr
        self._conn_callback = callback
        if self._addr_type is None or self._addr is None:
            return False
        self._ble.gap_connect(self._addr_type, self._addr)
        return True

    # Disconnect from current device.
    def disconnect(self):
        if not self._conn_handle:
            return
        self._ble.gap_disconnect(self._conn_handle)
        self._reset()

    # Issues an (asynchronous) read, will invoke callback with data.
    def read(self, callback):
        if not self.is_connected():
            return
        self._read_callback = callback
        self._ble.gattc_read(self._conn_handle, self._value_handle)

    # Sets a callback to be invoked when the device notifies us.
    def on_notify(self, callback):
        self._notify_callback = callback

    def _update_value(self, data):
        # Data is sint16 in degrees Celsius with a resolution of 0.01 degrees Celsius.
        self._value = struct.unpack("<h", data)[0] / 100
        return self._value

    def value(self):
        return self._value

ble_advertising.py

# Helpers for generating BLE advertising payloads.

from micropython import const
import struct
import bluetooth

# Advertising payloads are repeated packets of the following form:
#   1 byte data length (N + 1)
#   1 byte type (see constants below)
#   N bytes type-specific data

_ADV_TYPE_FLAGS = const(0x01)
_ADV_TYPE_NAME = const(0x09)
_ADV_TYPE_UUID16_COMPLETE = const(0x3)
_ADV_TYPE_UUID32_COMPLETE = const(0x5)
_ADV_TYPE_UUID128_COMPLETE = const(0x7)
_ADV_TYPE_UUID16_MORE = const(0x2)
_ADV_TYPE_UUID32_MORE = const(0x4)
_ADV_TYPE_UUID128_MORE = const(0x6)
_ADV_TYPE_APPEARANCE = const(0x19)


# Generate a payload to be passed to gap_advertise(adv_data=...).
def advertising_payload(limited_disc=False, br_edr=False, name=None, services=None, appearance=0):
    payload = bytearray()

    def _append(adv_type, value):
        nonlocal payload
        payload += struct.pack("BB", len(value) + 1, adv_type) + value

    _append(
        _ADV_TYPE_FLAGS,
        struct.pack("B", (0x01 if limited_disc else 0x02) + (0x18 if br_edr else 0x04)),
    )

    if name:
        _append(_ADV_TYPE_NAME, name)

    if services:
        for uuid in services:
            b = bytes(uuid)
            if len(b) == 2:
                _append(_ADV_TYPE_UUID16_COMPLETE, b)
            elif len(b) == 4:
                _append(_ADV_TYPE_UUID32_COMPLETE, b)
            elif len(b) == 16:
                _append(_ADV_TYPE_UUID128_COMPLETE, b)

    # See org.bluetooth.characteristic.gap.appearance.xml
    if appearance:
        _append(_ADV_TYPE_APPEARANCE, struct.pack("<h", appearance))

    return payload


def decode_field(payload, adv_type):
    i = 0
    result = []
    while i + 1 < len(payload):
        if payload[i + 1] == adv_type:
            result.append(payload[i + 2 : i + payload[i] + 1])
        i += 1 + payload[i]
    return result


def decode_name(payload):
    n = decode_field(payload, _ADV_TYPE_NAME)
    return str(n[0], "utf-8") if n else ""


def decode_services(payload):
    services = []
    for u in decode_field(payload, _ADV_TYPE_UUID16_COMPLETE):
        services.append(bluetooth.UUID(struct.unpack("<h", u)[0]))
    for u in decode_field(payload, _ADV_TYPE_UUID32_COMPLETE):
        services.append(bluetooth.UUID(struct.unpack("<d", u)[0]))
    for u in decode_field(payload, _ADV_TYPE_UUID128_COMPLETE):
        services.append(bluetooth.UUID(u))
    return services


def demo():
    payload = advertising_payload(
        name="micropython",
        services=[bluetooth.UUID(0x181A), bluetooth.UUID("6E400001-B5A3-F393-E0A9-E50E24DCCA9E")],
    )
    print(payload)
    print(decode_name(payload))
    print(decode_services(payload))


if __name__ == "__main__":
    demo()

main.py

import bluetooth
from ble import BLETemperatureCentral
import time
from umqtt.simple import MQTTClient
import config
import micropython
import gc

CACERT_PATH = "certs/aws-root-ca.pem"
KEY_PATH = "certs/private.pem.key"
CERT_PATH = "certs/certificate.pem.crt"


class Test:
    def __init__(self) -> None:
        micropython.mem_info()
        self.central = None
        self.mqtt = None

    def close(self):
        print("Closing")
        micropython.mem_info()
        if self.central:
            self.central.disconnect()
        if self.mqtt:
            self.mqtt.disconnect()

    def run(self):
        micropython.mem_info()
        self.mqtt = self.connect_mqtt(config.IOT_ENDPOINT, config.IOT_CLIENT_ID)
        micropython.mem_info()
        self.central = self.init_bt()

        while True:
            if self.central:
                while self.central.is_connected():
                    print(self.central.value())
                    time.sleep(1)

            time.sleep(1)

    def init_bt(self):
        ble = bluetooth.BLE()
        central = BLETemperatureCentral(ble)

        not_found = False

        def on_scan(addr_type, addr, name):
            if addr_type is not None:
                print("Found sensor:", addr_type, addr, name)
                central.connect()
            else:
                nonlocal not_found
                not_found = True
                print("No sensor found.")

        central.scan(callback=on_scan)

        # Wait for connection...
        while not central.is_connected():
            time.sleep_ms(100)
            if not_found:
                return

        print("Connected")
        return central

    def connect_mqtt(self, endpoint, client_id):
        with open(KEY_PATH, "r") as f:
            key = f.read()

        with open(CERT_PATH, "r") as f:
            cert = f.read()

        client = MQTTClient(
            client_id=client_id,
            server=endpoint,
            port=8883,
            keepalive=1200,
            ssl=True,
            ssl_params={"key": key, "cert": cert, "server_side": False},
        )
        print("Connecting to MQTT")
        client.connect()
        print("MQTT Connected")
        return client


if __name__ == "__main__":
    test = Test()
    try:
        test.run()
    finally:
        test.close()