circuitpython/examples/bluetooth/ble_uart_peripheral.py

# This example demonstrates a peripheral implementing the Nordic UART Service (NUS).

import bluetooth
from ble_advertising import advertising_payload

from micropython import const
_IRQ_CENTRAL_CONNECT                 = const(1 << 0)
_IRQ_CENTRAL_DISCONNECT              = const(1 << 1)
_IRQ_GATTS_WRITE                     = const(1 << 2)

_UART_UUID = bluetooth.UUID('6E400001-B5A3-F393-E0A9-E50E24DCCA9E')
_UART_TX = (bluetooth.UUID('6E400003-B5A3-F393-E0A9-E50E24DCCA9E'), bluetooth.FLAG_NOTIFY,)
_UART_RX = (bluetooth.UUID('6E400002-B5A3-F393-E0A9-E50E24DCCA9E'), bluetooth.FLAG_WRITE,)
_UART_SERVICE = (_UART_UUID, (_UART_TX, _UART_RX,),)

# org.bluetooth.characteristic.gap.appearance.xml
_ADV_APPEARANCE_GENERIC_COMPUTER = const(128)

class BLEUART:
    def __init__(self, ble, name='mpy-uart', rxbuf=100):
        self._ble = ble
        self._ble.active(True)
        self._ble.irq(handler=self._irq)
        ((self._tx_handle, self._rx_handle,),) = self._ble.gatts_register_services((_UART_SERVICE,))
        # Increase the size of the rx buffer.
        self._ble.gatts_write(self._rx_handle, bytes(rxbuf))
        self._connections = set()
        self._rx_buffer = bytearray()
        self._handler = None
        # Optionally add services=[_UART_UUID], but this is likely to make the payload too large.
        self._payload = advertising_payload(name=name, appearance=_ADV_APPEARANCE_GENERIC_COMPUTER)
        self._advertise()

    def irq(self, handler):
        self._handler = handler

    def _irq(self, event, data):
        # Track connections so we can send notifications.
        if event == _IRQ_CENTRAL_CONNECT:
            conn_handle, _, _, = data
            self._connections.add(conn_handle)
        elif event == _IRQ_CENTRAL_DISCONNECT:
            conn_handle, _, _, = data
            if conn_handle in self._connections:
                self._connections.remove(conn_handle)
            # Start advertising again to allow a new connection.
            self._advertise()
        elif event == _IRQ_GATTS_WRITE:
            conn_handle, value_handle, = data
            if conn_handle in self._connections and value_handle == self._rx_handle:
                self._rx_buffer += self._ble.gatts_read(self._rx_handle)
                if self._handler:
                    self._handler()

    def any(self):
        return len(self._rx_buffer)

    def read(self, sz=None):
        if not sz:
            sz = len(self._rx_buffer)
        result = self._rx_buffer[0:sz]
        self._rx_buffer = self._rx_buffer[sz:]
        return result

    def write(self, data):
        for conn_handle in self._connections:
            self._ble.gatts_notify(conn_handle, self._tx_handle, data)

    def close(self):
        for conn_handle in self._connections:
            self._ble.gap_disconnect(conn_handle)
        self._connections.clear()

    def _advertise(self, interval_us=500000):
        self._ble.gap_advertise(interval_us, adv_data=self._payload)


# ble = bluetooth.BLE()
# uart = BLEUART(ble)