Dynamic advertiser name using bluetooth library on pi pico w

[griffinsteffy19]

Is there a way to setup a custom advertiser name? I'd like to advertise with a pre-defined prefix and the machine unique id. I have only been able to set the advertiser name to predefined strings.

I am testing using the blue_simple_periphial example here.

[jimmo]

@griffinsteffy19 Yes the advertising payload can be whatever you like, as long as it's 31 bytes or fewer.

Can you share the code you're using.

[griffinsteffy19]

@jimmo I must have been hitting the 31 byte limit for the 4-5 combinations that I tried, and the predefined strings were always within the limit. Unlucky testing on my end!

For those in the future...

#This example demonstrates a UART periperhal.

import bluetooth
import random
import struct
import time
import machine
from micropython import const

import uasyncio as asyncio

_IRQ_CENTRAL_CONNECT = const(1)
_IRQ_CENTRAL_DISCONNECT = const(2)
_IRQ_GATTS_WRITE = const(3)

_FLAG_READ = const(0x0002)
_FLAG_WRITE_NO_RESPONSE = const(0x0004)
_FLAG_WRITE = const(0x0008)
_FLAG_NOTIFY = const(0x0010)

_UART_UUID = bluetooth.UUID("866cd78d-2bd9-4c02-a988-e5a6030af6eb")
_UART_TX = (
    bluetooth.UUID("be9ae2ed-a049-4797-933b-f9185002cac7"),
    _FLAG_READ | _FLAG_NOTIFY,
)
_UART_RX = (
    bluetooth.UUID("0241625a-e199-4ce5-8570-a1ef42469935"),
    _FLAG_WRITE | _FLAG_WRITE_NO_RESPONSE,
)
_UART_SERVICE = (
    _UART_UUID,
    (_UART_TX, _UART_RX),
)
_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

class BLESimplePeripheral:
    def __init__(self, ble, name="mpy-uart"):
        self._ble = ble
        self._ble.active(True)
        self._ble.irq(self._irq)
        ((self._handle_tx, self._handle_rx),
         ) = self._ble.gatts_register_services((_UART_SERVICE,))
        self._connections = set()
        self._write_callback = None
        self._payload = advertising_payload(name=name, services=[_UART_UUID])

    def _irq(self, event, data):
        # Track connections so we can send notifications.
        if event == _IRQ_CENTRAL_CONNECT:
            conn_handle, _, _ = data
            print("New connection", conn_handle)
            self._connections.add(conn_handle)
        elif event == _IRQ_CENTRAL_DISCONNECT:
            conn_handle, _, _ = data
            print("Disconnected", conn_handle)
            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
            value = self._ble.gatts_read(value_handle)
            if value_handle == self._handle_rx and self._write_callback:
                asyncio.create_task(self._write_callback(value))

    def send(self, data):
        for conn_handle in self._connections:
            self._ble.gatts_notify(conn_handle, self._handle_tx, data)

    def is_connected(self):
        return len(self._connections) > 0

    def _advertise(self, interval_us=500000):
        print("Starting advertising")
        self._ble.gap_advertise(interval_us, adv_data=self._payload)

    def on_write(self, callback):
        self._write_callback = callback

    def stop(self):
        self._ble.gap_disconnect(self._connections.pop())
        self._ble.active(False)


def on_rx(data):
    log.trace('data: ' + str(data))


if __name__ == '__main__':
    uuid = machine.unique_id().hex()[-4:]
    name = "TST-"+uuid
    print("ble service with name: %s" % (name))
    ble = bluetooth.BLE()
    bleService = BLESimplePeripheral(ble, name)
    bleService.on_write(on_rx)
    bleService._advertise()

    while True:
        asyncio.sleep(1)

[jimmo]

@griffinsteffy19 Please see Welcome (Please read before posting) for how to format code for posting.

FYI I would recommend using aioble if possible, it makes all of this so much simpler. The bluetooth module is designed just to be the low level interface.

[griffinsteffy19]

Sorry about the formatting, that’s what I get for trying to work too late.

I’ll look into that library. The sample code I sent you is intended for a low level library I’m writing in a bigger project.