MicroPython 蓝牙连接至 OBD BLE

Question

我正在尝试使用

obd2

将 Raspberry Pico W 连接到

BLE

适配器。 至于检测和连接

obd

我应该已经成功了，但现在我陷入了如何向

OBD

发送命令的困境，例如

ATZ

，

ATD

等

对于我正在使用

micropython

和

aioble

库的项目。

如果我理解它如何正确工作，我就充当中心并尝试连接到外围设备。

对于发送AT命令，我使用的是写入功能，在下面的代码中更清楚我在做什么，但是我如何检查从

obd

收到的响应？

由于该服务使用两种不同的

UUID

进行写入和读取，我是否应该创建两种不同的特征，一种用于读取，一种用于写入？

import aioble
import bluetooth
import machine
import uasyncio as asyncio


_OBD_UUID_SERVICE = bluetooth.UUID(0xfff0)
_OBD_UUID_CHARACTERISTIC = bluetooth.UUID(0xfff1)

led = machine.Pin("LED", machine.Pin.OUT)
connected = False
alive = False


async def find_remote():
    async with aioble.scan(duration_ms=5000, interval_us=30000, window_us=30000, active=True) as scanner:
        async for result in scanner:
            if (result.name() == "OBDBLE"):
                print("Found OBDBLE")
                for item in result.services():
                    print(item)
                if _OBD_UUID_SERVICE in result.services():
                    print("Found OBDBLE service")
                    return result.device
    return None


async def blink_task():
    print("Blink task started")
    toggle = True

    while True and alive:
        blink = 250
        led.value(toggle)
        toggle = not toggle

        if connected:
            blink = 1000
        else:
            blink = 250
        await asyncio.sleep_ms(blink)

    print("Blink task stopped")


async def peripheral_task():

    global connected, alive
    connected = False
    device = await find_remote()

    if not device:
        print("OBD device not found")
        return

    try:
        print("Connecting to", device)
        connection = await device.connect()

    except asyncio.TimeoutError:
        print("Timeout during connection")
        return

    async with connection:
        print("Connected")
        alive = True
        connected = True

   
        try:

            obd_service = await connection.service(_OBD_UUID_SERVICE)
            print(obd_service)
            obd_characteristic = await obd_service.characteristic(_OBD_UUID_CHARACTERISTIC)
            print(obd_characteristic)

        except asyncio.TimeoutError:
            print("Timeout discovering services/characteristics")
            return

    
        try:
            if obd_service == None:
                print("Obd Disconnected")
                alive = False
                connected = False

            if obd_characteristic == None:
                print("No Control")
                alive = False
                connected = False

        except asyncio.TimeoutError:
            print("Timeout during discovery/service/characteristic")
            alive = False
        
        print("Sending ATZ")
        obd_characteristic.write(b"ATZ",response=True)
        obd_characteristic.notified()
        data = await obd_characteristic.read()
        print(data)


    await connection.disconnected()
    print("Disconnected")


async def main():
    tasks = []
    tasks = [
        asyncio.create_task(blink_task()),
        asyncio.create_task(peripheral_task())
    ]

    await asyncio.gather(*tasks)

while True:
    asyncio.run(main())

这是输出：

Blink task started
Found OBDBLE
Found OBDBLE
UUID(0xfff0)
Found OBDBLE service
Connecting to Device(ADDR_PUBLIC, aa:bb:cc:12:22:33)
Connected
Service: 19 24 UUID(0xfff0)
Characteristic: 22 21 18 UUID(0xfff1)
Sending ATZ
b''
Disconnected

我使用应用程序找到了

UUID

，我将附上图像以便您检查

Answer 1

这是一个非常广泛的问题。有些方面已经在 https://stackoverflow.com/a/52139765/415982 中得到了解答，特别是您需要探测要使用的特征数量。这是特定于供应商的。

对于实际的通信，您需要使用 API 编写一个队列抽象，该 API 允许您发送命令，等待命令被组装（您也可能只收到部分答案），然后将整个答案传递给来电者。

不要忘记 ELM327 派生协议要求命令以

\r

终止。