2003款大众高尔夫MK4 OBD2通信连接故障求助

更新进展：手头4根OBD串口线里，有一根能响应AT指令，但发送获取支持PID的0100指令时，返回SEARCHING... UNABLE TO CONNECT.

我正在开发自定义APP以获取车载数据，最初使用Nexas BLE OBD适配器，它能在iPhone的CarScanner应用中正常工作。通过nRF Scan应用找到了适配所需的UUID，但在MacBook上通过BLE连接时，所有AT或PID指令都返回相同的固定响应。调试两天未解决，怀疑MacBook存在问题，于是切换到树莓派4设备，改用有线连接方式。

已知2003款高尔夫MK4的OBD通信采用Kline协议而非CAN总线，但初始化指令应该不存在差异。

BLE连接的JavaScript代码 #

const initializeButton = document.querySelector("#initializeOBD");
const status = document.querySelector("#status");
const responses = document.querySelector("#responses");

const OBD_SERVICE_UUID = "49535343-fe7d-4ae5-8fa9-9fafd205e455";
const OBD_CHARACTERISTIC_UUID = "49535343-6daa-4d02-abf6-19569aca69fe";
const OBD_CHARACTERISTIC_UUID1 = "49535343-aca3-481c-91ec-d85e28a60318";
const OBD_CHARACTERISTIC_UUID2 = "49535343-4c8a-39b3-2f49-511cff073b7e";
const initializationCommands = [
    "ATZ\r",
    "ATL0\r",
    "ATE1\r",
    "ATH1\r",
    "ATAT1\r",
    "ATSTFF\r",
    "ATDP\r",
    "ATDP\r",
];

initializeButton.addEventListener("click", async () => {
    try {
        const device = await navigator.bluetooth.requestDevice({
            filters: [{ namePrefix: "NEXAS" }],
            optionalServices: [
                OBD_SERVICE_UUID,
                OBD_CHARACTERISTIC_UUID,
                OBD_CHARACTERISTIC_UUID1,
                OBD_CHARACTERISTIC_UUID2,
            ],
        });

        status.textContent = "Connecting to device...";
        const server = await device.gatt.connect();
        status.textContent = "Connected. Initializing...";
        const service = await server.getPrimaryService(OBD_SERVICE_UUID);
        const characteristic = await service.getCharacteristic(
            OBD_CHARACTERISTIC_UUID
        );

        for (const command of initializationCommands) {
            responses.innerHTML += `<div>Sending command: ${command.trim()}</div>`;
            const encoder = new TextEncoder();
            await characteristic.writeValue(encoder.encode(command));
            await new Promise((resolve) => setTimeout(resolve, 1000));
            const value = await characteristic.readValue();
            const hexString = Array.from(new Uint8Array(value.buffer))
                .map((byte) => byte.toString(16).padStart(2, "0"))
                .join("");
            const bitArray = hexString
                .split("")
                .map((hexDigit) =>
                    parseInt(hexDigit, 16).toString(2).padStart(4, "0")
                )
                .join("");
            responses.innerHTML += `<div>Response (hex): ${hexString}</div>`;
            responses.innerHTML += `<div>Response (bit array): ${bitArray}</div>`;
        }

        responses.innerHTML += `<div>Initialization complete. Listening for RPM...</div>`;
        setInterval(async () => {
            const encoder = new TextEncoder();
            await characteristic.writeValue(encoder.encode("0100"));
            await new Promise((resolve) => setTimeout(resolve, 100));
            const value = await characteristic.readValue();
            const hexString = Array.from(new Uint8Array(value.buffer))
                .map((byte) => byte.toString(16).padStart(2, "0"))
                .join("");
            const bitArray = hexString
                .split("")
                .map((hexDigit) =>
                    parseInt(hexDigit, 16).toString(2).padStart(4, "0")
                )
                .join("");
            responses.innerHTML += `<div>0100 Response (hex): ${hexString}</div>`;
            responses.innerHTML += `<div>0100 Response (bit array): ${bitArray}</div>`;
            await characteristic.writeValue(encoder.encode("0170"));
            await new Promise((resolve) => setTimeout(resolve, 100));
            const value = await characteristic.readValue();
            const hexString = Array.from(new Uint8Array(value.buffer))
                .map((byte) => byte.toString(16).padStart(2, "0"))
                .join("");
            const bitArray = hexString
                .split("")
                .map((hexDigit) =>
                    parseInt(hexDigit, 16).toString(2).padStart(4, "0")
                )
                .join("");
            responses.innerHTML += `<div>0100 Response (hex): ${hexString}</div>`;
            responses.innerHTML += `<div>0100 Response (bit array): ${bitArray}</div>`;
        }, 2000);
    } catch (error) {
        status.textContent = "Failed to connect or test: " + error.message;
    }
});

代码运行输出 #

Initialize OBD
Connected. Initializing...
Responses:
Sending command: ATZ
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATL0
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATE1
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATH1
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATAT1
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATSTFF
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATDP
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Sending command: ATDP
Response (hex): 001800180000004800
Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000
Initialization complete. Listening for RPM...
0100 Response (hex): 001800180000004800
0100 Response (bit array): 000000000001100000000000000110000000000000000000000000000100100000000000

树莓派有线连接测试（Python + obd库） #

测试代码 #

import obd
obd.logger.setLevel(obd.logging.DEBUG)  # enables all debug information

baudrates = ['38400', '9600', '230400', '115200', '57600', '19200']
for i in range(1, 7):
    for item in baudrates:
        connection = obd.OBD(portstr="/dev/ttyUSB0", protocol=i, baudrate=item)
        cmd = obd.commands.SPEED  # select an OBD command (sensor)
        response = connection.query(cmd)  # send the command, and parse the response
        print(response.value)

部分运行输出 #

[obd.obd] ======================= python-OBD (v0.7.1) =======================
[obd.obd] Explicit port defined
[obd.elm327] Initializing ELM327: PORT=/dev/ttyUSB0 BAUD=19200 PROTOCOL=6
[obd.elm327] write: 'ATZ\r'
[obd.elm327] wait: 1 seconds
[obd.elm327] Failed to read port
[obd.elm327] read: b''
[obd.elm327] write: 'ATE0\r'
[obd.elm327] Failed to read port
[obd.elm327] read: b''
[obd.elm327] closing port
[obd.elm327] write: 'ATZ\r'
[obd.elm327] ATE0 did not return 'OK'
[obd.obd] Closing connection
[obd.obd] Cannot load commands: No connection to car
[obd.obd] ===================================================================
[obd.obd] Query failed, no connection available
None

所有输出均显示端口读取失败，未建立有效通信。也尝试过不指定参数的connection = obd.OBD()，问题依旧。原本以为切换到树莓派有线连接能解决MacBook上的问题，顺利读取车辆OBD数据，求技术建议或解决方案。

内容的提问来源于stack exchange，提问作者Volodymyr Samoilenko