Android Things 3 无法从 Raspberry PI 3 上的 rxtx 读取

Question

我有一个 Arduino 配置为继续在 TX 端口上写东西，它连接到我的带有 Android Things Developer preview 3 的 Raspberry Pi 3(我确信 RX/TX 电缆配置正确并且电压正常)。

我尝试了很长时间来使用 Android Things 库的 PeripheralManagerService 读取数据和写入数据。

启动应用程序时出现错误:

04-11 16:26:13.665 163-163/? I/peripheralman: type=1400 audit(0.0:44): avc: denied { read write } for name="ttyAMA0" dev="tmpfs" ino=1203 scontext=u:r:peripheralman:s0 tcontext=u:object_r:device:s0 tclass=chr_file permissive=1

04-11 16:26:13.665 163-163/? I/peripheralman: type=1400 audit(0.0:45): avc: denied { open } for path="/dev/ttyAMA0" dev="tmpfs" ino=1203 scontext=u:r:peripheralman:s0 tcontext=u:object_r:device:s0 tclass=chr_file permissive=1

04-11 16:26:13.665 163-163/? I/peripheralman: type=1400 audit(0.0:46): avc: denied { ioctl } for path="/dev/ttyAMA0" dev="tmpfs" ino=1203 ioctlcmd=5401 scontext=u:r:peripheralman:s0 tcontext=u:object_r:device:s0 tclass=chr_file permissive=1

我的代码:

public class MainActivity extends Activity {

private final int BUFFER_SIZE = 64;
private UartDevice rxtx;


public void configureUartFrame(UartDevice uart) throws IOException {
    // Configure the UART port
    uart.setBaudrate(9600);
}

public void writeUartData(UartDevice uart, String msg) throws IOException {
    byte[] buffer = msg.getBytes();
    int count = uart.write(buffer, buffer.length);
    Log.d(TAG, "Wrote " + count + " bytes to peripheral");
}

public void readUartBuffer(UartDevice uart) throws IOException {
    byte[] buffer = new byte[BUFFER_SIZE];
    int count;
    while ((count = uart.read(buffer, buffer.length)) > 0) {
        Log.d(TAG, "Read " + count + " bytes from peripheral");
        Log.d("Message", new String(buffer));
    }
}

@Override
protected void onStart() {
    super.onStart();
        try {
            writeUartData(rxtx, "teste");
            readUartBuffer(rxtx);
        } catch (IOException e) {
            e.printStackTrace();
        }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    PeripheralManagerService manager = new PeripheralManagerService();

    manager.getUartDeviceList();
    List<String> portList = manager.getUartDeviceList();

    if (portList.isEmpty()) {
        Log.i(TAG, "No UART port available on this device:");
    } else {
        Log.i(TAG, "List of RXTX available ports: - " + portList);
    }

    try{
       rxtx = manager.openUartDevice(portList.get(0));
       configureUartFrame(rxtx);
    }catch (IOException e){
        e.printStackTrace();
    }
}}

有人知道它会是什么吗？

Answer 1

我在您的代码中没有看到任何地方注册了 UartDeviceCallback。您如何轮询 UART 以获取新的传入数据？如果没有注册回调，您的应用程序将需要通过 UartDevice.read() 定期轮询 UART 以获取新的传入字节，我也没有在您的代码中看到这一点。唯一似乎被调用的地方是在 onStart() Activity 回调中。

回调是一种更有效的方法，所以我建议添加它。有关详细信息，请查看 UART Peripheral I/O Guide .