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I have a Arduino configured to keep writing things on TX port, that is connected to my Raspberry Pi 3 with Android Things Developer preview 3 (I am sure that the RX/TX cables are configured right and voltages are OK).

I am trying a long time to read data and write data using PeripheralManagerService of Android Things libs.

There is an error when I start the app:

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

My code:

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();
    }
}}

Someone know what could it be ?

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1 回答 1

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我在您的代码中没有看到UartDeviceCallback注册 a 的任何地方。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定期轮询 UARTUartDevice.read()以获取新的传入字节，我在您的代码中也没有看到。这似乎被调用的唯一地方是在onStart()活动回调中一次。

回调是一种更有效的方法，所以我建议添加它。有关更多详细信息，请查看UART 外设 I/O 指南。

于 2017-04-17T22:09:05.923 回答