Android Things 3无法在Raspberry PI 3上读取rxtx

Question

我有一个Arduino配置为保持写东西在TX端口，这是连接到我的树莓派3与Android的东西开发者预览版3（我确信RX/TX电缆配置正确和电压是确定的）。

我尝试了很长一段时间使用Android Things libs的外围设备管理服务读取和写入数据。

当出现错误时启动应用程序：

04-11 16:26:13.665 163-163/? I/peripheraman:type=1400审核（0.0:44）：avc:denied{read write}for name=“ttyam0”dev=“tmpfs”ino=1203 scontext=u:r:peripheraman:s0 tcontext=u:object\r:device:s0 tclass=chr\u file permissive=1

04-11 16:26:13.665 163-163/? I/peripheraldan:type=1400审核（0.0:45）：avc:denied{open}for path=“/dev/ttyAMA0”dev=“tmpfs”ino=1203 scontext=u:r:peripheraldman:s0tcontext=u:object\r:device:s0tclass=chr\u file permissive=1

04-11 16:26:13.665 163-163/? I/peripheraldan:type=1400审核（0.0:46）：avc:denied{ioctl}for path=“/dev/ttyam0”dev=“tmpfs”ino=1203 ioctlcmd=5401 scontext=u:r:peripheraldan:s0 tcontext=u:object\r:device:s0 tclass=chr\u 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();
    }
}}

有人知道会是什么吗？

Answer 1

我在您的代码中没有看到注册了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定期轮询UART。read（）获取新的传入字节，我在您的代码中也没有看到。似乎只有在onStart（）活动回调中调用过一次。

回调是一种更有效的方法，因此我建议添加它。有关更多详细信息，请参阅UART外围设备I/O指南。