android - 从 Android 到 Arduino 接收数据的延迟

Question

我正在通过 USB 将我的 android 设备连接到 arduino，并且我使用 bulkTransfer 立即从 arduino 接收数据，但是当我要使用相同的命令将确认信号发送回 arduino 时，它会在几秒钟后收到。

我的 arduino 模型是 DUE，而 arduino 侧代码是：

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(49, OUTPUT);
}
void loop() {
  String a;

  int sensorValue[64];
  for (int i = 0; i <= 63; i++)
  {
    sensorValue[i] = analogRead(A0) / 4;
    a = a + char(sensorValue[i]);
  }
  char b;
  while (1) {
    Serial.print(a);
    Serial.flush();
    delay(2);
    b = Serial.read();
    if (b == '1')
    {
      break;
    }
  }
  digitalWrite(49, HIGH);
  delay(2000);
  digitalWrite(49, LOW);
}

我的android端代码是：

public void onClick(View v) {
            synchronized (this) {
                if (usbDeviceConnection != null) {

                    Thread myThread = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            try {
                                int chunkCounter = 0;
                                String strTemp = null;
                                while (chunkCounter < 1) {

                                    byte[] message = new byte[64];

                                    final int result = usbDeviceConnection.bulkTransfer(endpointIN, message, 64, 10);

                                    if (result == 64) {
                                        for (int intTemp = 0; intTemp < 64; intTemp++) {
                                            strTemp += String.valueOf((char) message[intTemp]);

                                        }

                                        byte[] ack = new byte[1];
                                        ack[0] = 1; //1 means I've got this chunk
                                        synchronized(this) {
                                            int resultAck = 0;
                                            while (resultAck <= 0) {
                                                resultAck = usbDeviceConnection.bulkTransfer(endpointOUT, ack, 1, 10);
                                            }
                                        }
                                        chunkCounter++;
                                        if (chunkCounter == 1) {
                                            final String strTempFinal = strTemp;
                                            tempflag = true;
                                            runOnUiThread(new Runnable() {
                                                @Override
                                                public void run() {
                                                    txtGetData.setText(strTempFinal);
                                                }
                                            });
                                        }
                                    }
                                }
                            } catch (final Exception e){
                                runOnUiThread(new Runnable() {
                                    @Override
                                    public void run() {
                                        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
                                    }
                                });
                            }
                        }
                    });
                  myThread.start();


                }

任何帮助，将不胜感激。提前致谢。