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我目前正在将我从 C# 中获得的一些代码移植到 Java 以在 Android 系统上运行。

在我的代码中，我必须从具有 FTDI 芯片的板上读取一些数据。我正在尝试使用 FTDI 网站上的 java 驱动程序。

我可以连接到设备并向其正确发送命令（LED 应闪烁）。董事会似乎正在正确地向我发送数据。

bytesAvailable = ftDevice.getQueueStatus();返回预期的数字

int bytesRead = ftDevice.read(rxData, bytesAvailable);返回相同的数字

但是，在调用上述read()方法时，我在 logcat 中看到以下内容：无法从源读取数据！来自标签：readBulkInData::

我看不出这可能是什么。我尝试在我的代码中摆弄设备的设置，但无济于事。

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2 回答 2

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我解决了这个问题。

通过将整个读取指令序列（thegetQueueStatus()和 the read()）放在另一个Thread. 具体来说，我使用了AsyncTask, 并将阅读说明放入它的doInBackground()方法中。

于 2014-04-11T13:02:30.893 回答
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我已经修改了 FTDI 示例的一部分以进行写入并等待收到答案。这适用于 Parker Compax3 伺服驱动器的简单 HMI 应用程序。该序列每 100 毫秒触发一次。

        // part of FTDI example
        synchronized (ftDev) {
        if(ftDev.isOpen() == false) {
            return;
        }
        ftDev.setLatencyTimer((byte)16);
        String writeString = tvWrite.getText().toString()+"\r";
        byte[] writeByte = writeString.getBytes();
        // write
        ftDev.write(writeByte, writeString.length());

        // new - wait until the buffer have data - no fixed length of incoming data - 4 - 8 bytes     
        readRequest = true;
        startTimeRead = SystemClock.uptimeMillis();
        while (true){
            timeOutInMilliseconds = SystemClock.uptimeMillis() - startTimeRead;

            if (timeOutInMilliseconds > timeOutTime) // checking after 70ms
            {
                readSize = ftDev.getQueueStatus();
                if(readSize>0) {
                        mReadSize = readSize;
                if(mReadSize > READBUF_SIZE) {
                    mReadSize = READBUF_SIZE;
                }

                readCompleted = false;

                // call asynctask
                ReadAsyncTask task = new ReadAsyncTask();
                task.execute();

                // wait until asynctask has completed
                while (readCompleted = false){ // endless loop until asynctask have read
                    if (readCompleted = true){ // <- i know this is not necessary :-)
                        break;  
                    }
                }

                // if read completed, write values to string/textview
                if (readCompleted = true){
                    textView13.setText("Ok" + " " + mReadSize );
                    tvRead.setText(readString); //now it updates the textboxes, strings
                }
            }

            //do anything if there are no data after 70ms
            else{
                readString="**";
                textView13.setText("Timeout, no data");  
                }
            // go out, wait 30ms and do it again
            break;  
            }
        }
    }

这是异步任务

class ReadAsyncTask extends AsyncTask<Void, Void, Void>{  
      @Override  
      protected Void doInBackground(Void... params) {  

          int j = 0;
          ftDev.read(rbuf,mReadSize);
          for(j=0; j<mReadSize; j++) {
              rchar[j] = (char)rbuf[j];
          }

          // clear buffer
          ftDev.purge((byte) 1);

          // copy to string
          readString =String.copyValueOf(rchar,0,mReadSize);
          readCompleted = true;
          return null;
      }  
      @Override  
      protected void onPreExecute() {  
           super.onPreExecute();  
      }  
      @Override  
      protected void onPostExecute(Void result) {  
           super.onPostExecute(result); 
      }  
 }

更新后/棘手的电话，但它对我有用

public void requestCompax() {
    sendseq += 1;
    if (sendseq > 6){
        sendseq = 1;
    }

    switch (sendseq){
    case 1: //request planejado
        tvWrite.setText("O1903.1");         // *send "planejado"
        senddata();                         // call write and read serial
        tvIntrodutor.setText(readString);   // *normally received the answer must be here
        break;

    case 2: //request produzido
        tvWrite.setText("O1903.2");         // send produzido
        senddata();                         // call write and read serial
        tvPlanejado.setText(readString);    // *but received answer "planejado" - it comes here, next call later ?!?!
        break;

   case 3:  //request value caixas
        tvWrite.setText("O1903.3");         // * send caixas
        senddata();
        tvProduzido.setText(readString);    // same with produzido
        break;

    case 4: //request pulas
        tvWrite.setText("O1903.4");         
        senddata();
        tvCaixas.setText(readString);       // same with "caixas"
        break;

    case 5: //request caixas/hora
        tvWrite.setText("O1903.5");         
        senddata();
        tvPulas.setText(readString);         // same with pulas
        break;

    case 6: //request adiantar/atrasar
        tvWrite.setText("O1902.2");         //adiantar/atrasar
        senddata();
        tvCaixasHora.setText(readString);   //same with caixas/hora   
        break;

    default:

        break;
    }
}

有趣的是，在下一个 task.execute() 调用时更新字符串和文本框。这对我有用，可能有点棘手，但我只需要读写 5 个参数。

这里有人知道如何解决这个问题吗？这是在线测试并使用模拟器（10ms 延迟），结果相同。

于 2014-12-12T04:35:23.170 回答