Question

刚才，我碰巧有过于复杂的类型转换（我仍然不完全理解它们的类型）我通过串行链接将0到1024个值从Arduino传输到4个字节（int）。很快我就意识到我也可以发短路（2个字节）来快速通信2倍（而且我需要它非常快）。
所以这就是我在arduino上的C ++中所拥有的：

  // variable to store the value coming from the sensor
  unsigned short sensorValue = 0;  
  //Time when I last sent the buffer (serial link seems to need some rest)
  unsigned long last_time_sent = millis();
  //Buffer to save data I've collected
  byte buffer[256];
  //Position in buffer
  byte buffer_pos = 0;

  while(1) {
    //Get 0 - 1024
    sensorValue = analogRead(sensorPin);
    //(Try to) convert Short to two bytes. I don't even which is first and which is last
    for(byte i=0; i<2; i++) {
       //Some veird bit-shifting, all saved in buffer with an offset
       buffer[i+buffer_pos] = (byte)(sensorValue >> ((2-i) * 8));
    }
    //Iterate buffer position
    buffer_pos+=2;
    //Currently, I send the data allways
    if(true||millis()-last_time_sent>30||buffer_pos+2>=255)
      Serial.write(buffer, buffer_pos);
    //Temporary delay for serial link to rest
    delay(50);
  }

现在，在Processing中，java代码如下所示：

void serialEvent(Serial uselessParameter) {
  while (myPort.available() >= 2) {
    //java doesn't allow unsigned variables
    short number = 0;
    for(byte i=0; i<2; i++) {
      byte received = (byte)myPort.read();
      println("Byte received: "+Integer.toString((int)received));
      number |= myPort.read() << (2-i)*8;
    }
    //Save data for further rendering
    graph.add(number);  //Array of integers, java doesn't let me make array of short
  }
  //Clean old data
  while(graph.size()>MAX_GRAPH_SIZE)
    graph.remove(0);

}

我认为我在arduino方面有问题，因为我在输出中看到了这一点：

接收字节：0
  字节收到：-1
  产生的2字节数：-256

Arduino值应该发送大约681.（我有一个1位数的显示来检查大约的值。）

Answer 1

在C ++方面，使用htons()将s horts从h ost endianness to n etwork endianness（htons：举办网络短片）。
在Java端，从套接字读取，写入ByteArrayOutputStream;获得所有数据后，将此ByteArrayOutputStream的基础字节数组包装到ByteBuffer。
使用ByteBuffer的{{1}}。

C ++与Big endian的小端无符号短文用Java签名

1 个答案: