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                                                                                             Wels, am 2016-11-21

4.8Sending Binary Values from Processing to Arduino

Problem

You want to send binary bytes, integers, or long values from Processing to Arduino. For example, you want to send a message consisting of a message identifier “tag” and two 16-bit values.

Sie möchten Binärbytes, Ganzzahlen oder langen Werte von Verarbeitungs schicken Arduino. Zum Beispiel, um eine Nachricht, die aus einer Nachrichten-ID "tag" und zwei 16-Bit-Werte senden möchten.

Solution

Use this code:

// Processing Sketch              /* SendingBinaryToArduino * Language: Processing */import processing.serial.*;Serial myPort;  // Create object from Serial classpublic static final char HEADER    = 'H';public static final char MOUSE_TAG = 'M';void setup(){  size(512, 512);  String portName = Serial.list()[1];  myPort = new Serial(this, portName, 9600);}void draw(){}void serialEvent(Serial p) {  // handle incoming serial data  String inString = myPort.readStringUntil('\n');  if(inString != null) {         print( inString );   // echo text string from Arduino  }}void mousePressed() {  sendMessage(MOUSE_TAG, mouseX, mouseY);}void sendMessage(char tag, int x, int y){  // send the given index and value to the serial port  myPort.write(HEADER);  myPort.write(tag);  myPort.write((char)(x / 256)); // msb  myPort.write(x & 0xff);  //lsb  myPort.write((char)(y / 256)); // msb  myPort.write(y & 0xff);  //lsb}

When the mouse is clicked in the Processing window, sendMessage will be called with the 8-bit tag indicating that this is a mouse message and the two 16-bit mouse x and y coordinates. The sendMessage function sends the 16-bit x and y values as two bytes, with the most significant byte first.

Here is the Arduino code to receive these messages and echo the results back to Processing:

// BinaryDataFromProcessing// These defines must mirror the sending program:const char HEADER       = 'H';const char MOUSE_TAG    = 'M';const int  TOTAL_BYTES  = 6  ; // the total bytes in a message                          void setup(){  Serial.begin(9600);}void loop(){  if ( Serial.available() >= TOTAL_BYTES)  {     if( Serial.read() == HEADER)    {      char tag = Serial.read();      if(tag == MOUSE_TAG)      {        int x = Serial.read() * 256;         x = x + Serial.read();        int y = Serial.read() * 256;        y = y + Serial.read();        Serial.print("Received mouse msg, x = ");        Serial.print(x);        Serial.print(", y =  ");        Serial.println(y);      }      else      {        Serial.print("got message with unknown tag ");        Serial.write(tag);      }    }  }}

Discussion

The Processing code sends a header byte to indicate that a valid message follows. This is needed so Arduino can synchronize if it starts up in the middle of a message or if the serial connection can lose data, such as with a wireless link. The tag provides an additional check for message validity and it enables any other message types you may want to send to be handled individually. In this example, the function is called with three parameters: a tag and the 16-bit x and y mouse coordinates.

The Arduino code checks that at least MESSAGE_BYTES have been received, ensuring that the message is not processed until all the required data is available. After the header and tag are checked, the 16-bit values are read as two bytes, with the first multiplied by 256 to restore the most significant byte to its original value.