Send many variables from Unity To Arduino

Question

I'm trying to send many ints to my "masterArduino". Because the SerialPort object only send strings. I've tried many things including:

Creating a string from ints (didn't work because the size of the string.length is dynamic).
Then I tried to convert these ints to chars, this because all values are between 0-255, then put the char into a string and send it.

This sort of works. However, I think there is no value for 0 in char world. So the data is not right. But there must be a better way?

void sendInfo() {
    for (var i = 0; i < peltiers.Length; i++) {
        char tempHot = (char) peltiers[i].GetComponent<Peltier>().hot;
        char charTemp = (char) peltiers[i].GetComponent<Peltier>().temp;
        peltierInfo += tempHot.ToString();           
        peltierInfo += charTemp.ToString();                  
    } 
    sp.WriteLine(peltierInfo);
    Debug.Log(peltierInfo);
    sp.BaseStream.Flush();
    peltierInfo = "";         
}

Any help would be greatly appreciated! Thanks!

Arduino Code:

void loop() {
    int serialIndex = 0;  
    int i2cIndex = 0; 
    while (0 < Serial.available()) { // loop through all the received bytes 
    char bufferByte = 0;     
    bufferByte = Serial.read();
    serialBuffer[serialIndex] = (byte) bufferByte;  // put current index byte in array      
    serialIndex ++;                    // add index. 
    if (serialIndex%12==0 && serialIndex != 0) {
          sendBytes(0);      
       }
    } 
     //sendBytes(0);  
     delay(50);
}

void sendBytes(int slave) {
    byte i2cBuffer[12];
    int bufferIndex = slave * 12;
    for (int i = 0; i < 12; i++) {
        i2cBuffer[i] = serialBuffer[i + bufferIndex];
    }
    Wire.beginTransmission(slave+1);
    Wire.write(i2cBuffer, 12);
    Wire.endTransmission();  
}

there is 0 in the "char world", namely, '\0'. It's an unprintable empty character, if you try to print it you'll simply get an empty space. Do you have a problem with sending zeroes? — Dunno
– Dunno, Commented Mar 22, 2017 at 14:37

Dunno · Accepted Answer · 2017-03-22 15:28:58Z

To be able to send any integers, first encode them into a string, separate them by something (e.g the '\0' char) and then decode the string.

void sendInfo() {
    ...
    peltierInfo += peltiers[i].GetComponent<Peltier>().hot.ToString();
    peltierInfo += '\0';
    peltierInfo += peltiers[i].GetComponent<Peltier>().temp.ToString();
    peltierInfo += '\0';
    ...
}

void loop() {
    int serialIndex = 0;  
    int i2cIndex = 0;
    // set to how many digits there can be in an incoming number plus 1
    int maxNumberLen = 20; 
    char buffer[20];
    // position at which we now put a char that makes up our number
    char* currentCharPtr = buffer;
    while (0 < Serial.available()) { // loop through all the received bytes 
       char bufferByte = 0;     
       bufferByte = Serial.read();
       *currentCharPtr = bufferByte;
       // move pointer forward
       currentCharPtr ++;
       // end of a number in string
       if (bufferByte == '\0') {
           printf("Got number %s\n", buffer);
           // atoi parses string to int
           serialBuffer[serialIndex] = atoi(buffer); 
           serialIndex ++;                    
           if(serialIndex%12==0 && serialIndex != 0){
              sendBytes(0);
           }
           // fill buffer with zeros after we found a number
           memset(buffer, 0, 20);
           currentCharPtr = buffer;
       }
    } 
     //sendBytes(0);  
     delay(50);

 }

Thomas Huster · Accepted Answer · 2017-03-23 14:53:57Z

0

Thanks for the reply, your answer was exactly how i got it working. I just did it slightly different and didn't had the time to upload this post. What way is better, or is it just a matter of taste?

Unity

 void sendInfo()
{
    for (int i = 0; i < peltiers.Length; i++)
    {
        peltierInfo += ",";
        peltierInfo += peltiers[i].GetComponent<Peltier>().hot.ToString();
        peltierInfo += ",";
        peltierInfo += peltiers[i].GetComponent<Peltier>().temp.ToString("D3");
    }
    //Debug.Log(peltierInfo);
    sp.WriteLine(peltierInfo);
    sp.BaseStream.Flush();
    peltierInfo = "";
}

Arduino

void loop() {
   int serialIndex = 0;
   if(Serial.available() > 0){     
     while (0 < Serial.available()) {            // loop through all the received bytes 
        String bufferString;
        uint8_t bufferInt;
        bufferString = Serial.readStringUntil(','); 
        bufferInt = bufferString.toInt();      
        serialBuffer[serialIndex] = bufferInt;  // put current index byte in array      
        serialIndex ++;                          // add index. 
     }     
     sendBytes(0); 
   }
   delay(50);
}

thanks for the help!

answered Mar 23, 2017 at 14:53

Thomas Huster

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1 Comment

Dunno Over a year ago

oh, sorry, of course your version is better - I assumed you were using pure C for Arduino code. If you're using C++, then by all means use String instead of char arrays. I chose '\0' as a separator, simply because in pure C every string has to end with '\0' so it made my code simpler.

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