serial.write() five sensors and Processing

Question

To all of this, hope to formulate the question right.

In my project I have 5 sensors connected to Arduino, which I want to interpret via Seria.write() --> Processing.

Arduino:

firstSens = 100 + (155 * digitalRead(8));
secondSens = analogRead(A1)/4;
thirdSens = analogRead(A2)/4;
fourthSens = humData;
fifthSens = tempData;
int sensData[6] = {firstSens, secondSens, thirdSens, fourthSens, fifthSens};
int i;
for (i = 0; i < 5; i = i + 1) {
 Serial.write(sensData[i]);
}

Processing:

serialInArray[serialCount] = inByte;
 serialCount++;
if (serialCount > 4 ) {
 firstSens = serialInArray[0];
 secondSens = serialInArray[1];
 thirdSens = serialInArray[2];
 fourthSens = serialInArray[3];
 fifthSens = serialInArray[4];
 // print the values (for debugging purposes only):
 println(firstSens + "\t" + secondSens + "\t" + thirdSens + "\t" + fourthSens + "\t" + fifthSens);
 // Send a capital A to request new sensor readings:
 myPort.write('A');
 // Reset serialCount:
 serialCount = 0;

My problem is that sensors find their place in Processing's array randomly, so for example arduino's firstSens could be Processing's secondSens or fifthSens

Why is this happening and how can I control it?

Answer 1

What is happening is you are just spewing out a list of numbers:

4132
132
1928
3240
1239
238
3048
391
... etc ...

There is nothing anywhere to say what anything is.

You need to add that kind of information. Either as a "start of data" tag before each block, or with each line. For instance:

---START OF DATA---
4132
132
1928
3240
1239
---START OF DATA---
238
3048
391
... etc ...

Or:

0:4132
1:132
2:1928
3:3240
4:1239
0:238
1:3048
2:391

It is then up to your processing application to interpret the data and work out what is what.

Personally I like using the second method since it means you don't have to send all the data every time - you can send different values at different speeds of update and maintain a "current value" at the Processing end. For instance if you have one value that updates frequently and others that don't:

3:4132
1:132
3:1928
3:3240
3:1239
2:238
3:3048
0:391

You don't even have to use numbers, you could use words:

pressure:4132
temperature:132
pressure:1928
pressure:3240
pressure:1239
humidity:238
pressure:3048
rainfall:391

Answer 2

I have done similar code for our car project dash display

you're looking for something like this on your Arduino side:

 Serial.print("U*"); //A header
 Serial.print("A"); //a token to indicate the message payload
 Serial.print(avgRPM);
 Serial.println("");
 Serial.print("U*"); //A header
 Serial.print("B"); //a token to indicate the message payload
 Serial.print(avgVoltage);
 Serial.println("");
 Serial.print("U*"); //A header
 Serial.print("C"); //a token to indicate the message payload
 Serial.print(avgCurrent);
 Serial.println("");
 Serial.print("U*"); //A header
 Serial.print("D"); //a token to indicate the message payload
 Serial.print(avgThrottle);
 Serial.println("");
 Serial.print("U*"); //A header
 Serial.print("E"); //a token to indicate the message payload
 Serial.print(avgBrake);
 Serial.println("");

and something like this on processing side:

 if (port.available() > 0) {
 data = port.readStringUntil('\n');
 }
 String payload = "";
 if (data != ""){
 int offset = data.indexOf("U*"); //this is our Header (0x552A)
 if(offset>=0){
 payload = data.substring(offset+3, data.indexOf('\n'));
 switch(data.substring(offset+2, offset+3)){
 case "A":
 RPM = payload;
 break;
 case "B":
 voltage = payload;
 break;
 case "C":
 current = payload;
 break;
 case "D":
 throttle = payload;
 break;
 case "E":
 brake = payload;
 break;
 case "F":
 telemBits = payload;
 break;
 default:
 //packet not recognised
 }
 }
}