Issues interfacing Arduino sensor MPU6050 and Processing - arduino

Question

I have an MPU6050 gyroscope and accelerometer connected with Arduino through the I2C protocol. These sensor send a continuos stream of data into the Serial port with these instructions (in the arduino IDE):
Serial.print(euler[0] * 180/M_PI);
Serial.print(":");
Serial.print(euler[1] * 180/M_PI);
Serial.print(":");
Serial.println(euler[2] * 180/M_PI);
This come from an example sketch included in the library of the sensor and it just sends the value of yaw / pitch / roll to the serial port, separated by the colon.
Now there is the interesting part. I've always been fascinated about visualizing data, and so i want to build a sort of graph of these data coming from serial in Processing(this is part of a larger project that include a ultrasonic sensor, like a sort of radar).
So I wrote a short sketch on processing to catch that data in order to analyze and visualize it. This is the sketch:
import processing.serial.*;
Serial myPort;
String data; //Angle values
String[] splitted; //Array containing splitted data
float yaw, pitch , roll;
void setup()
{
myPort = new Serial (this, Serial.list()[0], 115200);
}
void draw()
{
while (myPort.available() > 0) //data arrived fromm serial
{
data = myPort.readStringUntil('\n');
//Data Parsing
splitted = data.split(":");
yaw = float(splitted[0]);
pitch = float(splitted[1]);
roll = float(splitted[2]);
println(yaw + " " + pitch + " " + roll);
}
}
This code doesn't work. There are 2 errors that alternate. One of them is:
ArrayIndexOutOfBondsException
And the other one:
NullPointerException
That points to the "splitted" array.
I think i got the problem. In a previous version of the Processing sketch i was using the:
readString() function
I think that, since data are sent to the Serial port in the Arduino sketch one at a time, the processing sketch sometimes catch only one, or two of the yaw, pitch, roll values, causing the array index to crash or to a nullPointerexception when no value is added to the array. I then changed the '''readString''' to the '''readStringUntil('\n')''', because, maybe the first packet will be lost but the other one coming next will always be cathed without breaking them (i catch the entire line). But there are the same errors, so I think my small experience can't help solving the problem anymore. I need your help.
Excuse me for my bad English, and thanks for any help.

Answer 1

You are on the right track. Here are a few pointers:
you can use a try/catch block so the sketch doesn't simply crash on an error
you can use bufferUntil() to tell the serial library to buffer bytes for you until a new line is encountered: it works well in tandem with serialEvent() which gets called automatically (so you don't need to use a while loop that would block rendering/the rest of the sketch)
you can check (and should) anything that could go wrong with the data (null string, empty string, not enough values within the string, etc.)
Here's a modified version of your sketch:
import processing.serial.*;
Serial myPort;
float yaw, pitch , roll;
void setup()
{
String[] portNames = Serial.list();
// skipp serial setup if there are no ports
if(portNames.length == 0){
println("no serial ports found");
return;
}
// try to open serial port, handle error
try
{
myPort = new Serial (this, portNames[0], 115200);
// buffer bytes(characters) until new line is hit
myPort.bufferUntil('\n');
}
catch(Exception e)
{
println("error opening port: " + portNames[0]);
println("double check the port is present and not used by other applications (e.g. SerialMonitor)");
e.printStackTrace();
}
}
void draw()
{
background(0);
text(String.format("yaw: %.2f \npitch: %.2f \nroll: %.2f", yaw, pitch, roll), 5, 15);
}
// serialEvent gets called when there's new data: no need an explicit blocking while loop
void serialEvent(Serial port){
try
{
// read string from serial
String rawSerialString = port.readString();
// exit on null string
if(rawSerialString == null)
{
println("received null string, skipping this serial message");
return;
}
// exit on empty string
if(rawSerialString.length() == 0)
{
println("received empty string, skipping this serial message");
return;
}
// trim white space (\r, \n, etc.)
rawSerialString = rawSerialString.trim();
// split and convert to float
float[] rotations = float(rawSerialString.split(":"));
// exit if message got jumbled up and values are missing
if(rotations.length < 3)
{
println("received less than 3 values, skipping this serial message");
return;
}
// finally extract values
yaw = rotations[0];
pitch = rotations[1];
roll = rotations[2];
println(yaw + " " + pitch + " " + roll);
}
catch(Exception e)
{
println("error reading/parsing serial data");
e.printStackTrace();
}
}

Answer 2

Obviously you receive lines with less than two colons.
Hard to tell from here what you should do then, but checking the length of the splitted array were the first step anyway. Either via if or as an Exception.