I’m getting started with collecting data using an Arduino board, but displaying it using Processing. Eventually, I want do collect the data from a Raspberry PI board, but I’m starting with an Arduino because I think it will be easier.

The first step is to hook up a temperature probe to the Arduino and start collecting data. I’m using a MAX31855 breakout board from Adafruit. I hooked it up as suggested in the tutorials:

MAX31855 DO to Arduino digital 3
MAX31855 CS to Arduino digital 4
MAX31855 CLK to Arduino digital 5

And then ran wires for ground and 3V.

Next I needed to download the Adafruit MAX31855 library. I unzipped the file and put it in my ~/Arduino/libraries directory. One thing I needed to do was rename their directory. It had underscores in it, which the Arduino IDE complained about. So I renamed the directory AdafruitMAX31855 and it worked fine.

Here is the code I loaded on the Arduino, which I basically copied from the Adafruit website, but took out all the comments to make it shorter.

#include "Adafruit_MAX31855.h"

int thermoDO = 3;
int thermoCS = 4;
int thermoCLK = 5;

Adafruit_MAX31855 thermocouple(thermoCLK, thermoCS, thermoDO);
void setup() {
  delay(500);  // wait for MAX chip to stabilize

void loop() {

After I loaded this, I could open up the serial port monitor and watch the temperatures get printed. So that was done. Now on to Processing. Eventually, I’d like to generate a graph of the data. But first, I just want to see if I can simply read the data from the serial port and print it out in the Processing console.

Here is the code for Processing:

import processing.serial.*;

Serial thePort;
String theString = null;
char endChar = '\n';

void setup()
  thePort = new Serial(this, Serial.list()[2], 9600);
  theString = thePort.readStringUntil(endChar);
  println(Serial.list());  // only need this to get the list of ports so you know which one to use

void draw()
  // everything happens in the serialEvent()  

void serialEvent(Serial thePort)
  theString = thePort.readStringUntil(endChar);
  if (theString != null)
    theString = trim(theString);

A few interesting things to note. You have to find out which port you’re using. On my mac, in the Arduino IDE, I have choices like this:

Screen Shot 2014-06-25 at 12.33.31 PM

In Processing, this command will give a list of all the available ports.


The output of that command will look like this:

/dev/cu.Bluetooth-Incoming-Port /dev/cu.Bluetooth-Modem /dev/cu.usbmodem1411 /dev/tty.Bluetooth-Incoming-Port /dev/tty.Bluetooth-Modem /dev/tty.usbmodem1411

I know from the Arduino IDE that I used /dev/cu.usbmodem1411 as the port. In the above array, that port is at position 2. So to open a connection to that port in Processing, I should use the command:

thePort = new Serial(this, Serial.list()[2], 9600);

This all works ok. I’m not that familiar with Processing, so I need to read up on it a bit more so I fully understand everything I did. And then the next step will be to move on to creating a graph.