Arduino graph software

Arduino graph using Processing

Update: Here is a link to my source code. Some very simple examples, without the buttons, saving data etc. 

This code is for those that want to draw fancy graphs with processing, and use the fasted method to communicate with the Arduino.

Arduino side:

  • Serially sending arrays for different graphs from the chip
       void PlottArray(int Cmd,int Array1[],int Array2[])
           Cmd  -> which graph is this data for?
       Array1[] -> The real time array. Measured micro-seconds
       Array2[] -> Array of measured voltages
  • Serially sending updates for different graphs from the chip

Processing side:

  • A graph class that makes graphing simple with Processing. Drawing bar graphs, smooth  line graphs etc can be quite a mission..

You just have to declare a graph object:  Graph VoltageAndCurrent;


  • Saving and loading data to a text file
  • Efficient serial link to the Arduino (Error checking etc)

Gobetwino: Arduino talking to Excel

Gobetwino is pretty easy use. The Arduino can now send words to the serial port and Gobetwino takes them as commands and does handy stuff like create csv’s send email etc. I’ve tested out this program by making the Arduino log the voltage of a discharging capacitor and send the details to Gobetwino to make a csv for Excel.



Log discharging capacitor, use FET's instead of BJT's if you want to avoid 0.6V drop

Arduino Code

//    Arduino code
//    Arduino to Excel using Gobetino

//      - Arduino logs 100 values
//      - Gobetwino takes these values and puts them in data.txt

//      - Excel Imports this file as a csv and draws the graph
// ==========< option 1 >==========
//      FIRST logs data to chip's sram,  THEN sends to pc using Gobetwino
//      - 1028 bytes can be stored

//      - readings are taken fast this way

// ==========< option 2 >==========
//      log straight to .txt with Gobetwino
//      - approximately a max of 37 readings/sec , depending on the serial speed you choose

//      - this way is safe (unlimited with the chips 1024 bytes of SRAM)
// ============< variables >==========

//  A0   -   Vcap
//  D3   -   button/switch    (trigger)

//  D4   -   transisters to charge & discharge cap
//  D5   -   LED 1

//  D6   -   LED 2 const int size = 100;
// number of readings (size of array must be constant)
// don't make it too big, arduino has limited memory const float Vss = 5.0;
// if you want to be more accurate measure arduino's Vss int arrayms[size];
// an arary to store time

// an arary store voltage
// counter
long startTime;

void setup() {
(2, INPUT); // button
(3, OUTPUT); // pin connected to transistor bases
pinMode(4, OUTPUT); // LED 1
pinMode(5, OUTPUT); // LED 2 LED's are used to show what stage the chip is in
pinMode(6, OUTPUT); // LED 3


void loop() {

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// /* test stuff
while(digitalRead(3)){}              // wait until I press pin 3 (trigger button)


Serial.println("#S|CPTEST|[]#");     // Use the CPTEST copy file command to make a copy of a new empty logfile

while(digitalRead(3)){}              //wait until I press pin 3 (trigger button)


digitalWrite(3, HIGH); // start charging capacitor
(500); // wait 500 ms for the capacitor to charge
(digitalRead(2)){ digitalWrite(6, HIGH);   }
digitalWrite(6, LOW);
(4, HIGH); // LED 1 tells you the capacitor should be charged

wait_until_pin_3_is_pressed(); // ------------------------------
startTime =
(3, LOW); // discharge capacitor
(a <= size )   {
millis()-startTime; // record time
analogRead(0); // record Vcap
delay(1); // wait however ms before taking the next reading }
digitalWrite(4, LOW); // If LED 1 doesn't switch off, there is a problem in stage 1
digitalWrite(5, HIGH); // LED 2 tells you that Stage 2 is ready to start

// ----------------------


(a <size){
// #S -> tells gobetwino to listen

// |LOGTEST|[ -> Gobetwino runs the LOGTEST command I made,
// which opens data.txt in this app's folder

// NOTE: there must already be a data.txt in the folder

double(arrayms[a])/1023*Vss, 3);
double(arrayA0[a])/1023*Vss, 3);
// # tells Gobetwino to stop paying attention
digitalWrite(5, LOW); // if LED2 doesn't switch off you're stuck in Stage 2
// end of void loop()
// somebody elses function I found to print doubles
void printDouble( double val, byte precision){

// prints val with number of decimal places determine by precision

// precision is a number from 0 to 6 indicating the desired decimial places

// example: printDouble( 3.1415, 2);

// prints 3.14 (two decimal places) Serial.print (int(val));

//prints the int part if( precision > 0) { Serial.print(".");

// print the decimal point

unsigned long frac; unsigned long mult = 1;

byte padding = precision -1; while(precision--)       mult *=10;

if(val >= 0)

frac = (val - int(val)) * mult;

else frac = (int(val)- val ) * mult;

unsigned long frac1 = frac;

while( frac1 /= 10 )       padding--;

while( padding--) Serial.print("0");

Serial.print(frac,DEC) ;   } }

void wait_until_pin_3_is_pressed() {

while( !digitalRead(2) ){   }

while( digitalRead(2) ){   }


How Gobetwino works

Before trying to use this program you should read the Gobetwino pdf. You basically have to open Gobetwino and create a command to handle .txt files. I did this by opening Gobetwino and creating a LOGTEST command to open log.txt

  1. Click on the Commands menu
  2. Selecting LGFIL (Log File command)
  3. Select the file location of an existing .txt file (data.txt in this case)

Now when the Arduino serially prints LOGTEST a .txt file is opened.

  • #s tells Gobetwino to pay attention
  • |LOGTEST| is the command I created with Gobetwino to open data.txt
  • [A,B,C] are variables printed to the file
  • # tells Gobetwino to stop paying attention


  1. Upload the code to the Arduino
  2. Create the LOGTEST command with Gobetwino
  3. Press the button on your circuit (capacitor discharges)

I then import the .txt with excel and create the following graph

The voltage of the discharging capacitor

Notice the capacitor doesn’t fully discharging because I used BJT’s instead of FET’s.