/**************INCLUDE ADAFRUIT LIBRARIES FOR DAC********************/
#include <Wire.h> // bunch of code to communicate with DAC
#include <Adafruit_MCP4725.h> // more code to use the DAC from adafruit.
/****************************DEFINE VARIABLES************************/
volatile long EncoderCount = 0; // variable to count pulses sent by the encoder
int ChannelA; // flag variables for channel A and B
int ChannelB;
float DiscAngle, PreviousDiscAngle; // define the DiscAngle variables
float DiscSpeed; // define the DiscSpeed variable
unsigned long Time, PreviousTime ; // define the time variables
Adafruit_MCP4725 mydac; // an instance of adafruit DAC class
int DACvalue = 0; // voltage to Motor controller is 5*DACvalue/4095
/*******************************************************************/
void setup() // code here will run once at the beginning:
{
Serial.begin(38400); // start serial communication through USB
pinMode(2, INPUT); // define encoder pins as inputs
pinMode(3, INPUT);
attachInterrupt(digitalPinToInterrupt(2), checkChannelA, CHANGE); // start interrupts on encoder pins.
attachInterrupt(digitalPinToInterrupt(3), checkChannelB, CHANGE);
 mydac.begin(0x62); // setup the DAC board
 mydac.setVoltage(0,false); // set DAC value to 0, to stop the motor at beginning.
 delay(3000); // pause the code to give you some time at the start
 // initialize the 'previous' variables before starting the loop
 PreviousDiscAngle = EncoderCount*2.0*M_PI/1024.0; // initialize the disc angle variable
 PreviousTime = millis(); // initialize the time variable
 delay(10); // wait a bit
}
void loop() // put your main code here, it will run repeatedly:
{
DiscAngle = EncoderCount*2.0*M_PI/1024.0; // convert encoder counts to angle
Time = millis(); // ask arduino for time in milliseconds
DiscSpeed = (DiscAngle-PreviousDiscAngle)/((Time-PreviousTime)/1000.0);
// This is numerical differentiation (get speed in rad/s)
float voltage = 1.5*(DiscSpeed - DesiredSpeed) ; //voltage you want to give to the motor
DACvalue = (voltage – c)/m; // convert voltage to DAC value. Voltage = m*DAC +c
// PLEASE TYPE THE VALUES OF c AND m
if(DACvalue > 4095) { DACvalue = 4095; } // limit the DAC value in the intended range.
if(DACvalue < 0) { DACvalue = 0; }
mydac.setVoltage(DACvalue,false); // set the voltage!

// print stuff on serial monitor
Serial.print(Time); // print time in ms
Serial.print(" "); // print space
Serial.print(DiscSpeed); // print disc speed in rad/s
Serial.print(" "); // print space
Serial.println(DACvalue); // print DAC value
// update the 'previous' variables before starting the next loop
PreviousDiscAngle = DiscAngle;
PreviousTime = Time;
delay(10); // pause to make loop time about 10ms for consistency.
}
/*************** Functions to count encoder ticks*****************/
void checkChannelA() { // Interrupt on A changing state
if (digitalRead(2) == HIGH) { // Low to High transition?
 ChannelA = 1;
 if (!ChannelB) {
 EncoderCount = EncoderCount + 1;
 }
}
if (digitalRead(2) == LOW) { // High-to-low transition?
 ChannelA = 0;
}
}
void checkChannelB() { // Interrupt on B changing state
if (digitalRead(3) == HIGH) { // Low-to-high transition?
 ChannelB = 1;
 if (!ChannelA) {
 EncoderCount = EncoderCount - 1;
 }
}
if (digitalRead(3) == LOW) { // High-to-low transition?
 ChannelB = 0;
}
}