Reading a Rotary Encoder Using an Arduino (using Interrupt) - Part 2/2

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In this tutorial I will be showing you how to read an encoder using your Arduino board using Interrupts.

I have used 4X encoding principle to increase the resolution four times.

The link to the first part of this tutorial:

The link to the Arduino official page to read more about Interrupts:

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I've edited the code in the video enabling it to output the wheel speed when the encoder is connected to a rotating wheel. Please let me know if you have any other problems regarding the tutorial.

//Encoder pins
const int encoderPinA = 2;
const int encoderPinB = 3;

//The number of pulses produced by the encoder within a revolution.
const int PPR = 12;
//The value is '1' if the encoder is not attached to any motor.
const int gearRatio = 64;
//When using 2X encoding the value is '2'. In this code 4X encoding is used.
const int decodeNumber = 4;
//record the cuurent number of pulses received
volatile long int currentPosition = 0;

unsigned int timer_previous = 0;
double wheel_turns = 0.0;
double current_wheel_distance = 0.0;
double previous_wheel_distance = 0.0;
double time_taken = 0;
double wheel_speed_mpms = 0.0;
double wheel_speed_mpm = 0.0;
double pi = 3.14;
double r = 0.04775; // Radius of the wheel in meters

void setup() {
pinMode (encoderPinA, INPUT_PULLUP);
pinMode (encoderPinB, INPUT_PULLUP);
attachInterrupt (digitalPinToInterrupt (encoderPinA), doEncoderA, CHANGE);
attachInterrupt (digitalPinToInterrupt (encoderPinB), doEncoderB, CHANGE);
Serial.begin (9600);
}
void loop() {
current_wheel_distance = (currentPosition * 2 * pi * r) / (PPR * gearRatio * decodeNumber) ; // Gives the distance which the wheel traveled. 'r' is the radius of the wheel in meters.
time_taken = micros() - timer_previous; // Time taken since the previous iteration of the loop.
wheel_speed_mpms = / time_taken; // This gives the speed in meters per microsecond.
wheel_speed_mpm = wheel_speed_mpms * * 60; // This gives the speed in meters per minute.

Serial.print(current_wheel_distance, 4);
Serial.print(" ");
Serial.print(wheel_speed_mpm, 4);
Serial.println();

timer_previous = micros();
previous_wheel_distance = current_wheel_distance;
}

void doEncoderA()
{
if (digitalRead(encoderPinA) != digitalRead(encoderPinB))
{
currentPosition++;
}
else
{
currentPosition--;
}
}
void doEncoderB()
{
if (digitalRead(encoderPinA) == digitalRead(encoderPinB))
{
currentPosition++;
}
else
{
currentPosition--;
}
}

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