Time is a technology

code for arduino

https://web.archive.org/web/20120105015729/http://wiki.makerbot.com/mre2

using the makerbot magnetic rotary encoder v2.1 here is the code

#define ENCODER_A_PIN 2
#define ENCODER_B_PIN 3

long position;

void setup()
{   
Serial.begin(19200);   
Serial.println("Started");    
pinMode(ENCODER_A_PIN, INPUT);   
pinMode(ENCODER_B_PIN, INPUT);    
attachInterrupt(0, read_quadrature, CHANGE);
} 


void loop()
{   
Serial.print("Position: ");   
Serial.println(position, DEC);   
delay(1000);
} 


 void read_quadrature()
{    
// found a low-to-high on channel A  
if (digitalRead(ENCODER_A_PIN) == HIGH)  
{      
// check channel B to see which way   
if (digitalRead(ENCODER_B_PIN) == LOW)       
position++;    
else       
position--;  
}  // found a high-to-low on channel A  
else                                          
{    
// check channel B to see which way    
if (digitalRead(ENCODER_B_PIN) == LOW)        
position--;    
else        
position++;  
}
}