Dangerous Prototypes Open Source Hardware

#define PHASE_A 2
#define PHASE_B 3
#define LED 13

static int counter=0,previous_counter=0,temp_counter=0;
static int CW_A=0,CCW_A=0,CW_B=0,CCW_B=0;

void setup()
{
  
  pinMode(PHASE_A,INPUT);
  pinMode(PHASE_B,INPUT);
  pinMode(LED,OUTPUT);
  
  digitalWrite(PHASE_A,HIGH);
  digitalWrite(PHASE_B,HIGH);
  attachInterrupt(0,rotary_read_A,RISING);
  attachInterrupt(1,rotary_read_B,FALLING);
  
  Serial.begin(9600);
}

void loop()
{
  //wait here forever
  
  if(counter!=previous_counter)
  {
  Serial.println(counter);
  
  previous_counter=counter;
  
  }
  digitalWrite(LED,HIGH);
  delayMicroseconds(counter);
  digitalWrite(LED,LOW);
  delayMicroseconds(500-counter);
  
  
}

void rotary_read_A()
{
  delay(50);
 ((digitalRead(PHASE_A)^digitalRead(PHASE_B))==1)?CW_A=1:CCW_A=1;

  (CW_A&CW_B==1)?temp_counter++:temp_counter--;
  (CCW_A&CCW_B==1)?temp_counter--:temp_counter++;
  counter=counter + (temp_counter/2);
  temp_counter=0;
  CW_A=0;
  CW_B=0;
  CCW_A=0;
  CCW_B=0;
  return;
}

void rotary_read_B()
{
  delay(50);
 ((digitalRead(PHASE_A)^digitalRead(PHASE_B))==0)?CW_B=1:CCW_B=1;
  return;
}