/*
Working out a quadrature encoder routine for ATtiny44

Encoder Signals A [Pin 12] & B [Pin 11] trigger ISRs 
Forward = Clockwise  controlled by H-bridge motor controller L298N [later: TB6612]
Enable starts/stops the motor controller
adding some false trigger recon'ing by a boolean var A_next
Motor runs back and forth several times with fixed number of steps to figure out mistakes in routine
No absolute positioning or init routine ATM
*/

const byte interrupt_A = 1;		//	Int 1 at Pin 12
const byte interrupt_B = 2;		//	Int 2 at Pin 11
const byte direction_pin = 5; //  can be any I/O pin you like
const byte enable = 6;     		//  can be any I/O pin you like
byte forward = true;			    //	for TB6612 a different method is required
volatile uint16_t steps = 255;// max. 65535 steps
volatile uint16_t stepsToGo = steps;  // init the countdown var
volatile byte A_next = true;  //the start is somewhat a guessing game. Will get better with init routine

void setup() {
  pinMode( direction_pin, OUTPUT);
  pinMode( enable, OUTPUT);
  pinMode(interrupt_A, INPUT_PULLUP);
  pinMode(interrupt_B, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(interrupt_A), ISR_A, CHANGE);
  attachInterrupt(digitalPinToInterrupt(interrupt_B), ISR_B, CHANGE);
  digitalWrite(direction_pin, forward);  // set direction pin high/low on H-bridge motor controller
  digitalWrite(enable, LOW);  //  start with motor OFF
}

void loop() {
    if(stepsToGo >= steps){       //  
      digitalWrite(enable, HIGH); //  Start the motor and keep it running 
      };
      if (stepsToGo == 0){
        digitalWrite(enable, LOW);  //  switch motor off and wait 1sec
        delay(1000);
        stepsToGo = steps;          //  reset the countdown
        forward = !forward;         //  reverse motordirection and restart motor (@next loop)
        digitalWrite(direction_pin, forward);
        };
}

void ISR_A(){
  if( A_next == true){  //  check if the interrupt is valid
  A_next = !A_next;   //  expect a B-channel trigger next time
  stepsToGo -= 1;     //  countdown the remaining steps 
  }
}

void ISR_B(){
  if( A_next == false){ //  check if the interrupt is valid
  A_next = !A_next;   //  expect a A-channel trigger next time
  stepsToGo -= 1;     //  countdown the remaining steps 
  }
}