control 2-phase stepper motor with Timer interrupt.

ardu_step_isr.ino

// 500us Timer interrupt to drive stepper motor.
// Coded by TinLethax 2022/6/17 +7
#define full_rev_step 200
#define motor_pulse 2
volatile uint8_t pulse_tog = 0;
volatile uint16_t pulse_cnt = 0;

#define motor_dir   3
uint8_t dir = 0;

#define motor_en  4 
#define motor_on digitalWrite(motor_en, 0)
#define motor_off digitalWrite(motor_en, 1)

volatile uint8_t pulse_gate = 0;

// timer interrupt handler
ISR(TIMER1_COMPA_vect) {
  TCNT1  = 0;                  //First, set the timer back to 0 so it resets for next interrupt
  pulse_tog = !pulse_tog;      //Invert LED state
  pulse_cnt = pulse_gate ? pulse_cnt + 1 : 0;// step counter
  digitalWrite(motor_pulse, pulse_tog & pulse_gate); //Write new state to the LED on pin D5
}

// Timer interrupt set up.
void timer_init() {
  cli();

  TCCR1A = 0;// Reset entire TCCR1A to 0
  TCCR1B = 0;// Reset entire TCCR1B to 0

  TCCR1B |= B00000100;// Set CS12 to prescalar 256

  TIMSK1 |= B00000010;// Set OCIE1A to 1 so we enable compare match A

  OCR1A = 31;// motor speed here. 62500 * interval in second uint = OCR1A number. in this case it's roughtly 500us
  sei();// enable interrupt

}

// Set stepper motor direction
// 0 -
// 1 - 
void set_dir(uint8_t set_dir){
  // sanity check
  if(set_dir > 1)
    return;
  dir = set_dir;
  digitalWrite(motor_dir, dir);  
}

// Steps to rotate (note, code blocking).
// input 0 will be invalid.
void set_step_blocking(uint16_t steps){
  if(steps == 0)// sanity check
    return;
    
  motor_on;
  pulse_gate = 1;
  while (pulse_cnt < steps);
  TCNT1  = 0;
  motor_off;
  pulse_gate = 0;
}

// rotate motor with angle (Degree) input. (note, code blocking).
// input 0 will be invalid.
void set_angle_blocking(int16_t degree){
  //sanity check
  if(degree == 0)
    return;
    
  set_dir(degree > 0 ? 1 : 0);// set direction
  degree = degree < 0 ? (degree * -1) : degree;// absolute value
  degree = map(degree, 0, 360, 0, 200);// remap 0-360 degree to 0-200 steps 
  set_step_blocking(degree * (uint8_t)((degree/360) + 1));// rotate
}

void setup() {
  // GPIOs
  pinMode(motor_pulse, OUTPUT);
  pinMode(motor_dir, OUTPUT);
  pinMode(motor_en, OUTPUT);
  dir = 1;
  digitalWrite(motor_en, 1);// enable is active low, turn it on later.
  // Debug
  Serial.begin(9600);

}

void loop() {
  Serial.println("Start");
  set_angle_blocking(45);
  delay(1000);
  Serial.println("Stop");
  delay(1000);
}