Arduino test sketch for cheap 2 phase incremental rotary encoder from AliExpress

encoder_test.ino

// Arduino test sketch for cheap 2 phase incremental rotary encoder from AliExpress
// https://www.aliexpress.com/item/32849332003.html

#define PIN_A_PHASE 2
#define PIN_B_PHASE 3

volatile unsigned int tick_counter, last_printed_tick_count = 0;

void setup() 
{
  Serial.begin(9600);
  
  pinMode(PIN_A_PHASE, INPUT_PULLUP);
  pinMode(PIN_B_PHASE, INPUT_PULLUP);
  
  attachInterrupt(0, a_phase_interrupt_handler, RISING);
}

void loop() 
{
  if (tick_count_changed_since_last_print())
  {
    Serial.println(tick_counter);
    update_last_printed_tick_count();
  }
}

bool tick_count_changed_since_last_print()
{
  return tick_counter != last_printed_tick_count;
}

void update_last_printed_tick_count()
{
  last_printed_tick_count = tick_counter;
}

bool is_encoder_rotating_clockwise()
{
  return digitalRead(PIN_B_PHASE) == LOW;
}

void a_phase_interrupt_handler()
{
  tick_counter = is_encoder_rotating_clockwise() ? tick_counter + 1 : tick_counter - 1;
}