/*
⚙️ How Standard Hobby Servos Work
1. Expect a 50 Hz signal (one pulse every 20 ms).
2. The pulse width (high time) determines the angle:
  a. 1.0 ms = 0° (full left)
  b. 1.5 ms = 90° (center)
  c. 2.0 ms = 180° (full right)
3. So: we need a PWM signal with:
  a. Period = 20 ms
  b. High time = 1–2 ms

🧪 Can Timer0 Fast PWM Do This?
Not directly — Fast PWM runs too fast and can’t give 20 ms periods easily.
Instead, we’ll use:
🕒 Option: Timer0 in CTC Mode + Manual Pulse Generation
1. Toggle the servo pin HIGH,
2. Delay 1–2 ms (based on desired angle),
3. Toggle LOW,
4. Wait the rest of the 20 ms period.
*/


#define F_CPU 8000000UL
#include <avr/io.h>
#include <util/delay.h>


#define SERVO_PIN PB1

void send_servo_pulse(uint16_t pulse_width_us) {
  PORTB |= (1 << SERVO_PIN); // Set pin high
    
  // Delay for desired pulse width (1000–2000 µs)
  /*
  This counts down from 0 to 99 if pulse_width_us is 1000, 
  or 0 to 199 if pulse_width_us is 2000.
  0 to 99 is 100 steps, add a delay of 10us (microseconds) between steps
  and you get 100 steps x 10 = 1000us. 1000us = 1.0ms (milisecond)
  It uses a loop of _delay_us(10) because _delay_us() with very small values
  can be inaccurate or optimized away, so chunking it is a good workaround.
  */
  for (uint16_t i = 0; i < pulse_width_us / 10; i++) {
    _delay_us(10);
  }
  
  PORTB &= ~(1 << SERVO_PIN); // Set pin low
}

int main(void) {
  DDRB |= (1 << SERVO_PIN); // Set SERVO_PIN as output

  while (1) {
    // Sweep from 0° to 180°

/*
    // this works for Wokwi
    send_servo_pulse(410); // 0
    _delay_ms(1000);
    send_servo_pulse(1350); // 90
    _delay_ms(1000);
    send_servo_pulse(2299); // 180
    _delay_ms(1000);
*/  

    
    for (uint16_t pulse = 1000; pulse <= 2000; pulse += 50) {
      send_servo_pulse(pulse);
      _delay_ms(20);  // 20 ms total period
    }
    // Sweep back
    for (uint16_t pulse = 2000; pulse >= 1000; pulse -= 50) {
      send_servo_pulse(pulse);
      _delay_ms(20);  // 20 ms total period
    }
    
  }
}