#define F_CPU 16000000L

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define nop() do { __asm__ __volatile__ ("nop"); } while (0)

// steppe port
#define sport PORTB
// externals
#define cport PORTD

// pins
#define enable_pin PB3
#define step_pin PB1
#define dir_pin PB2
#define enable_b_pin PD4
#define home_pin PD2
#define error_pin PD3

// work cycle
#define stop 0
#define search_home 1
#define duty_cycle 2
#define move_in_home 3

volatile unsigned int current_state = 0;
// forced home position
volatile unsigned int force_at_home = 0;
// duty cycle speed
unsigned int step = 0x047D;
// search home speed
unsigned int step_home = 0x047D;

// steps per revolution
unsigned int steps_per_rev = 800;
// revolution length in mm
unsigned int revolution_length = 25;
// duty cycle length in mm
unsigned int duty_length = 220;
// duty cycle length in steps
unsigned long int duty_steps = 0;
// current position in steps
volatile unsigned long int position = 0;
// steps to make when home first reached
unsigned int steps_in_home = 800;

// home state
inline int at_home(void) {
    if ((PIND & (1 << home_pin)) == 0) {
        return force_at_home;
    } else {
        return 1;
    }
}

// enable button
int enabled(void) {
    if ((PIND & (1 << enable_b_pin)) == 0) {
        return 1;
    } else {
        return 0;
    }
}

ISR(INT0_vect) {
    _delay_ms(10);
    if (current_state == search_home)
        if (at_home()) {
            current_state = move_in_home;
            position = steps_in_home;
            // move forward from home
            sport |= (1 << dir_pin);
        };
}

ISR(INT1_vect) {
    // active if level is high
    if ((PIND & (1 << error_pin)) != 0) {
        // this is error
        // stop everything
        TIMSK1 = 0;
        TCCR1A = 0;
        TCCR1B = 0;
        OCR1AH = 0;
        OCR1AL = 0;

        EIMSK = 0;
        PCICR = 0;
        PCMSK0 = 0;

        // turn off diode on arduino pin 13
        PORTB &= ~(1 << PB5);
    }
}

// level change on enable button pin
ISR(PCINT2_vect) {
    _delay_ms(50);
    if (enabled()) {
        PORTB |= (1 << PB5);
        // enable button pressed step enabled
        PORTB |= (1 << enable_pin);
        TCCR1B |= (1 << CS11);
        if (at_home()) {
            // duty cycle begin
            OCR1A = step;
            sport |= (1 << dir_pin);
            current_state = duty_cycle;
            position = duty_steps;
            force_at_home = 0;
        } else {
            // go home
            OCR1A = step_home;
            sport &= ~(1 << dir_pin);
            current_state = search_home;
        };
        TIMSK1 |= (1 << OCIE1A);
    } else {
        PORTB &= ~(1 << PB5);
        // enable button released - step disabled
        PORTB &= ~(1 << enable_pin);
        TCCR1B &= ~(1 << CS11);
        TIMSK1 &= ~(1 << OCIE1A);
    };
};

ISR(TIMER1_COMPA_vect) {
    if (current_state == duty_cycle) {
        position--;
        if (position == 0) {
            _delay_ms(10);
            OCR1A = step_home;
            sport &= ~(1 << dir_pin);
            current_state = search_home;
        }
    }
    else if (current_state == move_in_home) {
        position--;
        if (position == 0) {
            // step disabled at home
            PORTB &= ~(1 << enable_pin);
            TCCR1B &= ~(1 << CS11);
            TIMSK1 &= ~(1 << OCIE1A);
            force_at_home = 1;
        }
    };
}

int main(void) {
    _delay_ms(500);
    // step and dir pins - output
    // enable, home and error pins - input
    // activate pull-ups
    PORTB = 0xFF;
    PORTC = 0xFF;
    PORTD = 0xFF;
    DDRB = 0;
    DDRC = 0;
    DDRD = 0;
    nop();
    // step enable, step and dir to output
    sport &= ~((1 << step_pin) | (1 << dir_pin) | (1 << enable_pin));
    DDRB |= (1 << step_pin) | (1 << dir_pin) | (1 << enable_pin) | (1 << PB5);
    nop();

    // step
    // phase and frequency correct PWM and /8 divider
    TCCR1A = (0 << COM1A1) | (1 << COM1A0) | (0 << WGM11) | (1 << WGM10);
    TCCR1B = (1 << WGM13) | (0 << WGM12) | (0 << CS12) | (0 << CS11) | (0 << CS10);
    // 125(0x7d) is 8kHz (raise + fall) == 4 kHz total frequency
    OCR1A = step;
    // step will be enabled on button pressed
    TIMSK1 &= ~(1 << OCIE1A);

    // home switch on INT0
    // interrupt on any logical change for int0/1: ISC00 = 1 ISC01 = 0 ISC10 = 1 ISC11 = 0
    EICRA = (1 << ISC00) | (1 << ISC10);
    EIMSK |= (1 << INT0);

    // error switch on INT1
    EIMSK |= (1 << INT1);

    // enable button on PCINT0
    PCICR |= (1 << PCIE2);
    PCMSK2 |= (1 << PCINT20);

    duty_steps = (duty_length / revolution_length) * steps_per_rev * 2;

    sei();

    // diode on pb5 on
    PORTB |= (1 << PB5);

    while(1)
    {
        nop();
    }

    return 0;
}