#include <avr/io.h>

// stringify
#define STRINGIFY_HELPER(x)		#x
#define STRINGIFY(x)			STRINGIFY_HELPER(x)

// concatenate
#define CONCAT_HELPER(x, y)		x ## y
#define CONCAT(x, y)			CONCAT_HELPER(x, y)

// get argument
#define ARG_1(v1, v2)			v1
#define ARG_2(v1, v2)			v2
#define GET_PORT(args)			ARG_1 args
#define GET_BIT(args)			ARG_2 args

// actions on registers
#define SET(register, bit)		register |= 1 << bit
#define CLEAR(register, bit)	register &= ~(1 << bit)
#define TEST(register, bit)		register & 1 << bit
#define TOGGLE(register, bit)	register ^= 1 << bit

// actions on elements
#define SET_ELEM(elem)			SET(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
#define CLEAR_ELEM(elem)		CLEAR(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
#define TEST_ELEM(elem)			TEST(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
#define TOGGLE_ELEM(elem)		TOGGLE(CONCAT(PORT, GET_PORT(elem)), GET_BIT(elem))
#define MODE_OUTPUT(elem)		SET(CONCAT(DDR, GET_PORT(elem)), GET_BIT(elem))
#define MODE_INPUT(elem)		CLEAR(CONCAT(DDR, GET_PORT(elem)), GET_BIT(elem))
#define TOGGLE_PIN(elem)		SET(CONCAT(PIN, GET_PORT(elem)), GET_BIT(elem))
#define TEST_PIN(elem)			(TEST(CONCAT(PIN, GET_PORT(elem)), GET_BIT(elem)))
#define IS_PIN_SET(elem)		(TEST_PIN(elem) == 0)
#define IS_PIN_CLEAR(elem)		(TEST_PIN(elem) == 1)

// bits
#define D1	0
#define D2	1
#define D3	2
#define D4	4
#define SW1	2
#define SW2	4

// elements (port, bit)
#define LED1	(B, D1)
#define LED2	(B, D2)
#define LED3	(B, D3)
#define LED4	(B, D4)
#define BUTTON1	(D, SW1)
#define BUTTON2	(D, SW2)

// TIME
#define PRESCALE_VALUE				1024		// can be 1, 8, 64, 256, 1024
// table 16-5 : prescale sets
#define PRESCALE_SET(value)  \
									((value) == 1   ? (0<<CS12 | 0<<CS11 | 1<<CS10) : \
									 (value) == 8   ? (0<<CS12 | 1<<CS11 | 0<<CS10) : \
									 (value) == 64  ? (0<<CS12 | 1<<CS11 | 1<<CS10) : \
									 (value) == 256 ? (1<<CS12 | 0<<CS11 | 0<<CS10) : \
									 (value) == 1024? (1<<CS12 | 0<<CS11 | 1<<CS10) : \
													  (0<<CS12 | 0<<CS11 | 0<<CS10))
#define TIME_MS(ms)					(((F_CPU / PRESCALE_VALUE) * ms) / 1000)
#define PERIOD						1000
#define DUTY_CYCLE					10
#define PERCENT(percent, period)	(((float)percent / 100) * period)

// END MACROS


int main() {
	MODE_OUTPUT(LED2);

    SET(TCCR1A, WGM11);								// Table 16-4 : set timer in Fast PWM (Pulse With Modulation) mode with TOP = ICR1 (Mode 14)
	SET(TCCR1B, WGM12);
    SET(TCCR1B, WGM13);

	SET(TCCR1A, COM1A1);							// Table 16-2 : non-inverting mode, the LED will be ON for DUTY_CYCLE% of the time (CLEAR OC1A on compare match, SET OC1A at BOTTOM)

    ICR1 = TIME_MS(PERIOD);							// Table 16-4 : set the period (compare TOP value)
    
    OCR1A = TIME_MS(PERCENT(DUTY_CYCLE, PERIOD));	// 16.9.3 : set the duty cycle to DUTY_CYCLE% of the time on channel A -> OC1A (alternate function of PORTB1, aka LED2) is cleared when TCNT1 (the counter value) equals OCR1A

    TCCR1B |= (PRESCALE_SET(PRESCALE_VALUE));						// start the timer with the prescaler

	while(1) {
		continue;
	}
}