#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
#if (PRESCALE_VALUE == 1)
	#define PRESCALE_SET			(1 << CS10)
#elif (PRESCALE_VALUE == 8)
	#define PRESCALE_SET			(1 << CS11)
#elif (PRESCALE_VALUE == 64)
	#define PRESCALE_SET			(1 << CS10) | (1 << CS11)
#elif (PRESCALE_VALUE == 256)
	#define PRESCALE_SET			(1 << CS12)
#elif (PRESCALE_VALUE == 1024)
	#define PRESCALE_SET			(1 << CS10) | (1 << CS12)
#endif
#define TIME_MS(ms)					(((F_CPU / PRESCALE_VALUE) * ms) / 1000)

// END MACROS

int main() {
	MODE_OUTPUT(LED2);

	TCCR1B |= (1 << WGM12);			// Table 16-4 : set timer in CTC (Clear Time on Compare) mode, use bit WGM12, located in register TCCR1B (16.11.2)

	TCCR1A |= (1 << COM1A0);		// 14.3.1 : set Compare Output with COM1A0, it toggles OC1A on compare match (Table 16-1), OC1A is alternate function for PORTB1 (Table 14-3)

	OCR1A = TIME_MS(500);			// Table 16-4 : set CTC compare value, the counter is cleared to zero when the counter value (TCNT1) matches the OCR1A register

	TCCR1B |= (PRESCALE_SET);

	while(1) {
		continue;
	}
}