2.txt

NEC IR remote control decoder

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

enum STATE { S_IDLE, S_PREAMBLE, S_ADDRESS_0, S_ADDRESS_1, S_CODE_0, S_CODE_1, S_LAST };

static uint8_t state = S_IDLE;

#define EVENT_NEW_FRAME 2

uint8_t address = 0;
uint8_t code = 0;
uint8_t packet = 0;
uint8_t ibit = 0;

static uint8_t error = 0;

void necir_init(void)
{
	PORTB |= _BV(PINB0);    // pullup enable
	DDRB  &= ~_BV(PINB0);  // ICP1 as input

	TCNT1 = 0;            // start counting from zero
	TIMSK |= (1<<TICIE1); // enable input capture interrupts
	TCCR1A = 0;
	TCCR1B |= (1<<CS11)|(1<<CS10);  // timer prescaler 64, ICES1 falling edge
}

uint8_t necir_getaddress(void)
{
	return address;
}

uint8_t necir_getcode(void)
{
	return code;
}

void necir_superstate(char event)
{
	switch (event)
	{
		case 0:
		case 1:

			packet < 7)
			{
				ibit = 0;
				++state;
			}

			error = 0;

			break;

		case EVENT_NEW_FRAME:

			state = S_ADDRESS_0;
			ibit = 0;
			packet = 0;
			error = 0;

			break;

		default: break;
	}
}

void necir_event(char event)
{
	switch (state)
	{
		case S_ADDRESS_0:

			necir_superstate(event);

			if (state==S_ADDRESS_1)
			{
				address = packet;
			}

			break;

		case S_CODE_0:

			necir_superstate(event);

			if (state==S_CODE_1)
			{
				code = packet;
			}			

			break;

		default:
			necir_superstate(event);
			break;
	}
}

#define F_TIMER (F_CPU / 64)  // timer prescaler
#define HUNDRED_USEC (F_TIMER / 10000)  

ISR(TIMER1_CAPT_vect)
{
	unsigned int dpulse = ICR1; // read timer input capture register
	TCNT1 = 0;                  // reset counter

	//
	// decode the event and dispatch it to the state machine
	//

   	if (dpulse < 12 * HUNDRED_USEC) // 1.2 ms
   	{
		necir_event(0);
   	}
   	else if (dpulse < 23 * HUNDRED_USEC) // 2.3 ms
   	{
   		necir_event(1);
   	}
   	else if (dpulse < 136 * HUNDRED_USEC) // 13.6 ms
   	{
   		necir_event(EVENT_NEW_FRAME);
   	}
}