Avr rc5 remote control

Introduction

The test setup Just a quick snapshot of the test setup. An STK500 cruedly interfaced to a TSOP1736 soldered on a recycled prototype pcb.

Minimum circuit

Interfacing a standard Philips RC5 protocol remote control to an Atmel AVR should be easy. It shouldn't have to take neither much hardware nor code to do so. I've found that there is an official application note from Atmel describing how to do this. Atmels example is done in assembler and is fault tolerant, but it's difficult to understand. By doing it in C it becomes very simple and understandable.

The RC5 protocol

The Remote Control A worn Philips remote control used for testing.

I'm not going to provide you with my own version of how it works.
I suggest you read this: http://www.sbprojects.com/knowledge/ir/rc5.htm
That link also has a list of the command and address codes that you'll need.

The Code

The stripped down C code:

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

typedef union { 
	uint16_t raw;
	struct {
		unsigned cmd    : 6;	// LSB
		unsigned addr   : 5;
		unsigned toggle : 1;
		unsigned start  : 2;
		unsigned        : 2;	// MSB
	};
} rc5data;

static volatile int flag = 0;
static volatile rc5data data;

void init_int0()
{
	// Interrupt on INT0 pin going low
	MCUCR = (1 << ISC01);

	// Turn on INT0!
	GICR |= (1 << INT0);
}

SIGNAL (INT0_vect)
{	
	int pos = 0;

	if (!flag) {
		data.raw = 0;

		// triggers on falling edge of start bit 1.
		_delay_ms(0.2);

		while (pos < 14) {
			data.raw = (data.raw << 1) | ((~PIND & 0x04) >> 2);
			_delay_ms(1.8);
			pos++;
		}

		flag = 1;
	}
}

int main()
{
	init_int0();
	sei(); 		// Enable interrupts

	while(1) {	

		while(!flag);

		// Do with data from the remote control here what you like.
		flag = 0;
	}

	return 0;
}

External Links

• Application Note AVR410: RC5 IR Remote Control Reciever