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Old code with added readme
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‎.gitignore

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*.o
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*.elf
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*.hex
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*~

‎LICENSE

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RC5 (36KHz Phillips protocol) Decoding library for AVR
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Copyright (c) 2011 Filip Sobalski <[email protected]>
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Based on the idea presented by Guy Carpenter on http://deep.clearwater.com.au/rc5/
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.

‎Makefile

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AVRDUDE_MCU = m328p
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AVRDUDE_PROGRAMMER = stk500v1
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AVRDUDE_PORT = /dev/ttyACM0
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AVRDUDE_BAUDRATE = 115200
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AVRDUDE = avrdude
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AVRDUDEOPTS = -p $(AVRDUDE_MCU) \
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-c $(AVRDUDE_PROGRAMMER) \
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-P $(AVRDUDE_PORT) \
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-b $(AVRDUDE_BAUDRATE) \
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-F -D
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FREQUENCY = 16000000
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MCU = atmega328p
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CC = avr-gcc
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CFLAGS = -mmcu=$(MCU) -O2 -DF_CPU=$(FREQUENCY)L -Wall
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OBJCOPY = avr-objcopy
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OBJCOPYFLAGS = -j .text -j .data -O ihex
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PROJNAME = rc5
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OBJECTS = main.o rc5.o
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LD = avr-gcc
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LDFLAGS = -mmcu=$(MCU)
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all: $(PROJNAME).hex
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$(PROJNAME).elf: $(OBJECTS)
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$(LD) $(LDFLAGS) $(OBJECTS) -o $@
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$(PROJNAME).hex: $(PROJNAME).elf
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$(OBJCOPY) $(OBJCOPYFLAGS) $< $@
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%.o: %.c %.h
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$(CC) $(CFLAGS) -c $< -o $@
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upload: $(PROJNAME).hex
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$(AVRDUDE) $(AVRDUDEOPTS) -U flash:w:$<
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rebuild: clean all
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clean:
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$(RM) $(PROJNAME) *.o *.elf *.hex *~
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.PHONY: clean rebuild

‎README.md

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# RC5 (36KHz Phillips protocol) Decoding library for AVR
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Based on the idea presented by *Guy Carpenter* on [his site](http://deep.clearwater.com.au/rc5/).
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## What does it do?
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It decodes control codes produces by most of your household infrared remotes.
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## What can run it?
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Tested on __ATmega328P__ with __avr-gcc__ toolchain. Designed for 16MHz crystal.
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Should work on the __ATmega{4/8/16/32}8__ (yes, that means Arduino too) family without modification.
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Uses 16bit timer and an external interrupt.
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I you use a different clock then adjust the timer prescaler and pulse lengths accordingly.
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Should be trivial to adapt to other AVRs sporting a 16bit timer and an external interrupt.
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## What do I need to run it?
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The only additional component needed is an infrared receiver like __TSOP2236__ attached to PD2. Most of the
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standard receivers should work just fine.
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## The docs
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Check out the comments in headers/source. Example in `main.{c,h}` included.
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## Does it work?
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Yes, it does work flawlessly (at least for me). I built a project on it (*rlamp*) and never had any problems. The sensitivity achieved
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with __TSOP2236__ was astounding. I could point the remote anywhere, metres from the receiver and it would pick up
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the signal perfectly with every keypress.
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Copyright &copy; 2011 Filip Sobalski <[email protected]>

‎main.c

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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <util/delay.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "main.h"
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#include "rc5.h"
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/* RC5 lib test
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* Attach a LED to PB5 */
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int main()
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{
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RC5_Init();
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/* Set PB5 to output */
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DDRB |= _BV(PB5);
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/* Enable interrupts */
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sei();
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for(;;)
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{
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uint16_t command;
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/* Poll for new RC5 command */
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if(RC5_NewCommandReceived(&command))
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{
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/* Reset RC5 lib so the next command
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* can be decoded. This is a must! */
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RC5_Reset();
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/* Toggle the LED on PB5 */
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PORTB ^= _BV(PB5);
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/* Do something with the command
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* Perhaps validate the start bits and output
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* it via UART... */
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if(RC5_GetStartBits(command) != 3)
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{
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/* ERROR */
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}
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uint8_t toggle = RC5_GetToggleBit(command);
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uint8_t address = RC5_GetAddressBits(command);
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uint8_t cmdnum = RC5_GetCommandBits(command);
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}
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}
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return 0;
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}

‎main.h

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#ifndef MAIN_H
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#define MAIN_H
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#endif

‎rc5.c

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#include "rc5.h"
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#define SHORT_MIN 888 /* 444 microseconds */
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#define SHORT_MAX 2666 /* 1333 microseconds */
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#define LONG_MIN 2668 /* 1334 microseconds */
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#define LONG_MAX 4444 /* 2222 microseconds */
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typedef enum {
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STATE_START1,
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STATE_MID1,
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STATE_MID0,
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STATE_START0,
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STATE_ERROR,
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STATE_BEGIN,
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STATE_END
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} State;
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const uint8_t trans[4] = {0x01, 0x91, 0x9b, 0xfb};
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volatile uint16_t command;
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uint8_t ccounter;
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volatile uint8_t has_new;
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State state = STATE_BEGIN;
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void RC5_Init()
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{
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/* Set INT0 to trigger on any edge */
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EICRA |= _BV(ISC00);
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/* Set PD2 to input */
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DDRD &= ~_BV(PD2);
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/* Reset Timer1 Counter */
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TCCR1A = 0;
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/* Enable Timer1 in normal mode with /8 clock prescaling */
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/* One tick is 500ns with 16MHz clock */
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TCCR1B = _BV(CS11);
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RC5_Reset();
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}
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void RC5_Reset()
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{
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has_new = 0;
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ccounter = 14;
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command = 0;
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state = STATE_BEGIN;
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/* Enable INT0 */
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EIMSK |= _BV(INT0);
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}
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uint8_t RC5_NewCommandReceived(uint16_t *new_command)
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{
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if(has_new)
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{
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*new_command = command;
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}
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return has_new;
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}
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ISR(INT0_vect)
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{
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uint16_t delay = TCNT1;
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/* TSOP2236 pulls the data line up, giving active low,
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* so the output is inverted. If data pin is high then the edge
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* was falling and vice versa.
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*
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* Event numbers:
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* 0 - short space
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* 2 - short pulse
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* 4 - long space
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* 6 - long pulse
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*/
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uint8_t event = (PIND & _BV(PIND2)) ? 2 : 0;
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if(delay > LONG_MIN && delay < LONG_MAX)
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{
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event += 4;
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}
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else if(delay < SHORT_MIN || delay > SHORT_MAX)
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{
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/* If delay wasn't long and isn't short then
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* it is erroneous so we need to reset but
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* we don't return from interrupt so we don't
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* loose the edge currently detected. */
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RC5_Reset();
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}
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if(state == STATE_BEGIN)
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{
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ccounter--;
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command |= 1 << ccounter;
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state = STATE_MID1;
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TCNT1 = 0;
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return;
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}
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State newstate = (trans[state] >> event) & 0x03;
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if(newstate == state || state > STATE_START0)
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{
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/* No state change or wrong state means
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* error so reset. */
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RC5_Reset();
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return;
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}
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state = newstate;
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/* Emit 0 - jest decrement bit position counter
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* cause data is already zeroed by default. */
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if(state == STATE_MID0)
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{
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ccounter--;
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}
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else if(state == STATE_MID1)
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{
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/* Emit 1 */
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ccounter--;
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command |= 1 << ccounter;
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}
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/* The only valid end states are MID0 and START1.
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* Mid0 is ok, but if we finish in MID1 we need to wait
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* for START1 so the last edge is consumed. */
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if(ccounter == 0 && (state == STATE_START1 || state == STATE_MID0))
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{
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state = STATE_END;
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has_new = 1;
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/* Disable INT0 */
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EIMSK &= ~_BV(INT0);
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}
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TCNT1 = 0;
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}

‎rc5.h

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/*
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* RC5 (36KHz Phillips protocol) Decoding library for AVR
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* Copyright (c) 2011 Filip Sobalski <[email protected]>
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* based on the idea presented by Guy Carpenter
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* on http://deep.clearwater.com.au/rc5/
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*
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* Tested on ATmega328P. Designed for 16MHz crystal.
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* Should work on the ATmega{4/8/16/32}8 family
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* without modification. Uses 16bit timer and an
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* external interrupt.
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*
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* I you use a different clock then adjust the timer
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* prescaler and pulse lengths accordingly.
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*
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* Should be trivial to adapt to other AVRs sporting
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* a 16bit timer and an external interrupt.
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*
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*/
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#ifndef RC5_H
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#define RC5_H
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#include <stdint.h>
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#define RC5_GetStartBits(command) ((command & 0x3000) >> 12)
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#define RC5_GetToggleBit(command) ((command & 0x800) >> 11)
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#define RC5_GetAddressBits(command) ((command & 0x7C0) >> 6)
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#define RC5_GetCommandBits(command) (command & 0x3F)
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#define RC5_GetCommandAddressBits(command) (command & 0x7FF)
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/* Initialize timer and interrupt */
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void RC5_Init();
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/* Reset the library back to waiting-for-start state */
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void RC5_Reset();
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/* Poll the library for new command.
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*
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* You should call RC5_Reset immediately after
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* reading the new command because it's halted once
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* receiving a full command to ensure you can read it
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* before it becomes overwritten. If you expect that only
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* one remote at a time will be used then library
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* should be polled at least once per ~150ms to ensure
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* that no command is missed.
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*/
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uint8_t RC5_NewCommandReceived(uint16_t *new_command);
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#endif
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