SmaTrig 2.1

DIY Canon RC-1 infrared remote control clone

This article describes how to build a DIY low-budget AVR-based infrared remote control for Canon cameras. The reverse-engineered communication protocol of the RC-1 is described here. The RC-1 lets you trigger the camera instantly or with a delay of 2 seconds from a distance of up to 5 meters (~16 ft). It comes in very handy when taking long exposure pictures or for HDR photography. The presented circuit can be used as part of DIY interval triggers for smaller Canon cameras without the external trigger connector. In bracketing mode the RC-1 lets the camera shoot a whole series of images at once!
It is recommended to read the RC-1 communication protocol description first.

canon rc-1 disassembled

The Circuit

The first circuit I made was based very much on the original Canon (or Mitsumi, see image above) design. It used a crystal oscillator to provide a precise clock to the microcontroller. The IR-LED was driven by an additional NMOS transistor allowing higher current than the controller outputs can source. After I got it working, I simplified the schematics successively to reduce the part count and make it more easy to build. The schematics of the initial "high-end" version is here. The simplified version is shown in the picture below.

canon remote schematics

I was able to trigger the Canon EOS 400D from more than 5 meters (~16 ft) with both versions. The simple version had slightly more failed trigger attempts. I recommend to build the simplified version though.

In the simplified version the crystal oscillator was replaced by the internal 8 MHz oscillator, saving three external parts. The disadvantage of this solution is that the frequency is drifting slightly with the supply voltage and temperature. Details on this behaviour can be found in the "Electrical Characteristics" section of the Attiny25 data sheet. The most radical simplification was the elimination of the transistor. I found out experimentally that driving the IR-LED directly from paralleled microcontroller pins is powerful enough to trigger the camera from about 5 meters (~16 ft). Finally the voltage reducing diode has been dropped increasing the supply voltage to the "absolute maximum" value of 6 V. It seams to be no problem for the ATtiny25. I don't recommend to leave the mode selector input pin unconnected in the simplified version. I had some sporadic shots in the wrong mode.

AVR source code

The program (simplified version) was written in C and compiled with the avr-gcc compiler in the AVR-Studio. The _delay_ms function was used to generate the delays. After applying power to the controller, pin PB0 is tested for its level. If the level is high (pin not connected, internal pull-up active), the instant trigger signal is emitted. If the pin is tight to ground, the delayed trigger signal is send. After sending the pulses, the microcontroller is put in power-down mode to reduce the power consumption to the minimum. When the pushbutton is released, no current is drawn from the battery, except the leakage current of the capacitor. A high quality cap should be used to keep this current low. The LED output signal is present on pins PB1 and PB2. The pins should be used in parallel if driving the LED directly as in the simplified circuit version. For some inexplicable reasons I wasn't able to parallel more than two pins. Before compilation, the microcontroller clock frequency must be specified in the c-file header according to the oscillator used. If the internal 8 MHz oscillator is used as clock source, an F_CPU of 7.9 MHz is a good choice. The reason for the difference is the voltage drift of the internal RC-oscillator. The nominal frequency of 8 MHz is specified for a supply voltage of 3 V. It's decreasing slightly for higher supply voltages. The dependence is documented in a diagram it the data sheet of the controller.

#define F_CPU 7900000 // clock frequency, set according to clock used!

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

#define HPERIOD 0.01524
#define RATIO 0.4
#define NPULSES 16

#define LEDOFF 0b00000001
#define LEDON  0b00010111

int main(void)
	uint8_t i;

	DDRB  = 0b00010110; // pin PB0 is input, pins PB1-PB4 are output
	PORTB = 0b00000001; // pull-up for input pin PB0
	asm volatile ("nop");
	asm volatile ("nop");

	if ( PINB & (1<<PINB0) ) 


		_delay_ms(7.33); // instant


		_delay_ms(5.36); // delayed





The C source code and the hex-file for the simplified version can be downloaded here

C source code canon_remote.c
hex file canon_remote.hex


I used PonyProg to copy the hex-file into the controller and set the fuses. The fuse settings can be copied from this screenshot


By the way, most digital cameras are sensitive to infrared light in the preview mode, so you can see IR-diodes blinking on the display. This might be helpful for basic debugging of the remote control circuit.


Your RC-1 clone doesn't work?

  • Check, if any signal is present at the IR LED pins. Use a loudspeaker if no scope at hand.
  • In case you can't hear anything probably the programming went wrong or the clock source is not correct in the AVR.
  • If the signal is audible, use a video camera or a simple digital camera (mobile phone?) to check the IR signal. Cheap photo equipment is usually sensitive to IR light. In total darkness you can usually see IR LEDs glowing with the naked eye. Do not look directly into the beam! Is the polarity of the IR LED ok? An IR LED and an IR photodiode are two different things.
  • In case the IR light is visible and the camera not responding: Check camera settings, the remote/self-timer option must be on! If ok, check the program timing. The _delay_us() routines in the code need a proper setting of the F_CPU variable. A sound card can be used instead of a scope to analyse the signal. Check the max input voltage before!

Canon RC-1 IR remote control reverse-engineered
Attiny25 data sheet
PonyProg, my favourite AVR programming tool
A similar AVR based project for Nikon cameras

Comments (8)

Thanks dude. I was stucked with photo-transistor seeing only 2 pulses (not bursts) and wasted a day to figure out. Thanks to you now I'm going ahead with my timelapse machinery :)
#8 - wikrap1 - 08/14/2016 - 21:34
I guess the remote control will also work with the caps behind the switch. In this case you will allways loose the energy stored in the caps after disconnecting them due to the uC standby current. I didn't estimate whether the loss is bigger than in case of the caps constantly connected. In both version the batteries should hold for many years.
#7 - luk - 11/30/2009 - 10:43
Simple version
The hex file and the source code are for the simple version. In the initial version I used a crystal to get an exact clock. I modifed the text in a few places to clarify what is what.

#6 - luk - 11/27/2009 - 11:15
I need asm code for ATtiny 13
I need asm code for ATtiny13.
#5 - compo - 11/20/2009 - 23:51
Hello all,

Very nice and useful project, I mostly use PIC, can somebody send the hex code for it please.

Thankx in advance.

#4 - Tomas - 09/30/2009 - 09:23
I recently built my own simplified version with Attiny45 and would make the following suggestions:

- Modern tinyAVR's can run on a single 3V supply (up to 10MHz) and thus one CR2032 suffices and then the freq can be set to exactly 8MHz
- I use a while(1) loop within main() to perform several trigger attempts with 100ms delays, should one of them fail.
- The buffer cap can be eliminated, according to my experiences, the CR2032 can provide enough power.

My version consists of only a battery, switches, Attiny45, and a led with a resistor.
#3 - szali - 06/12/2009 - 11:51

If you have the source code for PIC, pls send to me via email:

This is a great project.

Thanks all.
#2 - falleaf - 11/10/2008 - 08:58
Great job! Thanks a lot. I tried 940nm diode and it worked as well.
I can also offer asm code for PIC 16F628A if anybody is interested.
#1 - Climebrg - 10/27/2008 - 17:18
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