Digital camera remote control

One of my friends wanted a microcontroller to send commands to a digital camera. There are lots of such projects on the web and there is even more cheap Chinese remote controllers but no remote does exactly what my buddy needed. He already had a hardware which I mentioned in previous post and a regular remote controller for his Olympus camera. First of all we had to generate 36KHz carrier frequency, we did it using Timer1 in CTC mode:

PORTB &= ~(1<<1);   //there is 0 on pin when OC1A is disabled

DDRB   |= (1<<1);   //OC1A pin works as output

TCCR1B |= (1<<WGM12) | (1<<CS10); //CTC mode and clock source selection

TCNT1 = 0;   //clear timer register

OCR1A = 14;   //1MHz/(2*36KHz) ~ 14

//TCCR1A |= (1<<COM1A0);   //enables OC1A output

Then we had to key carrier frequency with data which will convince camera to take a picture. Information sources we used were lirc drivers www.lirc.org and signals received from regular controller. Every bit consists from two consecutive states zero and one, meaning of a bit is encoded in length of the second state. This way transmission is immune against clock desynchronization. Data transmitted by remote controller which we reverse-engineered looks like this:  

It turned out that camera needs only that marked with red box part of a signal. Rest of transmission is redundant in case of that specific camera. Setting and clearing COMA10 bit controls whether carrier frequency is supplied to IR LED or not, we wrote simple preprocessor directives:

#define HEADER TCCR1A |= (1 << COM1A0); _delay_us(8853); TCCR1A &= ~(1 << COM1A0); _delay_us(4489);

#define ONE TCCR1A |= (1 << COM1A0); _delay_us(559); TCCR1A &= ~(1 << COM1A0); _delay_us(1670);

#define ZERO TCCR1A |= (1 << COM1A0); _delay_us(559); TCCR1A &= ~(1 << COM1A0);  _delay_us(555);  

And function sends a “take a picture” command to camera:

HEADER;

ZERO;ONE;ONE;ZERO;ZERO;ZERO;ZERO;ONE;ONE;ONE;ZERO;ONE;ONE;ONE;ZERO;ZERO;ONE;ZERO;ZERO;ZERO;ZERO;ZERO;ZERO;ZERO;ZERO;ONE;ONE;ONE;ONE;ONE;ONE;ONE;ONE;

Now when we knew that it works we'll clean up this code to make it non-blocking, neat and easy to read and maintain. The most important thing is that controlling digital camera is not_so_difficult_as_you_thought.