how would one go about detecting the length of the pulses?
When you get the falling edge of the IR pulse connected to INT5, the ISr sets Timer interrupt to take samples of the pulse width, this way you can detect a start bit a 0 or a 1.
Its better to take 3 samples and consider data valid if at least 2 out of three are correct.
Also make your interrupt routine in 2 parts, part to test for start bit and set start bit flag detected, another part to test for 0 or 1 if start bit has been detected.
I'd be looking for some code that detects a low and triggers an interupt routine. Write your own code, it is very easy!
The forumula is there, but its difficult.
if you consider frequency division difficult then use your calculator!
I've found some C++ examples of code to decode the pulses, but im trying to do it in ASM.
Read about how to use timers in the datasheet, its straight forward and you don't need ready made code.
Regards
Mahmood