PIC Beginner - Infrared Receiver and IR Protocol

[dhouston]

Please let me know:
1. How to calculate (pulse>100) is logic 1.
2. and PULSIN_MAX 1140 . why do you use 1140

I normally use RF where pulses & spaces are slightly different. I did the conversions to IR quickly, from memory and doing the math in my head so both figures are a bit on the high side.

IR transmitters (i.e. remotes) that used the NEC chip actually used numbers of carrier cycles as the unit of time rather than absolute number of µS. They were also battery operated so there could be some variation due to voltage variations. It is recommended to allow ±20% although that's probably generous with more modern remotes (the protocol has been around for about 40 years).

120% of 900 = 1080 instead of 1140.

With this method we are only able to measure the spaces which can be 0.56mS or 1.125mS. We just want to determine whether it is one or the other. A figure about halfway between the two values should work so 85 might be better than the 100 I used.

The NEC protocol is used by many manufacturers and you will encounter some that do not adhere exactly to the values given in the NEC datasheet so you need to build in a little flexibility.