PIC Beginner - Infrared Receiver and IR Protocol

[komoe01]

I changed pin assign.

The result is successfully done.

I test ten different kind of DVD Remote. Key positions are changed but all are work well.

Now I run my program for two different tasks using same key of two different remote (Sony and NEC Protocol).

** two ir protocol can use in same pic **

Adouston,
THANK YOU VERY MUCH for your kindly help.

I read NEC protocol and compare code.

Header is 9ms
- no header found, restart

If (stx<760) Then init

Space between header and body is 4.5ms
-wait space

While PortA.2=1:Wend

Each pulse is a 560µs long
A logical "1" takes 2.25ms to transmit (pulse 560µs + space )
a logical "0" is only half of that, being 1.125ms (pulse 560µs + space )

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

I say again. Thanks.

Moe.

[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.

[komoe01]

Thanks
dhouston
for your explanation.

Thanks
lester
for your suggestion.

Now I should stop this thread.


Moe