You can set the interrupt on both rising edge and falling edge , first set
it on rising edge , when the interrupt occurs set it on falling edge in the
rising edge interrupt routine and vice versa  , I think I did my reception
this way and I recall that the ir stream has a start bit of 20 us then 16
bit code  then 16 bit key code , depending on your remote control of course
. and the output is always hi the pulses are low. first you have to check
that the start bit is the right length otherwise you just ignore the rest
and the hi is 4 usec pulse and the low is 7 u sec , check it with a DSO or
logic analyzer . if u keep the key on the remote pressed down you get just
the start bit and 1 pulse  of certain duration and not the rest of the code
, this is useful for things like volume up and volume down etc .

----- Original Message -----
From: "Josh Koffman" <listsjosh@3MTMP.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, December 02, 2001 9:56 PM
Subject: [PIC]: What's the best way to decode IR?


> Ok, since I can't seem to find anyone that's really done exactly what I
> want to do, I seem to be forging new ground. Unfortunately, I'm not that
> great at it, so I have a few questions. I plan on using one of the
> little IR modules to decode the actual IR signal and give me a ttl out.
> The question now is, what's the best way to deal with it?  I'd like to
> stay away from just polling, because the PIC will be doing a bunch of
> other things, and I don't want to run the risk of missing IR pulses. I
> could use the external interrupt, so that every time there is a pulse
> I'd check a TMR. The problem I see there is that I have to set the
> interrupt to trigger on rising edge or falling edge, I can't do both. I
> don't want to mess with portB interrupt on change. I was thinking I
> could use the CCP module, but I don't really know how. I guess it would
> trigger when it receives a pulse from the IR module, then captures the
> value in the TMR. Then I could check the value of that against what my
> high and low timings should be, and go from there. Again I think I run
> into the rising/falling edge thing though. I'm really confused here. I'm
> sure that there is a solution somewhere, I just can't quite figure it
> out.
>
> If you have any ideas or suggestions, they will be appreciated!
>
> Thanks,
>
> Josh
> --
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> completely foolproof is to underestimate the ingenuity of complete
> fools.
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>
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