I built a device to decode IR remotes, but I based it on the arduino 
platform. The same idea applies to the pic though. I use a 555 timer to 
modulate the output since that was the easiest thing to set up and 
allows me to just output bits without concern for the modulation.  The 
way I handled the input was multiple receivers tied to one pin. The IR 
receivers like TSOP models are active low so they go low when they get a 
signal. I used 3 for the project. One for 36Khz, 38Khz, 40Khz , those 
are the main remote frequencies.

On the output I used 3 different pins depending on what modulation the 
signal needed. There are ways of doing it with just a micro but this was 
a lot easier to code and only required a single chip and a couple 555 
timer.

One problem with directv IR signals is that it sends multiple signals 
each time you press a button. Even if you have it set for the tv mode, 
when you press volume up, it first sends a signal  for the sat receiver 
to read ( this is how it detects and displays the message, remote is in 
tv mode on the screen), it then sends whatever the programmed code is 
for the tv. You have to separate those out in the code or it will just 
confuse it as to what the protocol is.

This is what the raw output looks like when pressing the some buttons on 
my directv remote, - is a low, no - is a high, time is in microseconds.
UP:
Raw (20): -29900 3000 -1150 1250 -1150 650 -550 650 -550 1250 -550 650 
-550 600 -1200 1200 -550 1250 -1150 650
DOWN:
Raw (20): -29900 3050 -1150 1200 -1200 600 -550 650 -550 1250 -550 650 
-600 1200 -550 1250 -1150 600 -550 650
LEFT:
Raw (20): -29950 3000 -1150 1250 -1150 650 -550 650 -550 1200 -600 600 
-600 1200 -1150 1250 -1150 650 -1150 650
RIGHT:
Raw (20): -29900 3050 -1150 1200 -1150 650 -550 650 -550 1250 -600 600 
-1150 650 -550 1200 -1150 650 -1150 650


Now notice what happens when I press volume up with the remote 
programmed for my tv.
Raw (20): 14722 6000 -1150 1250 -1150 650 -600 600 -1150 650 -1150 1200 
-600 600 -1150 650 -550 1250 -1150 650

Decoded NEC: AF548B7 (32 bits)
Raw (68): -16714 9000 -4500 550 -500 600 -550 550 -550 600 -550 550 
-1650 600 -550 550 -1650 600 -550 550 -1700 550 -1650 600 -1650 600 
-1650 600 -500 600 -1650 600 -500 600 -1650 600 -550 550 -1650 600 -550 
550 -600 550 -1650 600 -500 600 -550 550 -550 600 -1650 550 -550 600 
-1650 600 -1650 550 -600 550 -1650 600 -1650 550 -1650 600

It sent first a code to the directv receiver to tell it I had pushed a 
key, then the code to control volume on my brand of tv. I hope this helps.
Mark H.





Mark Perri wrote:
>
> If I may ask, how do you have your PIC modulate your signals to 
> transmit?  I'm beginning to build a remote control as well.  Do you have 
> a dedicated port putting out 38 kHz and then another port generating the 
> codes, which you gate together with external hardware, or do you have 
> one port doing all the work?
>
> Mark
>
>   

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