I just did this recently, with an IR LED with a PIC12F629 for the transmi=
tter=20
and a 3-pin 38khz IR receiver module with a PIC16F628 for the receiver.  =
I=20
came up with my own 8-bit coding scheme, which has start and stop bits.  =
The=20
receiver module goes low when it senses a 38khz signal, so I used...

=09(1)  Wait for negative-edge interrupt
=09(2)  Interrupt off.  Set TMR0 for 0.5 T (where pulse (bit) width =3D T=
)
=09(3)  Read pin state and set in a register (let's call it CODE)
=09(4)  Set TMR0 for 1 T
=09(5)  Read pin state
=09(6)  Left-shift into the CODE register
=09(7)  Repeat from step 4 until 8 total bits received.
=09(8)  Ensure blank for some interval time, then reset, interrupt on, et=
c.

The first 0.5 T sets the point of reading to be in the middle of the puls=
e.

Then check the code with what you have.  Fairly simple.

Cheers,
-Neil.



On Saturday 17 April 2004 08:54 am, Matt Marsh scribbled:
> Hi guys,
>
> For my second PIC project, I'm going to need to detect a button
> being pressed on an IR remote control. I've done a small amount of
> research on this and from what I've read I'm going to need to hook
> up an IR receiver to one of the pins and then time how long pulses
> last (and/or the gaps between them depending on the remote).
>
> So, in order to determine how long a pulse lasts I'm thinking that
> I'm going to need to do something like:
>
>   - loop waiting for pin to go high
>   - reset TMR0
>   - loop waiting for pin to go low
>   - value in TMR0 now contains length of time of pulse
>
> I just wanted to get some feedback whether I'm thinking of this in
> the right way, or whether there is some other technique that is
> generally used for timing pulses etc.
>
> Thanks,
> Matt

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