Decoding an incoming infrared signal: need advice

[flotulopex]

Hello,

I'm making a small TV remote based on a 12F683.

It is not finished yet but I have a question about how important the carrier's frequency is.

I've made some test with my SONY TV at different carrier frequs, but I couldn't notice any difference in the operatin distance between the TV and the remote (it works over 8 meters). Maybe my TV is very "sensible" to any IR remote signal and this is not a trustfull test.

As different suppliers use different IR-Receivers with different specifications especially the carrier frequency (mainly between 36 and 40kHz), I'd like to know much importance is to give to this parameter.

Since the remote is going to "learn" from different remotes (= different brands = different carrier freq), I think best to adjust this freq accordingly.

Using mister_e's PicMultiCalc program, I've noticed that I can almost generate the frequency range in a 0,5kHz resolution (36 / 36,5 / 37 / 37,5 / etc).

Does anyone know if it is worth (or mandatory) to have a higher precision?

If yes, can I achieve this with a PIC easely or should I go for an external pulse-generator (or any other system)?

[dhouston]

Most of the receivers in A/V gear have a fairly wide bandwidth (+/- 5kHz) so this is not super-critical for typical use. I designed a CF card IR transmitter for use with PDAs a few years back. Using a single emitter driven by 3.3V, the tested range exceeded 30m.

[Bruce]

Like Dave says, it's not normally critical. Especially in relatively noise free environments
where you have a good strong IR signal.

But, if you need the absolute maximum range, under less than favorable conditions, then
it's a lot more important. If your carrier frequency is spot-on the center band-pass frequency
of the IR receiver, it's more likely to work under less than optimum conditions.

The IR receiver is more sensitive to the signal when it's spot-on the center band-pass
frequency.

Even little things like matching the wavelength of the IRLED to the IR receiver can make a
BIG difference if it has to work reliably under various conditions.