pic microcontroller discussion list <> wrote on Wednesday, June 04, 2003
5:24 PM:

> Do you know what the required sample rate would need to be?
> And could you explain a little more what you mean about the
> RC5 'toggle bit' needing special treatment.  I have never
> tried this either, but I have thought of a few projects for
> controlling audio/video equipment from different parts of the
> house by placing detectors all over the house to control
> switching of audio and video connections to different rooms or to the
> backyard.

I do that, using a PIC version (approx 4 components!) of my older circuit
posted at
http://www.geocities.com/nigelorr/ir_extend.html
(it uses a 555 and works fine, but a PIC is more fun...)

I've recently moved house, so cabling is just getting started (just one IR
link from the kitchen to an A/V amp in a cupboard so far!), but it worked
well in my previous house using the old circuit.
It should be good for at least 10 receivers (depends on receiver sink
current and pullup resistor choice).  It can also be linked into a PC,
using the UIR/IRMAN circuit (also PIC-based) at
http://fly.cc.fer.hr/~mozgic/UIR/
but I've only tested that to see it work, not installed it properly.  I
will get round to updating the geocities page with the easier PIC design
'one day'...

If you just demodulate and remodulate the IR signal, you don't need to
worry about the toggle bit (it is used to signify 'key held down'), but you
need to deal with it if you want to decode the IR, eg to process it.  Your
only concern is remodulating at the correct frequency, I just use 38kHz, it
works for all my equipment, but some has reduced range.  If you want,
connect an IR led to a scope as a photodiode (as discussed here a few
months ago) and point your remote at it, you can get an accurate measure of
the real modulation frequency of any problem remotes.

Nigel
--
Nigel Orr, Design Engineer                 nigel@axoninstruments.co.uk
Axon Instruments Ltd., Wardes Road,Inverurie,Aberdeenshire,UK,AB51 3TT
               Tel:+44 1467 622332 Fax:+44 1467 625235
                   http://www.axoninstruments.co.uk

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