Re: Motorola home control

[nobody@xxxxxxxxxxxx (Dave Houston)]

"jibberjabber" <none@xxxxxxxxx> wrote:

>Ok, that looks doable without too much trouble.  I'm using BASCOM...sooo
>easy

There are a couple of Application Notes on the BASCOM site dealing with
capturing and decoding Sony IR codes. The techniques will be similar. There
are also application notes on Microchip's web site that show how to do it
using PIC ASM. Even though the PIC ASM code won't be of any use, the
techniques used have universal application.

The signal which I used at the very bottom of my article on RF Noise vs.
Signal is about as tough as it can get. That signal is sent three times and
has no obvious lead-in but you can find the beginning of a single code by
looking for the space/pulse sequence composed of the final space of one copy
and first pulse of the next copy. There will always be some such feature
that you can use. Remember - the guy who designed the protocol also has to
capture/decode it.

In this specific case, the code shown is the preamble sent by RF capable
Pronto remotes. It precedes all RF codes sent to their RF extenders and
identifies which RF extender should handle the code, the channel, and IR
carrier frequency. But there's a special secret ingredient that simplifies
things for the receivers in the RF extenders. The signal is double modulated
by the both the data envelope and by ~38kHz. The superregenerative receiver
I used (and recommended to you) cannot turn on/off fast enough to reproduce
the 38kHz bursts so you get the data envelope directly. The Pronto RF
extender's receiver can deal with the 38kHz and it will ignore any codes
that lack it. IOW, its output will be as clean and noise free as the typical
IR receiver.