wrote in message
...
On Jun 2, 2:49 am, "N_Cook" wrote:
Like breaking a combination lock you need a "tell " to work on.
Assuming a piece of kit, impossible to get a remote control for and
"universal " remotes do not register any change to the otherwise
dead kit.
If you broke into a ground or supply line to the microcontroller
and
monitored the supply current , would there be staged changes of
current when
exercised by various , but vast majority wrong, IR signals?
ie simple swept 30 to 50 KHz oscillator source would you pick up on
say
38KHz as the basic required "carrier" frequency ?
Varying mark/space of gated pulses at that "carrier" f, would you
pick up on
the correct mark/space
?
Then would there be a recognisable respone to various random
"nibbles" that
are parts of the required coding ?

Years back I wanted to use a Sony remote (had extras) to control
something completely different. I bought a 38KHz IR receiver and sat
down with a scope and watched what happened and quickly found there is
a method to the madness. Different width pulses, repeated inverted
patterns, preambles. It wasn't too big a deal to write assembly code
to receive and decode a stream. Later with an early HDTV (before
integrated tuners) and set top box I did the same again and this time
received, transcoded and transmitted the same command to the other
boxes. BTW both Sony and Samsung (10 years + old) used 32 bits 8
start, 8 'unit ID' and 16 data bits sent as an 8 bit block followed by
the same pattern inverted. I haven't looked at anything recent.

It's really nothing more than an optical modem but everybody has
different protocols. They don't WANT to make it easy .

The problem is the large variety of codes and carrier frequencies
available. There isn't enough room to to store all the variants in a
low power system. I believe the Logitech Harmony is programmed via the
PC so only needs a small amount of memory. I know they're expensive -
that's why I don't have one but many folks swear by them (and a few
swear at them).

G²

+++++

When VCRs first came and no r/c option I used an old TV remote and made up a
decoder and 4 programme timer from CMOS and relays to the VCR switches to
make it remotely channel changeable and more than 1 , as it stood, timed
record