On Mon, Aug 2, 2010 at 12:42 PM, Christoph Bartelmus [off-list ref] wrote:

Hi!

Jon Smirl "jonsmirl@gmail.com" wrote:
[...]

quoted

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Got one. The Streamzap PC Remote. Its 14-bit RC5. Can't get it to properly
decode in-kernel for the life of me. I got lirc_streamzap 99% of the way
ported over the weekend, but this remote just won't decode correctly w/the
in-kernel RC5 decoder.

quoted

Manchester encoding may need a decoder that waits to get 2-3 edge
changes before deciding what the first bit. As you decode the output
is always a couple bits behind the current input data.

You can build of a table of states
L0 S1 S0 L1  - emit a 1, move forward an edge
S0 S1 L0 L1 - emit a 0, move forward an edge

By doing it that way you don't have to initially figure out the bit clock.

The current decoder code may not be properly tracking the leading
zero. In Manchester encoding it is illegal for a bit to be 11 or 00.
They have to be 01 or 10. If you get a 11 or 00 bit, your decoding is
off by 1/2 a bit cycle.

Did you note the comment that Extended RC-5 has only a single start
bit instead of two?

It has nothing to do with start bits.
The Streamzap remote just sends 14 (sic!) bits instead of 13.
The decoder expects 13 bits.
Yes, the Streamzap remote does _not_ use standard RC-5.
Did I mention this already? Yes. ;-)

If the remote is sending a weird protocol then there are several choices:
  1) implement raw mode
  2) make a Stream-Zap protocol engine (it would be a 14b version of
RC-5). Standard RC5 engine will still reject the messages.
  3) throw away your Stream-Zap remotes

I'd vote for #3, but #2 will probably make people happier.

Christoph

-- 
Jon Smirl
jonsmirl@gmail.com