On Wed, 2010-07-28 at 09:46 -0400, Jon Smirl wrote:
> Let's be really sure it is NEC and not JVC.
>
> > > 8850 4350 525 1575 525 1575
> > > 525 450 525 450 525 450
> > > 525 450 525 1575 525 450
> > > 525 1575 525 450 525 1575
> > > 525 450 525 450 525 1575
> > > 525 450 525 450 525 23625
>
>
> NEC timings are 9000 4500 560 1680 560 560 etc
>
> JVC timings are 8400 4200 525 1575 525 525
>
> It is a closer match to the JVC timing. But neither protocol uses a
> different mark/space timing -- 450 vs 525
I assume you mean "different mark/space timing for the symbol for which
they are the same length" (in NEC that's the '0' symbol IIRC).
I've noticed different mark/space timings for the '0' symbol from NEC
remotes and with some RC-5 remotes. I usually attribute it to cheap
remote designs, weak batteries, capacitive effects, receiver pulse
measurement technique, etc.
Here's an example of NEC remote from a DTV STB remote as measured by the
CX23888 IR receiver on an HVR-1850:
8257296 ns mark
4206185 ns space
leader
482926 ns mark
545296 ns space
0
481296 ns mark
1572259 ns space
1
481148 ns mark
546333 ns space
0
479963 ns mark
551815 ns space
0
454333 ns mark
1615519 ns space
1
435074 ns mark
591370 ns space
[...]
I don't know the source of the error. I would have to check the same
remote against my MCE USB receiver to try and determine any receiver
induced measurement errors.
But, in Maxim's case, the difference isn't bad: 450/525 ~= 86%. I would
hope a 15% difference would still be recognizable.
> Also look at the repeats. This is repeating at about 25ms. NEC repeat
> spacing is 110ms. JVC is supposed to be at 50-60ms. NEC does not
> repeat the entire command and JVC does. The repeats are closer to
> following the JVC model.
>
> I'd say this is a JVC command. So the question is, why didn't JVC
> decoder get out of state zero?
Is JVC enabled by default? I recall analyzing that it could generate
false positives on NEC codes.
Regards,
Andy
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