[vdr] Re: Problems while switching channels -> seems to be a diseqc problem

[Oliver Endriss <o.endriss@gmx.de>]

Reinhard Walter Buchner wrote:
> Oliver Endriss wrote:
> > snapshot of a non-working DiSEqC sequence with
> >a digital oscilloscope. I'd like to take a look on the
> >generated signals and compare them with the spec.
>
> Hmm, might be interesting. Do you think some DVB
> cards generate sloppy signals?

I think that there are too much problem reports about DiSEqC 
to be ignored.

I'm using a full DiSEqc sequence without any voltage/toneburst 
commands. Even with this setup switching is not very reliable,
unless I add some retransmissions. It's just a work-around.

Yesterday I played around with my diseqc.conf and found that 
*sometimes* the *first* DiSEqC command sequence [...] doesn't work.
So I added a dummy DiSEqC command at the begining of the line
and now it seem to work...

Unfortunately I can't take snapshots of the generated signals with 
my antique oscilloscope :-)

> In Rolf's case, the only other thing I can think of, is that the
> DVB card isn't producing a clean 22kHz signal (meaning
> the 22kHz is either lower or higher) and that his switch is
> being picky about the carrier frequency.

There are many possible causes:
- too low/high voltage of the 22kHz signal
- wrong frequency
- glitches in the signal
- bad waveform
- tone-burst too short/long
- ...

Basically, DiSEqC is nothing else than turning the 22kHz tone on
or off. With the full-featured cards this is (unfortunately) done by 
the AV7110 firmware...

Oliver



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