[linux-dvb] Re: Full featured card summary

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Sunday 14 March 2004 22:36, Holger Waechtler wrote:
> On Sunday 14 March 2004 23:35, Andrew de Quincey wrote:
> > > If you specify a bus voltage of 13 or 18V you definitely don't mean
> > > VOLTAGE_OFF but expect the LNBP working, everything else is a bug.
> >
> > Yeah, it seemed to have changed from being set to VOLTAGE_13 in the
> > initialisation tables to being set to VOLTAGE_OFF by default... somewhere
> > between the 1.0.1 and the 1.1.0 release.
> >
> > Defaulting to VOLTAGE_OFF makes sense though; no point powering up the
> > LNB until its actually needed. What do you think of Johannes' idea of it
> > auto powering up on frontend open?
>
> makes not really sense -- you can't really tune a LNB wothout setting up
> polarisation plane and the band selection switch before, can't you?
>
> As soon you submit the polarisation selection command (VOLTAGE_13V or
> VOLTAGE_18V) you already powered up the LNB. The only important thing is to
> maintain the delay times required by the spec, the diseqc.c example shows
> how this can get implemented.

I think the problem was they're using DISEQC 1.0/2.0 switches, but weren't 
using the older voltage-based polarisation selection commands, assuming that 
the frontend would have automatically applied some power to the LNB (BTW: I 
do know the sequence in the DISEQC spec says you should specify the voltage; 
I use that exact sequence in my code).

I suppose its a matter of how tolerant we want to be of userspace programs.. I 
mean, we already turn OFF the LNB power automatically, why not turn it on as 
well?


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