[linux-dvb] Re: diseqc in DVB/apps/szap/szap.c

[Andreas Oberritter <andreas@oberritter.de>]

On Wed, 2003-04-23 at 22:20, Franck Arnaud wrote:
> In function diseqc of DVB/apps/szap/szap.c we have:
> 
>  (sat_no / 4) % 2 ? SEC_MINI_B : SEC_MINI_A);
> 
> if sat_no is the satellite number we always get the same result for 
> the typical 1-4. I think the "/ 4" should not be there:
> 
>  sat_no % 2 ? SEC_MINI_B : SEC_MINI_A);
>  
> (this should have no impact on modern diseqc switches which I think 
> listen to proper commands rather than this, but I have a dumb one.)

The upper one may be valid if you have up to 8 single diseqc lnbs
connected to a 8/1 diseqc switch. but i think szap wouldn't work then
anyway because it does not repeat diseqc messages.

The lower one seems more typical, e.g. having one toneburst switch to
switch between two quattro lnbs.

OT:
I wonder why the diseqc specification says, that toneburst has to be
sent after the diseqc message. Think of having one toneburst A/B switch,
two Diseqc 4/1 switches and eight diseqc lnbs.

If one would like to switch from lnb 0 to lnb 4, then the diseqc message
will reach switch A and toneburst will then switch from A (range 0..3)
to B (range 4..7), so lnb 4 will never hear the message, which is bad,
because:
1.) the diseqc switch B does then not know which input should be used.
2.) the diseqc lnbs rely on these message to change polarization and
band.

Any opinions on how to handle such a case without violating the specs?

Regards,
Andreas



-- 
Info:
To unsubscribe send a mail to listar@linuxtv.org with "unsubscribe linux-dvb" as subject.