[linux-dvb] Re: Driver problems

[Jussi Alanärä <jalanara@dc.turkuamk.fi>]

On Mon, 2 Feb 2004, Torbjörn Jansson wrote:

> > In the syslog I get a line like: "DVB: VES1820(0): pwm=0x40"
> > I'll have to try changing it.
> >
> > If this works, maybe a few lines in some readme file coud be
> > added to the
> > dvb drivers so that others that run into the same problem
> > atleast know what
> > to try.

Agree, had to do a LOT of research before finding this bit of information.

> > What does this pwm thing do?
> > In the windows app the channel frequencies is for example
> > 322.012Mhz but on
> > linux after running a scan it's 322Mhz. Coud this have
> > anything to do with
> > it?
> >
> >
>
> I have tried changing the pwm value and checked that it was used but it
> didn't help.
> The channel changing problems is still there.

How much and in which direction did you try? And what card you are using?

I have a Siemens DVB-C and problems began after local cable company
changed from QAM64 to QAM128. It seems, that Siemens is very picky on
lower frequencies when using QAM128. After changing PWM from around 0x40
to 0x70 (found by trial and error) Verror rate on channels below 200MHz is
something like 5000 and on frequencies above 300MHz Verror rate is below
1000 and above 400MHz frequencies below 100.

Before changing the PWM value, Verror rate was some where above 100k.

> First time I run czap I get this and bad reception:
> ---------------------
> [szap]# ./czap DisMix
> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
>  42 DisMix:322000000:INVERSION_AUTO:6875000:FEC_NONE:QAM_64:4100:4356:1016
>  42 DisMix: f 322000000, s 6875000, i 2, fec 0, qam 3, v 0x1004, a 0x1104

Try not to use auto_inversion, seems also cause some trouble. Use
inversion_on or inversion_off, which ever it is.

> And then if I try to run czap again it doesn't lock and I get this:
>
> ---------------------
> [szap]# ./czap DisMix
> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
>  42 DisMix:322000000:INVERSION_AUTO:6875000:FEC_NONE:QAM_64:4100:4356:1016
>  42 DisMix: f 322000000, s 6875000, i 2, fec 0, qam 3, v 0x1004, a 0x1104
> status 07 | signal 9b9b | snr d2d2 | ber 000041a0 | unc ffffffff |
> status 07 | signal ffff | snr f0f0 | ber 000041a0 | unc ffffffff |

Check kernel logs (dmesg), when playing with PWM and getting bad
reception, I did see a LOT of ARM crashes, Outcom errors and so on.
Reloading the driver helps.


/Jussi


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