[linux-dvb] Re: DVB-C tuning problems caused by inittab changes in ves1820.c since 2003-05-24

["Robert Schlabbach" <robert_s@gmx.net>]

From: "Peter Bieringer" <pb@bieringer.de>
>  u8 ves1820_inittab [] =
>  {
> -       0x69, 0x6A, 0x9B, 0x0A, 0x52, 0x46, 0x26, 0x1A,
> +       0x69, 0x6A, 0x9B, 0x12, 0x12, 0x46, 0x26, 0x1A,
>
> Rolling back this diff, all works fine again here with newest driver
>
> I'm sure not familiar with this driver/chip, but sure the developers
> can describe the reason for this change.

That's what CVS comments are for. The corresponding CVS comment is:

"use Robert's suggestions for CLKCONF (0x03) and CARCONF (0x04)
please test in your local networks and report problems"

The old values meant:

CLKCONF = 0x0A = DYN | CLK_C[2:0]=2
CARCONF = 0x52 = CAR_P[2]=1 | CAR_P[1:0]=1 | CAR_C[3:0]=2

The new values are the default values taken from the VES1820 data sheet:

CLKCONF = 0x12 = GAIN3 | CLK_C[2:0]=2
CARCONF = 0x12 = CAR_P[2]=0 | CAR_P[1:0]=1 | CAR_C[3:0]=2

The reason for this change was that I found my Siemens Cable card often had
problems locking after a channel change, due to the DYN and CAR_P[2] bits,
which seem to cause the VES1820 to get stuck. These bits extend the carrier
acquisition range, which is typically not necessary, since the frequencies
in a cable system are usually correct.

But the GAIN3 bit may be causing a problem. Could you try a few variations
of these two register settings and report back which work for you? For
CARCONF, I'd prefer to leave the CAR_P[2] bit off, so there'd only be 0x12
to test. For CLKCONF, we should test variations of DYN, so please try:

0x69, 0x6A, 0x9B, 0x02, 0x12, 0x46, 0x26, 0x1A,
(No DYN, No GAIN3, No CAR_P[2])

0x69, 0x6A, 0x9B, 0x0A, 0x12, 0x46, 0x26, 0x1A,
(DYN, No GAIN3, No CAR_P[2])

If the first of these two works, I'd suggest that one, i.e. only change the
0x12 in the fourth position to 0x02 (disable the GAIN3 bit).

Regards,
--
Robert Schlabbach
e-mail: robert_s@gmx.net
Berlin, Germany



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