[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>
> First card: pwm=52
> f 354000000:
> ves1820.c: AFC (32) -215625Hz
>
> Second card: pwm=48
> f 354000000:
> ves1820.c: AFC (1) -6738Hz

Hmm, does this card possibly work with CARCONF=0x12, or does it require
CARCONF=0x52 as well?

> Are these jumps in AFC depending on frequency normal?

Hmm, I don't know why it's jumping between + and -, but I have it changing
with the frequency as well. Do you have DVB-C channels at 113 and 121 MHz
as well? It'd be interesting to see what AFC readings you get there.

> Is my first card buggy?

Not necessarily buggy, but the PWM value seems to be off.

> Hmm, in which direction? And how per card?
> Will wait for further tests now in which direction I should change pwm

Hmm, let's worry about the "per card" later ;) Let's only look at your
first card for the time being. To be honest, I don't know in which
direction to change the PWM, just try lowering, then raising it (from 52)
and see what reduces the AFC readings. Then try to find the PWM value for
the minimum AFC on this card. Then try changing the CARCONF to 0x12 and see
if the card can still lock...

I have to say I have never tried it, but it _might_ be possible to write
into the EEPROM on the card. In that case, if you find the correct PWM
value, you could write it to the EEPROM and would not require _any_ changes
to the DVB driver. Of course, you should be very careful when writing to
the EEPROM - I'd recommend saving it's original contents (it's only 256
bytes) to a file first. Then try writing to only the last byte of the
EEPROM (actually, the first page of it, which is the only one used, I2C
address 0xA0, subaddress 0xFF), which holds the PWM value...

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



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