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

[Peter Bieringer <pb@bieringer.de>]

--On Saturday, August 16, 2003 05:46:02 PM +0200 Robert Schlabbach
<robert_s@gmx.net> wrote:

>> I'm not sure about your comment that frequencies in cable systems are
>> usually correct. Earlier versions display AFC information somewhere
>> and I saw a not very small difference.
> 
> Aha! Your card may be mis-tuned. The Siemens cards have a TDA9819 IF
> amplifier on them, with a VCO-controlled output frequency. That frequency
> is modified by using the infamous "PWM" output, which is supposedly
> measured INDIVIDUALLY for each card after manufacturing and then written
> to the EEPROM on the card.
> 
> The PWM value for your card may be incorrect, or maybe your card's
> characteristics changed due to aging.
> 
> As to why you are no longer seeing the AFC displayed, the CVS comment
> says:
> 
> - printk() -> dprintk() for AFC in ves1820.c
> 
> So you could just change it back to get the AFC displayed again (or
> somehow enable dprintk output...)
> 
> Then take a look at read_pwm() in VES1820.C. Also enable the dprintk
> output there (e.g. by changing it to printk as well). What PWM value is
> displayed? If it's 0xFF, your EEPROM is damaged.
> 
> Either way, try inserting a line to override the PWM value and try a few
> values and see if you can minimize the AFC output. What optimum value do
> you come up with?

Ok, I've extend the ves1820 driver for module options capability for
CARCONF, CLKCONF and PWM (at the moment private patch, but if per-card
config is working, I will submit them).

I found that the PWM on my first card is really not the proper one.
EEPROM: 0x52
Best: 0x38

AFC is now between 0 and -1/1


> After you have found an optimal PWM value, try changing the CARCONF
> register back to 0x12 again. Does it work now?

Yes, after adjusted PWM, newer default CARCONF (0x12) will work proper.
I get already on the first czap line "FE_HAS_LOCK"


Because of this parameters (especially PWM) need to be set per card, I ran
into a problem: how to get the card number in following functions:

int ves1820_attach (struct dvb_i2c_bus *i2c)

int ves1820_init (struct dvb_frontend *fe)

Hopefully anyone can help me here.

        Peter
-- 
Dr. Peter Bieringer                     http://www.bieringer.de/pb/
GPG/PGP Key 0x958F422D               mailto: pb at bieringer dot de 
Deep Space 6 Co-Founder and Core Member  http://www.deepspace6.net/


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