[linux-dvb] Re: Technisat AirStar 2 PCI card

[John Dalgliesh <johnd@defyne.org>]

On Mon, 29 Nov 2004, Nico Sabbi wrote:
>
> Unfortunately VHF channels don't tune.
> The reason is that the drivers always use the 20.4 Mhz clock, while
> for bandwidth 7 and 6 the right clock to use is the 19.2 Mhz one.

You legend! No wonder it isn't working for me here - all channels
including UHF ones are 7 MHz in Australia.

> Hopefully someone knows how to program  these settings :)

Which settings are you talking about? Currently the only thing the linux
driver does with bandwidth is to program the TRL_NOMINAL_RATE register
with the 20.48 MHz clock settings. The manual includes an example for a
19.6267 MHz clock also. It would be pretty easy to calculate the correct
values for a 19.2 MHz clock, if that indeed is the rate and not a typo.

But I guess you are talking about something else ... there must be some
setting (a gpio?) which changes the clock frequency from 20.48 to 19.x.

Hmmm! Ok, further digging in the MT352 manual reveals that the CLK_Mode of
CLOCK_CTL is being set to 0x0, a setting which attracts the note: "Only
for 8 MHz OFDM reception". Furthermore, the table indicates that were this
field set to 0xA instead, it would magically convert the 20.48 MHz crystal
freq into a 19.6267 MHz ADC clock.

Sounds good! I'm going to give it a try.

Also, I can't help wondering why it is that the DVICO personalities of
MT352 can get away with setting it to 0x8 (another 20.48 MHz setting,
without the evil note) and leaving it at that. They don't seem to care
about switching the ADC clock.

Anyway, I guess I should stop rambling and give it a try...

{P^/