[linux-dvb] FE_GET_FRONTEND of alps_bsrv2.c: frequency error?

[Wolfgang Thiel <w-thiel@gmx.net>]

Hi,

I'm having problems with FE_GET_FRONTEND of alps_bsrv2.c:

    case FE_GET_FRONTEND:
    {
        struct dvb_frontend_parameters *p = arg;
        s32 afc;

1.      afc = ((int)((char)(ves1893_readreg (i2c, 0x0a) << 1)))/2;
2.      afc = (afc * (int)(p->u.qpsk.symbol_rate/8))/16;

3.      p->frequency += afc;

Here are some numbers. I'm reporting the frequency of FE_SET_FRONTEND,
and the value of 'afc' after 1.:

1276000  -10
1288000  -7
1281000  -3
1282000  +2
1291000  +12

This was taken on a SR 27,500 transponder.

The value of 'afc' after 2. doesn't make much sense to me, and the
'+=' in 3. doesn't make sense to me either: shouldn't that be a '-=', once
the value of 3. is correct?

Am I missing something?

Is there some official link to the datasheet explaining the registers of this
tuner?


I stumbled upon this problem when switching from a > one-year-old driver
version to a current one: the new one needs 9-10 seconds to look with one
dish, the old one needed about 1 second: thanks to good old Dbox-1 I found
out that my LNB is off by about 9 MHz, and that's the locking problem:
it locks perfectly if I change the frequency accordingly, but it would
be nice to get this info from the linux driver as well ;-)

Wolfgang



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