[linux-dvb] [PATCH] cx24123 (NOVA S plus) signal strengh reporting

Romain DEGEZ romain.degez at smartjog.com
Fri Jan 13 13:47:05 CET 2006


Sigmund Augdal Helberg wrote:
>>> On Fri, 2006-01-13 at 10:44 +0100, Romain DEGEZ wrote:
>>>
>>>I'll try differents things (our 3 methods, cable plugged or not and maybe a longer cable to
>>>obtain a small decrease in the signal strength).
>>>Moreover maybe the register (3A) that set the value we should obtain by reading the 3B register
>>>is not set correctly but by reading the specs, everythings seems OK to me (but i'm very far to
>>>be an expert in DVB internals...)
>>>
>>>I'll try this right now and keep you posted.
>>
>>plugged   = 12% = 0x21 = 0010 0001
>>unplugged = 43% = 0x6f = 0110 1111
>>
>>value + 0x80:
>>plugged   = 62% = 0xa1 = 1010 0001
>>unplugged = 93% = 0xef = 1110 1110
>>
>>~(value - 1):
>>plugged   = 87% = 0xdf = 1101 1111
>>unplugged = 56% = 0x91 = 1001 0001
>>
>>interessant things:
>>43 - 12 = 31
>>93 - 62 = 31
>>87 - 56 = 31
>>
>>mhhh ok, what to do with that ?
>>mhh 31 =  2^5-1 -> nice but so what ? ;-)
>>
>>Note that with the old card, signal strength is exactly OxO when unplugging the cable.
> 
> We're really out of my leage now. I think the interresting finding here
> is that with your change, the signedness of the reported signal is
> correct. That is, at better signal gives higher values. I peeked at
> other tuners drivers and it seems they often do stuff like adding
> offsets and multiplying with some factor, I guess this will have to be
> done for this card as well.
> 
> Sigmund

Hello,

Thanks for your answer :-)

I was having such a feeling too (about the offset and multplying things) but wanted
another point of view as I found this a little crude :-)

I'll try to find a way to slowly decrease the signal of my reference card in order to
guess a linear factor.

Maybe Steve can help us here as he may have a look at the Windows drivers ?

-- 
Romain DEGEZ, System and Network Administrator

SMARTJOG S.A.
16 Place de la République, 75010 Paris, FRANCE
http://www.smartjog.com
Phone :  +33.1.49.96.63.19
Fax :    +33.1.49.96.64.05
Mobile : +33.6.84.24.65.21
romain.degez at smartjog.com


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