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Date: Tue, 22 May 2012 15:42:22 +0200
From: Gianluca Gennari <gennarone@gmail.com>
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To: Antti Palosaari <crope@iki.fi>,
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CC: Devin Heitmueller <devin.heitmueller@gmail.com>
Subject: Re: SNR status for demods
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Il 22/05/2012 11:09, Antti Palosaari ha scritto:
> 
> Basically, but not every case, there seems to be 3 different way:
> 1) return raw register value without any calculation
> 2) 0.1 dB
> 3) scaled to 0-0xffff using some formula
> 
> Very many drivers seems to do some dB handling even finally scaling it
> to some value.
> 
> regards
> Antti

Another one (from staging):

as102-fe.c:        Pierrick Hascoet, Devin Heitmueller            linear MER

I can provide a trivial patch to convert it to the more common 0.1 dB
format, if you think it's useful.

This note comes from the driver:

/*
 * Note:
 * - in AS102 SNR=MER
 *   - the SNR will be returned in linear terms, i.e. not in dB
 *   - the accuracy equals ±2dB for a SNR range from 4dB to 30dB
 *   - the accuracy is >2dB for SNR values outside this range
 */

Regards,
Gianluca