From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout1.informatik.tu-muenchen.de ([131.159.0.12]) by www.linuxtv.org with esmtp (Exim 4.63) (envelope-from ) id 1KreLw-0002q5-ON for linux-dvb@linuxtv.org; Sun, 19 Oct 2008 21:54:19 +0200 Received: from braindead1.acher.org (91-65-149-111-dynip.superkabel.de [91.65.149.111]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.in.tum.de (Postfix) with ESMTP id E2E00AF42 for ; Sun, 19 Oct 2008 21:54:12 +0200 (CEST) Date: Sun, 19 Oct 2008 21:54:10 +0200 From: Georg Acher To: Linux-dvb Message-ID: <20081019195409.GW6792@braindead1.acher> References: <412bdbff0810171104ob627994me2876504b43c18d8@mail.gmail.com> <2207.1224273353@kewl.org> <412bdbff0810171306n5f8768a2g48255db266d16aa8@mail.gmail.com> <5905.1224308528@kewl.org> Mime-Version: 1.0 Content-Disposition: inline In-Reply-To: <5905.1224308528@kewl.org> Subject: Re: [linux-dvb] [RFC] SNR units in tuners List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linux-dvb-bounces@linuxtv.org Errors-To: linux-dvb-bounces+mchehab=infradead.org@linuxtv.org List-ID: On Sat, Oct 18, 2008 at 06:42:08AM +0100, Darron Broad wrote: > The trouble there is that the scaling for the cx24116 already works > from an end-user perspective. The value derived in the code is > a possible maximum of 160 from the chip. REELBOX decided on 176 > which may be more accurate. The reelbox code was just a heuristic approach to scale the value so that less than 30-40% is where the trouble starts... I've more or less matched it to femon's colors. There was no intention to indicate dBs, as end users don't understand dBs anyway ;-) The docs for the 24116 say that the snr is measured in 0.1dB steps. The absolute range of registers a3:d5 is 0 to 300, so full scale is 30dB. I doubt we will see the 30dB in a real-world setup... The signal strength in 9e/9d is the value of the AGC voltage. Register da seems to contain the estimated power level (-25 to -70dBm), but there's no further information about that (step size etc). I guess the firmware derives it from the AGC settings. -- Georg Acher, acher@in.tum.de http://www.lrr.in.tum.de/~acher "Oh no, not again !" The bowl of petunias _______________________________________________ linux-dvb mailing list linux-dvb@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb