linux-kernel - rf69_get_lna

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Message-ID: <7edef67c-f01f-48dc-4575-634f14515ec1@smarthome-wolf.de>
Date:   Thu, 14 Dec 2017 18:08:11 +0200
From:   Marcus Wolf <marcus.wolf@...rthome-wolf.de>
To:     Marcin Ciupak <marcin.s.ciupak@...il.com>,
        Oliver Graute <oliver.graute@...il.com>
Cc:     devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Marcin Ciupak <marcin.s.ciupak@...il.com>,
        Marcus Wolf <linux@...f-entwicklungen.de>,
        Simon Sandström <simon@...anor.nu>
Subject: rf69_get_lna_gain

Hi!

This is an information for all of you, doing experiments with real hardware!

I wanted to explain, what this lna_gain stuff is used for:

If you are receiving messages from different sender (let's say several 
thermometers), it may happen (e. g. due to different distance and 
different battery level) that the automatic gain control of the receiver 
amp isn't able to work correctly. E.g. if it gets a very strong singal 
first and a very weak afterwards, it is possible, that the agc isn't 
capable to recognize the second telegram predictable.

The procedure, need to be done in such a case is:
Switch on agc. Wait for a correct telegram to be received. Read the 
lna_gain_current value and store it. This is the gain setting for 
optimal reception for one of your sender. You now can set gain_select to 
this value, in order to receive stuff from this sender (instead of using 
agc).
If you want to receive stuff from an other sender, you may want to try 
with different other settings. As soon, as you have success, you can 
store this value and use it for receiving stuff from that sender.

Since I have just a 35m² flat, it is quite hard to have a setup, to test 
such stuff. In summer I did some experiments on the pavement, but the 
experimental code never was integrated in the productional source repo, 
because I focused on tx first. Deeper use of rx is planned for late 
spring next year.

If you want to do experiments with rx of signals with different 
strength, maybe you want to save a copy of the abstracions 
(rf69_set_lna_gain and rf69_get_lna_gain) befor they get deleted in 
staging-next.

Regards,

Marcus