From: Gui Iribarren <gui@altermundi.net>
Date: Mon, 12 Aug 2013 21:41:44 -0300
Subject: [ath9k-devel] [Spectral Scan PATCH] Continuous Spectral Scan
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References: <20130726152655.06c7pv7piug0g4sc@webmail.uth.gr>
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To: ath9k-devel@lists.ath9k.org

On 07/26/2013 09:26 AM, hounos at uth.gr wrote:
> Hello,
>
> I am working on the specral sensing mode of the Atheros 9380. I am using the
> compat 3.9-rc4-2 driver. This driver was already pathced for the spectral scan
> mode.
>
> I would like to perform a continuous scan, either in a channel or multiple and
> gather spectrum samples in the
> /sys/kernel/debug/ieee80211/phy0/ath9k/spectral_scan0  file endlessly until I
> stop its operation manually.
>
> Looking the source code, I saw some references for the endless mode.
> Theoretically as understood this function is already deployed in the driver.

Yes, what was not so clear at first sight (at least for me) is that you 
have to issue a "trigger" to actually start getting samples
(Thanks Simon for the tip ;) )

so

     cd /sys/kernel/debug/ieee80211/phy0/ath9k
     echo background > spectral_scan_ctl
     echo trigger > spectral_scan_ctl

will fill in the spectral_scan0 file endlessly, collecting a huge number 
of samples per second, until any of this happens:

     echo disable > spectral_scan_ctl

or

     iw wlan0 scan
     # i understand a scan resets the card flags in some way
     # or maybe it's an unexpected possibility (i.e. bug :P)

or if you let it run for long enough without cat'ting spectral_scan0, it 
will also stop collecting samples (looks like spectral_scan0 buffer gets 
filled up or something)

hope that helps,

you can find further, more specific information here:
https://wiki.freebsd.org/dev/ath_hal%284%29/SpectralScan

and i'll try to update this blogpost with info about "continuous mode"
blog.altermundi.net/article/playing-with-ath9k-spectral-scan/

Cheers!

gui