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Subject: Re: [PATCH,RFC] avoid radio noise on sansa clipplus

Re: [PATCH,RFC] avoid radio noise on sansa clipplus

From: Stefan Seyfried <>
Date: Thu, 08 Nov 2012 13:07:06 +0100

Hi Jonas,

Am 08.11.2012 12:47, schrieb Jonas Wielicki:
> On 07.11.2012 10:11, Stefan Seyfried wrote:
>> On my sansa clip+, there is a quiet, ticking noise on weak fm radio
>> channels.
>> I found out that this is probably due to the cpu being woken up to
>> update the display 5 times a second, even if the display is turned off.
> This seems surprising to me. I expected rockbox to stop updating the
> display, at least on the WPS,

The WPS is a different screen than the FM radio screen, so it might
behave differently.
However, from a quick look at the code it seems to me that the WPS
screen also does update 5 times per second, even if the display is
turned off, but my understanding of the code is very basic at best for
now and I need to find out how to use the debugging and logging
infrastructure to actually verify my findings.

> to avoid over-use of CPU while the display
> is turned off, which might be the case for most of the time, e.g. on an
> iriver target where you can bind the enabledness of the display to the
> Hold key.
> In that context, I appreciate your work and would love to see it in
> master some time, seems like that could increase battery lifetime.

Yes, originally I only thought about the FM radio interferences, but
battery life immediately came to my mind after thinking about that.

I'll investigate this further.

Best regards,

Stefan Seyfried
Linux Consultant & Developer -- GPG Key: 0x731B665B
B1 Systems GmbH
Osterfeldstra├če 7 / 85088 Vohburg /
GF: Ralph Dehner / Unternehmenssitz: Vohburg / AG: Ingolstadt,HRB 3537
Received on 2012-11-08

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