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Subject: Re: LCD backlight dimming
From: Linus Nielsen Feltzing (
Date: 2004-03-16

roland wrote:
> does somebody know, at which rate the led`s of the display can be
> switched on/off? maybe dimming could be done by switching the display
> on/off very quickly - by software.

On the recorder, the backlight is controlled by the Real Time Clock,
using a square wave output. The square wave can have different
frequencies in 16 discrete steps from 0Hz to 32kHz, but the duty period
can't be changed, it's always a square wave. So we can forget dimming on
the recorder.

On the player, however, the backlight is controlled by a port pin, so
there is a possibility to dim it by toggling the pin. I'm not sure I see
the point in doing so, but some people may find it "cool".

> at least, there have been recorders out there which were able to dim
> (i saw a videoclip somebody posted on this list). do we know that was
> a hardware or a software-based dimming?

Yes, there is a hardware flaw in some recorders, especially FM and V2,
which causes the backlight to dim slowly instead of turning off. I have
not been able to control this behaviour, and certainly not control the
dim rate.


Page was last modified "Jan 10 2012" The Rockbox Crew