[Sugar-devel] Grayscale screen implementation query

[Sumit Srivastava]

Thank you, Walter and James.

I've appropriately answered the questions after reading valuable inputs
provided from both of you.

Regards
Sumit


On Tue, 4 Jun 2019, 3:00 pm James Cameron, <quozl at laptop.org> wrote:

> Thanks for asking.
>
> A kernel configuration file is used to select colour or grayscale
> mode in the driver, and thus the display controller ASIC.  This is in
> the kernel sources.
>
> The keyboard shim detects brightness control keys and manages the
> backlight power.  When the backlight is turned off, the grayscale mode
> is enabled.  When the backlight is turned on, the grayscale mode is
> disabled.  This is in the keyboard shim sources.
>
> On the XO-1.75 and XO-4 models, a reverse biased red LED in the same
> SMT package as the green storage LED is used as an ambient light
> sensor.  The power management daemon (powerd) detects high ambient
> light and turns off the backlight and turns on the grayscale mode.
> The backlight is turned off to save power, and increase running time
> on battery.  This is in the powerd sources.
>
> However, without any change to backlight brightness or mode switching,
> full sunlight does appear as greyscale, because the human eye can't
> discern the small amount of colour emitted by the backlight compared
> to the large amount of white light reflected from the sun.
>
> On Tue, Jun 04, 2019 at 12:48:38AM +0530, Sumit Srivastava wrote:
> > Hi, all!
> >
> > Here's a query that has been directed at me on the internet, however I
> don't
> > have any idea about the grayscale implementation of the screen in XO-1.
> How
> > does it switch from colour to grayscale and on what basis is it decided?
> >
> > >The original query:
> > {"generic Josh number 96" asks
> > "Do you know if the display is switching modes with the greyscale thing?
> Very
> > curious how the screen works"}
>
> > _______________________________________________
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> > Sugar-devel at lists.sugarlabs.org
> > http://lists.sugarlabs.org/listinfo/sugar-devel
>
>
> --
> James Cameron
> http://quozl.netrek.org/
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>
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