XO BW mode (was Re: Guidance sought on collaboration techniques)

[Gary C Martin]

On 14 Feb 2009, at 10:16, Bert Freudenberg wrote:

>
> On 13.02.2009, at 19:27, Gary C Martin wrote:
>>
>> Note the backlight goes through the colour refractive screen magic,
>> even in BW mode, so it's not as sharp as with the backlight 100% off
>
> That explanation is horrendously wrong. Please do not perpetuate the  
> rumor of "modes" in the display hardware. There are none.

Horrendously wrong? Wow... well Bert you've been with the project for  
way longer than me so I do trust you to be right, I must have hit a  
nerve, sorry.

> And, there is no "refractive screen magic", that idea did not make  
> it into production. The backlight uses regular r/g/b color filters.

Was my 'refractive' faux pas your only reason for using 'horrendously  
wrong'? I guess the term I should have given there was  
'transflective', apologies to optical geeks everywhere. I couldn't see  
any obvious errors else where.

> The blur you see in color mode is the DCON performing anti-aliasing  
> by adding color components from the four neighboring pixels into  
> each pixel (e.g., for a red pixel it takes the red components of the  
> surrounding pixels into account, etc).
>
> In early DCON drivers it was possible to toggle the anti-aliasing  
> independently of the backlight intensity, so you could clearly see  
> its effect. IIUC this capability has now been coupled to the  
> backlight intensity, which is fine in regular use, but takes away  
> the possibility to easily demonstrate what's happening.

You do appear to be wrong here. Have access to three XOs here (two MP  
and one B4) that all happily respond to the below command:

       su
       echo 1 > /sys/devices/platform/dcon/output

Disables colour while leaving the backlight setting alone, allowing a  
slightly crisper BW display with backlight on if you want it (close  
look at text edges reminds me of the little colour pixels you get with  
sub-pixel resolution tricks on conventional screens), and:

       su
       echo 0 > /sys/devices/platform/dcon/output

Enables colour while leaving the backlight setting alone, allowing a  
'colour display' mode when the backlight is potentially off (not a  
very useful combination as it's the backlight that goes through the  
colour layer so you're left looking at a slightly soft BW image from  
just reflected light).

I can try and take some pixel macro photos of the effect if it makes  
you feel better? :-)

	http://wiki.laptop.org/go/Display#DCON_screen_driver_chip

--Gary

> - Bert -