On 2009-10-09, Joerg Reisenweber <jo...@openmoko.org> wrote: > [Timo Juhani Lindfors Fr 9. Oktober 2009]: > > Joerg Reisenweber <jo...@openmoko.org> writes: > > > A completely white screen with ~40% backlight consumes same amount of > power as > > > a completely black screen (-content) with backlight "dim" (=off) > > > > > > (=> a black screen eats as much power as a backlight set to 40%) > > > > > > (DUT: FR A7 SHR-U0808) > > > > I wrote > > > > http://iki.fi/lindi/openmoko/display-current-measurement1.pl > > > > to test this. However, here white screen with 40% brightness consumes > > significantly more than black screen with 0% brightness: > > > > >dbg running echo 102 > /sys/class/backlight/gta02-bl/brightness > > >dbg sleeping for 60 seconds for current to stabilize > > >dbg taking 10 samples with 10-second delays > > >dbg current now 102750, mean 102750.0000, deviation -1.0000, range > [...] > > >dbg running xset dpms force off > > >dbg sleeping for 60 seconds for current to stabilize > > >dbg taking 10 samples with 10-second delays > > >dbg current now 48000, mean 48000.0000, deviation -1.0000, range > 0.0000 > [...] > > 1: I didn't use xset dpms force off, I rather let SHR (or probably > FSO-framework) do it's dim-job, like it always does by default when hooked up > to wallcharger. No idea what is actually done on dim, or if it is > exactly "xset dpms force off" > (btw if dpms force off actually switches off LCM and glamo video clock, I'd be > rather surprised to see any difference from a light or dark video buffer > content) > > 2: I used current indicator LED on that wallcharger to positively find the > sketch program when dimmed with a virgin white screen uses significantly less > current than when dimmed with a painted black screen (and erasing all the > black brought it back to "power-saving mode", so it's not been any difference > in state of that program - like filled history buffer etc) > > 3: the probing during suspend was mainly due to the wallwart LED indicator > has its optimum resolution here, whereas it hardly differs for 190mA vs 220mA > e.g > Nevertheless I suspect the power consumption difference will be similar in > normal backlit state, and probably isn't related to dimming at all (except > for the rationale it's rather senseless to keep a black screen during > backlight LED off) > > > The compare to ~40% backlight power consumption was a rough guess just to > illustrate the magnitude of the effect, based on same LED readout on the > wallwart charger > > I can't tell why your results are like that, but obviously your setup differs > somewhat to mine.
What happens if you do the same test with the screens flex cable disconnected? _______________________________________________ hardware mailing list hardware@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/hardware