• Registered: 2009-10-17
  • Posts: 7

Topic: Maximum screen brightness with battery?

I've been running my old local flash file (designed on Chumby Classic) on my new Chumby One, and have encountered an interesting bug.  It works fine off the power supply, but when running on an NP-120, I don't get any image at all (although the sound works just fine).  The flash movie manually controls the screen brightness, alternating between 0 and 65536.  Is there a limit placed on screen brightness when running of the battery?  If so, what is it, so I can alter my code accordingly?

Thanks, as always.

  • From: Austin, TX
  • Registered: 2009-05-07
  • Posts: 471

Re: Maximum screen brightness with battery?

There's been talk that when the power is switched to the battery, brightness is automatically reduced.  Are you sending new values to /sys/devices/platform/stmp3xxx-bl/backlight/stmp3xxx-bl/brightness ?  Doing that via echo on the command line worked for me on my C1 under both battery and adapter power.

unwiredben's Website

  • Duane
  • Duane
  • Blue Octy
  • Offline
  • From: San Diego, CA
  • Registered: 2006-08-24
  • Posts: 8,197

Re: Maximum screen brightness with battery?

Yes, there is indeed a limit on the brightness when on battery.

Duane's Website

  • Registered: 2008-06-27
  • Posts: 518

Re: Maximum screen brightness with battery?

We abuse the backlight class driver a bit by making "max_brightness" be writeable.  When you're plugged in, it's 100, and when you go on battery it gets dropped to 50 by a script.  It will take the value in "brightness" and scale it by "max_brightness" percent.  So if you have brightness at 100 and set max_brightness to 50, then 100% will become half as bright.

It's kind of a weird arrangement, but I think it's easier to deal with than the alternatives.

These files are located in /sys/class/backlight/stmp3xxx-bl/ if you'd like to fiddle around with them.  The script that gets called to change everything is /usr/chumby/scripts/power_state_changed.sh

  • Registered: 2009-11-30
  • Posts: 34

Re: Maximum screen brightness with battery?

I just got a NP-120 battery for my Chumby One....it lasted just over an hour. when running Pandora, the screen seemed to be full brightness the entire time....no dimming on battery power. Are all widgets affected?

--tom