Power leakage: save 40mW by turning GSM on

Rask Ingemann Lambertsen rask at sygehus.dk
Sat Jan 17 17:31:38 CET 2009

On Fri, Jan 16, 2009 at 11:09:06PM -0200, Werner Almesberger wrote:
> I'm continuing this thread on the more appropriate hardware list.
> Background: I'm trying to get the system into a very low-power
> state (and very low power variation state) so that I can measure
> the effect of the various WLAN power saving options. This yielded
> a few surprises. Instead of a few mW, I ended up with suspend
> power in the order of up to 0.4W :-(
> suspend                                  81.90mA  82.96mA  85.91mA  1.043mA

   If mine is as bad as that too, no wonder I don't get 48 h suspend time.

> This run is without all the other power cutting I did yesterday.
> So things like BT and GPS are up and running.
> My best-case suspend power is still about 80mW, so I haven't found
> the black hole yet.

   I don't know if it helps you any, but I've found that something related
to the GSM part is not turned off when it's supposed to, drawing about 19
mA. I have a GTA02 with the Debian distribution and use LXDE as desktop
environment. I have uninstalled xscreensaver and pcmanfm to keep them from
wasting CPU cycles. I have commented out zhone in my .xsession.

   After a reboot and turning off wifi, leaving BT, GPS, and GSM off, I get:
$ sleep 60 && cat /sys/devices/platform/bq27000-battery.0/power_supply/bat/{status,current_now,voltage_now}

   The 60 second delay is for the screen to blank. If I start up zhone, let
it run for a while and then close it, I get this instead:

$ sleep 60 && cat /sys/devices/platform/bq27000-battery.0/power_supply/bat/{status,current_now,voltage_now}

   Or about 77 mW lost somewhere.

Rask Ingemann Lambertsen
Danish law requires addresses in e-mail to be logged and stored for a year

More information about the hardware mailing list