u-boot low-battery handling
mail at mmontour.net
Sat Aug 30 20:12:13 CEST 2008
Mike Montour wrote:
> I'll try to send an updated u-boot patch in the next day or two.
I've attached a patch with my most recent changes, and there is a
corresponding GTA02v5 binary at
http://members.shaw.ca/mmontour/neo/u-boot-mm-2008083001.udfu for anyone
who wants to try it out (at his/her own risk). There might be problems
on pre-production GTA02v5s that don't have the LED-current-limiting rework.
This version flashes the Aux LED once at startup and then checks the
battery level. If the battery is very low it gives three quick flashes
on the Aux LED and then shuts off. If the battery level is above this
threshold but still below 3.4V it loops for about 10s waiting to detect
>= 500mA USB power, flashing the Aux LED at a slower rate. Pressing the
Aux button will bypass these checks.
When the device is turned off cleanly (through the neo1973_poweroff()
function), the PMU is programmed not to wake on USB and to limit the
battery fast-charge current to 100mA. This probably violates the USB
battery charging specification, but it is necessary (at least on my
hardware revision) to recover from the case of a fully-discharged
battery whose internal cutoff has triggered.
This patch is still a work in progress (probably not suitable for
merging into the stable tree), but I'm going to take a break from it for
a while and look more at Qi and the Linux PCF50633 driver.
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