[Gta04-owner] Sporadic USB charging issue identified

Andreas Kemnade andreas at kemnade.info
Tue Feb 19 14:31:04 CET 2013

On Tue, 19 Feb 2013 09:25:07 +0100
Dr. H. Nikolaus Schaller <hns at goldelico.com> wrote:

> [... VBUSUNPLUGEN stuff]
> This discussion IMHO reads almost the same as:
> http://e2e.ti.com/support/power_management/pmu/f/43/p/40863/142624.aspx
> And I think we already were close to this point:
> http://lists.goldelico.com/pipermail/gta04-owner/2012-March/002057.html
> (see PS: at the end of the posting).
see also 
For a number of scenarios where charging does not work.
and also

Problems you get with VBUSUNPLUGEN off:
Battery full detection works by detecting current falling below a
threshold. So if Vbus drops, the current will also drop and  a full
battery is detected. Then after 4 seconds if Vbat is below 3.9V it
tries to restart charging.

About software controlled charging: It is not so software controlled as
you might think. You do not need to do more about current controlling
during charging. What you need to care about is: mainly the long term
The long term timeouts which the automated charging uses.
The current lowers correctly CC/CV mode is done correctly. But current
is not turned off. So the battery will charge forever with a very low
current. That is not recommended so you need to switch it off. But that
is not time critical. But I if i remember correctly there was also a
bit to enable that. 
About unplug handling: If charging is enabled and nothing is connected
you will have battery voltage output at the usb port. If you
short-circuit that the gta04 will switch off immediately.

I am using linear charging when i power my gta04 from my bike hub
dynamo (i have script for that for turning that on and off). I have
VBUSUNPLUGEN off on boot now and use the full hardware controlled
automatic charging. I never use software controlled charging with wall

> So how do we get a good solution into the drivers?

I should really clean up my kernel and send some patches as a starting
point. I thought nobody really cares about my crazy problems. 

Andreas Kemnade
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