[Gta04-owner] Phoenux drained and resuscitated

Dr. H. Nikolaus Schaller hns at goldelico.com
Mon Oct 24 06:55:02 CEST 2011


Am 22.10.2011 um 20:12 schrieb Christoph Mair:

> Am Samstag, 22. Oktober 2011, 11:16:48 schrieb Neil Jerram:
>> On Sat, 22 Oct 2011 11:58:55 +0200, Dr. H. Nikolaus Schaller wrote:
>>> Hi Neil,
>> 
>> Hi Nikolaus,
>> 
>>> Yes! Linux initializes the USB charger in one of the earlier steps
>>> and then the system comes up.
>>> 
>>> As long as your PC supplies enough current (>500 mA) and you don't
>>> switch on too many high
>>> power consumers (WLAN, WWAN), there should be some remainder for
>>> charging the battery.
>> 
>> Well so far I haven't touched WLAN or WWAN, so I presume they're still
>> switched off.  And with the GTA02 it was always said that it could draw
>> 500mA from a USB connection.
>> 
>> Presumably, then, with the wall charger - which supplies 1000mA - it
>> will always be possible to recover from a drained battery?
> 
> If I understand the problem correctly the wall charger won't help you here, 
> because it does not contain an USB host controller. The power management chip 
> allows only 70mA to be drained from the USB connection until a valid endpoint 
> (host) allows more (up to 500mA). I think the GTA04 does not recognise the 
> wall charger as a "special device" which can supply more current.

The GTA04 hardware simply draws as much as it gets. I think all this signalling
through D+, D- and the ID pin of an OTG connector is to tell the GTA04 that
it should not draw too much - or tell the provider to supply more.

Currently, the drivers just enable USB charging without current limitation.

Yet another area for experimentation...



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