freerunner: charging and usb-host mutually exclusive?
andy at openmoko.com
Tue Mar 11 21:58:37 CET 2008
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Somebody in the thread at some point said:
> Hi Andy!
> Am Di 11. März 2008 schrieb Andy Green:
>> - gpg control packet
>> Somebody in the thread at some point said:
>>>> Currently the pump that provides 5V for the external device is enabled
>>>> whenever we are in host mode. I don't know what that thing will do if
>>>> we provide 5V externally too, probably it will be okay but it needs
>>> You wrote "currently". Does that mean with a software change we might
>>> turn off the pump and reenable charging while in host mode?
>> The situation is that there is only one bit that controls if we are
>> physically in host mode (this bit comes out of a PMU GPIO and can be
>> controlled by the CPU).
> This bit not only controls the power pump and pulldown, but also the U4905
> RT9711BPB power switch for _inbound_ power supply. So for the given
> hw-design, there's no way to have
> the GTA02 powered from outside (this is the point!)
> while in hw-hostmode.
WAH missed U4905, you are quite right Joerg :-(
>> it won't "see" the insertion. I guess you could add 15K pulldowns
>> permanently if you knew you would only use it in externally-powered-host
>> mode but it is a bit sucky.
> Well, i understand you suggest to detect insertion of usb-device and high
> speed mode while pulldown on, and then (triggered by some user interaction -
> for we just can't detect the power reverse feed, that is if pump won't smoke)
> switch EN_USBHOST GPIO to disable pump (and pulldown) and enable
> charging/powering the GTA02 via RT9711BPB & PMU, while still keeping logical
> hostmode for the interface.
No, I was just noting you could put the CPU peripheral logic into host
mode but leave the EN_USBHOST signal low. Then you could add 15K
pulldowns as a hack, and it would all work. But it is a bit of a mess
and would then only work in this externally powered host mode.
> Anyway not having external power at all while in logical hostmode seems to be
> a nogo. This has to be solved somehow.
Too late I think :-/
> BTW: all this might be a lot easier with a simple coax type power connector
> for feeding PMU *external_charger* path by a simple classic nokia style wall
Wah dude it is great hearing from you :-) You're catching my errors and
you read the datasheet :-))) That's right the PMU "adapter" path is unused.
>> So we must do the test to find out where we are.
> I'm sure the pump won't care, but that's not the point.
Yeah the pump didn't care. But your observation about U4905 explains
why HDQ reported no charging with EN_USBHOST asserted... it wasn't
because the battery suddenly became full :-((
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