[GreatFET] hw design: gpio-controlled power

David Hubbard david.c.hubbard+hackrf at gmail.com
Sat Jan 28 16:21:20 EST 2017

On Friday, January 27, 2017, Michael Ossmann <mike at ossmann.com> wrote:
> On Wed, Jan 18, 2017 at 02:04:38PM -0600, David Hubbard wrote:
>> I see that the GreatFET One schematic includes a way to disconnect the
>> VBUS power from the AP7333 regulator and VCC.
> There isn't a way to disconnect it, but the USB host is protected from
> current that might occur if a neighbor is supplying power.
>> I was wondering if a hardware change could be made which allows the
>> to switch off power to the header pins, neighbors, etc. (I began thinking
>> about this as I worked on USB suspend on the HackRF One.)
> That could be done, but I would prefer not to do it.  Neighbors that draw
> significant current should have a mechanism allowing the microcontroller
to put
> them in a low power state, but this should be separate from cutting the
> supply to the neighbor.  It should be possible to shut down a single
> without shutting down all attached neighbors.
> This is also complicated by the fact that a neighbor may be used to supply
> power to GreatFET One.  If power is supplied by a neighbor, then a "turn
> neighbor power" function would become a "turn off power to self"
function, and
> it would leave any attached neighbors powered on without microcontroller
> supervision.  That might be an acceptable risk if it were the only way to
> down neighbors during normal (USB-attached) use, but I think it is better
> neighbors to provide a separate power-down function.

Ok, that's a good way to do it.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist3.pair.net/pipermail/greatfet/attachments/20170128/e8170af8/attachment.html>

More information about the GreatFET mailing list