[Soekris] USB power switching? (net4801/Linux)

[THORNTON Simon]

Hi,

Just a thought but you could cut the 5V track connected to pin 1 of the USB plug 
and insert a 5V normally closed (NC) relay between the USB connector and the cut 
track. Drive the relay using one of the GPIO pins with a transistor across the 5V 
power  rail of the soekris, make sure you put a diode across the relay contacts. 
There are various simple relay driver circuits around that will do this safely 
without damaging the GPIO chip.  To reset the USB device you turn on the relay 
for 1 sec (cuts the power) then turn it off, the NC means that the device will be 
powered on unless you energise the relay.

Rgds,

Simon


-----Original Message-----
From: soekris-tech-bounces at lists.soekris.com 
[mailto:soekris-tech-bounces at lists.soekris.com] On Behalf Of Randall Nortman
Sent: Sunday, May 04, 2008 22:09
To: soekris-tech at lists.soekris.com
Subject: [Soekris] USB power switching? (net4801/Linux)

I have a remote system with a USB device that apparently is prone to
locking up such that it needs to be power cycled (or unplugged and
plugged back in).  A reboot of the system is not adequate to bring it
back to life, because the device (apparently) retains power during the
reboot.  Does the USB controller in the net4801 permit power to the
devices to be switched off under software control?  And if so, do the
Linux drivers support this?  I fear the answer is no to at least one
of those questions, because lsusb -v shows this under the hub
descriptor:
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