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I am looking for solution to reboot ASUS Nexus 7 tablet solely from USB power. If USB power is turned off tablet to shutdown, and boot up again only when USB power is on. Prefer the battery to be still connected, but don't mind disconnecting it if you have a solution that works well. Looking for an experienced embedded software. Any solution that can be used to unfreeze a hard locked Android device via USB is welcome.
If you can get the connectors, this is a fairly simple engineering problem that I was able to get down to two n channel mosfets and some resistors, running the USB power as an inverse power switch. A single MOSFET across the power switch works fine for activating the switch when given 5V to the Gate. The other MOSFET inverts the USB power to only go to 5V when missing. This just needs to be hooked to the battery for reliable power. When I try to use switch Positive, it doesn't have enough to turn on.
With the above setup, you would hold USB power down for as long as needed to reboot (10+ sec), then bring back up. Eliminates the micro that I was going to use inside. You can also use usb power to wake if needed by short power cycle. It all comes down to finding the power connectors.
Solution needs to be plug & plug, no soldering. Must have low profile, 60mmx13mmx3.5mm area where battery control electronics are located. Must provide working prototype and shipped. Must has use common easy to find component for later mass production. Upon confirmation of prototype, your solution must be prepared for mass reproduction. View attached schematic and photos form previous engineer, who is currently unable to continue this project.
Additional Project Description:
03/05/2013 at 0:59 PKT
NOTE: SOLUTION MUST BE A RELIABLE WAY TO REBOOT NEXUS 7 EVEN WHEN KERNEL PANICS. The 10 second power reset is lower level than Android. It is a hard reset at any time. Android kernel status must not affect it.