[Nut-upsdev] Designing a Raspberry Pi "UPS"

[Gary Marsh]

Hey folks,

I'm designing a power management card for a Raspberry Pi, for an embedded application. Basically, here's the bits and pieces that would be on the card:

- A 12V SLA battery charger, which can be powered from a wall wart or solar panel.

- A pair of 12V->5V switching regulators, one powering the Pi and the other powering a built-in 4-port USB hub.
- A USB capable microcontroller which manages the card and reports the battery/charge status to the Pi over USB.


I'm envisioning the card acting like a UPS or a laptop battery. If local mains/solar electricity is available, the battery charges. If not, the Pi and its peripherals run off the battery. My application is data acquisition in places where power isn't easily available or isn't reliable, but there might be lots of other uses - I plan to release the design under a Creative Commons license when I'm done, so other people can build and mess with the design.

Anyway the hardware design is no problem for me, and I've got a bit of experience implementing USB HID and CDC, but as far as making something that's reasonably "plug and play" with Linux/NUT I don't really know where to start.

I'm hoping I can create a generic HID UPS or battery class, and have everything "just work", but I'm not sure if this is the case. Anyone mind giving me a few pointers in the right direction?

Thanks!
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