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power controller with low-batt signal to usb out?
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power controller with low-batt signal to usb out?

by rpcy on Tue Jun 09, 2020 3:55 pm

We all know if you kill the power to a running Raspberry Pi, its operating system may not like it, and the microSD card may be compromised to the point where the system won't boot again. The cure is to always shutdown Linux down properly. But that's not always possible or convenient. So we use an uninterruptible power supply (UPS), and its internal battery can keep the Pi happy during brownouts or temporary mains power loss. Of course, if the mains are out long enough, the battery drains, and we're back in the same situation. And the cure for THAT is for the UPS to signal the Pi when the battery voltage is drooping too far. Ok, the powerboost 1000 has a low-batt output -- use that to signal the Pi to do an orderly shutdown.

If the PB1000 is in the same box as the Pi that's a good answer. But what I really want is a standalone box with microUSB in, an internal battery, and USB-A out. And here's the kicker: I want the low-batt signal to occur ACROSS THE USB-A OUTPUT. I don't want to run a separate wire. Does anyone know of any UPS/battery charger/power supply modules (similar to PB1000) that can send a USB message through the output USB to the Pi?

rpcy
 
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Re: power controller with low-batt signal to usb out?

by mikeysklar on Tue Jun 09, 2020 4:56 pm

Hello rpcy,

Great question about clean shutdown to make sure your Pi filesystem comes back cleanly when power is lost. At Adafruit we had taken a different approach and that was to use a read-only filesystem.

https://learn.adafruit.com/read-only-raspberry-pi

Looking at the schematic and FAQ fo the PB1000 it looks like you will need to tie a Pi GPIO to the LBO pin to detect low battery. You cannot get the data over USB.

https://learn.adafruit.com/adafruit-pow ... #downloads

mikeysklar
 
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