Add UPS/advanced power management

[patricktokeeffe]

Make units resistant to data corruption by adding a PowerBoost 1000 to function as UPS. Current design proposal:

• connections
  • unregulated 5V input to enclosure (wall wart, solar panel, etc) → PowerBoost 1000
  • PowerBoost 1000 ←→ LiPo battery
  • PowerBoost 1000 → Raspberry Pi, sensors, GPS, etc (everything except the cell modem)
  • TBD: detect whether powerboost has charge current
  • TBD: status LED(s) for enclosure
• functionality proposal #\1
  • unit powers on automatically whenever charge current is provided to the enclosure
  • unit remains powered on whenever charge current is provided
  • when battery reaches low level, unit powers itself off
    • pulls powerboost enable low to keep 5V output off while charging continues?
    • does it detect a complete power removal, and then 'reset' to turn on when power is restored?
• functionality proposal #\2
  • unit powers on automatically whenever charge current is provided to the enclosure
  • unit remains powered on whenever charge current is provided
  • unit powers off whenever charge current is removed (ie does not drain battery)
• functionality proposal #\3
  • hardware "on/off" on enclosure exterior
  • if switch is
    • ON: unit automatically turns on whenever charge input or sufficient battery level detected
    • OFF: unit turns off, or remains off if already off
  • powerboost recharges battery regardless of "on/off" switch position