---
id: device-power
title: Power Management State Machine
sidebar_label: Power Management
---

Long battery life is one of the main goals of this project. Based on initial measurements, the current code should run for about three days between charging (assuming using a t-beam with a 3500mAh 18650 battery). This will hopefully be increased to around eight days in the future.

## States

From lower to higher power consumption.

- Super-Deep-Sleep (SDS) - Everything is off, CPU, radio, Bluetooth, and GPS. It only wakes due to timer or button press. We enter this mode only after no radio comms for a few hours - used to put the device into what is effectively "off" mode.
  - onEntry: setBluetoothOn(false), call doDeepSleep
  - onExit: (standard bootup code, starts in DARK)
- Deep-Sleep (DS) - CPU is off, radio is on, Bluetooth and GPS are off. Note: This mode is never used currently, because it only saves 1.5mA vs Light-Sleep - (Not currently used).
- Light-Sleep (LS) - CPU is suspended (RAM stays alive), radio is on, Bluetooth is off, and GPS is off. Note: currently GPS is not turned off during light sleep, but there is a TODO item to fix this.
  - NOTE: On NRF52 platforms (because CPU current draw is so low), light-sleep state is never used.
  - onEntry: setBluetoothOn(false), setGPSPower(false), doLightSleep()
  - onIdle: (if we wake because our led blink timer has expired) blink the led then go back to sleep until we sleep for ls_secs
  - onExit: setGPSPower(true), start trying to get GPS lock: gps.startLock(), once lock arrives service.sendPosition(BROADCAST)
- No Bluetooth (NB) - CPU is running, radio is on, GPS is on, Bluetooth is off, and screen is off.
  - onEntry: setBluetoothOn(false)
  - onExit:
- Running Dark (DARK) - Everything is on except screen.
  - onEntry: setBluetoothOn(true)
  - onExit:
- Serial API usage (SERIAL) - Screen is on, device doesn't sleep, and Bluetooth is off.
  - onEntry: setBluetooth off, screen on
  - onExit:
- Full On (ON) - Everything is on, can eventually timeout and transition to a lower power state.
  - onEntry: setBluetoothOn(true), screen.setOn(true)
  - onExit: screen->setOn(false)
- Has Power (POWER) - Screen is on, device doesn't sleep, Bluetooth on, and will stay in this state as long as we have power.
  - onEntry: setBluetooth off, screen on
  - onExit: