FR: Power Management

[ntlhui]

During potting and normal idle behavior, FW 3.21.0 can cause the fin to drain the LiPo to unsafe levels.

Add power watchdogs. This should be a separate thread that always runs during FW execution. If the fin is not on a charger and drops below 3.7 V, the fin should shut down with no wakeups enabled.

During normal sleep, the fin should probably wake up every X hours to check its battery state. If the fin battery drops below 3.7 V, the fin should shut down with no wakeups enabled.

We should also do a power study to identify the following current draw characteristics:

• Normal sleep with wet/dry wake enabled
• Deep sleep with wet/dry wake disabled
• Deploy with high rate IMU, 1 Hz temperature, 1 Hz wet/dry, 1 Hz GPS
• Data upload during connect
• Data upload during upload
• Charge mode

[ntlhui]

Battery check interval should be set to be able to resolve 0.1 V

Also validate battery voltage/energy curve for the specific batteries selected.

[stevegtaylor]

Battery is draining very on test fin. When batter is very low, the fin begins to exhibit undetermined behavior (e.g. trying to deploy when plugged into PC). Battery died on it's own over a period of a day of sleep. After charge up to 3.2V, the fin was able to enter charging state, but the battery appears to be draining even in the charging state. After a matter of minutes, it resumed undetermined behavior.

Power draw never dropped below 15mA. Test was conducted twice, with fin connected and then unconnected. Fin fluctuated in between incorrect states (e.g. CLI while unplugged), before eventually appearing it entered sleep state. Current draw never dropped below 15mA, and jumped up to 40mA at times (deploying state).

Battery in fin: DTP 605068, 3.7V, 2000mAh

[stevegtaylor]

Current draws:
Charge mode - 17mA
Deploying state - 40mA