Put momobox to sleep when not being used

[blairfrandeen]

The firmware runs continuously when the batteries are connected. Goal is to have the pico go into sleep mode after some amount of idle time, and then awake upon a signal from the hall sensor.

A good starting point with resources is here: https://ghubcoder.github.io/posts/deep-sleeping-the-pico-micropython/

May be better to also read this post about dormant and sleep modes: https://ghubcoder.github.io/posts/awaking-the-pico/

This is micropython based (momobox currently uses circuit python), so may not be fully applicable.

A good thing to start with is to measure the current draw from the batteries during the following operations:

• idle time
• RFID request
• playing a song
• song paused

[blairfrandeen]

Some measurements made with a DMM:

Condition	Current Draw [mA]
Standby	65.6
Playing	70-110
Paused	68.6
RFID Chip present without magnet	70.6
Magnet present, no RFID	69.5
RFID, no magnet, after magnet had been activated	74
Crashed	45

The 2X batteries I'm using have a capacity of 1500 mAh (3000 total). 3000 mAh / 70 mA = 42 hours
This operating time matches our experience with the momobox so far, although we typically get to about 24-30 hours before it turns off.

It may be promising to reduce power usage by rewriting the firmware in a lower level language that isn't constantly running an interpreter. For comparison, running "blinky" in Rust only takes 22-24 mA