New Feature: programmable power management

[microbit-mark]

Is your feature request related to a problem? Please describe.

User story: I need to make a sensing device that lasts a long time on batteries. Thus the device needs to power off under program control, and power up on an event, take a measurement, then go to sleep again.

Describe the solution you'd like
CODAL offers a power management API https://github.com/lancaster-university/microbit-v2-samples/blob/master/source/samples/PowerManagementTest.cpp and there is a published spec https://github.com/microbit-foundation/spec-power-management. It would be useful to surface this in MicroPython

Describe alternatives you've considered
None

Additional context
Add any other context or screenshots about the feature request here.

[microbit-carlos]

Proposal:

• docs: Add Power Management documentation. bbcmicrobit/micropython#754

[dpgeorge]

Initial power module has been implemented in 009fbd2.

It currently does not support the run_every argument to deep_sleep(). But everything else is there.

I noticed that deep_sleep() doesn't work very well. Some issues I noticed are:

• if ms and buttons are specified then only ms works (buttons do not wake it)-
• specifying buttons=button_b also allows waking it by button A
• the first time deep_sleep(1000) is called, the microphone LED comes on after it wakes

[microbit-carlos]

Thanks Damien!

I've updated the PR with the discussion over ther: bbcmicrobit/micropython#754

It currently does not support the run_every argument to deep_sleep().

Is that due to some technical limitation or barrier?

if ms and buttons are specified then only ms works (buttons do not wake it)-

I wasn't able to replicate this one in CODAL, but I have found a related issue:

• uBit.power.deepSleep(ms) blocks until the ms time has elapsed lancaster-university/codal-microbit-v2#221

When trying this in the REPL, power.deep_sleep() does block until time has elapsed, but the 1 appears on the display as soon as the button is pressed:

MicroPython b781e65 on 2022-08-23; micro:bit v2.0.0 with nRF52833
Type "help()" for more information.
>>> import power
>>> display.show("1")
>>> power.deep_sleep(ms=20000, buttons=button_a)

specifying buttons=button_b also allows waking it by button A

Is this a bug in MicroPython? I haven't been able to replicated in CODAL v0.2.40 with this example:

#include "MicroBit.h"

MicroBit uBit;

int main() {
    uBit.init();

    uBit.display.print("!");
    uBit.sleep(400);

    uBit.buttonB.wakeOnActive(true);
    uBit.power.deepSleep();

    uBit.display.print("Up");

    while (true) {
        uBit.sleep(100);
    }
}

I wasn't able to replicate this on the REPL either after a reset button press:

MicroPython b781e65 on 2022-08-23; micro:bit v2.0.0 with nRF52833
Type "help()" for more information.
>>> import power
>>> display.show("1")
>>> power.deep_sleep(buttons=button_a)

However, if I then called again power.deep_sleep() with a different buttons value, the old still woke up the micro:bit.

MicroPython b781e65 on 2022-08-23; micro:bit v2.0.0 with nRF52833
Type "help()" for more information.
>>> import power
>>> display.show("1")
>>> power.deep_sleep(buttons=button_a)
>>> power.deep_sleep(buttons=button_b)

the first time deep_sleep(1000) is called, the microphone LED comes on after it wakes

This is capture in the CODAL issue tracker and should be fixed by the next release:

• MakeCode power extension wakes up and incorrectly turns ON mic LED lancaster-university/codal-microbit-v2#200

[microbit-carlos]

Ah, I think we need to clear the wake up sources on every call to power.deep_sleep():

• codal_app/microbithal: Add microbit_hal_power_clear_wake_sources(). #113