4. EXT: Power Management V2

The reset button can be used to manually control the power modes of the microbit.

4.1. Sleep

When powered by USB, press and hold power/reset for 5 seconds to enter sleep. The microbit power LED will dim from bright red to off. It will then flash on/off, showing you that it is still connected to the power source. Press power/reset to wake up.

Removing the USB power cable and re-adding it will also wake the microbit.

4.2. Power off

When powered by battery, press and hold power/reset for 5 seconds to power off the microbitThe microbit power LED will dim from bright red to off. It will then remain off until you press the power/reset to wake up. Disconnecting the USB and battery power supply will also power off the microbit.

Inserting a USB power lead will also wake the device.

4.3. Wake

Pressing the power/reset again when in sleep/power-off mode will wake the microbit and your program will restart.

Removing the USB power cable and re-adding it will also wake the microbit.

Warning

Mu v1.1.1 doesn’t yet support the power module. Sep 2022.
Use the online micropython editor instead: https://python.microbit.org/v/3
Thonny v 4 can also be used.

4.4. Power module

This module lets you manage the power modes of the microbit V2.

See: https://microbit-micropython.readthedocs.io/en/stable/power.html

4.5. Power down the microbit

There are two low power modes:

Off: The power mode with the lowest power consumption, the only way to wake up the board is via the reset button, or by plugging the USB cable while on battery power. When the board wakes up it will restart and execute the program from the beginning.
Deep Sleep: Low power mode where the board can be woken up via multiple sources (pins, button presses, or a timer) and resume operation.

4.6. Power off

power.off(): Power down the board to the lowest possible power mode.

This is the equivalent to pressing the reset button for a few seconds, to set the board to “Off mode”.

The microbit, not on battery power, will only wake up if the reset button is pressed.

If on battery power, connecting a USB cable can wake it as well.

Waking up from this mode starts the program from the beginning.

The code below uses button-B pressing to power down the microbit.

Press the reset button to wake it and restart the program from the beginning.

from microbit import *
import power


display.scroll("starting up", delay=60)
while True:
    if button_b.is_pressed():
        display.scroll("power off", delay=60)
        power.off()
    display.show(Image.HAPPY)
    sleep(200)

Tasks

Fix the code in 2 places so that it shows the image NO for 1 second before powering off if the B-button is pressed at any time.

from microbit import *
import power


display.show(Image.YES)
while True:
    if button_b.is_pressed():
        display.show(Image.NO)
        power.off()
    display.show(Image.HAPPY)
    sleep(1000)
    display.show("?")
    sleep(1000)

4.7. Deep Sleep

power.deep_sleep(ms=None, wake_on=None, run_every=False)

Parameters:

ms – A time in milliseconds to wait before it wakes up.
wake_on – A single instance or a tuple of pins and/or buttons to wake up the board, e.g. deep_sleep(wake_on=button_a) or deep_sleep(wake_on=(pin0, pin2, button_b)).
run_every – Set to True to wake up with each microbit.run_every scheduled run.

Set the microbit into a low power mode where it can wake up and continue operation.
The program state is preserved and when it wakes up it will resume operation where it left off.
Deep Sleep mode will consume more battery power than Off mode.
The wake up sources are configured via arguments.
If no wake up sources have been configured it will sleep until the reset button is pressed (which resets the board) or, if on battery power, when the USB cable is inserted.
See: https://microbit-micropython.readthedocs.io/en/stable/microbit.html

The code below uses button-B pressing to go into a deep sleep.
wake_on=button_a allows pressing button-A to wake it.
ms=30 * 60 * 1000 is a 30 minute deep sleep.
run_every=False prevents run_every events from waking it.

from microbit import *
import power

display.scroll("starting up", delay=60)
while True:
    if button_b.was_pressed():
        display.scroll("deep sleep", delay=60)
        sleep(300)
        power.deep_sleep(wake_on=button_a, ms=30 * 60 * 1000, run_every=False)
        display.scroll("waking", delay=60)
    display.show(Image.HAPPY)
    sleep(200)

4.8. Deep sleep wake via run_every

run_every(callback, days=None, h=None, min=None, s=None, ms=None)

Parameters:

callback – Function to call at the provided interval.
days – Sets the days mark for the scheduling.
h – Sets the hour mark for the scheduling.
min – Sets the minute mark for the scheduling.
s – Sets the second mark for the scheduling.
ms – Sets the millisecond mark for the scheduling.

Schedule to run a function at the interval specified by the time arguments.
Each argument corresponds to a different time unit and they are additive.
So run_every(min=1, s=30) schedules the callback every minute and a half.

run_every can be used in two ways:

As a Decorator - placed on top of the function to schedule. For example:

from microbit import *

@run_every(days=1, h=1, min=20, s=30, ms=50)
def my_function():
    display.scroll("running decorator")

As a Function - passing the callback as a positional argument. For example:

from microbit import *

def my_function():
    display.scroll("running function")

run_every(my_function, s=30)

The code below renews a deep sleep every 24 hours.
The microbit scrolls the temperature every 60 seconds
wake_on=None prevents button pressing from waking it.
day_ms = 24 * 60 * 60 * 1000 and ms=day_ms is a day long deep sleep.
run_every=True allows run_every events to wake it.
The decorator, @run_every(s=60), causes the wakeup_call() to run every 60 seconds.

from microbit import *
import power
import radio

# Choose own group in pairs 0-255
radio.config(group=8)
# Turn on the radio
radio.on()

@run_every(s=60)
def wakeup_call():
    temp = temperature()
    display.scroll(temp)

day_ms = 24 * 60 * 60 * 1000
while True:
    # renew deep sleep every day
    power.deep_sleep(wake_on=None,ms=day_ms,run_every=True)