QUERY · ISSUE

rp2: Can't wake from lightsleep with Pin IRQ

openby peterhinchopened 2021-03-15updated 2026-03-24

port-rp2

On a pin change this code sample toggles the LED but never outputs "got here".

from machine import Pin, lightsleep
p25 = Pin(25, Pin.OUT)
p0 = Pin(0, Pin.IN, Pin.PULL_UP)
def foo(_):
    p25(not p25())  # Toggle the LED

p0.irq(foo, trigger=Pin.IRQ_FALLING)
while True:
    lightsleep()
    print('Got here')

The docs indicate that to fix this, the IRQ should be instantiated with wake=machine.SLEEP. Unfortunately this constant does not exist.

CANDIDATE · PULL REQUEST

WIP: rp2: Make GPIO wakeup from lightsleep consistent.

openby projectgusopened 2024-12-18updated 2025-04-09

bugport-rp2

Summary

Make the Pin.irq() wakeup behaviour more consistent on rp2. Closes https://github.com/micropython/micropython/issues/7035 and partial fix for https://github.com/micropython/micropython/issues/16180

Goal is that any pin which has Pin.irq() and a trigger set will wake rp2 port from any machine.lightsleep() call.

Details

Currently:

A Pin with an irq() trigger is a wakeup source only when machine.lightsleep(n) is used with a timeout, and only if an IRQ handler is set.

After this PR:

A Pin with an irq() trigger is a wakeup source from both indefinite machine.lightsleep() and machine.lightsleep(n) with a timeout.
A Pin with an irq() trigger is a wakeup source even if no handler function is set.

TODOs

Waking RP2040 repeatedly from machine.lightsleep() with no timeout and USB causes the USB connection to misbehave and eventually the CPU hangs. This is the same thing fixed for lightsleep with a timeout in https://github.com/micropython/micropython/pull/15111 and https://github.com/micropython/micropython/pull/15301 . However, with no timeout argument the RP2 goes to the lower power "DORMANT" mode so keeping USB clock running isn't an option. Calling tud_disconnect()/tud_connect() or tud_deinit()/tud_init() before and after going to dormant mode doesn't seem to be enough to fix this. One heavy-handed workaround would be to not select DORMANT if USB is enabled, just call WFI instead. However, then the wakeup conditions are a lot different which may be confusing if developing and testing via USB and then deploying...
Test on RP2350. I have hardware coming, otherwise help is welcome.
This implementation doesn't match the machine.Pin docs re: irq(wake=) argument. However, I think only cc3200 port has actually implemented this argument as documented, so the fix here might be to make the docs match the current reality rather than the other way around.

This work was funded through GitHub Sponsors.

Testing

Trade-offs and Alternatives

It seems like machine.lightsleep() has had very limited utility until now (i.e. no possible wake source?) so maybe we should refactor to only use DORMANT mode for deep sleep where we don't have to worry about recovering the USB peripheral. Keeping clocks running does increase consumption, though.