RP2350 lightsleep broken on battery

[chhu]

Port, board and/or hardware

pico 2 w

MicroPython version

v1.27.0 (2025-12-09)

Reproduction

from machine import Pin
import machine
import time

led = Pin("LED", Pin.OUT) # Use the built-in LED

just to indicate when a reset occured

led.off()
time.sleep(1)
led.on()
time.sleep(1)
machine.lightsleep(60_000)

Expected behaviour

LED should go out for 1s every 62s.

Observed behaviour

Keeps blinking in 1s intervals when on battery power (Vsys), disconnected USB. WLAN off.

Additional Information

Same behavior with deepsleep. My work-around is
now = time.time()
wake = now + 60
while now < wake:
machine.lightsleep(60_000)
now = time.time()

but goal was to save power. With this loop it is idling at 0.15W versus 0.2W with time.sleep. Bummer. Is this a limitation of the pico 2 w?
Thanks!

Code of Conduct

Yes, I agree

[Josverl]

@chhu,
I have converted this to a discussion as I cannot reproduce the issue on any of the Rp2040 or rp2350 builds, and is seem that you are asking a question on how to get this to work , rather than report an issue.

I think the problem may be in your code. machine.lightsleep() returns after the sleep is finished.
In your code same there is no loop, so the code just stops at the end of the script.

When I wrap that snippet in in an `while True:' loop, so that there is actually a loop to continue, it works just fine.

# main.py 
from machine import Pin
import machine
import time

led = Pin("LED", Pin.OUT) # Use the built-in LED

while True:
    led.off()
    print("LED OFF")
    time.sleep(1)
    led.on()
    print("LED ON")
    time.sleep(1)

    machine.lightsleep(10_000)

    print(f"Woke up from lightsleep at {time.ticks_ms()} ms\n"
          "reason: {machine.reset_cause()}"
        )

With a deepsleep() the same code will work, but never reach the statements after the deepsleep().
rather it will restart the Pico, and will reload and execute main.py from line 1.