RP2350 the watchdog timer does not count down while lightsleep is running
Port, board and/or hardware
Raspberry Pi Pico2
MicroPython version
MicroPython v1.25.0 on 2025-04-15; Raspberry Pi Pico2 with RP2350
Reproduction
Copy the following into wdt_lightsleep_2350.py.
from machine import lightsleep, WDT
from time import sleep_ms
wdt = WDT(timeout=5000)
lightsleep(3000)
sleep_ms(3000)
print('Should not print')
sleep_ms(3000)
Do 'mpremote run wdt_lightsleep_2350.py'.
Expected behaviour
Expect the same behavior seen when the lightsleep is replaced with sleep_ms.
File wdt_sleep_ms_2350.py
from machine import lightsleep, WDT
from time import sleep_ms
wdt = WDT(timeout=5000)
sleep_ms(3000)
sleep_ms(3000)
print('Should not print')
sleep_ms(3000)
>> mpremote run wdt_sleep_ms_2350.py
Traceback (most recent call last):
File "/home/picompute/.local/bin/mpremote", line 8, in <module>
sys.exit(main())
Note: most of traceback removed.
This time the print did not execute because the watchdog timer triggered during the second sleep_ms(3000).
Observed behaviour
The print statement does execute and the watchdog timer triggers during the last sleep_ms(3000).
>> mpremote run wdt_lightsleep_2350.py
Should not print
Traceback (most recent call last):
File "/home/picompute/.local/bin/mpremote", line 8, in <module>
sys.exit(main())
Note: most of traceback removed.
Additional Information
I have changes to lightsleep in modmachine.c which fix this problem.
I will prepare a pull request with this fix.
The root cause is the watchdog timer does not count down while lightsleep() is running.
This problem is RP2350 specific and is not seen on RP2040.
Code of Conduct
Yes, I agree
RP2040 will lockup if a watchdog timeout occurs while lightsleep() is running
Port, board and/or hardware
Raspberry PI Pico
MicroPython version
MicroPython v1.25.0 on 2025-04-15; Raspberry Pi Pico with RP2040
Reproduction
Test file named wdt_lightsleep.py.
from machine import lightsleep, WDT
wdt = WDT(timeout=3000)
lightsleep(5000)
Do 'mpremote run wdt_lightsleep.py'.
>> mpremote run wdt_lightsleep.py
Traceback (most recent call last):
File "/home/picompute/.local/bin/mpremote", line 8, in <module>
sys.exit(main())
^^^^^^
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/mpremote/main.py", line 569, in main
handler_func(state, args)
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/mpremote/commands.py", line 463, in do_run
_do_execbuffer(state, buf, args.follow)
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/mpremote/commands.py", line 437, in _do_execbuffer
ret, ret_err = state.transport.follow(timeout=None, data_consumer=stdout_write_bytes)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/mpremote/transport_serial.py", line 184, in follow
data = self.read_until(1, b"\x04", timeout=timeout, data_consumer=data_consumer)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/mpremote/transport_serial.py", line 123, in read_until
elif self.serial.inWaiting() > 0:
^^^^^^^^^^^^^^^^^^^^^^^
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/serial/serialutil.py", line 594, in inWaiting
return self.in_waiting
^^^^^^^^^^^^^^^
File "/home/picompute/.local/pipx/venvs/mpremote/lib/python3.11/site-packages/serial/serialposix.py", line 549, in in_waiting
s = fcntl.ioctl(self.fd, TIOCINQ, TIOCM_zero_str)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 5] Input/output error
>> mpremote
mpremote: no device found
Expected behaviour
Expect it to behave the same as if lightsleep were replaced with time.sleep_ms.
Call this test file wdt_sleep_ms.py
from machine import WDT
from time import sleep_ms
wdt = WDT(timeout=3000)
sleep_ms(5000)
In this case, after do 'mpremote run wdt_sleep_ms.py'.
After 3 seconds mpremote will report an OSError because the RP2040 does a soft reset.
Run mpremote again and it will connect successfully.
Observed behaviour
The RP2040 seems to get stuck. After running 'mpremote run wdt_lightsleep.py' attempts to connect running mpremote fail.
On my Raspberry Pi 4 I see an error message of 'mpremote: no device found'.
A power cycle is required to recover.
One more observation, I have a USB power meter connected between the PI 4 and RPI Pico.
Normally it reports about 19 milli-amps consumed, about 5 milli-amps while the lightsleep is running.
After the test completes it reports about 1.00 milli-amps.
Additional Information
I have changes to lightsleep in modmachine.c which fix this problem.
I will prepare a pull request with this fix.
The root cause is lightsleep turns off the ROSC.
When the watchdog timeout occurs the Power-On State Machine does not re-initialize it.
This occurs because the PICO-SDK function _watchdog_enable() zero's sm_hw->wdsel bits for the ROSC and XOSC.
The behavior reported here is seen on RP2040 only.
Code of Conduct
Yes, I agree