problem with Timer and @micropython.native

[stefdev49]

Hello,

while using an esp32 :

Chip is ESP32-D0WDQ6 (revision v1.0)
Features: WiFi, BT, Dual Core, 240MHz, VRef calibration in efuse, Coding Scheme None
Crystal is 40MHz

I have noticed that functions decorated with @micropython.native prevent Timer from working reliably.
Here's an example code :

from machine import Timer
import micropython
from time import time_ns

@micropython.native
def isr():
    print('Timer interrupt!')

# if you remove the @micropython.native decorator,
# there will be 4 isr() messages as expected, but only one if you leave it.
@micropython.native
def long_lived_function():
    start = time_ns()
    while time_ns() - start < 2_000_000_000:
        pass

# launch timer interrupt every 500 ms
tim0 = Timer(0)
tim0.init(period=500, mode=Timer.PERIODIC, callback=lambda t: isr())

long_lived_function()

I couldn't find something relevant in the documentation. Is this the expected behavior ? Is there any way to get the Timer work even when using @micropython.native ?

Regards,
Stef

[robert-hh]

It seems to be the (usual) problem with a tight loop. The loop:

    while time_ns() - start < 2_000_000_000:
        pass

prevents other tasks to start. If you use for instance sleep_ms(1) instead of pass in the loop, the scheduler gets a chance to run the isr. In non-native code, the scheduler can get active between python statements. But that does not happen with native code.

[stefdev49]

Hello,

thank you for the answer, amazingly, with sleep_us(156) interrupts are triggered, but with sleep_us(155) and below, they don't.

This example with the loop is just an "cut-down" setup, I get this problem with a more complex program (driving a hub75 led panel, with display refresh done in a function called by timer).
When all other functions are decorated with @micropython.native there is no more interrupts (crt-c doesn't work either) and no display, no matter how long the functions are.

So it's a matter of the scheduler not being called because all code is native ?

Regards

[robert-hh]

Native and viper code is intended to be used for a few time critical sections of the code.

This limit of 155 is actually part of the code. The scheduler is only called if the remaining wait time for sleep_us() is larger than 155 µs. See fucntion delay_us() in esp32/mphalport.c.