How to enable IRQs before exiting a program.

[davefes]

Trying to disable IRQs on a WeAct 8MB flash board. Appears that if IRQs are not enabled before exiting the program then bad things happen. I have read comments about USB comms getting messed-up if IRQs are not enabled.

I tried catching a CTRL-C and re-enabling IRQs befor exiting, but could not get that to work.

from machine import Pin
from stm import GPIOA, GPIO_BSRRL, GPIO_BSRRH
import machine
import time


@micropython.viper
def ir_pulse(gpio: ptr16, pin: int, on: int, off: int):  # on=12 => 2.00 us on WeAct F411 (? MHz)
    ptr_on = ptr16(uint(gpio) + uint(GPIO_BSRRL))        # on=0  => 0.167 us (PYB)
    ptr_off = ptr16(uint(gpio) + uint(GPIO_BSRRH))       # --> 96.5 ns per on-loop (PYB)
    bit = 1 << pin                                       # (=16 clock cycles)
    ptr_on[0] = bit

    while(on > 0):
        on -= 1

    ptr_off[0] = bit

    while(off > 0):
        off -= 1


pa1 = Pin('A1', mode=Pin.OUT)
isr = machine.disable_irq()

while True:
    try:
        ir_pulse(GPIOA, 1, 12, 55, 10)
    except KeyboardInterrupt as err:
        machine.enable_irq(isr)
        print('exiting properly')
        time.sleep(1)

I am guessing that as interrupts are disabled, then Ctrl-C is not going to work.

How do I ensure interrupts get enabled before closing the program?

[GitHubsSilverBullet]

Why not disable and enable interrupts only within you time-sensitive function?

[rkompass]

Fully agree. E.g. put the

# Disable interrupts
state = machine.disable_irq()

and

# Enable interrupts
machine.enable_irq(state)

(from the docs)
at the begin and end of the ir_burst viper function, for example. Like so:

# on=12 => 2.00 us on WeAct F411 (95 MHz)
@micropython.viper
def ir_burst(gpio: ptr16, pin: int, on: int, off: int, count: int):
    state = machine.disable_irq()
    ptr_on = ptr16(uint(gpio) + uint(GPIO_BSRRL))
    . . . 
    machine.enable_irq(state)

You may add ordinary MP code into a viper program. That then leads to a call of the bytecode interpreter for that instruction, which is not as precise temporally as the pure viper code. But if you do it at the beginning and the end of the viper program that is not relevant, because your burst timing is not affected.

[davefes]

Thanks both. I was trying incorrectly to debug the code while IRQs were disabled. I will try not to do that again!