How to disable/MASK an exti line ON THE FLY

[Craig1]

I'm currently trying to implement a button interrupt and need to disable the button interrupt after the initial call to the isr to avoid excessive interrupt triggering due to debounce. I'm using STM32CUBEIDE/MX currently. The button works as desired if I use

HAL_NVIC_DisableIRQ(EXTI9_5_IRQn); (in interrupt)

//do some stuff

HAL_NVIC_EnableIRQ(EXTI9_5_IRQn); (in main)

but this is non-ideal as it disables exti lines 5 through 9.

I've been trying to mask the EXTI line using EXTI_IMR. This seems to work for the first button press, but I'm never able to re-trigger the ISR

EXTI->IMR &= ~(EXTI_LINE_5);//in ISR

EXTI->IMR &= (EXTI_LINE_5);//in main

Thoughts?

[Craig1 · Accepted solution]

DOH! forgot my coffee this morning, sorry this works:

EXTI->IMR &= ~(EXTI_LINE_5);//in ISR

EXTI->IMR |= (EXTI_LINE_5);//in main

[waclawek.jan]

Thanks for coming back with the solution. Can you please select our post as Best so that the thread is marked as resolved.

JW

[deckhard]

Masking is needed if the interrupt is a level interrupt.

To my understanding the EXTI controller is only Edge triggered so not sure why masking is needed.

[Pavel A.]

@deckhard​ 

> To my understanding the EXTI controller is only Edge triggered so not sure why masking is needed.

Masking can be useful for shared EXTI interrupt vectors such as EXTI15_10, EXTI9_5.

It allows to temporary delay only one EXTI pin interrupt without affecting others on the same NVIC vector.

-- pa

[Piranha]

Just adding to what Pavel told - it can be used for sections or modes of code to make the code interrupt-safe relative to a specific interrupt.

[waclawek.jan]

Careful with this, the effect of such disable may be delayed...

JW

[deckhard]

Ok that makes sense

[deckhard]

That is why the HAL does not natively support masking?

[waclawek.jan]

No. Cube/HAL inevitably covers only a limited subset of possible functionality, only what is authors deem "usual".

JW