How to disable/MASK an exti line ON THE FLY

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

JW

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.

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

JW

As Jan noted, there are gotchas related to interrupt disabling at peripheral level. This is explained in ARM Application Note 321, section 4.9 "Disabling interrupts at peripherals".

@deckhard​ 

That solution doesn't work for me. In my case the line that signals an IRQ comes from an ADC and it uses the same line for SPI data output, so after I get the IRQ and then read the result from the ADC I get multiple IRQs unless I disable EXTI 9-5. It solves this problem but I have another peripheral using pin 7 for an IRQ so I don't really want 5-9 disabled together. Here is my code:

Mike.

  //EXTI->IMR &= -(EXTI_LINE_5); // Disable interrupts on line 5 while we read ADC. THIS DOESN'T WORK - NEED TO FIND A FIX... TODO

  HAL_NVIC_DisableIRQ(EXTI9_5_IRQn); //Disable interrupt pins as pin5 will toggle when we read from ADC. Would rather fix the line above.

  spi3TxRxResult = HAL_SPI_TransmitReceive(&hspi3, spi3TxBuffer, ADC_Reading, 4, 2); // 2ms timeout.

  if (spi3TxRxResult != HAL_OK) Error_Handler();

  ADC_Ch = ADC_Reading[3] & 0x03;

  Chan_Status[ADC_Ch] = ADC_Reading[3] >> 4;

  Chan_Reading[ADC_Ch] = ((ADC_Reading[0] & 0x7F) << 16) + (ADC_Reading[1] << 8) + ADC_Reading[2];

  EXTI->PR = 1 << 5; // Clear pending register for this EXTI Pin.

  HAL_NVIC_EnableIRQ(EXTI9_5_IRQn); // Re-enable interrupts. Would rather fix and use the line below.

  //EXTI->IMR |= (EXTI_LINE_5); // Re-enable interrupts on line 5. THIS DOESN'T WORK - NEED TO FIND A FIX... TODO

Which STM32?

//EXTI->IMR &= -(EXTI_LINE_5)

Not *minus*, but *tilde* (for bitwise inversion).

JW

I am using the STM32F407VETx - I assume any in the STM32F4 family would work the same.

I thought the *minus* was weird but clearly that is what is in this post. I had tried with *tilde* and had the same results.

Mike.

> I assume any in the STM32F4 family would work the same.

Maybe yes, maybe not. Probably yes, but "probably" means little when facing a problem.

> I thought the *minus* was weird but clearly that is what is in this post.

No, it's not. A bad font is used in this mockup of a forum. Zoom up that post if your browser allows it, or, better, copy/paste that text into your programmer's editor.

Read out the EXTI register content before and after the operation and check/post.

How and where is EXTI_LINE_5 defined?

JW

Well, bad font for sure!

OK so I changed to the tilde and looked at EXTI->IMR before (0x48B5) and after (0x48B0).

EXTI_LINE_5 is defined in stm32f4xx_hal_exti.h as:

#define EXTI_LINE_5            (EXTI_GPIO    | 0x05u)  /*!< External interrupt line 5 */

Seems weird to me that it isn't a single bit...

Mike.