I am working with a NRF52 DK and I want to alter the SAADC_IRQHandler nrfx_saadc_irq_handler.

References:

• ..modulesnrfxsocnrfx_irqs_nrf52832.h: #define nrfx_saadc_irq_handler SAADC_IRQHandler
• ..modulesnrfxmodulessrcnrfx_saadc.c: void nrfx_saadc_irq_handler(void) { ... }
• ..modulesnrfxmodulesincludenrfx_saadc.h: void nrfx_saadc_irq_handler(void);

I am using Nordic’s nrfx_saadc driver, but found a flaw for my application’s use. I am using the SAADC where a timer comparison triggers the SAMPLE task via the PPI peripheral. If I need to perform an early stop, I would like to still know how many samples were taken at that time and there is currently no accessible way for me to retrieve this value.

I see a couple options for this:

1. I can replace the PPI peripheral to just control the timer’s callback to still call a SAMPLE task on the SAADC, in this way, I can still capture the number of samples taken.

   • My concern is with the power consumption. If I go this route, I am making is so the timer wakes interrupts the CPU to call the sample task whereas the PPI peripheral performs a direct write to the SAADC register and gets the interrupt from the SAADC completing the measurement only.

2. I can replace Nordic’s SAADC implementation with my own to cause the behavior I want

3. Instead of rewriting the nrf_saadc driver, I was thinking I could just overwrite the SAADC_IRQHandler to call:

#define app_saadc_irq_handler SAADC_IRQHandler
static uint32_t irq_iterations = 0U;
void app_saadc_irq_handler(void)
{
  // capture STOPPED signal before nrfx_saadc_irq_handler clears
  if (nrf_saadc_event_check(NRF_SAADC_EVENT_STARTED))
  {
    irq_iterations++;
  }

  // still perform IRQ handling
  nrfx_saadc_irq_handler();
}

This would in turn allow me to control the local variable irq_iterations for my use while still allowing the underlying SAADC driver to control as before.

What I’m struggling with is replacing the Nordic’s SAADC_IRQHandler reference to my own instance without affecting the library files.

Is this good practice for me to do? Is there another option? Any suggestions?