Long Delay between triggering GPIOTE event and his execution

[Markus Aerni]

Hi

I use the nRF51 Development Kit and the pin_change_int example.

when i push the button the LED changes but there is a delay of 16us.

is this normal ? can i speed this up ? 

Blue is the Button Signal 

Red is the LED signal

[Håkon Alseth]

Hi,

 

The interrupt latency for the Cortex M0 is 16 cycles == 1 us @ 16M. 

The remainder of the time is processing in the nrf_drv_gpiote library (interrupt handler), as this library handles both PORT and IN[n] events. The PORT event uses the SENSE functionality, which is a level trigged signal, not a edge-trigged signal. In order to detect toggle operations, you emulate edge-triggering by inverting the SENSE (going from HIGH to LOW polarity), which may account for the processing time.

You can switch to use the IN[n] events by setting "high accuracy" when configuring your pin, which shall decrease processing time needed: GPIOTE_CONFIG_IN_SENSE_TOGGLE(true)

GPIOTE IN[n] usage does use more current than the PORT event.

 

If this is too much of a jitter, I'd recommend that you implement GPIOTE PORT directly, like done here: https://github.com/NordicPlayground/nrf51-powerdown-examples/blob/master/system_on_wakeup_on_gpio/main.c

 

Best regards,

Håkon