PPI Auto Reset Timer In Counter Mode

[snoopy20]

  // motion frequency capture
  NRF_PPI->CH[CFG_PPI_TASKER_CHANNEL_MOTION_CAPTURE].EEP = CFG_TASKER_PIF_TIMER->EVENTS_COMPARE[1]; // wire timer compare
  NRF_PPI->CH[CFG_PPI_TASKER_CHANNEL_MOTION_CAPTURE].TEP = CFG_MOTION_PIF_TIMER->TASKS_CAPTURE[1]; // wire ppi to timer capture
  NRF_PPI->CH[CFG_PPI_TASKER_CHANNEL_MOTION_CLEAR].EEP = CFG_TASKER_PIF_TIMER->EVENTS_COMPARE[1]; // wire timer compare
  NRF_PPI->CH[CFG_PPI_TASKER_CHANNEL_MOTION_CLEAR].TEP = CFG_MOTION_PIF_TIMER->TASKS_CLEAR; // wire ppi to reset count
  NRF_PPI->CHENSET = 1 << CFG_PPI_TASKER_CHANNEL_MOTION_CAPTURE_POS;  // enable ppi channel
  NRF_PPI->CHENSET = 1 << CFG_PPI_TASKER_CHANNEL_MOTION_CLEAR_POS;  // enable ppi channel

The only way I can see to do it is by two separate PPI calls. So Timer1 "tasker" is firing both the capture and clear... but will they execute sequentially?

[Edvin]

Hello,

If you capture and clear at the same time, then you have a chance of capturing 0. PPI tasks are done by HW directly, so it will not wait for the capture to finish before clearing.

I am not sure exactly what your timer is doing, but often when this question comes up it usually turns out that the clearing of the timer is not strictly necessary. And why do you need to capture when you know the value of the timer? (It clears when it reaches the set value, right?)

Best regards,

Edvin

[snoopy20]

yes, and iirc, app_timer is needed for using the softdevice...