How to use timer to to count periodically

[Marmalade]

I want to use a timer to get a fixed time interval, so I use a 32-bit timer to count from 0 to 10000, and use PPI to clear the counter when it is captured to 10000, such as:

NRF_PPI->CH[0].EEP = (uint32_t)&NRF_TIMER3->TASKS_CAPTURE[2];
NRF_PPI->CH[0].TEP = (uint32_t)&NRF_TIMER3->TASKS_CLEAR;

Would it happen that the counter is still counting before the zero clearing operation is completed, resulting in a period of 10002 instead of 10000?

Will this problem still occur if I use the shortcut register?

Is there any other way for me to get an accurate period?

Thanks very much!

[Dmitry]

Hi,

EEP should point to an event, such as NRF_TIMER3->EVENTS_COMPARE[2].
Use of shortcut is preferable but the behavior should be the same - the timer resets just hitting CC[2].

[Marmalade]

Sorry for my mistake.

If I use NRF_TIMER3->EVENTS_COMPARE[2] to trigger TASKS_CLEAR, will the timer resets to 0 instantly without any delay? Or is there any method to eliminate that delay?

[Dmitry]

There should not be any delay, if you set CC[2] to 10000, timer will count 9998→9999→0→1...