Counting edges with PPI and GPIOTE

RE: Counting edges with PPI and GPIOTE

Constantin — Wed, 13 Nov 2019 10:55:39 GMT

Okay I've solved it: The issue is that you can not read the current count of the timer without triggering a capture. I solved it with:

NRF_TIMER4->TASKS_CAPTURE[2] = 1;
toggle_count = NRF_TIMER4->CC[2];

Maybe adding this information to the documentation or exampel is worth it.

Thanks

RE: Counting edges with PPI and GPIOTE

Sigurd — Wed, 13 Nov 2019 09:37:58 GMT

Please check the return codes from nrfx_timer_init() and the nrfx_ppi_x functions, and make sure that they return NRFX_SUCCESS (=0). If you are not able to find the root cause of the issue, please post your main.c file and/or a full example that shows the issue.

RE: Counting edges with PPI and GPIOTE

Constantin — Tue, 12 Nov 2019 20:01:30 GMT

Hi Sigurd,

okay that sound reasonable. But I am still not getting any count when I call

toggle_count = nrfx_timer_capture_get(&m_timer, NRF_TIMER_CC_CHANNEL0);

It only gives permanent 0. Although the line the toggling. What Am I missing?

RE: Counting edges with PPI and GPIOTE

Sigurd — Tue, 12 Nov 2019 16:41:18 GMT

The gpiote interrupt is not enabled, only the event is enabled, i.e. last argument in nrf_drv_gpiote_in_event_enable(PIN_IN, false) is set to false.

Same applies to the timer used for counting, the function nrf_drv_timer_compare_int_enable() and nrf_drv_timer_extended_compare() is not used to enable any interrupt for that timer.

In the example, the m_timer_read interrupt is only used to periodically print the counter value.

Also, the example I linked to does by default not put the CPU to sleep. Something like the snippet below should be added to main() while-loop in order to do that.

    if (NRF_LOG_PROCESS() == false)
    {
                        // Wait for an event.
        __WFE();
        // Clear the internal event register.
        __SEV();
        __WFE();
    }

RE: Counting edges with PPI and GPIOTE

Constantin — Tue, 12 Nov 2019 15:40:01 GMT

Thanks for the reply. The issue is that in the example there are two interrupt routines. But I want to solve it without any interrupt routine. Why do I have to enter a timer_handler and a gpiote handler?
This consumes CPU without optimization.

RE: Counting edges with PPI and GPIOTE

Sigurd — Tue, 12 Nov 2019 13:43:04 GMT

Hi,

Check the code attached at the end of this post (inside the gpiote_timer_ppi.zip)