How to trigger 2 timers on same PPI event

RE: How to trigger 2 timers on same PPI event

mzarling — Thu, 10 Oct 2019 17:25:27 GMT

Thank you for posting your code. It made me go back and review mine and I found a mistake in the ppi channel enable for the new channel. It is working for me now.

RE: How to trigger 2 timers on same PPI event

Andy — Thu, 10 Oct 2019 14:23:36 GMT

I tried it and it works.

uint32_t err_code = nrf_drv_ppi_init();
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_ppi_channel_alloc(&m_adc.saadc_restart_ppi_channel);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_ppi_channel_alloc(&m_adc.timer_stop_ppi_channel);
APP_ERROR_CHECK(err_code);

// Make sure that the SAADC is always started when it ends a conversion
err_code = nrf_drv_ppi_channel_assign(m_adc.saadc_restart_ppi_channel,
									  nrf_saadc_event_address_get(NRF_SAADC_EVENT_END),
									  nrf_saadc_task_address_get(NRF_SAADC_TASK_START));
APP_ERROR_CHECK(err_code);

// Stop the timer when SAADC finishes a conversion
err_code = nrf_drv_ppi_channel_assign(m_adc.timer_stop_ppi_channel,
									  nrf_saadc_event_address_get(NRF_SAADC_EVENT_END),
									  nrf_drv_timer_task_address_get(&m_adc_timer, NRF_TIMER_TASK_STOP));
APP_ERROR_CHECK(err_code);

// Enable SAADC restart PPI channel
err_code = nrf_drv_ppi_channel_enable(m_adc.saadc_restart_ppi_channel);
APP_ERROR_CHECK(err_code);

// Enable timer stop PPI channel
err_code = nrf_drv_ppi_channel_enable(m_adc.timer_stop_ppi_channel);
APP_ERROR_CHECK(err_code);

RE: How to trigger 2 timers on same PPI event

mzarling — Thu, 10 Oct 2019 13:53:08 GMT

I tried that previously with the following lines at the end of the code I showed above. The timer4 event handler never happens, but the timer2 event handler still does. Timer4 is set up just like timer2, except with different compare count value. This is why I figured I was doing something wrong.

status = nrfx_ppi_channel_assign(m_ppi_channel2, spi_end_event, count_task2);
APP_ERROR_CHECK(status);

RE: How to trigger 2 timers on same PPI event

haakonsh — Thu, 10 Oct 2019 12:16:39 GMT

Yes, that's true, and much easier.

RE: How to trigger 2 timers on same PPI event

Andy — Thu, 10 Oct 2019 12:13:19 GMT

Isn't it possible to just allocate a second PPI channel with the same EEP and a TEP pointing to the task of another timer?

RE: How to trigger 2 timers on same PPI event

haakonsh — Thu, 10 Oct 2019 11:59:07 GMT

You can use the EGU — Event generator unit to create another event, and you can then fork that event into two tasks.

See EGU HAL.