PPI

RE: PPI

haakonsh — Mon, 10 Feb 2020 12:17:25 GMT

You need to trigger a capture task to get the value of the TIMER.

If you trigger the CAPTURE[1] task the value of the TIMER will be loaded into the CC[1] register.

The use of a Capture task enables real-time periodic sampling of the TIMER in counter mode.
F. ex. if you want to know how many times a pin has gone from low to high position every 625µs(arbitrary number) you can set up another TIMER to trigger the Capture task every 625µs. You're then guaranteed that the value read by the CPU is correct regardless of its load at the time, as long as you read the register before the next 625µs period that is.

RE: PPI

JayPRab — Fri, 07 Feb 2020 15:00:35 GMT

Hi, Haakonsh,

You're right, but that didn't help to get a count increase in the Timer2 TASKS_COUNT register...

Am I not enabling something?

I DO get a notification in the GPIOTE EVENTS_IN[0] register when I twiddle the input pin...

RE: PPI

haakonsh — Wed, 05 Feb 2020 09:00:24 GMT

NRF_PPI->CH[VIBE_CHANNEL_NUMBER].EEP = (uint32_t)&NRF_GPIOTE->EVENTS_IN

I think it should be:

NRF_PPI->CH[VIBE_CHANNEL_NUMBER].EEP = (uint32_t)&NRF_GPIOTE->IN[VIBE_CHANNEL_NUMBER]

Also, you need to make sure that the channel number for both GPIOTE and PPI is actually available. I believe the PPI driver has a function for finding a free channel at run-time, at least in SDK 9: nrf_drv_ppi_channel_alloc