RTC+DPPI+SPIM+DMA

RE: RTC+DPPI+SPIM+DMA

joey — Wed, 17 Sep 2025 00:49:55 GMT

I didn't use channel 0 and assigned other channels instead, as I saw that channel 0 was occupied in my Zephyr-based code.

RE: RTC+DPPI+SPIM+DMA

tim-remoticom — Mon, 15 Sep 2025 10:08:09 GMT

Hi there, we are trying the same thing with the GRTC channel 0.

Channel 0 is hard-coded as the main channel in `nrf_grtc.h`.
Is it safe to change this value? Or is channel 0 hardcoded in other places as well?

Zephyr doesn't seem to be using the Interval feature.

RE: RTC+DPPI+SPIM+DMA

joey — Mon, 01 Sep 2025 10:31:09 GMT

Thank you for your reply.
I am currently using the GRTC for timing, but I am encountering some issues.

I am currently using NRF54L15 with SDK version 3.0.0, and I want to implement GRTC auto-reload without using interrupts. My main goal is to reduce CPU usage and utilize the peripheral DPPI for operations as much as possible.

The manual states that only Channel 0 supports hardware auto-reload, while other channels can be configured via the CC_ADD register. However, in Zephyr, Channel 0 is already used for RTOS timing, so I am applying for other channels for comparison.
For other channels, I am trying to implement GRTC auto-reload using DPPI, but there seems to be no CC_ADD operation among the tasks.

Does this mean I cannot avoid interrupts to achieve GRTC compare reloading?

Thanks

RE: RTC+DPPI+SPIM+DMA

Sigurd — Mon, 01 Sep 2025 09:31:29 GMT

Hi!

There is no RTC on nRF54L15, but you can use the GRTC's Periodic Interval functionality to generate a event at a fixed interval: https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/grtc.html#d762e391

You would need to use the Array List functionality for this use-case. See https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/easydma.html#ariaid-title4

We don't have any official examples for this, but maybe this example could be of help: https://github.com/too1/ncs-spi-arraylist-example/tree/master