Hardware CSN handling in NRF52840

[riataman]

Hey I'm doing some SPI transfer in response to a GPIOTE in event. I'm targeting the NRF52840 and kind of went with the following answer:

https://devzone.nordicsemi.com/f/nordic-q-a/18645/no-slave-select-on-spim-xfer-using-ppi-and-gpiote

In believing that there's no automatic handling of the CSN pin (SS). But I'm reviewing the nrf52840 documentation more closely and seems like hardware CSN support was actually added. But is seems like the SPI library hasn't been updated to take advantage of that hardware feature? Any suggestion on how to setup that up while still mostly using library functions? Is that even possible?

Also I'm correct in my reading that there are 16Mhz and 32Mhz modes now in the nrf52840? Same question if there's an easy way to enable those?

[MartinBL]

Hi,

There is no HW CSN implementation yet and adding it to the current drivers and libraries would probably require a lot of work. The good news though, is that it will be implemented in the next SDK release which will be available in a not too distant future. 

SPIM instance 3 (SPIM3) supports 16 MHz and 32 MHz frequencies. We had some struggles making it work in the earlier engineering IC versions and we considered to drop it. That is why the features are not properly documented yet.

Remember to watch out for the erratas: New and inherited anomalies.

-Martin

[Rob Philip]

Hey..

I have this exact issue - only SPI seems to be implemented in the drivers, not SPIM (with CSN). Any ideas when the "next" SDK supporting SPIM with CSN will be available? 

[MartinBL]

SDK 15 was released last week. In the new drivers SPIM3 supports HW CSN. https://developer.nordicsemi.com/nRF5_SDK/