nRF52 SPI Manager Need gap between bytes

[BitsAndBytes]

I'm using nRF52 and SDK 15.2 with SPI Manager (NRF_SPI_MNGR_ENABLED) with EasyDMA disabled. Some of the external chips I'm communicating with via SPI can't handle consecutive bytes back-to-back. They require a time gap between each byte sent. I've tried several routes, but so far the only way I can get a gap is to put only 1 byte in each nrf_spi_mngr_transfer_t and putting several of them in a nrf_spi_mngr_transaction_t.

This is not desired because it quickly fills up my transaction queuing, increases the code to manage simple payloads, and greatly increases the overall communication time.

When putting multiple bytes in 1 transfer, it tends to group the first 2 bytes together and then the rest have gaps (see image). (this is with EasyDMA disabled, with EasyDMA enabled all the bytes are grouped).

Is there a way to ensure always a gap? I know 'gap' is subjective but even a hand full of tCLKs would work

I searched the forum and found a couple links related but no solutions:

- devzone.nordicsemi.com/.../nrf52832-spi-psel-sck-timing
- devzone.nordicsemi.com/.../spi-transaction-manager---ncs-chip-select-behavior

Thanks for any suggestions.

[Stian Røed Hafskjold]

Hi, I'm not really sure if there are any easy ways to do this with the SPI driver. You can consider implementing your own SPI driver and combine it with a TIMER instance to send the bytes in a regular interval.

[BitsAndBytes]

Thanks for reply. In the meantime, I remove the use of SPI Manager and am sending bytes directly in app context. It works, but I'm not too excited about it because the 'waitTilNotBusy' calls between bytes are blocking code instead of async callbacks. Oh well, the overall communication burst time is sub-millisecond so hopefully won't impact the other app context operations.