Pending async SPI read and from-slave write simultaneous

RE: Pending async SPI read and from-slave write simultaneous

Christoffer Brask — Mon, 03 Nov 2025 14:25:52 GMT

I don't know if Kenneth are better to help me, but I have created a separate thread (private) https://devzone.nordicsemi.com/support/353533 but we haven't come up with a good solution yet.

RE: Pending async SPI read and from-slave write simultaneous

Einar Thorsrud — Mon, 03 Nov 2025 13:27:56 GMT

Hi,

I do not have any specific advice but I am also not sure to what extent your case differ from the one in the original question. Can explain in detail what it is you want to do and in what way it is problematic?

RE: Pending async SPI read and from-slave write simultaneous

Christoffer Brask — Mon, 03 Nov 2025 10:04:20 GMT

Einar Thorsrud Do you have any suggestions on how to accomplish this?

RE: Pending async SPI read and from-slave write simultaneous

Christoffer Brask — Fri, 31 Oct 2025 12:36:29 GMT

David Demelier Did you come up with a solution? I also a dedicated GPIO (DRDY pin) on my slave but using spi_read in one thread and calling spi_write from another, makes my spi_read return with non valid data and the SPI master does not receive the right data from spi_write

RE: Pending async SPI read and from-slave write simultaneous

Einar Thorsrud — Wed, 28 Aug 2024 12:59:10 GMT

Hi,

[quote user=""]The real issue is that we may need to send data to the master using a custom reversed logic based on a GPIO interrupt in which the master device will then read from the NRF54L15. This unusual scenario is at this time not possible to modify.[/quote]

To me this seems like a quite common scenario, where the SPI slave (nRF in this case) asserts a GPIO when it has data to send, which can be an interrupt pin on the SPI master device. But as you write this is unusual I wonder if I misunderstood something? If so, can you elaborate?

[quote user=""]From what I've experimented through the zephyr SPI API, it's impossible to have a pending spi_read nor spi_read_signal call and at the same time have a spi_write or spi_write_signal function, in that case it will spinlock until the previous transaction completed.[/quote]

SPI transactions are by nature bidirectional, but there are helper functions for only sendign or receiving. To do both, use spi_transceive(). But note that this means that read and write happens as part of the same transaction. You have a separate read and write operation pending or ongoing at the same time.