Which application to start from for nRF9160 as SPI slave?

[JWizard]

Hi,

I intend to use the nRF9160 as an LTE module. I will send data to be transmitted to the nRF9160 and receive data from the nRF9160 via SPI.

I have read in numerous places that Nordic recommends to start projects from an example project.

Which example application is suitable for this?

[Didrik Rokhaug]

Hi.

 

I have read in numerous places that Nordic recommends to start projects from an example project.

 While that was more true for the nRF5 SDK, it is not a bad idea for the nRF Connect SDK (NCS).

However, NCS does not have any SPI slave samples at the moment. However, you can take a look at the spi_fujitsu_fram sample to see how the SPI driver is used in master-mode:

https://github.com/NordicPlayground/fw-nrfconnect-zephyr/tree/v1.14.99-ncs2-branch/samples/drivers/spi_fujitsu_fram

Note that you might have to add an overlay file to make in work on the nRF91.

There is also this unofficial sample made by one of my colleages: https://github.com/Rallare/fw-nrfconnect-nrf/tree/nrf9160_samples/samples/nrf9160/spi

However, you should be aware that the last one might not have been updated for a while.

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You can find the API for the SPI driver here: https://github.com/NordicPlayground/fw-nrfconnect-zephyr/blob/master/include/drivers/spi.h

To configure the SPI peripheral as a slave, you need to set that as one of the flags in the operation field in the spi_config struct.

You will also have to enable it in the device tree, by setting the SPI node compatible with "nordic,nrf-spis", and setting the "csn-pin" and "def-char" properties, in addition to those required by the SPI peripheral regardless of the operation mode. You can read this file to see what properties are required: https://github.com/NordicPlayground/fw-nrfconnect-zephyr/blob/master/dts/bindings/spi/nordic%2Cnrf-spis.yaml

Let me know if you encounter any problems.

Best regards,

Didrik