nrfx peripheral resource sharing

Overview

This sample shows how to use in Zephyr nRF peripherals that share the same ID and base address. Such peripherals cannot be used simultaneously because they share certain hardware resources, but it is possible to switch between them and use one or the other alternately. Because of the current driver model in Zephyr and the lack of possibility to deinitialize a peripheral that is initialized by a driver at boot, such switching cannot be achieved with Zephyr APIs. Therefore, this sample uses the nrfx drivers directly for those peripheral instances that are to be switched (SPIM2 and UARTE2) while the standard Zephyr drivers are used for other instances of the same peripheral types (UARTE0 is used by the standard Zephyr console and SPIM1 is used for performing additional sample transfers).

The sample uses two buttons:

  • by pressing Button 1 user can request a transfer to be performed using the currently initialized peripheral (SPIM2 or UARTE2)

  • by pressing Button 2 user can switch between the two peripherals

When no button is pressed, every 5 seconds a background transfer using SPIM1 is performed.

The sample outputs on the standard console the hex codes of all sent and received bytes, so when the proper loopback wiring is provided on the used board (between the MOSI and MISO pins for SPIMs and between the TX and RX pins for the UARTE), it can be checked that what is sent by a given peripheral is also received back. Without such wiring, no data is received by UARTE and all zeros are received by SPIMs. Refer to the overlay files provided in the samples/boards/nordic/nrfx_prs/boards directory to check which pins on the boards supported by the sample are assigned as MOSI/MISO and TX/RX pins.

Requirements

This sample has been tested on the Nordic Semiconductor nRF9160 DK (nrf9160dk/nrf9160) and nRF5340 DK (nrf5340dk/nrf5340/cpuapp) boards.

Building and Running

The code can be found in samples/boards/nordic/nrfx_prs.

To build and flash the application:

west build -b nrf9160dk/nrf9160 samples/boards/nordic/nrfx_prs
west flash

Press Button 1 to trigger a sample transfer on SPIM2 or UARTE2. Press Button 2 to switch the type of peripheral to be used for the transfer.

When no button is pressed, a background transfer on SPIM1 is performed.