Zephyr peripheral pin remap with overlay file

Question

My application uses a SPI LED driver, which I routed on a PCB to the most convenient pins for routing.

I have already tested my firmware on a nRF52833 DK with an Arduino shield. This uses the spi3 pin assignment on the default DTS.

arduino_spi: &spi3 {
status = "okay";
sck-pin = <23>;
miso-pin = <22>;
mosi-pin = <21>;
cs-gpios = <&arduino_header 16 GPIO_ACTIVE_LOW>; /* D10 */
};

Now i want to remap this spi3 to the pins I used for routing. To do so I have included the following line on my CMakeLists.txt:

set(DTC_OVERLAY_FILE "${CMAKE_CURRENT_SOURCE_DIR}/nrf52833dk_nrf52833.overlay")

And my overlay file looks like this:

&spi3 {
status = "okay";
sck-pin = <26>; //P0.26
miso-pin = <40>; //P1.08
mosi-pin = <5>; //P0.05
cs-gpios = <31>; //P0.31
};

I tested this modification running some dupont cables to the appropiate pins, still with the nRF52833. What does work is changing the pin assignment on the code, for example using a custom structure like:

const struct spi_cs_control ctrl =
{
.gpio_dev = DEVICE_DT_GET(DT_NODELABEL(gpio0)),
.delay = 0,
.gpio_pin = 31,
.gpio_dt_flags = (GPIO_ACTIVE_LOW)
};

Which is the best way to get this to work?

It doesn't look like the overlay file is doing anything, as my code doesn't work.

Håkon Alseth · Accepted Answer

Hi,

This is not the correct format for the cs-gpios member:

cs-gpios = <31>; //P0.31

You can see the expected format in the yml file for the generic spi controller:

https://github.com/nrfconnect/sdk-zephyr/blob/v2.6.99-ncs1-rc1/dts/bindings/spi/spi-controller.yaml#L24-L63

For your scenario, where you want to use P0.31, it should be:

cs-gpios = <&gpio0 31 GPIO_ACTIVE_LOW>;

I tested this modification running some dupont cables to the appropiate pins, still with the nRF52833. What does work is changing the pin assignment on the code, for example using a custom structure like:

const struct spi_cs_control ctrl =
{
.gpio_dev = DEVICE_DT_GET(DT_NODELABEL(gpio0)),
.delay = 0,
.gpio_pin = 31,
.gpio_dt_flags = (GPIO_ACTIVE_LOW)
};

Which is the best way to get this to work?

The code has omitted the defines that were emitted by the compiled device tree, as you're not fetching the cs-gpios member, which is just fine (you end up in the same scenario), but if you change it in dts, nothing will happen on the application level.

You can use these helper macros:

https://github.com/nrfconnect/sdk-zephyr/blob/v2.4.99-ncs2/subsys/disk/disk_access_spi_sdhc.c#L844-L848

As long as you set this in the top of main:

https://github.com/sigurdnev/ncs-playground/blob/master/samples/spi_test/src/main.c#L11

Kind regards,

Håkon

Zephyr peripheral pin remap with overlay file

Top Replies