Proper use of DTS files to describe GPIOs in Zephyr?

RE: Proper use of DTS files to describe GPIOs in Zephyr?

Einarh — Wed, 27 Apr 2022 08:54:41 GMT

2. hm, the only thing I can think of is that Segger might define DTC_OVERLAY_FILE for you, since the build system won't keep looking for an overlay file if this variable is defined. As I said I would try to add your overlay file to DTC_OVERLAY_FILE.

3. I don't think there's a straight forward way to use "gpiocus_0" instead of "gpiocus0" to access your node, but you can look through the Devicetree API to see if you find a function that suits your needs. As I said you can input the label property, which you can name whatever you want, directly into the device_get_binding function if you find that cleaner.

-Einar

RE: Proper use of DTS files to describe GPIOs in Zephyr?

mytzyiay — Tue, 26 Apr 2022 17:02:54 GMT

For #2: the build system normally does detect overlays under boards/, but that doesn't work under Segger. Maybe I'm importing the project incorrectly?

For #3: is there a way I can omit the "gpiocus0" label entirely and just reference "gpiocus_0" from the C code? It's annoying having two slightly different names pointing to the same node -- an unnecessary layer of abstraction (at least in my use case).

RE: Proper use of DTS files to describe GPIOs in Zephyr?

Einarh — Tue, 26 Apr 2022 12:11:12 GMT

Hello

1. The compatible property is there to help the build system find the right binding for the hardware node. If you only want to define a basic gpio input, then the "gpio-keys" binding is the most basic binding you'll get and works just fine. Otherwise, there are many bindings defined in dts/bindings/gpio/ in your Zephyr install, among them "nordic, nrf-gpio", maybe that could work for your application? I would recommend having a look at these binding define files to get an idea of how they differ. You could also define your own binding, but unless you want very specific functionality that isn't available in the already defined ones, I don't think it will be necessary.

2. This sounds strange to me, the build system should be able to detect overlay files in the boards/ directory. You could try to set the CMake variable DTC_OVERLAY_FILE manually to contain your overlay file as described here.

3. Yes, there are many helper functions in Zephyr's Devicetree API that you can use to obtain the node identifier. For your node you could for example use DT_NODELABEL(gpiocus0). You can also input the label property directly into the device_get_binding function, in your case device_get_binding("Custom gpio 28") I believe. The aliases are commonly used just to make the code more readable.

4. Yes this is a good point, many newcomers to Zephyr seem to have trouble with the devicetree.

Best regards,

Einar