Problem using nRF Connect SDK devicetree GPIO definitions in code

RE: Problem using nRF Connect SDK devicetree GPIO definitions in code

luc_eac — Tue, 29 Mar 2022 12:44:58 GMT

For future visitors, I have figured out what I was missing.

I was unaware that the device tree file is only half of the story and that the system also needs a binding to link the dts configuration to a template which specifies the possible fields of a dts node. This binding is what you put in the "compatible" field.

In my case I defined a file in my board folder under dts/bindings/eac,testpin.yaml, which contains:

description: GPIO used as testpin

compatible: "eac,testpin"

include: base.yaml

properties:
  status:
    required: true

  gpios:
    type: phandle-array
    required: true
    description: |
      GPIO to use as testpin.

And added to my dts node:

tp: testpin {
	compatible = "eac,testpin";
	gpios = <&gpio0 22 0>;
	status = "okay";
};

RE: Problem using nRF Connect SDK devicetree GPIO definitions in code

luc_eac — Thu, 03 Mar 2022 14:06:18 GMT

Hi Øyvind,

Thank you for your answer. I have seen the button examples, but the trouble is I am not trying to implement a button here. I am implementing a GPIO pin.

Looking at the Zephyr device tree documentation they make it seem like you can just create a node (which I named tp) and include a "gpios" parameter to it to define a gpio. All of the examples look like this, roughly..

gpio1: gpio@... { };

gpio2: gpio@... { };

n: node {
        gpios = <&gpio1 10 GPIO_ACTIVE_LOW>,
                <&gpio2 30 GPIO_ACTIVE_HIGH>;
};

Looking at the nRF Connect view in Visual Studio Code under the devicetree tab the pin is also recognised as a GPIO node with the name tp, so sómething is happening..

I have tried adding my own source file to the dts configuration, but that made no difference.

testpins {
	compatible = "testpin";

	tp: tspn {
		gpios = <&gpio0 22 0>;
		label = "TP42";
	};
};

How do I configure just a regular old GPIO in the devicetree (not tied button or led drivers) to use in my own code?

RE: Problem using nRF Connect SDK devicetree GPIO definitions in code

Øyvind — Thu, 03 Mar 2022 13:36:08 GMT

Hello,

Looks like the DTS configuration you have attached is missing the whole configuration, and you have only part of the configuration. E.g. look at nrf\boards\arm\thingy91_nrf9160\thingy91_nrf9160_common.dts

From here you can see how they have configured the button connected to the nRF9160:

buttons {
	compatible = "gpio-keys";

	button0: button_0 {
		gpios = <&gpio0 26 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
		label = "Button 1";
	};
};

&gpio0 {
	status = "okay";
};

Edit: You should also have a look at the basic button sample in Zephyr (zephyr\samples\basic\button\src\main.c)

Kind regards,
Øyvind