Devicetree overlay for simple GPIO

[Lorozco]

It seems like there are lots of questions regarding simple GPIOs and devicetree, but I can't quite find something that describes my problem:

I am using the nrf52840dk, and I successfully created an overlay file to read/write to an I2C device, but I am having trouble adding a simple GPIO pin to my overlay file.

First, I tried adding the following to my overlay file:

columnswitchint: column_switch_input

    {

             compatible = "gpio-keys";

            gpios = <&gpio0 2 GPIO_ACTIVE_LOW>;

            label = "Column Switch Input Signal";

    };

When I try to build, I get the error "Property not mentioned in "/" ".  

Next, I tried declaring the pin like the 'buttons' definition in the .dts file for the blinky example:

sample_gpio_signals

{

    compatible = "gpio-keys";

    columnswitchint: column_switch_input

    {

           

            gpios = <&gpio0 2 GPIO_ACTIVE_LOW>;

            label = "Column Switch Interrupt Signal";

    };

};

This results in the error "Node column_switch_input should have "compatible" property".

Finally, I tried moving the compatible property down into the node:

sample_gpio_signals

{

    columnswitchint: column_switch_input

    {

   

            compatible = "gpio-keys";

            gpios = <&gpio0 2 GPIO_ACTIVE_LOW>;

            label = "Column Switch Interrupt Signal";

    };

};

And this results in the error "Property not mentioned in "gpio-keys".  Obviously 'gpios' is one of the only two properties declared in gpio-keys, so I'm stuck.

What am I missing here?  

[Menon]

Hello,

Thank you for clarifying your issue.

But I think this has been discussed in various other tickets. For eg: Look at this ticket from my colleague there he shows how to add this in overlay file.

Let me know if this not what you are looking for. Please expect a delay after this response as I will be away for Christmas vacation and whole Devzone is working understaffed.

Kind Regards,

Abhijith

[Lorozco]

Just to close this out - your link above helped me figure out my issue (which was due to my unfamiliarity with devicetree syntax!)

To add new nodes, the correct syntax is 

/{
SampleSignals
    {
     compatible = "gpio-keys";
      input_signal1: input_signal1
      {
         gpios = <&gpio0 2 GPIO_ACTIVE_HIGH>;
          label = "Name your GPIO Signal";
        };
    };
};

However, if you are overriding something like an i2c bus, then no 'root'  syntax is required:

&i2c0
{
    new_i2c_device0: i2c_device@30
    {
        compatible = "i2c-device";
        reg = < 0x30 >;
        label = "First new I2C device";
    };
};

Adding the two snippets above to an .overlay file works and does not require modifying the original .dts file in the sdk directories.

Thanks again for the help!