Device tree

[Andy_K]

Hi,

I am getting to grips with the device tree and when i add an over lay file to the project, the 'new' devices are flagged with the waring that theyre being over ridden else where although i have no idea where. Also, VS generates a number of warnings relating to the .dts and .dtsi files (which i havent modified).

How can i find where the over ride is happening?

Thanks.

[Simonr]

Hi

I think this overwrite is happening because you're trying to use the P0.10 (and/or P0.09) as a GPIO, when this is by default set as an NFCT pin. You need to explicitly set these as GPIOs to get GPIO functionality from them with the following addition to your devicetree: 
&uicr { nfct-pins-as-gpios; };

Please try that and get bck to me if you're still seeing the same issue. If you haven't already, check out the Nordic DevAcademy and the nRF Connect SDK fundamentals and intermediate courses to get a better grasp of the nRF Connect SDK and Zephyr development environment.

Best regards,

Simon

[Andy_K]

Hi,

Thank you for pointing out that they are NFCT pins. I changed LED1 to p0.27 in the blinky example using an overlay and connected an external LED. The LED behaved as expected.

When including the line

 

    &uicr { 
        nfct-pins-as-gpios; 
    };

The build fails with an error that wasnt previously present. removing the '&' from uicr allows the build to complete but seemingly has no effect upon the pin as the external LED does not toggle.

[Simonr]

You're using an NRF52840 DK here, correct? If so, some HW alterations are necessary to use the P0.09 and P0.10 pins as well. To use these pins as GPIO, R44 and
R46 must be not connected (NC) and R43 and R45 must be shorted with an 0R resistor. If not, the physical output will still be onto the NFC antenna.

Best regards,

Simon