Hello Bo,

We have a general help page for Device Tree: https://docs.zephyrproject.org/latest/guides/dts/index.html

In your particular case, you need to set port b pin 22 as output.

Device Tree:

The purpose of DT is to describe the HW of the board (boot time @ Linux, compile time @ Zephyr).

K64F’s DT file is found in: boards/arm/frdm_k64f/frdm_k64f.dts I expect this is what you are looking at. It also includes file dts/arm/nxp/nxp_k6x.dtsi where port b is set using nxp,kinetis-gpio.yaml. Dtsi file is a generic dts include file that describes the SoC (we may have another board with the same SoC on it).

Add the following to frdm_k64f.dts to use gpiob from nxp_k6x.dtsi:

&gpiob {

    status = "ok";

};

You can comment out/remove the following to remove he led configuration on the same pin:

        red_led: led_0 {

            gpios = <&gpiob 22 0>;

            label = "User LD1";

        };

Code:

You can’t configure a pin as in/out, using DT, we have board’s pinmux.c (in boards/arm/frdm_k64f) to do that. This is because GPIO should be dynamic during the application.

pinmux_pin_set(portb, 22, PORT_PCR_MUX(kPORT_MuxAsGpio));

The code above sets pin as GPIO (for the led in the case above). Then set pin to output and send a signal:

#include <gpio.h>

    pinmux_pin_set(portb, 22, PORT_PCR_MUX(kPORT_MuxAsGpio));

    struct device *gpiob =

           device_get_binding(DT_NXP_KINETIS_GPIO_GPIO_B_LABEL);

    gpio_pin_configure(gpiob, 22, GPIO_DIR_OUT);

    gpio_pin_write(gpiob, 22, 0);

DT_NXP_KINETIS_GPIO_GPIO_B_LABEL can be found in files zephyr/include/generated/generated_dts_board*** (relative to build folder) this is the effect of setting portb in dts.

Regards,

Andrei Gânsari