GPIOS: Init one pin using hog

GPIO pin initialization can be carried out by the internal Zephyr GPIO driver, we just need to indicate in the device tree using hogs which is basically a child node for each port where we can set the pin as input or output

main.c

#include <zephyr/kernel.h>
#include <zephyr/drivers/gpio.h>

/* get the node identifier from its label, in this case will be gpio@50400 for port 2 */
#define LED_NODE DT_NODELABEL( gpio2 )

int main( void )
{
    /* From the default devicetree get the gpio0 reference */
    const struct device * gpio2 = DEVICE_DT_GET( LED_NODE );

    /* No need to call any initialization function */

    while(1)
    {
        /* Toggle pin 9 from port 2 using a port function */
        gpio_pin_toggle( gpio2, 9 );
        /* 300ms Delay */
        k_msleep( 300 );
    }
    return 0;
}

app.overlay

/* phandle for gpio2 port */
&gpio2 {
    /* Declare an internal node name led-0 for pin 9 */
    led_0: led-0{
        gpio-hog;
        /* config pin 9 as  */
        gpios = <9 GPIO_ACTIVE_HIGH>;
        /* Set pin as output with  init state as high level */
        output-high; 
    };
};

prj.conf

# Disable optimizations
CONFIG_NO_OPTIMIZATIONS=y
# Include GPIO drivers in system config (KCONFIG)
CONFIG_GPIO=y
# Option to init pins using the DTC
CONFIG_GPIO_HOGS=y