// configuration code
...
    // Configure GPIO_PIN7 as input and set its initial value as high
    LE_FATAL_IF(GPIO_PIN7_SetInput(GPIO_PIN74_ACTIVE_HIGH) != LE_OK,
                "Couldn't configure GPIO_PIN7 as default input high");

    // Although there is an external pullup resistor, we need to enable the internal resistor too,
    // because gpioSysfs doesn't support disabling the resistors
    GPIO_PIN7_EnablePullUp();

    // Register a callback function
    LE_FATAL_IF(GPIO_PIN7_AddChangeEventHandler(GPIO_PIN7_EDGE_BOTH, GPIO_PIN7_ChangeCallback, NULL, 50) == NULL,
                "Couldn't add event handler to GPIO_PIN7");

...

static void GPIO_PIN7_ChangeCallback
(
    bool state,
    void *ctx
)
{   
    LE_INFO("GPIO_PIN7 changed state to : %d \n", state);
}