Here’s a program that tests the buttons,
int main(void){ // Configure LED-pins as outputs, and buttons as inputs with pullup nrf_gpio_range_cfg_input(BUTTON_START, BUTTON_STOP, BUTTON_PULL); nrf_gpio_range_cfg_output(LED_START, LED_STOP); while (true) { if (! nrf_gpio_pin_read(BUTTON_0)) nrf_gpio_pin_set(LED_0); else nrf_gpio_pin_clear(LED_0); if (! nrf_gpio_pin_read(BUTTON_1)) nrf_gpio_pin_set(LED_1); else nrf_gpio_pin_clear(LED_1); }}