GPIO does not sense button press

Question

I have a project that uses the nRF51822_xxAA chip with a pull-up button connected to pin 9. Using a meter, I have verified that the pin drops low (0 V) when the button is pressed so I'm confident that the button hardware is working. However I get no response in the code. I have written a simple test program that also does not get any button input. The test project does not use the SoftDevice (to keep things simple) but my real project does use S110 SoftDevice. I'm using Keil as my dev system and I'm using SDK 10.0.0

I have tried several variants using app_gpio, nrf_drv_gpio, app_button, etc. Nothing seems to work.

Here is my code snippet:

#include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "nrf_gpio.h"
#include "app_gpiote.h"

#define BUTTON_0 	9		// pin 9

#define APP_GPIOTE_MAX_USERS    1

uint8_t button_state;

app_gpiote_user_id_t m_app_gpiote_my_id;

void app_error_handler(uint32_t error_code, uint32_t line_num, const uint8_t * p_file_name)
{
    NVIC_SystemReset();
}

void gpiote_event_handler(uint32_t event_pins_low_to_high, uint32_t event_pins_high_to_low)
{
    if (event_pins_high_to_low & (1 << BUTTON_0))
		button_state = true;
    
    if (event_pins_low_to_high & (1 << BUTTON_0))
		button_state = false;
}

/**
 * @brief Function for application main entry.
 */
int main(void)
{
    uint32_t err_code;

    nrf_gpio_cfg_sense_input(BUTTON_0, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_SENSE_LOW);
    
    APP_GPIOTE_INIT(APP_GPIOTE_MAX_USERS);    
    err_code = app_gpiote_user_register(&m_app_gpiote_my_id, (1 << BUTTON_0), (1 << BUTTON_0), gpiote_event_handler);
    APP_ERROR_CHECK(err_code);
    
    err_code = app_gpiote_user_enable(m_app_gpiote_my_id);
    APP_ERROR_CHECK(err_code);
	
    while(true)
    {
        nrf_delay_ms(500);
    }
}

I appreciate any help.

Brent · Accepted Answer

I have actually discovered what the problem what. It turns out the GPIOTE functions expect the internal pin number (i.e. P0_17) and not the physical pin number. In my case the physical pin number was 9 which internally was P0_17. Replacing the "9" with "17" allows it to get the button state. This is very confusing especially when you consider that other GPIO functionality want the physical pin numbers (i.e. UART).