RE: getting an interrupt when any of multiple GPIO pins change

David — Tue, 07 Mar 2017 01:09:49 GMT

Thank you very much Jørn for the thorough answer. Very helpful!

RE: getting an interrupt when any of multiple GPIO pins change

Jørn — Mon, 06 Mar 2017 13:47:10 GMT

Hello David

The pin_change_int example uses high accuracy sensing to sense change in the pin. When using high accuracy you can detect high-speed changes in several pins simultaneously, but in nRF51822 there are only 4 GPIOTE channels which means you can only detect changes in up to 4 pins. It also requires the use of a high frequency clock which increases power consumption.

If low accuracy (Port event) is used you can detect changes in up to 32 pins, but you cannot detect high-speed changes as it uses a low frequency timer. In addition to this it can only detect change in one pin at a time. If changes in two pins happen simultaneously only one change will be sensed. A combination between high and low accuracy can be used by changing the value of

in_config.hi_accuracy

from true to false between gpiote_in_inits.

Remember to change the "GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS" in sdk_config.h to the correct number of events you need. If you try to create more low power events than is defined here you will get a NO_MEM error.

The following code is a modification of the pin_change_int example, and uses high accuracy for 4 inputs, and low accuracy for additional two inputs. GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS in sdk_config.h is here set to 2.

#ifdef BSP_BUTTON_0
    #define PIN_IN BSP_BUTTON_0
#endif
#ifdef BSP_BUTTON_1
    #define PIN_IN2 BSP_BUTTON_1
#endif
#ifdef BSP_BUTTON_2
    #define PIN_IN3 BSP_BUTTON_2
#endif
#ifdef BSP_BUTTON_3
    #define PIN_IN4 BSP_BUTTON_3
#endif

#define PIN_IN5 16 //pin P0.16
#define PIN_IN6 15 //pin P0.15

#ifndef PIN_IN
    #error "Please indicate input pin"
#endif

#ifdef BSP_LED_0
    #define PIN_OUT BSP_LED_0
#endif
#ifdef BSP_LED_1
    #define PIN_OUT2 BSP_LED_1
#endif
#ifdef BSP_LED_2
    #define PIN_OUT3 BSP_LED_2
#endif
#ifdef BSP_LED_3
    #define PIN_OUT4 BSP_LED_3
#endif
#ifndef PIN_OUT
    #error "Please indicate output pin"
#endif

void in_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
	switch(pin)
	{
		case PIN_IN:
			nrf_drv_gpiote_out_toggle(PIN_OUT);
			break;
		case PIN_IN2:
			nrf_drv_gpiote_out_toggle(PIN_OUT2);
			break;
		case PIN_IN3:
			nrf_drv_gpiote_out_toggle(PIN_OUT3);
			break;
		case PIN_IN4:
			nrf_drv_gpiote_out_toggle(PIN_OUT4);
			break;
		case PIN_IN5:
			nrf_drv_gpiote_out_toggle(PIN_OUT);
			nrf_drv_gpiote_out_toggle(PIN_OUT3);
			break;
		case PIN_IN6:
			nrf_drv_gpiote_out_toggle(PIN_OUT2);
			nrf_drv_gpiote_out_toggle(PIN_OUT4);
			break;
		default:

			break;
	}
}

/**
 * @brief Function for configuring: PIN_IN pin for input, PIN_OUT pin for output,
 * and configures GPIOTE to give an interrupt on pin change.
 */
static void gpio_init(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_gpiote_init();
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_out_config_t out_config = GPIOTE_CONFIG_OUT_SIMPLE(false);

    err_code = nrf_drv_gpiote_out_init(PIN_OUT, &out_config);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_out_init(PIN_OUT2, &out_config);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_out_init(PIN_OUT3, &out_config);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_out_init(PIN_OUT4, &out_config);
    APP_ERROR_CHECK(err_code);
		
		//configure pins for high accuracy
    nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_HITOLO(true); 
    in_config.pull = NRF_GPIO_PIN_PULLUP;
		
    err_code = nrf_drv_gpiote_in_init(PIN_IN, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_in_init(PIN_IN2, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_in_init(PIN_IN3, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_in_init(PIN_IN4, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);
		
	//Configure low accuracy for the remaining 2 pins
	in_config.hi_accuracy=false; 
		
    err_code = nrf_drv_gpiote_in_init(PIN_IN5, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_gpiote_in_init(PIN_IN6, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);

	//Enable pin events, interrupt is specifically enabled for high accuracy pins to function.
	//For low accuracy interrupt is always enabled.
    nrf_drv_gpiote_in_event_enable(PIN_IN, true);
    nrf_drv_gpiote_in_event_enable(PIN_IN2, true);
    nrf_drv_gpiote_in_event_enable(PIN_IN3, true);
    nrf_drv_gpiote_in_event_enable(PIN_IN4, true);
	nrf_drv_gpiote_in_event_enable(PIN_IN5, true);
	nrf_drv_gpiote_in_event_enable(PIN_IN6, true);
}



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

    while (true)
    {
        // Do nothing.
    }
}

Best regards

Jørn Frøysa