Detect High to Low and Low to High EDGE using GPIO PORT Event

Question

Hi, 
 I am using the pin change interrupt example provided in the SDK examples. By setting the input sense to NRF_GPIOTE_POLARITY_LOTOHI, the interrupt handler is called and in that i again set the input sense to NRF_GPIOTE_POLARITY_HITOLO so that next time it senses the high to low edge. But it never senses HITOLO. I am not able to find the reason for why this is happening. 
 Here is a example of the code 
 nrf_drv_gpiote_init();
nrf_drv_gpiote_out_init = GPIOTE_CONFIG_OUT_SIMPLE(false);
nrf_drv_gpiote_in_config_t in_config;
in_config.sense = NRF_GPIOTE_POLARITY_LOTOHI;
nrf_drv_gpiote_in_init(PIN_IN, &in_config, gpiote_event_handler);
 
 Now in the event handler gpiote_event_handler
case GPIOTE_CONFIG_POLARITY_LoToHi gets called in which i perform LED toggling and set the 
 in_config.sense = NRF_GPIOTE_POLARITY_HITOLO
 
 Now the next time it should sense High to Low Edge but it never goes into the case GPIOTE_CONFIG_POLARITY_HiToLo 
 What could be the reason for this? I am using S110 and SDK10.

Øyvind Karlsen · Accepted Answer

Looking at the nrf_drv_gpiote_in_init() function we see that in order for the sense to be changed the driver has to operate in high accuracy mode.

ret_code_t nrf_drv_gpiote_in_init(nrf_drv_gpiote_pin_t pin,
                                  nrf_drv_gpiote_in_config_t const * p_config,
                                  nrf_drv_gpiote_evt_handler_t evt_handler)
{
    ASSERT(pin < NUMBER_OF_PINS);
    ret_code_t result = NRF_SUCCESS;
    /* Only one GPIOTE channel can be assigned to one physical pin. */
    if (pin_in_use_by_gpiote(pin))
    {
        result = NRF_ERROR_INVALID_STATE;
    }
    else
    {
        int8_t channel = channel_port_alloc(pin, evt_handler, p_config->hi_accuracy);
        if (channel != NO_CHANNELS)
        {
            if (p_config->is_watcher)
            {
                nrf_gpio_cfg_watcher(pin);
            }
            else
            {
                nrf_gpio_cfg_input(pin,p_config->pull);
            }

            if (p_config->hi_accuracy)
            {
                nrf_gpiote_event_configure(channel, pin,p_config->sense);
            }
            else
            {
                m_cb.port_handlers_pins[channel-NUMBER_OF_GPIO_TE] |= (p_config->sense)<< SENSE_FIELD_POS;
            }
        }
        else
        {
            result = NRF_ERROR_NO_MEM;
        }
    }
    return result;
}

Alternately you can just write to the register CONFIG[n] and set the polarity yourself, please refer to chapter 15 of the nRF 51 reference manual.

Best regards,

Øyvind

Detect High to Low and Low to High EDGE using GPIO PORT Event

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