Read GPIO pin status through a characteristic.

RE: Read GPIO pin status through a characteristic.

Priya — Mon, 19 Dec 2016 06:42:36 GMT

Thanks Jorgen, It worked for me :)

RE: Read GPIO pin status through a characteristic.

Jørgen Holmefjord — Fri, 16 Dec 2016 13:27:52 GMT

Yes, I forgot to mention the addition of the & sign, I have updated my initial answer to include this change.

RE: Read GPIO pin status through a characteristic.

Priya — Fri, 16 Dec 2016 13:21:29 GMT

Thanks Jorgen, let me try them and get back to you.

RE: Read GPIO pin status through a characteristic.

Jørgen Holmefjord — Fri, 16 Dec 2016 13:19:54 GMT

I have created examples for both GPIO/Timer and GPIOTE sense alternatives: gpio_char_example.zip, gpiote_sense_char_example.zip. Please have a look at these. They are both tested with PCA10028 (nRF51 DK) and PCA10040 (nRF52 DK) boards.

RE: Read GPIO pin status through a characteristic.

Priya — Fri, 16 Dec 2016 13:06:42 GMT

Yes, I have enabled the notifications through my app. But after that also I am getting a constant value 0x01. (I don't know, what does it mean.)

I have changed attr_char_value.p_value = value; to attr_char_value.p_value = &value; because with the previous one it was giving error of invalid conversion from uint8_t to uint8_t*.

RE: Read GPIO pin status through a characteristic.

Jørgen Holmefjord — Fri, 16 Dec 2016 12:56:33 GMT

You should also be able to do the update of the characteristics using GPIO sensing/GPIOTE. Comment out the content of the timer_timeot_handler() function, add the following GPIOTE handler function:

static void gpiote_event_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
    int32_t temperature = 0;
    temperature = nrf_drv_gpiote_in_is_set(INPUT_PIN);
	our_temperature_characteristic_update(&m_our_service, &temperature);
}

In main(), add the following:

nrf_drv_gpiote_init();
nrf_drv_gpiote_in_config_t config = GPIOTE_CONFIG_IN_SENSE_TOGGLE(true);
nrf_drv_gpiote_in_init(INPUT_PIN , &config, gpiote_event_handler);
nrf_drv_gpiote_in_event_enable(INPUT_PIN, true);

RE: Read GPIO pin status through a characteristic.

Jørgen Holmefjord — Fri, 16 Dec 2016 12:50:03 GMT

Yes, I have tested it. Have you remembered to enable notifications after connecting to the device?

RE: Read GPIO pin status through a characteristic.

Priya — Fri, 16 Dec 2016 11:15:38 GMT

Hi @jorgen, I am doing as accordingly you instructed me. but nothing changes. please help me what should i need to change? Have you tested..is this working?

RE: Read GPIO pin status through a characteristic.

Jørgen Holmefjord — Fri, 16 Dec 2016 10:04:07 GMT

If you followed the characteristics tutorial to the end, you should have a characteristics reporting temperature gathered from the IC at a regular interval. If you want to change the application to report state of a pin on this charactersistics instead, this is the changes you need to make:

Define the pin: #define INPUT_PIN 28
Configure pin as input in main(): nrf_gpio_cfg_input(INPUT_PIN , NRF_GPIO_PIN_NOPULL);
Change timer_timeout_handler() function to read pin state and pass this to the characteristic update function:

static void timer_timeout_handler(void * p_context)
{
   int32_t pin_state = 0;
   pin_state = nrf_gpio_pin_read(INPUT_PIN);
   our_temperature_characteristic_update(&m_our_service, &pin_state);
   nrf_gpio_pins_toggle(BSP_LED_2);
}

The characteristics should now be updated with the pin state on any change.

If you want the characteristics to be only 1 byte long, and also report the correct pin state on initialization, you also have to change the following:

In our_char_add(), change attr_char_value.max_len, attr_char_value.init_len, value and attr_char_value.p_value to:

attr_char_value.max_len  = 1;
attr_char_value.init_len = 1;
uint8_t value            = nrf_gpio_pin_read(INPUT_PIN);
attr_char_value.p_value  = &value;

In our_temperature_characteristic_update(), change len to 1.

Best regards,

Jørgen

RE: Read GPIO pin status through a characteristic.

Priya — Thu, 15 Dec 2016 14:05:21 GMT

Hi jorgen, my gpio pin is acting as an input. If I'm not wrong then it means it will update the value but i couldn't be able to read it through the characteristic? Please help me in finding the solution. If there are some examples available which can help me regarding this stuff please help me!

RE: Read GPIO pin status through a characteristic.

Jørgen Holmefjord — Thu, 15 Dec 2016 12:27:14 GMT

Should the pin be input or output? I'm not aware of any way you can read the GPIO state from the characteristics, but you can run a periodic timer that updates the characteristics value with the state of the pin at a given interval.