A switch instead of a button

[mc]

we use peripheral: exemple ble_app_blinky central: exemple_ble_app_bliky-c

Instead of a button we have a Switch. When we set the Switch to "on" the led go on. That's ok. But when we let the position of the Switch "on" and then reseat the bords, the led don't go on.

What do we have to change on the code?

Thank you very much for the help!

[Jørn]

Hello mc

The ble_app_blinky example uses the app_buttons module, which configures the pin for GPIOTE port events, see page 70 of the nRF51 series reference manual. Port events triggers on the rising edge of the GPIO DETECT signal, see page 56 of the reference manual. When the button is pressed a GPIOTE event is triggered, and it ends up at the app_buttons module. The app_buttons module compares the current pin state with the pins active state (in the example active state is set to 0). If the pin is high a 0 is transmitted, if the pin is low a 1 is transmitted. When you flip the switch and reset the boards there isn't a rising transition of the DETECT signal after the GPIOTE has been configured, and the port event is never triggered. To get the initial state of the led correct you would need to do a pin read on startup, and then transmit the initial state state.

==EDIT==

I made a quick fix. It's not optimal, but it will update the initial value of the button when the client enables notifications. I modified the ble_lbs.c file for the peripheral in the following way

I added

#include "boards.h" 

to the top of the file, I added the function

void init_state_update(ble_lbs_t * p_lbs)
{

            ret_code_t err_code;
            ble_gatts_hvx_params_t params;
            uint8_t button_state = 0;
            if(nrf_gpio_pin_read(BSP_BUTTON_0)==0)
            {
            button_state=1;
            }
            uint16_t len = sizeof(button_state);
        
            memset(&params, 0, sizeof(params));
            params.type = BLE_GATT_HVX_NOTIFICATION;
            params.handle = p_lbs->button_char_handles.value_handle;
            params.p_data = &button_state;
            params.p_len = &len;
            err_code = sd_ble_gatts_hvx(p_lbs->conn_handle, &params);
            nrf_gpio_pin_read(BSP_BOARD_LED_3);
            APP_ERROR_CHECK(err_code);

}

close to the top of the file, and I modified the on_write function

/**@brief Function for handling the Write event.
 *
 * @param[in] p_lbs      LED Button Service structure.
 * @param[in] p_ble_evt  Event received from the BLE stack.
 */
static void on_write(ble_lbs_t * p_lbs, ble_evt_t * p_ble_evt)
{
    ble_gatts_evt_write_t * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;

    if ((p_evt_write->handle == p_lbs->led_char_handles.value_handle) &&
        (p_evt_write->len == 1) &&
        (p_lbs->led_write_handler != NULL))
    {
        p_lbs->led_write_handler(p_lbs, p_evt_write->data[0]);
    }
		
    else if (p_evt_write->handle == p_lbs->button_char_handles.cccd_handle)
    {
        if(p_ble_evt->evt.gatts_evt.params.write.len==2)
        {
					init_state_update(p_lbs);
        }
    }    
}

This checks if the write is a cccd change, and sends a notification of the initial button value. DO NOTE the button value updated here is entered separately from the one defined in main.c, so if you change the pin you will need to change it both in main.c and in ble_lbs.c. You could move the pin defines to a common header file to avoid this.

Best regards

Jørn Frøysa

[Jørn]

I have updated my answer with some code.