Setting Custom Gatt characteristic data.

[Thomas]

Hi,

I want to set a custom value to my Gatt characteristic value. I can do this by writing to the characteristic in my app or the NRF_connect application. 

What I want to do is based on an event or the data I receive to change the GATT characteristic data for my app to receive. I tried using this code which, did not change the data.

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//err_code = ble_cus_custom_value_update(p_cus, p_ble_evt,m_custom_value);

//APP_ERROR_CHECK(err_code);

//I pass in a fixed value for testing into m_custom_value

uint32_t ble_cus_custom_value_update(ble_cus_t * p_cus, ble_evt_t const * p_ble_evt, uint8_t custom_value)

{

NRF_LOG_INFO("In ble_cus_custom_value_update. \r\n");

if (p_cus == NULL)

{

return NRF_ERROR_NULL;

}

uint32_t err_code = NRF_SUCCESS;

ble_gatts_value_t gatts_value;

// Initialize value struct.

memset(&gatts_value, 0, sizeof(gatts_value));

gatts_value.len = sizeof(uint8_t);

gatts_value.offset = 0;

gatts_value.p_value = &custom_value;

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//err_code = ble_cus_custom_value_update(p_cus, p_ble_evt,m_custom_value);
//APP_ERROR_CHECK(err_code);
//I pass in a fixed value for testing into m_custom_value

uint32_t ble_cus_custom_value_update(ble_cus_t * p_cus, ble_evt_t const * p_ble_evt, uint8_t custom_value)
{
    NRF_LOG_INFO("In ble_cus_custom_value_update. \r\n"); 
    if (p_cus == NULL)
    {
        return NRF_ERROR_NULL;
    }

    uint32_t err_code = NRF_SUCCESS;
    ble_gatts_value_t gatts_value;

    // Initialize value struct.
    memset(&gatts_value, 0, sizeof(gatts_value));

    gatts_value.len     = sizeof(uint8_t);
    gatts_value.offset  = 0;
    gatts_value.p_value = &custom_value;

    // Update database.
    err_code = sd_ble_gatts_value_set(p_cus->conn_handle,
                                      p_cus->custom_value_handles.value_handle,
                                      &gatts_value);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    // Send value if connected and notifying.
    if ((p_cus->conn_handle != BLE_CONN_HANDLE_INVALID)) 
    {
        ble_gatts_hvx_params_t hvx_params;

        memset(&hvx_params, 0, sizeof(hvx_params));

        hvx_params.handle = p_cus->custom_value_handles.value_handle;
        hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;
        hvx_params.offset = gatts_value.offset;
        hvx_params.p_len  = &gatts_value.len;
        hvx_params.p_data = gatts_value.p_value;

        err_code = sd_ble_gatts_hvx(p_cus->conn_handle, &hvx_params);
    }
    else
    {
        err_code = NRF_ERROR_INVALID_STATE;
    }


    return err_code;
}

What I need to know is how to update this data value so I can transfer useful data between the two devices (mobile application and nordic board).

Note I am trying to do this within my GATT connection itself.

Note using SDK15 , PCA10056 NRF52840-dk Segger,

Thanks