How to add an additional characteristic to the NUS service

Question

I tried to add an additional characteristic to NUS service as below. 
 However, any mobile apps could find only existing Nordic Rx and Nordic Tx characteristics, other than the new characteristics. 
 Based on the several experiment, only two characteristics under NUS service should be allowed. 
 Can you please let me know how to add the new one under NUS service? 
 FYI, there is no error though. 
 uint32_t ble_nus_init(ble_nus_t * p_nus, const ble_nus_init_t * p_nus_init)
{
 uint32_t err_code;
 ble_uuid_t ble_uuid;
 ble_uuid128_t nus_base_uuid = NUS_BASE_UUID;

 VERIFY_PARAM_NOT_NULL(p_nus);
 VERIFY_PARAM_NOT_NULL(p_nus_init);

 // Initialize the service structure.
 p_nus->conn_handle = BLE_CONN_HANDLE_INVALID;
 p_nus->data_handler = p_nus_init->data_handler;
 p_nus->is_notification_enabled = false;

 
 // Add a custom base UUID.
 err_code = sd_ble_uuid_vs_add(&nus_base_uuid, &p_nus->uuid_type);
 VERIFY_SUCCESS(err_code);

 ble_uuid.type = p_nus->uuid_type;
 ble_uuid.uuid = BLE_UUID_NUS_SERVICE;

 // Add the service.
 err_code = sd_ble_gatts_service_add(BLE_GATTS_SRVC_TYPE_PRIMARY,
 &ble_uuid,
 &p_nus->service_handle);
 
 VERIFY_SUCCESS(err_code);
 
 // Add the RX Characteristic.
 err_code = rx_char_add(p_nus, p_nus_init);
 VERIFY_SUCCESS(err_code);

 // Add the TX Characteristic.
 err_code = tx_char_add(p_nus, p_nus_init);
 VERIFY_SUCCESS(err_code);
 
	// Add A new Characteristic.
	err_code = a_new_char_add(p_nus, p_nus_init);
	VERIFY_SUCCESS(err_code);


 return NRF_SUCCESS;
} 
 
 static uint32_t a_new_char_add(ble_nus_t * p_nus, const ble_nus_init_t * p_nus_init)
{
 uint32_t err_code = 0; // Variable to hold return codes from library and softdevice functions
 
 ble_gatts_char_md_t char_md;
 ble_gatts_attr_md_t cccd_md;
 ble_gatts_attr_t attr_char_value;
 ble_uuid_t char_uuid;
 ble_gatts_attr_md_t attr_md;
 
 memset(&cccd_md, 0, sizeof(cccd_md));
 BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);
 BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.write_perm);
 cccd_md.vloc = BLE_GATTS_VLOC_STACK;
	
 memset(&char_md, 0, sizeof(char_md));
 
 char_md.char_props.read = 1; 
 char_md.char_props.write = 1;
 char_md.p_cccd_md = &cccd_md;
 char_md.char_props.notify = 1;
 char_uuid.type = p_nus->uuid_type;
 char_uuid.uuid = BLE_UUID_ASI_CHARACTERISTC_UUID;
 
 memset(&attr_md, 0, sizeof(attr_md));
	
 BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);
 BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);
	
 attr_md.vloc = BLE_GATTS_VLOC_STACK;
 attr_md.rd_auth = 0;
 attr_md.wr_auth = 0;
 attr_md.vlen = 1;

 memset(&attr_char_value, 0, sizeof(attr_char_value));
 attr_char_value.p_uuid = &char_uuid;
 attr_char_value.p_attr_md = &attr_md;
 attr_char_value.max_len = 128;
 attr_char_value.init_len = 128;
 uint8_t value[128] = {0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
 0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0};
 attr_char_value.p_value = value;

 // ASI_JOB: Step 2.E, Add a new characteristic to the service
 err_code = sd_ble_gatts_characteristic_add(p_nus->service_handle,
 &char_md,
 &attr_char_value,
 &p_nus->char_handles);
 APP_ERROR_CHECK(err_code);
 
 printf("
Service handle: %#x
", p_nus->service_handle);
 printf("Char value handle: %#x
", p_nus->char_handles.value_handle);
 printf("Char cccd handle: %#x

", p_nus->char_handles.cccd_handle);

 return NRF_SUCCESS;
}

Vidar Berg · Accepted Answer

Have you tested this, I think it should work, but still think that sd_ble_gatts_value_get() is redundant since you can retrieve the same data from the p_ble_evt->evt.gatts_evt.params.write.data pointer. Please try code below if it doesn't work: 
 static void on_write(ble_nus_t * p_nus, 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_nus->rx_handles.cccd_handle)
 &&
 (p_evt_write->len == 2)
 )
 {
 if (ble_srv_is_notification_enabled(p_evt_write->data))
 {
 p_nus->is_notification_enabled = true;
 }
 else
 {
 p_nus->is_notification_enabled = false;
 }
 }
 else if 
 (
 (p_evt_write->handle == p_nus->char_handles1.cccd_handle)
 &&
 p_evt_write->len == 2)
 )
 
 if (ble_srv_is_notification_enabled(p_evt_write->data))
 {
 printf("Notification enabled
");
 }
 else
 {
 printf("Notification disabled
");
 }
	
 else if (
 (p_evt_write->handle == p_nus->tx_handles.value_handle)
 &&
 (p_nus->data_handler != NULL)
 )
 {
 p_nus->data_handler(p_nus, p_evt_write->data, p_evt_write->len);
 }
	else if ( (p_evt_write->handle == p_nus->char_handles1.value_handle) && (p_evt_write->len == 4))
	{
 uint32_t data_buffer0;
 
 memcpy(&data_buffer0, p_evt_write->data, sizeof(uint32_t));
 p_nus->gpio_output_write_handler(p_nus, data_buffer0)
 
	)	
}

How to add an additional characteristic to the NUS service

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