Multiple Connection NUS(Nordic UART Service) Error (8 or 13313)

[Aser]

Hello
I'm now trying to implement the IOS Phones (Central) - Device (Peripheral) liver UART using Multiple Connection - Nordic Uart Service.
Devices tried to send a UART signal to the phone first, but it kept...
We could observe that 13313err_code or NRF_ERROR_INVALID_STATE Error occurred.
Looking at the log, it is confirmed that p_nus ->is_notification_enabled is false.

Can you tell me what caused this error?

Also, is the return value parameter p_nus->conn_handle in the ble_nus_string_send function specifying one of the Multiple Connection Devices?

uint32_t ble_nus_string_send(ble_nus_t * p_nus, uint8_t * p_string, uint16_t length)
{
    ble_gatts_hvx_params_t hvx_params;

    VERIFY_PARAM_NOT_NULL(p_nus);

    if ((p_nus->conn_handle == BLE_CONN_HANDLE_INVALID) || (!p_nus->is_notification_enabled))
    {
        return NRF_ERROR_INVALID_STATE;
    }

    if (length > BLE_NUS_MAX_DATA_LEN)
    {
        return NRF_ERROR_INVALID_PARAM;
    }

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

    hvx_params.handle = p_nus->tx_handles.value_handle;
    hvx_params.p_data = p_string;
    hvx_params.p_len  = &length;
    hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;

★    return sd_ble_gatts_hvx(p_nus->conn_handle, &hvx_params);
}

Thank you so much for reading my question and for your interest.

[awneil]

Aser said:

NRF_ERROR_INVALID_STATE Error occurred

So what state was it in ?

BLE_CONN_HANDLE_INVALID would suggest 'Not Connected'

[Aser]

No, it's definitely connected to the phone, and there's no disconnect log on the device.

When Disconnected, I set the log below to be uploaded, but it didn't.
Also, I couldn't see any signs of Disconnection on my phone.
It's definitely connected.

Disconnection Log : 

00> APP:INFO:Connection 0x0 has been disconnected. Reason: 0x13

[Aser]

What I'd like to do now is...
With multiple cell phones connected at the same time.
You need to get data from IOS using UART.
However, if multiple IOS receive reception at the same time, there is a phenomenon that data cannot be processed because it is not received properly.
So, we want to designate one IOS unit first to process the data request transmission and then receive and process the data of each IOS device sequentially.
However, we sent the data request from the device to IOS first, but we are facing difficulties in implementing it due to an error even though the connection is maintained.

[run_ar]

This was answered here: https://devzone.nordicsemi.com/f/nordic-q-a/76128/multiperipheral-ios-not-connection-issue