iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

Benjamin — Mon, 29 Sep 2025 08:00:17 GMT

Hi Hinnerk,
Thanks you for the new details.

For the trace, you need to filter for the connection. The sniffer capture the connection request to learn the parameters to hop in sync with the devices. Please see the exercise for a step-by-step guide on how to do it. We will need this trace to help you with your problem.

Regards,
Benjamin

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

HinnaX — Thu, 25 Sep 2025 11:08:01 GMT

Hey Benjamin,
thanks again for your reply. So the trace was filtered for the nrf52840 device with mac address d0:bf:29:46:08:ed
The iPhone I not sure, because it used a random address.
So RSSI with a iPhone or Google Pixel 6 tested are that

range 1-3 meters = RSSI -30 up to -50
range 3-6 meters = RSSI -50 up to -75
range 6-15 meters = RSSI -75 up to -90
> 15 meters are disconnect

TX power is set to max with

CONFIG_BT_CTLR_TX_PWR_ANTENNA=127

I'm also try out this config

CONFIG_BT_LL_SW_SPLIT=y
CONFIG_BT_CTLR_ADVANCED_FEATURES=y
CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y
CONFIG_BT_CTLR_TX_PWR_PLUS_8=y

and set the TX power for the connection event handler to +8dBm

    uint16_t conn_handle;
    bt_hci_get_conn_handle(conn, &conn_handle);
    set_tx_power(BT_HCI_VS_LL_HANDLE_TYPE_CONN,
                 conn_handle,
                 8);

static void set_tx_power(uint8_t handle_type, uint16_t handle, int8_t tx_pwr_lvl)
{
    struct bt_hci_cp_vs_write_tx_power_level *cp;
    struct bt_hci_rp_vs_write_tx_power_level *rp;
    struct net_buf *buf, *rsp = NULL;
    int err;

    buf = bt_hci_cmd_create(BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL,
                            sizeof(*cp));
    if (!buf)
    {
        printk("Unable to allocate command buffer\n");
        return;
    }

    cp = net_buf_add(buf, sizeof(*cp));
    cp->handle = sys_cpu_to_le16(handle);
    cp->handle_type = handle_type;
    cp->tx_power_level = tx_pwr_lvl;

    err = bt_hci_cmd_send_sync(BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL,
                               buf, &rsp);
    if (err)
    {
        uint8_t reason = rsp ? ((struct bt_hci_rp_vs_write_tx_power_level *)
                                    rsp->data)
                                   ->status
                             : 0;
        LOG_WRN("Set Tx power err: %d reason 0x%02x\n", err, reason);
        return;
    }

    rp = (void *)rsp->data;
    LOG_INF("Actual Tx Power: %d\n", rp->selected_tx_power);

    net_buf_unref(rsp);
}

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

Benjamin — Thu, 25 Sep 2025 10:32:24 GMT

Hi Hinnerk,

We cannot see the connection in the trace. Please filter for the connection. You can refer to this lesson lesson for guidance

What RSSI do you observe with other devices (two DKs, another phone)?
What is the TX Power?

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

HinnaX — Wed, 24 Sep 2025 09:01:25 GMT

Hey Benjamin,
thanks again for your reply. We testet it again and it happens sometimes that the connection will be lost.
We test it now with iOS 26, so the iOS Update doesnt change anything.
I've createad a sniffer trace.

devzone.nordicsemi.com/.../iOS_5F00_26_5F00_connection_5F00_lost_5F00_nrf52840.pcapng

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

Benjamin — Thu, 18 Sep 2025 10:35:32 GMT

Hi,
Why would you not be able to do a trace? You can easily do it with a DK. nRF-Sniffer-for-Bluetooth-LE
Also, do you experience the same issue with iOS 26?

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

HinnaX — Mon, 15 Sep 2025 12:47:07 GMT

Hey Benjamin,
thanks for your reply. Yes it happens on multiple iOS devices with these iOS version.
Unfortunately I can't provide a sniffer trace.
I see that the rssi value is very bad. After 3-5 meters these value is -85dBm to -90 dBm.
Now I try to increment the TX Power. This improves the rssi value to -75dBm.
Are there any option to improve the connection.

RE: iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

Benjamin — Mon, 15 Sep 2025 10:20:09 GMT

Hi Hinnerk,
Does the issue happen on multiple iOS devices and only 18.6.2?
Could you provide a sniffer trace?

Best regards,
Benjamin