nRF5340 disconnection event is not triggered during OTA

RE: nRF5340 disconnection event is not triggered during OTA

Amanda Hsieh — Thu, 17 Sep 2026 18:45:00 GMT

What mobile application are you using? Could you try the nRF Device app? Do you get the same issue with the nRF Device app?

RE: nRF5340 disconnection event is not triggered during OTA

AKV — Thu, 17 Sep 2026 04:43:27 GMT

We need to update both the Net Core and App Core. The issue occurs both when the Net Core is updated and when it is not updated.

In the attached log, we are updating the same firmware again, which is why it shows the Net Core update as failed. However, the Net Core failure is reported in the application logs and is triggered by the disconnection that occurred before it.

As per the HCI logs, the device did not respond to the phone for nearly 500 ms. Essentially, the radio was inactive for an extended period. Since the supervision timeout is 420 ms, an RF response gap of around 500 ms would trigger a disconnection event on the master side.

So, please investigate why the radio remained inactive for approximately 500 ms and identify the root cause of this radio inactivity/disconnection.

RE: nRF5340 disconnection event is not triggered during OTA

Amanda Hsieh — Wed, 16 Sep 2026 13:08:44 GMT

Do you really need to update the net code?

In your log:

If unchanged, do not upload image index 1 at all.

This avoids the failure mode entirely for the common “app-only update” case, with no firmware change and no Pixel-specific hack.

RE: nRF5340 disconnection event is not triggered during OTA

AKV — Wed, 16 Sep 2026 04:05:40 GMT

Hi,

We are using NCS 2.6.1 with CONFIG_BT_HCI_ACL_FLOW_CONTROL=n. The issue occurs only with Pixel phones and is not reproducible with other phones.

These are the current Bluetooth buffer configuration settings:
- CONFIG_BT_BUF_ACL_TX_COUNT=30
- CONFIG_BT_BUF_ACL_RX_COUNT=6
- CONFIG_BT_CTLR_SDC_TX_PACKET_COUNT=21
- CONFIG_BT_BUF_CMD_TX_COUNT=10

Since the product is already in the market and we cannot make changes to the firmware/code, is there any workaround that can be implemented from the application side to address this issue?

RE: nRF5340 disconnection event is not triggered during OTA

Amanda Hsieh — Tue, 15 Sep 2026 15:47:04 GMT

Hi,

What NCS version are you using? Could you try the latest version, v3.4.0?

There is a known issue: NCSDK-32999

If you are using the affected version, please apply the workaround in your project. See my colleague's example in this post.

Regards,
Amanda H.