52833 Issue when actively connecting to Bluetooth devices appears rf noise

[llly]

I am adding a feature to our device to actively connect to a Bluetooth printer and send data to it, but I am now encountering an issue that I cannot solve.

I currently have three Bluetooth printers, which I refer to as a, b, and c. a and b are the same model, while c is from a different brand. When connecting these printers using our developed 52833 device, connecting a is very stable, almost without any RF noise issues. Connecting b has lower stability and occurs more frequently with this problem. However, connecting c has never succeeded; as soon as the connection starts, it gets disconnected immediately. The disconnection reason is 0x3e, which is BLE_HCI_CONN_FAILED_TO_BE_ESTABLISHED

These three printers should all be working properly. I connect them with my phone, and there won't be any issues; they can all be used normally

So how should this problem be solved?

[Amanda Hsieh]

Hi, 

The disconnection reason 0x3E (BLE_HCI_CONN_FAILED_TO_BE_ESTABLISHED) is the HCI “Connection Failed to be Established” error. It means the link was started but never completed successfully, so the controller reports a failed connection instead of a normal disconnect. It just tells you that the connection setup did not complete (often due to RF issues, timing/parameter problems, or peer-side rejection), and you need to inspect the detailed HCI/BT logs around the connection attempt to see what went wrong.

I would suggest you enable full Bluetooth debug logging, such as CONFIG_BT_DEBUG_LOG=y (and, if available, CONFIG_BT_HCI_CORE_DEBUG, CONFIG_BT_CONN_DEBUG, CONFIG_BT_L2CAP_DEBUG, CONFIG_BT_ATT_DEBUG). Capture logs from the moment you start scanning/connecting until the 0x3e disconnect. You can also use nRF Sniffer for Bluetooth LE to capture logs to compare their behaviors in the air. 

Regards,
Amanda H.

[llly]

I also captured some data packets using 52840dk and Wireshark. 66:23:d3:ea:8d:a9 is a Bluetooth printer, and f2:0f:1c:de:00:0d is a device with a 54l10 chip. My operation is to have the 54l10 chip connect to this Bluetooth printer. Is this log helpful for analyzing the issue?

0x3e.pcapng