nRF54L15-DK used with BlueZ, connecting to other peripheral BLE devices, automatic disconnection after connection

[Tinao]

After using the official example hci_uart with the nRF54L15-DK, it is configured as an HCI controller. I used bluetoothctl commands like scan on and connect to scan for peripheral devices (dual-mode Bluetooth headphones and a BLE debug assistant in peripheral mode) and establish connections. Using info + MAC address, I could see the connect status displayed as yes, indicating a successful connection. However, the connection would disconnect after about a minute. Below is the event capture from btmon. I've tried various approaches, but this issue persists. I'm hoping you can suggest solutions. However, when I use nRF Connect for mobile as the host device to connect to the nRF54L15-DK, the connection remains stable. Why is that?

[JONATHAN LL]

However, when I use nRF Connect for mobile as the host device to connect to the nRF54L15-DK, the connection remains stable. Why is that?

Do you have to option to test on another device? Could be that the computers BLE and the DK maybe has some issues. So if you can test on another computer or with another external BLE device on the computer to see if issue presist? 

What version of NCS are you using?

Have you tested another sample also, to see if it also has the same issue? 

Regards,
Jonathan

[Tinao]

Thank you very much for your response. I've also tried other approaches. When I use another nRF54L15-DK as the BLE peripheral, it maintains a stable connection. I suspect the initial unstable connection might have occurred because the tool didn't exchange data after establishing the connection, causing it to be deemed useless and subsequently disconnected. I'm using NCS version 3.1.1. However, I'd like to consult you on another issue: if I want to change the PHY channel during the connection process—such as switching between PHY Coded S2 or S8—I've found that attempting to negotiate this change via HCI commands doesn't always succeed. I suspect this is due to RSSI. I plan to attach an external attenuator via the SMA port to adjust the RSSI value and improve the success rate of changing PHY Coded S2/S8. Do I need to modify the board hardware before attaching the attenuator externally, or can I connect it directly to the SMA structure?

[JONATHAN LL]

Tinao said:

Do I need to modify the board hardware before attaching the attenuator externally, or can I connect it directly to the SMA structure?

You dont need to do any other modifications to the Kit, if you have something that can connect directly to the SWF connector then that is fine. 

We use one of these SWF connectors MM8130-2600RA2, so if you find a connector\adapter for that then that is fine. 

Regards,
Jonathan

[Tinao]

Right, thank you for your response.

[JONATHAN LL]

Happy to help!