conn failed to establish. RF noise?

[Hayden Ball]

We're seeing the following intermittently while attempting to connect from a Mac/iOS Central.

Using Android as a Central does not produce the same error.

[00:00:33.054,656] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:33.054,931] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:34.374,511] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:34.374,816] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:34.644,561] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:34.644,836] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:35.154,479] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:35.154,754] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:35.334,289] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:35.334,564] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:35.724,487] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:35.724,761] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:36.114,410] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:36.114,685] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:36.505,371] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:36.505,645] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:36.685,363] <wrn> bt_conn: conn 0x20003878 failed to establish. RF noise?
[00:00:36.685,638] <inf> bluetooth: Disconnected (reason 0x3e)

[00:00:37.282,043] <wrn> bt_l2cap: Ignoring data for unknown channel ID 0x003a
[00:00:38.182,312] <inf> bluetooth: Disconnected (reason 0x13)

Sometimes the connection eventually establishes, sometimes it doesn't.

Running the BT peripheral sample, the error does not occur.

Are you able to suggest any debugging steps, please, or suggestions as to why the behaviour might be different with the two centrals?

[Hayden Ball]

I think I've narrowed this down to being something to do with extended advertising, but I'm not 100% confident.

[Hayden Ball]

Okay, yes.

This can be easily reproduced using the extended_adv advertiser sample:

west build -b nrf21540dk/nrf52840 zephyr/samples/bluetooth/extended_adv/advertiser -DCONFIG_LOG=y -DCONFIG_SHELL=y
west flash

[00:01:11.272,644] <wrn> bt_conn: conn 0x20002920 failed to establish. RF noise?
Disconnected, reason 0x3E
Connection object available from previous conn. Disconnect is complete!
Remote disconnected early...
Disconnected state! Restarting advertising
Starting Extended Advertising
Connected (err 0x00)
Connected state!
Initiating disconnect within 5 seconds...
[00:01:11.452,545] <wrn> bt_conn: conn 0x20002920 failed to establish. RF noise?
Disconnected, reason 0x3E
Connection object available from previous conn. Disconnect is complete!
Remote disconnected early...
Disconnected state! Restarting advertising
Starting Extended Advertising
Connected (err 0x00)
Connected state!
Initiating disconnect within 5 seconds...
[00:01:11.961,669] <wrn> bt_conn: conn 0x20002920 failed to establish. RF noise?
Disconnected, reason 0x3E
Connection object available from previous conn. Disconnect is complete!
Remote disconnected early...
Disconnected state! Restarting advertising
Starting Extended Advertising
Connected (err 0x00)
Connected state!
Initiating disconnect within 5 seconds...
[00:01:12.442,321] <wrn> bt_conn: conn 0x20002920 failed to establish. RF noise?
Disconnected, reason 0x3E
Connection object available from previous conn. Disconnect is complete!
Remote disconnected early...
Disconnected state! Restarting advertising
Starting Extended Advertising
Connected (err 0x00)
Connected state!
Initiating disconnect within 5 seconds...

[Asbjørn]

Hello Hayden, 

the specifics related to extended advertising and iOS makes me want to ask you to check the iOS version you have initially. About a year ago, we saw customers having issues with a version of iOS 17 and extended advertising giving out similar error messages as you see and report. https://forums.developer.apple.com/forums/thread/743372

If it's not the iOS version you have, could you detail a bit which version you do have and which HW you have to try to recreate the issue here on my end.

Best regards

Asbjørn

[Hayden Ball]

This test was run under iOS 17.4.1 on iPhone 14, and also MacOS 15.3 on MacBook Pro M3 (16 Nov-2023).

I will re-run the test on iOS 18.3.

I am running the firmware sample on nRF21540-DK (PCA 10112).

[Hayden Ball]

I can confirm that I get the same result while running iOS 18.3 on iPhone 14.