conn failed to establish. RF noise?

RE: conn failed to establish. RF noise?

Kenneth — Mon, 10 Mar 2025 10:17:48 GMT

Hello,

My simple understanding is that there is a slightly timing difference between the two, both are within specifications, but the timing of the zephyr stack will vary a bit more, and in this case it seems that indirectly help (though it can also occur with the zephyr stack when timing is the same).

Kenneth

RE: conn failed to establish. RF noise?

Hayden Ball — Fri, 07 Mar 2025 08:49:55 GMT

Hi Kenneth,

For my understanding and interest, are you able to share the difference between the Zephyr stack and Softdevice stack during the connection flow, and suggest why the interaction with iOS might be different between the two?

RE: conn failed to establish. RF noise?

Kenneth — Wed, 05 Mar 2025 15:01:13 GMT

Hi,

After discussing internally I have learned this is unfortunately an issue in iOS, and we need for them to fix this.

Kenneth

RE: conn failed to establish. RF noise?

Kenneth — Tue, 04 Mar 2025 18:15:48 GMT

Hello,

I will need to take a second look at this. Thanks for sharing.

Edit: Likely will not be able to do a second sniffer trace until next week for comparison.

Kenneth

RE: conn failed to establish. RF noise?

Hayden Ball — Tue, 04 Mar 2025 17:09:33 GMT

Thank you Kenneth.

I have noticed that if I switch to using `CONFIG_BT_LL_SW_SPLIT`, the connection is established correctly.

Can you confirm you also see this behaviour?

RE: conn failed to establish. RF noise?

Kenneth — Tue, 04 Mar 2025 16:57:26 GMT

Hi,

I can confirm I see the same here, looking at the Apple Accessory Design Guidelines:
https://developer.apple.com/accessories/Accessory-Design-Guidelines.pdf

I get the impression that the extended advertisement is not mentioned in specific under 52.3 Advertising PDU, so it may be that this is work in progress at the moment.

What I can see from the sniffer log is that the phone do send the AUX_CONNECT_REQ packet, but do not follow up with any actual connection packets:
E.g. failing to establish:

E.g. working:

Kenneth

RE: conn failed to establish. RF noise?

Hayden Ball — Thu, 27 Feb 2025 16:42:43 GMT

Thank you for looking into this Kenneth

RE: conn failed to establish. RF noise?

Kenneth — Thu, 27 Feb 2025 13:48:22 GMT

Looks like I need to make a on-air sniffer trace of this issue, to see if I can narrow down what is the problem. I may not be able to do that before next week.

Kenneth

RE: conn failed to establish. RF noise?

Hayden Ball — Mon, 24 Feb 2025 15:35:54 GMT

Yes. You can reproduce this using the nRF21540-DK (PCA 10112), using the sample listed on my second post:

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

RE: conn failed to establish. RF noise?

Kenneth — Mon, 24 Feb 2025 14:03:33 GMT

We will take a look, do you by any chance have some simplified project we can run here to recreate the issue on a DK?

Kenneth

RE: conn failed to establish. RF noise?

Hayden Ball — Fri, 21 Feb 2025 09:25:58 GMT

Hello Kenneth,

Sorry for the delay.

Turning off WiFi does not help.

Please find attached a pcap captured with mini-moreph, along with a trace from the iPhone's sysdiagnose feature (the latter zipped as your forums wouldn't accept the pklg file).

I started the connection attempt slightly after 09:17 UTC.

The relevant MAC addresses appear to be 72:23:05:93:B3:C1 and C2:F1:36:E3:54:88.

devzone.nordicsemi.com/.../minimoreph.pcapng

devzone.nordicsemi.com/.../sysdiagnose.pklg.zip

RE: conn failed to establish. RF noise?

Kenneth — Tue, 18 Feb 2025 12:04:27 GMT

Hello,

Asbjørn is out of office today, do you have some on air sniffer logs (e.g. using nRF Sniffer for BLE) for the different setups you have tested here, so we can look at the wireshark files (.pcapng) to potentially look at the differences?

Does turning off WiFi on the iOS change anything?

Kenneth

RE: conn failed to establish. RF noise?

Hayden Ball — Thu, 13 Feb 2025 11:25:34 GMT

Thanks Asbjørn.

I'd need a bit more guidance to check this, I'm afraid.

It's an off-the-shelf nRF21540-DK (PCA 10112, Power Source set to VDD, SW6 set to Default), and an unmodified sample from nRF Connect SDK @ v2.9.0 (from my earlier post).

RE: conn failed to establish. RF noise?

Asbjørn — Thu, 13 Feb 2025 09:19:53 GMT

Thank you Hayden for the follow up, I've been talking to developers here and the assumption was that it was the iOS version, but it seems we have also met similar cases when there's been issues with the timing related to clock selections, it's just unuasual that you don't get the same failure when connecting with Android, but there's a chance that android devices have a larger timing window that enables this to work.

Anyways, may I ask you to check you clock sources.

Q1: Are you using INTCAP setting on the 32MHz crystal and what is it set to compared to your crystal Cl value?

Q2: LFCLK source, same INTCAP question if you are using 32kHz crystal. If you are using LFRC as source, what settings are you using for that? If you set LFCLK source to be LFSYNT as a trial, do you still see the same issue? LFSYNT will use the 32MHz to generate the 32kHz, but will more accuracy at the cost of higher current consumption, but it''s useful as a clock source test.

Best regards

Asbjørn

RE: conn failed to establish. RF noise?

Asbjørn — Thu, 13 Feb 2025 09:19:34 GMT

Anyways, may I ask you to check you clock sources.

Q1: Are you using INTCAP setting on the 32MHz crystal and what is it set to compared to your crystal Cl value?

Best regards

Asbjørn

RE: conn failed to establish. RF noise?

Hayden Ball — Mon, 10 Feb 2025 15:14:12 GMT

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

RE: conn failed to establish. RF noise?

Hayden Ball — Mon, 10 Feb 2025 14:51:27 GMT

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).

RE: conn failed to establish. RF noise?

Asbjørn — Mon, 10 Feb 2025 14:37:05 GMT

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

RE: conn failed to establish. RF noise?

Hayden Ball — Fri, 07 Feb 2025 16:42:45 GMT

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...

RE: conn failed to establish. RF noise?

Hayden Ball — Fri, 07 Feb 2025 11:42:40 GMT

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