RF Noise during connection to NRF54L15 from windows?

[Dairlab]

Dear All,

In our company, we have replaced the NRF52811 (ublox module) with NRF54L15 (raytac module) for new batches of products.

The fw is a simple BLE to UART bridge with Zephyr.

We noticed something curious: when connecting to it, we often (I would say on average 3 times out of 10) receive the error "bt_conn: con 0x20001330 failed to establish. RF noise?"

We had thought it could be a problem related to the fw, but:

- trying to connect from mobile, either IOS or Android, it never happens

- trying from Mac, it never happens

but from different windows systems (10 and 11) the problem is reproducible, quite easily (Using a simple connection with LE Explorer or Web Bluetooth from Chrome).

In order to try excluding a problem specific to our fw, we used the sample peripheral_hr available in zephyr and we observed the same behaviour as described above.

In order to avoid a problem specific to our board, we used our fw on the NRF54L15DK eval board with the same symptoms.

Has anyone faced such issues?

Best,

Dairlab

[Simonr]

Hmm, okay. And this behavior is seen with both the LE explorer and Web Bluetooth apps, correct? Can you try setting up a phone with the nRF Connect app as advertiser/peripheral and see if you see the same kind of connection issues with other peripherals connecting to the Windows PC as well? Potentially if you have I.E. an nRF52 or 53 series DK to test with as well.

Also, can you share what application you've flashed onto the nRF54L15 DK when you're able to reproduce this. Are you using either of the Bluetooth samples in NCS or a custom application?

Best regards,

Simon

[Dairlab]

Dear Simonr, thank you for the reply.

Some details:

1) we tried on NRF52811, Ublox BMD 360 Evaluation board and we don't have any issues (20/20 successful connection from both mobile and windows pc)

2) we tried on NRF54L15DK evaluation board, and we have random RF noise problems, 6 times in 20 connections attempts from two windows PC, 0/20 issues from mobile.

Regarding the fw, we are using a custom one (which we are happy to share privately) but also using NCS sample "peripheral_hr" the behaviour is the same.

Thank you in advance.

[Susheel Nuguru]

Just pitching in with my 2 cents here.

Dairlab said:

1) we tried on NRF52811, Ublox BMD 360 Evaluation board and we don't have any issues (20/20 successful connection from both mobile and windows pc)

Are you compiling other SoCs with the same project settings just changing the board files or are you compiling them completely under different SDKs and setups? If you are compiling all these with different SDKs then you are not comparing apples to apples. 

The configuration with nRF54L might be different like using different connection parameters, different PHY and probably even using extended adv etc where the other two which are working might not be using.

I would sniff air packets for working and not working setup and try to figure out what is different between the two. I would also suggest you to use some conservative (slow) advertising and connection parameters on nRF54L for tests.

CONFIG_BT_CTLR_PHY_2M=n
CONFIG_BT_CTLR_PHY_CODED=n
CONFIG_BT_CTLR_PHY_LE_1M=y
CONFIG_BT_EXT_ADV=n

But the above are just some examples, more should be revealed when you compare the air packets sniffs.

[Dairlab]

We are using the exact same code, using main branch of zephyr, only changing the board files. 
regarding sniffing the packets, unfortunately we have never done that. If you could kindly point us to some references on how to do it, we will be happy to share the results.