5340, Zephyr failure to connect to Polar Heart rate strap; ble wireshark trace

[OwainIncus]

Hi ,

I have compiled in Heart rat relay into my app; can scan and connect to simulator and garmin HR straps; but fail to connect to polar.
My debug log shows...

So security is encryption, no auth and I get an "unspecified" error.

I have done a BLE wireshark trace; but cannot see anything in the trace to indicate the issue.

Would be grateful if someon could look and give me a clue to whats going wrong.

Here is wireshark trace....

polarHrmActiveScanConnectFail.pcapng

Regards,

Owain

[Hung Bui]

Hi Owain, 

Have you tried to test using the central_uart example to connect to the Polar ? 

Do you use CONFIG_BT_SMP_SC_ONLY in your project configuration ? 
This will force the pairing to only Secure Connection. It doesn't seem the Polar band support Secure Connection. 

There is some discussion here with the same error BT_SECURITY_ERR_UNSPECIFIED and related to nRF53 and legacy pairing: 

https://github.com/zephyrproject-rtos/zephyr/issues/37228

Could you try CONFIG_BT_TINYCRYPT_ECC=y to see if it work. Note that you may need to rebuild and reflash hci_rmsg

I would suggest to double check using nRF52 which doesn't seems to have this error. 

[OwainIncus]

Config for the App does not have CONFIG_BT_SMP_SC_ONLY set; and has CONFIG_BT_TINYCRYPT_ECC set.
I will attach the .config. Can you anything wrong in the BLE trace or does all look good?

The 37228 issue sounds pretty much like what I am getting....

0042.config.txt

[OwainIncus]

simplePolarNotL2Secure.pcap.pcapngI Can try that, but this Polar H10 heartstrap works if I do not request the security change to L2.

This Polar Hear Strap the H10 is one of the most widely used heart monitors in the world. This and the Garmin are the devices used by 99% of athletes using a monitor.

As I think I have said I have tinkered with the peripheral uart example to change uuid etc; and I have tried with a standard 5340 dk (non-secure).

I get the same behaviour.

Here a trace without the switch to L2; and we do see the update for the PHY update in this trace. And they do agree to use 2M phy.

[Hung Bui]

Hi Owain, 

Could you let us know the result if 2Mbps was not requested ? 
There could be a chance that it still support 2Mbps but the PHY request came at the wrong time and it trigger a corner case causing the problem. 

And please provide us the trace when you use central uart to connect to the HR. I would assume PHY request was not sent (?). 

As far as I know the Polar H10 may actually use Nordic's Softdevice on it and we did have an issue earlier with these old Softdevices that they doesn't support PHY request change. 

[OwainIncus]

Hi Hung,

the SimplePolarNotL2Secure.pcap.pcapng added above was the standard 5340 dk without the request to switch to L2 security. The Phy negotiation takes place and gets negotiated to 2M.

Where can I disable the PHY negotation to get a trace with L2 requested and restricted to 1M phy?

Regards,
Owain

[Hung Bui]

Hi Owain, 

I would need to see how you implemented it in your code. 

But you can try setting 

CONFIG_BT_CTLR_PHY_2M=n in the controller (on the nRF53 you need to add it to the hci_rpmsg). 

I would assume you don't call bt_conn_le_phy_update() in your application ? 

[OwainIncus]

You may have cracked it...

CONFIG_BT_AUTO_PHY_UPDATE=n

Here trace for simple project. I am now going to try in our standard company prodject.

SimplePolarL2NoPhyNeg.pcap.pcapng

[Hung Bui]

Hi again Owain, 

Thanks for the update. Now we can narrow the issue down. 
I would suggest to set

CONFIG_BT_AUTO_PHY_UPDATE=n

CONFIG_BT_USER_PHY_UPDATE=y

Then you can control when you want to request 2Mbps (if you plan to use it) in your application by calling bt_conn_le_phy_update() to switch PHY. 
I would suggest to call the function after the link is encrypted.

This way we can avoid the corner case where the PHY request is not responded before the encryption request. 

[OwainIncus]

Hi Hung,

I can now confirm this was the issue. In this case with Security L2 and the PHY negotiation the Polar H10 did not work. Turning off our central starting the PHY negotiation worked.

Turning off L2 and leaving PHY neotiation on worked also.

This does look as if it is an isssue of the Polar H10; which I believe is there latest version. SW 5.0.0, FW 3.1.1 as reported in device information service.

Many thanks for all your support. Without your help and knowledge we would not have been able to work our way around this Polar device bug.

Kind Regards,
Owain