DevAcademy Bluetooth LE connection problems

RE: DevAcademy Bluetooth LE connection problems

EdSwarthout — Thu, 21 Nov 2024 01:58:46 GMT

Just to add another data point, on a Samsung Note20,I was seeing the immediate disconnect too:

[00:01:36.259,674] <inf> Lesson3_Exercise1: Connected
[00:01:36.637,481] <inf> Lesson3_Exercise1: Disconnected. Reason 42

On a 2nd phone (Samsung S24 Ultra), it did stay connected once, but then stopped.

I rebooted both phones and now all is working fine.

RE: DevAcademy Bluetooth LE connection problems

Jas39 — Sun, 14 Jan 2024 23:15:57 GMT

This might be worth mentioning in the excersice FAQ as the Samsung S21 is a rather common device.

Any knowledge if this is resolved in later bt-stacks from Samsung?

RE: DevAcademy Bluetooth LE connection problems

Jas39 — Sun, 14 Jan 2024 23:14:03 GMT

I have also stumbled into this issue with a Samsung 21. Works fine with a Sony Experia.

I have tried Lars approach of setting:

CONFIG_BT_PHY_UPDATE=n

But to no avail. I got the same behaviour on the Samsung regardless.

But alas, removing the bond and restarting the phone makes it work!

Hopefully this can save someone else some time...

RE: DevAcademy Bluetooth LE connection problems

Lars M — Sun, 16 Jul 2023 20:45:32 GMT

Thanks a lot Einar for your help! This makes sense.

I try to find the name of the chipset, but I'm not sure if I'm successful. Do you know if it is BCM4389? It seems to be for the Ultra-version of S21, but maybe it's also for the one just named S21 (SM-G991B/DS).

/Lars

RE: DevAcademy Bluetooth LE connection problems

Einarh — Fri, 14 Jul 2023 09:53:18 GMT

The way it doesn't follow the standard has to do with the timing and sequencing of these update procedures.

In this specific case, LL_CONNECTION_UPDATE_IND is a procedure that takes several BLE events to complete, but when the phone receives the LL_PHY_REQ from the peripheral it responds to this immediately instead of waiting for LL_CONNECTION_UPDATE_IND to complete first. That's where it violates the specification.

The phones that are affected are the ones with the same Broadcom Bluetooth controller chipset as your Samsung phone. Possibly devices other than Samsung with the same chipset also.

This firmware bug has actually been fixed by Broadcom, but Samsung has yet to push this fix to their phones.

-Einar

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 12 Jul 2023 19:35:59 GMT

In what way does Samsung not follow the standard? It seems it is LL_CONNECTION_UPDATE_IND with 7.5 ms that is the problem. But the information about CONFIG_BT_PERIPHERAL_PREF_MIN_INT says that the connection interval can be 7.5 ms. So why does it not work?

I'm wondering what could be expected if I develop a device that will be used by a lot of customers. Then for sure some will get connection problem. It would not be pleasant if a customer buys a device and his/her phone can't connect. If this is a known issue for some phones this must have happened a lot of times before. Do you know how that is handled? It feels that the safest way to go is to set CONFIG_BT_PHY_UPDATE=n. But then 2M can't be used. Or are there other ways?

Will a problematic phone model always behave the same way? I mean, if I test another Samsung S21 with an unchanged exercise, will it also fail to connect?

It might be interesting to know what exact models that have problem. But it would be more interesting to know the proportion between problematic phones and those that work. I guess it's hard to say an exact ratio, but how many phones are known to have connection problems?

Are there any tablets that also show connection problems?

I haven't had any problems with with my phone and any Bluetooth devices before. Though, I'm not sure how many that are classic Bluetooth and how many that are BLE.

Best regards,
Lars

RE: DevAcademy Bluetooth LE connection problems

Einarh — Tue, 11 Jul 2023 10:26:17 GMT

[quote user="Lars M"]Does any of Samsung or Nordic not follow the BLE standard?[/quote]

Yes exactly, the problem is that some Samsung phones don't follow the BLE standard.

So in your specific connection procedure, you end up in an undefined state and time out. Once you've established the first successful connection, your phone will remember the connection parameters, and the connection procedure will be different which means the error does not occur anymore.

I'm not sure exactly what phones are affected, only that it's a known issue with some Samsung phones right now. There have also been similar issues with iPhones previously. If it's important to you I could look into more specifically what phones are affected.

-Einar

RE: DevAcademy Bluetooth LE connection problems

Lars M — Tue, 11 Jul 2023 05:04:39 GMT

By setting CONFIG_BT_PHY_UPDATE=n I get connection in the exercises working, great! At least those exercises in lesson 4. But now I can't use 2M, doesn't feel good.

After I set CONFIG_BT_PHY_UPDATE=n, I also tested to set back to CONFIG_BT_PHY_UPDATE=y. Then connection works. Strange. And 2M is used with 50 ms communication interval. The LL_CONNECTION_UPDATE_IND is missing this time.

Testing connection for another unaltered exercise from lesson 4 does not work, just as before. But setting CONFIG_BT_PHY_UPDATE=n makes it work. And connection works after setting it back to "y". Just as the scenario for previous exercise. This holds for all three exercises in lesson 4.

It feels like my phone recognizes the various projects. Can it be like that?

I have captured some logfiles, I attach four files from lesson 4 exercise 2. In the first file the exercise is unchanged, and connection doesn't work. The second file has CONFIG_BT_PHY_UPDATE=n. There is an LL_CONNECTION_UPDATE_IND with 7.5 ms as before, but then a lot of "new" communicaton goes on before the connection is established. Can you get some interesting information from this? Right before the connection is established there is a new LL_CONNECTION_UPDATE_IND with new parameters.

In the third file is CONFIG_BT_PHY_UPDATE set to "y" again. As mentioned above, now connection works. The fourth file has CONFIG_BT_PHY_UPDATE=n. Here all the "new" communication is missing.

Another thing that I don't understand is that CONFIG_BT_PERIPHERAL_PREF_MIN_INT says that the connection interval can be 7.5 ms, which my phone asks for when the connection doesn't work. Shouldn't LL_CONNECTION_UPDATE_IND with 7.5 ms work? Or is there something else that causes connection to not work?

Does any of Samsung or Nordic not follow the BLE standard?

[quote userid="111520" url="~/f/nordic-q-a/100349/devacademy-bluetooth-le-connection-problems/435146"]this is a known issue with some Samsung phones related to the PHY update procedure.[/quote]

Do you know which/how many phones from Samsung that have this issue?

Is it only Samsung?

Best regards,
Lars

devzone.nordicsemi.com/.../1-Capture-Samsung-S21-less4-exer2-CONFIG_5F00_BT_5F00_PHY_5F00_UPDATE_3D00_y.pcapng

devzone.nordicsemi.com/.../2-Capture-Samsung-S21-less4-exer2-CONFIG_5F00_BT_5F00_PHY_5F00_UPDATE_3D00_n.pcapng

devzone.nordicsemi.com/.../3-Capture-Samsung-S21-less4-exer2-CONFIG_5F00_BT_5F00_PHY_5F00_UPDATE_3D00_y.pcapng

devzone.nordicsemi.com/.../4-Capture-Samsung-S21-less4-exer2-CONFIG_5F00_BT_5F00_PHY_5F00_UPDATE_3D00_n.pcapng

RE: DevAcademy Bluetooth LE connection problems

Einarh — Fri, 07 Jul 2023 08:33:47 GMT

Hello

I just received an update clarifying that this is a known issue with some Samsung phones related to the PHY update procedure.

It should work if you disable the PHY update from the peripheral side.

In order for this to work with the PHY update on your Samsung phone, this issue would have to be addressed by Samsung.

Best regards,

Einar

RE: DevAcademy Bluetooth LE connection problems

Einarh — Thu, 22 Jun 2023 13:47:40 GMT

Hi, ignore the "suggested answer", I misclicked..

I've forwarded this internally at Nordic now, and someone is trying to reproduce this with a phone similar to yours.

I'll let you know if I get any updates.

-Einar

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 21 Jun 2023 13:59:49 GMT

It feels this never comes to an end. Now I have run lesson 4 exercise 1, and now the connection problem is back. Lesson 3 exercise 2 works fine, and also MMS. But when I go back to lesson 4 exercise 1, the connection problem is still there, the phone hasn't changed behaviour (at least not to make this program work). I also tried lesson 1, and now that works.

I have captured a lot. I attach the files, numbered in the order they are logged. Though, actually there is nothing new. Every time conenction works, LL_CONNECTION_UPDATE_IND is missing. And every time connection doesn't work, LL_CONNECTION_UPDATE_IND is present.

/Lars

devzone.nordicsemi.com/.../1-Capture-dk-first-phone-less4-exer1-not-working_2C00_-before-less3-exer2.pcapng

devzone.nordicsemi.com/.../2-Capture-dk-first-phone-MMS-working_2C00_-before-less3-exer2.pcapng

devzone.nordicsemi.com/.../3-Capture-dk-first-phone-less4-exer1-not-working_2C00_-before-less3-exer2-after-MMS.pcapng

devzone.nordicsemi.com/.../4-Capture-dk-first-phone-less3-exer2-working.pcapng

devzone.nordicsemi.com/.../5-Capture-dk-first-phone-less4-exer1-not-working_2C00_-after-MMS-after-less3-exer2.pcapng

devzone.nordicsemi.com/.../6-Capture-dk-first-phone-less1-exer1-working_2C00_-after-MMS-after-less3-exer2.pcapng

devzone.nordicsemi.com/.../7-Capture-dk-first-phone-less4-exer1-not-working_2C00_-after-MMS-after-less3-exer2-after-less1.pcapng

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 21 Jun 2023 11:57:25 GMT

Hi again,

Another thing that makes this not really satisfactory is that I had my phone working with my own-made BLE-project at the same time as the phone didn't work with the DevAcademy-projects. For my project, the phone didn't send LL_CONNECTION_UPDATE_IND as every other time when the connection works.

[quote userid="102842" url="~/f/nordic-q-a/100349/devacademy-bluetooth-le-connection-problems/431000"]I have made my own BLE-program (called MMS), which is a light version of NUS. Here the connection works fine. It is also possible to send characters to and receive notifications from my dk, and also disconnect. The only difference in the connection process seems to be the lack of LL_CONNECTION_UPDATE_IND in my project.[/quote]

So maybe there is more to this than just the possibility that the parameter updates have made my phone behave in a new way. It obviously behaved differently depending on project before.

/Lars

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 21 Jun 2023 10:13:56 GMT

[quote userid="111520" url="~/f/nordic-q-a/100349/devacademy-bluetooth-le-connection-problems/432232"]Then it seems like this was the tweaking of parameters needed to make it work, and it also seems like your phone remembers these parameters.[/quote]

Ok, it's maybe like that. Though, it would be nice to know it for sure. But maybe it's hard to get to know that.

But if it is like this, these update of parameters used in lesson 3 exercise 2 should be present in all BLE-programs to prevent a phone to behave like mine.

/Lars

RE: DevAcademy Bluetooth LE connection problems

Einarh — Wed, 21 Jun 2023 08:57:50 GMT

[quote user="Lars M"]After the last part of lesson 3 exercise 2, connection always works. And that part has to do with some connection parameters (data length and time).[/quote]

Then it seems like this was the tweaking of parameters needed to make it work, and it also seems like your phone remembers these parameters. Hard to say exactly what made the difference without being able to reproduce the error though.

[quote user="Lars M"]Can you say something about the red mark in packet 214? Why is it red when corresponding packet in another capture is not red? They look pretty much the same, apart from the red-marked comes after LL_CONNECTION_UPDATE_IND.
[/quote]

The red mark seems to indicate an unexpected sequencing of packets yes, the peripheral sending a PHY_REQ when the central expects a reply to its CONNECTION_UPDATE_IND.

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 21 Jun 2023 06:00:20 GMT

Hi again,

The last part in previous post is solved. I had to restart my computer, and after that there is no automatic connection.

/Lars

RE: DevAcademy Bluetooth LE connection problems

Lars M — Tue, 20 Jun 2023 09:37:53 GMT

That's the problem, I can't make it not work anymore. After the last part of lesson 3 exercise 2, connection always works. And that part has to do with some connection parameters (data length and time). Can something in this process have affected my phone to behave differently in coming connections?

It's a little while ago so I don't really remember, but most likely the file "Capture dk and phone, 3 tries.pcapng" is capture from lesson 1. As the two files I attached in previous post.

Can you say something about the red mark in packet 214? Why is it red when corresponding packet in another capture is not red? They look pretty much the same, apart from the red-marked comes after LL_CONNECTION_UPDATE_IND.

Another thing that I have encountered is that during these connection problems I have run the desktop program. Every time that I power on the dk that I used with the desktop program (I am playing with two dk:s) the PC automatically connects to it. I go into Windows settings and tell the computer to forget the device. Everything seems to work (the device disappears from the device list), but nonetheless the computer connects to it when it is turned on. I have manually added the dk, and then removed it, but it doesn't help. The computer connects to the dk no matter if it is in the list or not. The only way that I have found out to prevent my computer to connect to it is to turn off Bluetooth in the computer. Is there anything I can do to make the computer to really forget my dk?

/Lars

RE: DevAcademy Bluetooth LE connection problems

Einarh — Mon, 19 Jun 2023 14:55:12 GMT

Hm interesting, yes it seems to be the LL_CONNECTION_UPDATE_IND packet that causes this, but I'm not sure what causes it to appear.

It would be interesting to see the difference in your configuration for exercise 1 when it works and doesn't.

-Einar

RE: DevAcademy Bluetooth LE connection problems

Lars M — Mon, 19 Jun 2023 11:51:38 GMT

Hi,

Now I have completed the three first lessons with all exercises. Suddenly on the last part in lesson 3 exercise 2, the connection started to work. After a while when I had palyed around a bit with the configs in prj.conf, I went back to earlier exercises. And now they also work without any updates. So strange! I have captured several wiresharkfiles for lesson 1 exercise 1. They differ a bit, but every time the connection process works. There are some things that differ between these files and "Capture dk and phone, 3 tries.pcapng" that I attached earlier. On packet no 214 (LL_PHY_REQ) in "Capture dk and phone, 3 tries.pcapng", there is a red mark telling something is wrong. Corresponding packet in a new file where connection works, doesn't show an error (I attach two files for lesson 1 exercise 1). But I can't see what causes the red mark in the old file. Is it wrong expected answer on LL_CONNECTION_UPDATE_IND sent just before?

Another difference is that LL_CONNECTION_UPDATE_IND is not present when connection works. In the exercise where connection suddenly started to work, connection parameters are adjusted. Can something in this process have affected my phone to behave differently in coming connections? Feels a bit strange, but maybe?

/Lars

devzone.nordicsemi.com/.../Capture-dk-first-phone-less1-exer1-working.pcapng

devzone.nordicsemi.com/.../Capture-dk-first-phone-less1-exer1-working-2.pcapng

RE: DevAcademy Bluetooth LE connection problems

Lars M — Fri, 16 Jun 2023 13:32:28 GMT

Hi,

Now I have tested to set 7.5 ms, but with exactly the same behaviour.

I have tested the project both at my office and at home (the original version, not 7.5 ms). At home there should be much less devices communicating. Now I also have tested lesson 2 exercise 3, lesson 3 exercise 1, and lesson 4 exercise 1, and the same connection problem happens there. The different behaviours between the my project and those I have tested from DevAcademy can be repeated, it doesn't seem to be depending on the environment.

The differences I see in Wireshark begins with packets 213/116 during the connection process. Then some more differeces can be seen before only the master sends from packet 219 (where things go wrong), while the master and slave both send when connection works fine. So it seems that something makes my phone behave differently between the projects. Though, I haven't been able to figure out where the difference is.

/Lars

RE: DevAcademy Bluetooth LE connection problems

Einarh — Fri, 16 Jun 2023 11:52:14 GMT

I stumbled over this case very similar to yours:

Disconnect after connect parameters update

It seems to indicate that in a noisy radio environments, as your office might be judging by your first capture logs, you might have more luck using a smaller connection interval. So maybe it could be a good idea to request 7.5ms from the peripheral right away.

This one is similar too, but I'm not sure there is anything directly applicable to your problem there:

LL_CONNECTION_UPDATE_IND before response to Connection Parameters Update Request causes disconnect

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 14 Jun 2023 11:53:21 GMT

I have made my own BLE-program (called MMS), which is a light version of NUS. Here the connection works fine. It is also possible to send characters to and receive notifications from my dk, and also disconnect. The only difference in the connection process seems to be the lack of LL_CONNECTION_UPDATE_IND in my project. Instead there is an empty PDU (packet 116 compared to 213). Maybe there is some info from the device that makes the phone want to use 7.5 ms in the first case, but not in my project. I have tried to compare the autoconf.h-files, but haven’t yet found something that could be interesting to adjust. Do you see something in the connection process that may cause different behaviours of the phone?

PHY 2M seems to work, and there is 50 ms connection interval.

/Lars

devzone.nordicsemi.com/.../Capture-MMS-first-phone_2C00_-connect-UART-disconnect.pcapng

RE: DevAcademy Bluetooth LE connection problems

Einarh — Wed, 14 Jun 2023 11:25:51 GMT

It's probably your phone that ignores it yes. The peripheral can state its preferences but in the end it's up to the central unit to set the connection parameters. You could play around with other parameters and see if they make a difference, maybe you're able to communicate with your phone if you request to use PHY 1M for example.

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 14 Jun 2023 09:54:05 GMT

Interesting suggestion. Now I have tested to set CONFIG_BT_PERIPHERAL_PREF_MIN_INT=39 in prj.conf, but it is the same behaviour. I see in autoconf.h that the setting has taken effect. Without this config in prj.conf, it is CONFIG_BT_PERIPHERAL_PREF_MIN_INT=24 in autoconf.h (should be 30 ms, not 7.5 ms). So even with the default 24 it should be much bigger than 7.5 ms. Is it my phone that doesn't care about it, or is there something wrong with the config?

Seems strange to use a red colour when something is correct. But maybe the LED is used that way.

/Lars

devzone.nordicsemi.com/.../Capture-dk-and-first-phone_2C00_-CONFIG_5F00_BT_5F00_PERIPHERAL_5F00_PREF_5F00_MIN_5F00_INT-39.pcapng

RE: DevAcademy Bluetooth LE connection problems

Einarh — Wed, 14 Jun 2023 09:26:13 GMT

[quote user="Lars M"]There is an opcode, LL_CONNECTION_UPDATE_IND, that is present in the communication where things don’t work. That is where the 7.5 ms connection interval is set. Can that be the problem?[/quote]

Yes this seems to be the main difference I can see. You could try to set a minimum preferred connection interval in your peripheral's prj.conf file:

CONFIG_BT_PERIPHERAL_PREF_MIN_INT=[number]

You could for instance set it to 39, which seems to be the connection interval with the other phone.

[quote user="Lars M"]After CONNECT_IND is sent from a phone, the next few opcodes differ in order between the two phones. Why is that? Does It matter?[/quote]

It looks like the phones are doing the same things just in a slightly different order, I don't think it should matter.

[quote user="Lars M"]

I also notice that the RGB_LED is lit red on my nRF52840 dongle (with the sniffer firmware) as long as the connection is established. Is that correct?

[/quote]

I'm not sure what the led is supposed to indicate and I'm not sure where it's documented, but indicating an established connection would make sense yes.

-Einar

RE: DevAcademy Bluetooth LE connection problems

Lars M — Wed, 14 Jun 2023 07:47:12 GMT

Now I have tested to connect via another phone, a Samsung Galaxy A13 5G. Everything seems to work fine: connection, reading button status, button notifications, controlling the LED and disconnecting. I have attached the Wireshark file where all these features are tested. Obviously, something differs from my first phone (Samsung Galaxy S21 5G). There is an opcode, LL_CONNECTION_UPDATE_IND, that is present in the communication where things don’t work. That is where the 7.5 ms connection interval is set. Can that be the problem?

After CONNECT_IND is sent from a phone, the next few opcodes differ in order between the two phones. Why is that? Does It matter?

I also notice that the RGB_LED is lit red on my nRF52840 dongle (with the sniffer firmware) as long as the connection is established. Is that correct?

/Lars

devzone.nordicsemi.com/.../Capture-dk-and-second-phone.pcapng