Android BLE issues on parallel (5+) connection establishments

RE: Android BLE issues on parallel (5+) connection establishments

Hung Bui — Tue, 13 Aug 2024 11:47:33 GMT

Hi Tomas,

Please create a new ticket for your question. I would suggest to use the sniffer to track what happen on each link.
When doing DFU, the throughput requirement is high, so I am not sure having multiple connections doing DFU at the same time would be the best idea.

RE: Android BLE issues on parallel (5+) connection establishments

Tomas Markovic — Tue, 30 Jul 2024 12:40:46 GMT

Hi, I know that this is an old question, but I'm having a similar issue with 5 parallel connection when performing DFU via BLE on Android/iOS. Connection initialization is failing for some devices with GATT_ERROR (133). When I performed one by one or 2-3 in parallel, it is ok.

Do you have some solution to avoid this?

I have plan to try synchronize the connection process, but didn't tried yet.

Thank you

RE: Android BLE issues on parallel (5+) connection establishments

ovrebekk — Tue, 13 Jul 2021 07:01:38 GMT

Hi Niklas

Unfortunately it seems both our Android developers are on summer leave until August 😞

I am afraid it will be limited how much we can look into this until they are back, since July is already a very hectic time in support.

I have one question though: On the devices where you see stability issues, are you able to solve these issues by removing one of the links?
In other words, if 6 link is unstable, will 5 links be stable?

Best regards
Torbjørn

RE: Android BLE issues on parallel (5+) connection establishments

niklas.dahlheimer — Mon, 12 Jul 2021 10:13:31 GMT

Hi Torbjørn,

thank you for your response!

I get your point about the frequently used 2.4GHz band. We could totally live with connection delays/bad bandwidth etc. if we would get reliable error-codes/infos from the Android Bluetooth stack. But these "random" and unpredictable errors I described above are kind of "gamling" in a production environment.

We've tested with different Android devices (Google Pixel, LG, Samsung) and most of the time with 6 devices. So the hard limit of 7 devices /thanks for the linkto the thread) should not apply in this cases, unless the Android Gatt cache is not cleaned up properly in time. We definitly call gatt.close() on every disconnect, so the cache SHOULD be cleaned up properly.

I would love to here from you after you had a chat with your Android engineers! I know it's a rare usecase.

Maybe we could build a test app with the Blinky app as counterpart .So we could reduce the issue to it's core without any vendor specific stuff. I will discuss this with my colleagues.

Best regards
Niklas

RE: Android BLE issues on parallel (5+) connection establishments

ovrebekk — Sun, 11 Jul 2021 11:22:42 GMT

According to this thread there is a hard limit of 7 connections in Android, but different phones might have different capabilities, and might be limited to less than 7 connections also.

Have you tested this on different Android phones, or just a single one?

I can check next week if our Android developers have some practical experience with this, but in general it is rare to develop mobile applications that rely on a high number of connected devices.
Because phones have to schedule many different 2.4GHz based protocols, such as BLE, classic Bluetooth and WiFi, it is usually limited how many connections and how high throughput you get, compared to the performance of an nRF52 device running the SoftDevice.

Best regards
Torbjørn