Bluetooth broadcast debugging/troubleshooting

[pcakl]

Hello,

I am wondering if there is any way how to troubleshoot the bluetooth messaging from a city hub. Program runs fine and print-out the correct values (using print command while connected to PC) however I am trying to understand whether it successfully sends out the same values via ble.broadcast function as well. Is there a way to see if the broadcast message has been sent ?

My program is a "master" hub which listens on approx 10 channels for data sent from other hubs and then I am trying to broadcast on channel 99 some information out after "massaging" the received data. I have other hubs that do listen on this channel 99 for this information sent by this master hub. It seems like when master is actually receiving information from 10 hubs/channels sometimes the broadcasting does not seem to work - the receiving hubs (listening on channel 99 which is used as broadcast channel from the master) do not seem to be getting the data. When it is more like 5 hubs/channels it seems to be fine. Can this be related to memory capacity or something ? I am thinking of maybe getting one of the Inventor/Prime hubs to run this master program but it is not cheap so I want to make sure it will resolve this issues.

Many thanks in advance for any ideas.
Pavel Cakl

[dlech]

information from 10 hubs/channels

I'm not sure we've ever tried this many at once! I don't think I even have that many hubs.

Can this be related to memory capacity or something ?

The Bluetooth chips in the city and techic hubs do seem to get overwhelmed sometimes and not function correctly. The firmware there is a black box to us, we can't say for sure what causes the problems. It could very likely be a memory issue.

I am thinking of maybe getting one of the Inventor/Prime hubs to run this master program but it is not cheap so I want to make sure it will resolve this issues.

We can't offer a money-back guarantee that it will work, but we can say that it has a much better Bluetooth chip.

If you don't care that the central station is official LEGO, you could buy a cheap microcontroller with BLE and use that instead. The protocol is pretty simple, so it shouldn't be too hard to program, especially with the help of AI agents these days.

[pcakl]

So after that 1 second timeout if there is no new data it gives me None ?

[dlech]

The timeout means no advertisements have been received at all for one second. It doesn't matter if the data is "new" or not (in other words, the broadcaster doesn't have to keep calling hub.ble.broadcast(data), it will keep broadcasting in the background).

[pcakl]

OK. So I guess I found how it works in my case:

When I run the script/program with the hub only broadcasting it sends all data fine and the receiving side gets all messages.

However, when I run the same script/program with the hub also observing on multiple channels the data is either not being sent or being sent as None - I have no way how to tell. I am getting None when I read from the channel - this happens randomly e.g. I get the data XY times OK and then XY times I am getting None when I try to read every 100 miliseconds. So my guess the bluetooth chip is getting overwhelmed and either not sending the data or sending them as None. I assume not sending at all.

[dlech]

Yes, the Bluetooth chip (or firmware rather - that we can't change) on the City and Technic hubs isn't the greatest. If you are connected to a computer and trying to broadcast and/or observer, it doesn't always work well. Or if you disconnect from the computer and try to broadcast and observe at the same time, sometimes it will fail as well.

[pcakl]

Yes exactly what I am seeing. It does the same thing with the Inventor hub which I recently obtained and tested today as well. But observing multiple channels works fine even on the CityHub so I will change my architecture slightly hoping it will work out with only a need for observing. Much appreciated all the answers !

[BertLindeman]

Bluetooth messages between Pybricks hubs work better when the hub is not connected to the PC.

When the PC is connected, the hubs have to share the Bluetooth channel between the PC and hub(s).
That makes the messages between hubs less stable.

If you disconnect the hub from the PC, the connection works much more smoothly.
This is especially true for the City Hub and the Technic Hub.

[pcakl]

Yes I am aware of that. But I am seeing problems when all hubs are being disconnected from PC. That is why I was asking if there is any way how to troubleshoot and see if the message has been sent. Probably via some bluetooth network sniffing or something I guess but that is too advanced for me. I will see if that Prime hub will do any different.