Unable to run programs off the hub

[JJHackimoto]

Hi,

I just started using Pybricks Block coding for a complicated bowling pinsetter build, that uses three technic hubs that communicate with each other.
I have transferred over my program by hand from the PoweredUp app, and divided it into three separate programs, one for each hub. The hubs then send values to each other using the broadcasting feature.
I've installed the firmware on all three hubs, downloaded and ran the program (running the program doesn't do anything at this point since they all just wait for commands from each other), and I've then turned the hubs off.

Now the problem. When I turn the hubs back on, they all just search for a bluetooth connection (rapid doubleblinking blue light). Pressing the green button once during this process does nothing. I expected the program to run and the light to fade in and out, but that's not the case. My expectation is based on this: https://pybricks.com/install/technic-boost-city/

Connecting them all from separate chrome tabs doesn't work either. When trying to run a program with more than one hub connected, it hangs when downloading to the hub at 48%. I also have the following error in the Chrome inspector, but idk if that has anything to do with this: "DOMException: GATT operation failed for unknown reason."

I'm sure the Pybricks firmware is installed since the blue flashing doesn't stop after the same amount of time as the original firmware did when not touching it.

Does anyone have a clue as to what could be going on?

Hardware:
Three Lego Technic hubs running the latest stable beta version (downloaded from the beta since I use block coding)
M1 Pro MacBook Pro running Google Chrome

[laurensvalk]

To make sure it's not an issue with your program, can you try running something like the following?

This should help you verify whether starting it with the button works or not.

It's possible that the program stopped for another reason. For example, maybe one of your motors wasn't plugged in?

It's often most practical to do this sort of test while you're still connected to your computer. That way, you can see that kind of errors when they occur.

---

When using Hub to Hub communication, it's important to note that the observe command will report None if there is no data from another hub yet. If you'd use None to set the speed of a motor, for example, you'd get an error and the program would stop. We may be able to give more suggestions if you share your program :)

[laurensvalk]

Thanks Bert! I must have missed the part about the crash. Would you mind posting just the Python code to a dedicated issue?

Can it be reproduced with just the devices attached as described?

[laurensvalk]

Maybe it's the same issue as #1357.

The Technic Hub doesn't seem to like multitasking combined with Bluetooth.

[JJHackimoto]

Thanks Bert for checking this! I'll try to rearrange the program to avoid it using broadcasting while multitasking, if possible, while waiting for the bug to be fixed. :)

[laurensvalk]

We released a new beta version that should fix this. You can try it out with the new firmware at https://beta.pybricks.com/

If you've used that page before, it may take a few minutes for the latest version to load in the background. If you go to settings/about, you'll see 3.4.0b1 as the new version. When you do, you can go ahead and update the firmware or try new features.

[JJHackimoto]

Thank you!

I had to do the installation process about five times for each hub since it kept timing out with the following error: "The hub took too long to respond. Restart the hub and try again.". After that, they all started fine and no crashes occurred!

I marked your reply as the answer since it solved my initial problem. However, I've now done some testing and there's still a bug present here. Broadcasting and receiving values work fine, however, the variables won't update in the entire program at once. See my simple program attached. I have two parallell programs running at different intervals. One hub sends the "TriggerDistributor" value (true) by broadcasting. This value won't be changed for about three seconds or so, and then go back to being false. This is picked up by the first print function and shows in the console, however the other print function in the lower program will always print false. This is a problem since I'm using these values in different parts of the program, usually with "wait until" blocks, waiting until the variable becomes true.

If this is an actual bug, do you want me to create a separate issue for it?

[laurensvalk]

Good catch! Yes, I think I see where the bug might be. Feel free to create a dedicated issue for it. Thanks!

I think the global keyword isn’t included properly in the generated code.

[BertLindeman]

However, the hub now crashes when I try to run the program. (It turns off right away) No errors appear in the console either.

Maybe it's the same issue as #1357.

The Technic Hub doesn't seem to like multitasking combined with Bluetooth.

Tested the original program and commented-out the observe and broadcast statements.
No more crash seen then.
So looks like #1357 indeed.

[EDIT] Added a link to here in #1357 (Thought those were made automagically)

[laurensvalk]

It's probably due to:

https://github.com/pybricks/pybricks-micropython/blob/master/pybricks/common/pb_type_ble.c#L430-L443

So we need to fix #1096.

Prediction came true 😄

Due to a new upcoming editor feature, I think multi-tasking is going to get a lot more testing fairly soon. I kind of suspect there will still be some issues to resolve when lots of multitasking is being used, and this is probably one of them.

Originally posted by @laurensvalk in #1096 (comment)

[dlech]

There is a pull request to fix this if anyone wants to try out the firmware there. pybricks/pybricks-micropython#216