[Bug] Hub can freeze when connecting Xbox Controller

[BertLindeman]

Describe the bug
A program with 3 car definitions hangs and powers-off (almost all times) if the xbox controller is OFF

To reproduce
Steps to reproduce the behavior:

1. go to beta.pybricks.com
2. Add or open the program below
3. Connect the hub
4. Keep the xbox controller OFF
5. Run the program
6. See the steer motor calibrate 3 times and then on the last turn spin at high speed. And the hub animations stops and soon the hub powers off.

If this does not crash the first time, then try first a run where the xbox does connect and retry with the xbox controller OFF.

Expected behavior
The program do the 3 steer calibrations and with the steer in zero position wait for the xbox to connect, or timeout.

Screenshots
Video showing a stop without power-off:

extra info

1. Problem not seen with V3.6.1 Pybricks MicroPython ci-release-86-v3.6.1 on 2025-03-11; SPIKE Prime Hub with STM32F413VG (Tried 10 times)
2. Problem does occur on the current beta firmware and with firmware of primehub-firmware-build-4577-gitfcfdf4e0

test program
Python program to be able to look at #2532 due to 3 cars in one program.

from pybricks.hubs import InventorHub
from pybricks.iodevices import XboxController
from pybricks.pupdevices import Motor, ColorSensor, UltrasonicSensor
from pybricks.parameters import Button, Color, Direction, Port, Side, Stop
from pybricks.robotics import Car, DriveBase
from pybricks.tools import wait, StopWatch

hub = InventorHub()
print(1)
frontR = Motor(Port.A)
print(2)
frontL = Motor(Port.B)
print(3)
middle = Motor(Port.C)
print(4)
backR = Motor(Port.D)
print(5)
backL = Motor(Port.F)
print(6)
steer = Motor(Port.E)

print(7)
carA = Car(steer, (frontR, frontL))
print(8)
carB = Car(steer, (middle))
print(9)
carC = Car(steer, (backL, backR))

print(10)
xbox = XboxController()

print(11)
print(f"xbox.joystick_left() {type(xbox.joystick_left())} {xbox.joystick_left()[1]}")

print(12)

while True:
    speed = xbox.joystick_left()[1]
    # print(f"speed {speed}")
    carC.drive_speed(speed)
    carC.steer(xbox.joystick_right()[0])
    wait(100)

The program has the prints to see where it crashes.

[laurensvalk]

Thanks @BertLindeman. This is very helpful.

[laurensvalk]

I've been able to reproduce this once or twice, but not consistently unfortunately.

[BertLindeman]

Reproduce steps on beta firmware

1. disconnect usb (not relevant for the stop, but see below)
2. connect hub to pc
3. xbox off
4. run the program
5. after 3 calibrations set on the xbox-ctrl ( and maybe even pairing mode)
6. After xbox-ctrl connected: press the hub button to stop the program
7. xbox off
8. press the hub button to start the program (not on the gui thistime)
9. see the result

With the USB cable connected the hub stops but does not power-off.
On battery power the hub stops and powers off.
Can be this is put a bit too sure, I did not do dozens of test of each situation.

[BertLindeman]

I've been able to reproduce this once or twice, but not consistently unfortunately.

Also on the latest scenaio?

[laurensvalk]

Thanks for the trouble, but testing with the beta firmware is no longer very relevant, since we've already fixed a lot of things for the XboxController. But I was able to reproduce it on the newer fcfdf4e like you said at least once, so this one is still there.

For what it's worth, my test setup (including our virtual tests) have the "steering motor" on Port C. And no motor on Port D. That did not make a difference for this test (on fcfdf4e it was still reproducible) but it makes my life easier. Thanks!

I've been able to reproduce this once or twice, but not consistently unfortunately.

Also on the latest scenaio?

Earlier I reproduced it a few times in a row, but now I don't see it at all anymore.

[BertLindeman]

First hit I had was on fcfdf4e went to beta due to the OP mentioning it (I think).

OK back on fcfdf4e now.

Two tests:

1. run via beta gui - F5 or run-button - xbox-ctrl OFF
   Never gets stopped (10 tests)

2. run via beta gui - F5 or run-button - xbox-ctrl ON
   First run succeeds. But the next run (via hub button press) stops

In short the NEXT run stops after a successful connect to the xbox-ctrl.

A fresh load and run program does not fail.

Does the xbox connection leave anything behind?
How does the xbox-connection code drive the motor (which we happen to use to steer) to full speed?

The firmware correctly stops in this situation: Motor out of control.

[BertLindeman]

One car definition is enough.

Simplified to

from pybricks.hubs import InventorHub
from pybricks.iodevices import XboxController
from pybricks.pupdevices import Motor
from pybricks.parameters import Port
from pybricks.robotics import Car
from pybricks.tools import wait

hub = InventorHub()
print(5)
backL = Motor(Port.F)
print(6)
steer = Motor(Port.C)  # was Port.E
print(9)
carC = Car(steer, backL)
print(10)
xbox = XboxController()
print("12 connected - stopping the program after 2 seconds")
wait(2000)

Same result first run goes OK next run stops the hub.

( Not related: Had to power-off the hub to re-pair to the xbox-ctrl)

[BertLindeman]

One more, than I'll shut up.

As simple as I could get it: issue_2533_nocar_crash_no_motor

from pybricks.hubs import InventorHub
from pybricks.iodevices import XboxController
from pybricks.tools import wait
print("instantiate hub")
wait(10)  # to be sure we see the text
hub = InventorHub()
print(10)
xbox = XboxController()
print("Connected - stopping the program after 1 second")
wait(1000)

First run with connected xbox controller is OK and the next run fails.

Log window after the two runs:

instantiate hub
10
Connected - stopping the program after 1 second
instantiate hub
10

Video of running the program from the PC and restart after that run with the hub button:

Maybe the title of this issue is a bit wrong.