Large Angular Motor 45602 causes Technic Hub (88012) to disconnect or crash when initialized on Pybricks 3.6.1

[kpennock]

When attempting to initialize or run a SPIKE Large Angular Motor (45602) on a Technic Hub (88012) running Pybricks firmware v3.6.1, the hub immediately drops the Bluetooth connection and becomes unresponsive. I have tried 2 different motors on all 4 ports.
The same 2 motors work normally on a SPIKE Prime Hub with the same Pybricks version. Additionally, other sensors such as the color and distance sensor, work as expected on the Technic Hub, so it seems that only the motors are having difficulties with Pybricks.

With the following program, the hub connects to Bluetooth, prints "Initializing motor...", then pauses, disconnects from bluetooth, and stalls.

from pybricks.hubs import TechnicHub
from pybricks.pupdevices import Motor
from pybricks.parameters import Port

# Initialize the hub
hub = TechnicHub()

# Initialize the Large Angular Motor (45602) on Port D
motor = Motor(Port.D)
print("Motor initialized successfully.")

# Run the motor forward for 3 seconds
motor.run_time(500, 3000, then=Stop.HOLD)

# Now run it backward for 3 seconds
motor.run_time(-500, 3000, then=Stop.HOLD)

# Print to show it is done
print("Motor run successfully.")

I expected the motor to turn forward and backward and print messages, but the program froze during motor initialization and dropped the Bluetooth connection so no print statements were reached. I have tried all 4 ports on the technic hub with no success. I have also tried multiple programs that operate with the motor initialization line commented out, but fail as soon as I uncomment the motor initialization line. I have verified that the motors work normally on Spike Prime hub and that sensors (distance, color) work on the technic hub. The only problem seems to be the large angular motors.

[dlech]

This sounds like something is causing the hub to crash. I'm not sure what it could be though since most of the firmware code is shared between hubs.

You could try running the nightly build of the firmware to see if the issue has already been fixed.

https://nightly.link/pybricks/pybricks-micropython/workflows/build/master

[kpennock]

Will do. Thank you.
Just did. Even worse results. Now the motors are not even recognized by the firmware in the latest nightly build, with an error message stating that no device was connected to the target port.

[BertLindeman]

Did you also try to define Stop like this:

from pybricks.parameters import Port, Stop

I get this error without it:

Motor initialized successfully.
Traceback (most recent call last):
  File "issue_2395_orig.py", line 13, in <module>
NameError: name 'Stop' isn't defined

[EDIT}
Tested with
('technichub', '4.0.0a0', 'ci-build-4272-v3.6.1-523-g4cc72417 on 2025-10-07')
and
('technichub', '3.6.1', 'ci-build-3937-v3.6.1-231-gd76f61ae on 2025-07-11')

[dlech]

Even worse results

I would say that printing an error message is better than losing the Bluetooth connection because the hub crashed. 😄

Other than using a logic analyzer to spy on the signal or building a special debug build of the firmware, I'm not sure how we could debug the motors any more though. Since you said that they work fine on other hubs and other sensors work fine on this hub, it kind of rules out any hardware issues.

[kpennock]

I included Stop this time:

from pybricks.hubs import TechnicHub
from pybricks.pupdevices import Motor
from pybricks.parameters import Color, Port, Stop
from pybricks.tools import wait

hub = TechnicHub()

print("Beginning...")
hub.light.on(Color.GREEN)
wait(2000)
motor = Motor(Port.B)
hub.light.on(Color.WHITE)
wait(2000)
motor.run(500)  # runs motor at 500 deg/s
hub.light.on(Color.RED)
wait(2000)
hub.light.off()
motor.stop(Stop.HOLD)

The code never gets to the Color.White. It just freezes on Green, never making it past the motor instantiation.

[kpennock]

I admire your positive outlook☺️

…

On Mon, Oct 13, 2025 at 3:28 PM David Lechner ***@***.***> wrote: *dlech* left a comment (pybricks/support#2395) <#2395 (comment)> Even worse results I would say that printing an error message is better than losing the Bluetooth connection because the hub crashed. 😄 Other than using a logic analyzer to spy on the signal or building a special debug build of the firmware, I'm not sure how we could debug the motors any more though. Since you said that they work fine on other hubs and other sensors work fine on this hub, it kind of rules out any hardware issues. — Reply to this email directly, view it on GitHub <#2395 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACHGF76IRY3P5QTH5FSU3QL3XQDP7AVCNFSM6AAAAACJCCYDL2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJYHE3DANJWGM> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[BertLindeman]

I ran your program on my Technichub and it runs fine until the syntax error on the last line

motor.stop(Stop.HOLD)

motor.stop() has no arguments.

But the program shows GREEN, WHITE and RED with a large Spike motor on Port B.

Do you see any messages in the log area below the python code?
I got:

Beginning...
Traceback (most recent call last):
  File "issue_2395_test2.py", line 18, in <module>
TypeError: function takes 1 positional arguments but 2 were given

[kpennock]

No, no messages other than the printed "Beginning..." text before hub init. It just freezes on green and is silent. Looks like a different behavior. than what you are seeing. Just to be clear, I switched back to the stable version of Pybricks (removed the latest nightly build that wouldn't recognize that the motor was even connected to the port).

…

On Mon, Oct 13, 2025 at 3:59 PM Bert ***@***.***> wrote: *BertLindeman* left a comment (pybricks/support#2395) <#2395 (comment)> I ran your program on my Technichub and it runs fine until the syntax error on the last line motor.stop(Stop.HOLD) motor.stop() has no arguments. But the program shows GREEN, WHITE and RED with a large Spike motor on Port B. Do you see any messages in the log area below the python code? I got: Beginning... Traceback (most recent call last): File "issue_2395_test2.py", line 18, in <module> TypeError: function takes 1 positional arguments but 2 were given — Reply to this email directly, view it on GitHub <#2395 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACHGF7YXGZS5IS5IZLQYNK33XQHDNAVCNFSM6AAAAACJCCYDL2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJZGA2TMNRTGQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[BertLindeman]

Thanks for your response.

My tests ran with stable 3.6.1 and a 4.0 pre-alpa firmware with out problem.
Tried two different hubs too.

In no way am I a hardware technician.
But could this have to do with a bad contact or cable problem?
Hard to proove though.

[kpennock]

I thought I eliminated the hardware error possibility by verifying that the motors run on both: - the technic hub running LEGO firmware - the spike prime hub running LEGO firmware, and that other devices (2 sensors) work on the Technic Hub (running Pybricks) on the same ports I had the motors connected to. So in my mind, the motors and the ports seem like they should be fine. But I am not sure what else to do if a similar setup seems to be working fine for you. I really appreciate your time on this. Thanks for trying to help me figure this out.

…

On Mon, Oct 13, 2025 at 4:18 PM Bert ***@***.***> wrote: *BertLindeman* left a comment (pybricks/support#2395) <#2395 (comment)> Thanks for your response. My tests ran with stable 3.6.1 and a 4.0 pre-alpa firmware with out problem. Tried two different hubs too. In no way am I a hardware technician. But could this have to do with a bad contact or cable problem? Hard to proove though. — Reply to this email directly, view it on GitHub <#2395 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACHGF74KAGRJHGTEK2JRQ5T3XQJLHAVCNFSM6AAAAACJCCYDL2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJZGA4TQOBXG4> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[kpennock]

And the probability that both new motors have a similar hardware problem seems pretty small. On Mon, Oct 13, 2025 at 4:33 PM Kelly Pennock ***@***.***> wrote:

…

I thought I eliminated the hardware error possibility by verifying that the motors run on both: - the technic hub running LEGO firmware - the spike prime hub running LEGO firmware, and that other devices (2 sensors) work on the Technic Hub (running Pybricks) on the same ports I had the motors connected to. So in my mind, the motors and the ports seem like they should be fine. But I am not sure what else to do if a similar setup seems to be working fine for you. I really appreciate your time on this. Thanks for trying to help me figure this out. On Mon, Oct 13, 2025 at 4:18 PM Bert ***@***.***> wrote: > *BertLindeman* left a comment (pybricks/support#2395) > <#2395 (comment)> > > Thanks for your response. > > My tests ran with stable 3.6.1 and a 4.0 pre-alpa firmware with out > problem. > Tried two different hubs too. > > In no way am I a hardware technician. > But could this have to do with a bad contact or cable problem? > Hard to proove though. > > — > Reply to this email directly, view it on GitHub > <#2395 (comment)>, > or unsubscribe > <https://github.com/notifications/unsubscribe-auth/ACHGF74KAGRJHGTEK2JRQ5T3XQJLHAVCNFSM6AAAAACJCCYDL2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJZGA4TQOBXG4> > . > You are receiving this because you authored the thread.Message ID: > ***@***.***> >

[BertLindeman]

And the probability that both new motors have a similar hardware problem
seems pretty small.

I agree and have no more hints at the moment.

[kpennock]

Thanks again for all your help. Appreciate it.

…

On Mon, Oct 13, 2025 at 4:41 PM Bert ***@***.***> wrote: *BertLindeman* left a comment (pybricks/support#2395) <#2395 (comment)> And the probability that both new motors have a similar hardware problem seems pretty small. I agree and have no more hints at the moment. — Reply to this email directly, view it on GitHub <#2395 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACHGF73OUBDNQ5XLNYGVEBT3XQL7DAVCNFSM6AAAAACJCCYDL2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJZGE2DOMBVHE> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[BertLindeman]

Just a hunch: what if the batteries are at the end of their live?

A motor needs more power than a sensor.

Adjusted your program to show the battery voltage:

from pybricks.hubs import TechnicHub
from pybricks.pupdevices import Motor
from pybricks.parameters import Color, Port, Stop
from pybricks.tools import wait

hub = TechnicHub()

print(f"{'Beginning...':<16}\t {hub.battery.voltage()/1000:>4.2f} V")
hub.light.on(Color.GREEN)
print(f"\t{'Green':<16} {hub.battery.voltage()/1000:>4.2f} V")
wait(2000)
print(f"\t{'Define motor':<16} {hub.battery.voltage()/1000:>4.2f} V")
motor = Motor(Port.B)
print(f"\t{'White':<16} {hub.battery.voltage()/1000:>4.2f} V")
hub.light.on(Color.WHITE)
wait(2000)
print(f"\t{'Run motor':<16} {hub.battery.voltage()/1000:>4.2f} V")
motor.run(500) # runs motor at 500 deg/s
print(f"\t{'Red':<16} {hub.battery.voltage()/1000:>4.2f} V")
hub.light.on(Color.RED)
wait(2000)
hub.light.off()
# motor.stop(Stop.HOLD)
motor.stop()
print(f"\t{'motor stopped':<16} {hub.battery.voltage()/1000:>4.2f} V")

My output looks like this at the moment:

Beginning...             7.43 V
        Green            7.43 V
        Define motor     7.45 V
        White            7.45 V
        Run motor        7.44 V
        Red              7.44 V
        motor stopped    6.90 V

You see that the voltage after 2 seconds motor run drops by half a volt.
Quite a lot.
Maybe this shows us something?

What if you turn the motor slower e.g. 100 in stead of 500?