ValueError: A different mode has already been set!

[BzowK]

Good Morning -

Just installed HX711 on Raspberry Pi 4 and successfully tested it using example.py from the hx711py library after editing script to use 20 & 21. Installed your plugin in OctoPrint, but always shows "Loading" in console. If I tear it in plugin config, it goes to 0g, but never shows any measurements.

Looked in octoprint.log and found the below:

2022-01-21 09:25:23,202 - octoprint.plugin - ERROR - Error while calling plugin filament_scale
Traceback (most recent call last):
  File "/home/pi/oprint/lib/python3.7/site-packages/octoprint/plugin/__init__.py", line 271, in call_plugin
    result = getattr(plugin, method)(*args, **kwargs)
  File "/home/pi/oprint/lib/python3.7/site-packages/octoprint/util/__init__.py", line 1737, in wrapper
    return f(*args, **kwargs)
  File "/home/pi/oprint/lib/python3.7/site-packages/filament_scale_enhanced/__init__.py", line 50, in on_startup
    self.hx = HX711(20, 21)
  File "/home/pi/oprint/lib/python3.7/site-packages/filament_scale_enhanced/hx711.py", line 27, in __init__
    GPIO.setmode(GPIO.BCM)
ValueError: A different mode has already been set!

Not a Python expert, but seems there's a conflict setting the mode as GPIO.BCM perhaps after a recent OP update? What may be done to address this?

UPDATE: Did see that another plugin, LED Strip Control; sets GPIO.BOARD which may be the conflict. That plugin works, though; and is used. Would potential fix be as easy as changing "GPIO.BCM" to "GPIO.BOARD" in hx711.py, then changing the 20, 21 values in init.py to board pin numbers? (In middle of long print currently, so can't test.)

Thank You

[techman83]

The underlying issue and fix is described in #17 (along with #18) - The problem is that it's fixed to one type. So this would be currently incompatible with LED Strip Control. Switching it would likely make it incompatible with things that use GPIO.BCM. Now you could hack in a change to get it working for you and report back.

I've been getting back into 3D printing, so I'll take a look at fixing my sensor and seeing how much it would take to clean up the config.

[BzowK]

Got it working by changing...

• From GPIO.BCM to GPIO.BOARD on line 27 in /home/pi/oprint/lib/python3.7/site-packages/filament_scale_enhanced/hx711.py
• Changing from BCM numbers (20, 21) to Board numbers (38, 40) on line 50 in /home/pi/oprint/lib/python3.7/site-packages/filament_scale_enhanced/init.py
• Changing lines 36 & 37 to match board numbering in /home/pi/oprint/lib/python3.7/site-packages/filament_scale_enhanced/init.py

After a reboot, all's good. Thanks!

[techman83]

Ok perfect! That'll be super useful for swapping/migrating settings back and forth 🙂

[ScrimpyD]

Posting a note that I am glad I found this because today I was adding an HX711 to my Pi4 and had the same issue.