Leandro Toledo's Blog

Controlling USB powered LED Light Strip on Raspberry Pi with OctoPrint and uhubctl

Leandro Toledo -

I've been trying to find a way to control the USB LED lights inside my printer's enclosure without the need of additional smart plugs. This article shows how it's possible to do it with a Raspberry Pi.

Requirements

For the Raspberry Pi 4B only; if the VL805 firmware is older than 00137ad (check with sudo rpi-eeprom-update) you may have to update the firmware. Do it at your own risk!

Optional

This article won't cover how to install Tasmota or add it to OctoPrint but there's an excellent video showing how to on Daniel's Crosslink channel.

How does it work?

uhubctl is a utility that allows controlling USB power on USB hubs.

The USB ports on the Raspberry Pi are ganged power switching controlled, meaning, we can only turn on or off all the ports at once; so keep that in mind, especially if you have other USB devices connected to it.

In my case, I have a Tasmota-enabled Smart Plug that controls the power of my Ender 3 V2 (which is connected to the Raspberry Pi over USB) and a LED light strip that is also connected to one of its USB ports.

When I turn the printer on, using OctoPi's interface, OctoPrint-Tasmota Plugin powers on the Tasmota Smart Plug, and uhubctl enables all the Raspberry Pi USB Ports; bringing the LED lights on and allowing OctoPrint to communicate with the printer.

How to install it?

  1. On your OctoPi's terminal, install the dependencies:
    $ sudo apt-get install libusb-1.0-0-dev
  2. Clone the uhubctl repository:
    $ git clone https://github.com/mvp/uhubctl
  3. Compile and install from source:
    $ cd uhubctl
    $ make
    $ sudo cp uhubctl /usr/local/bin
  4. Add the pi user to the dialout group:
    $ sudo usermod -a -G dialout pi
  5. Add udev rules to the USB hub you'd like to control:
    $ sudo vi /etc/udev/rules.d/52-usb.rules
    SUBSYSTEM=="usb", ATTR{idVendor}=="2109", MODE="0664", GROUP="dialout"

    Important Note: "2109" is the idVendor for the Raspberry Pi 4B's USB hub, if you have a different model, you can run lsusb to identify the correct idVendor.
  6. Reboot the Raspberry Pi:
    $ sudo reboot
  7. At this point you should be able to control the USB Hub and the USB LED light strip attached to it; to power it off:
    $ uhubctl -l 1-1 -a off
  8. To power it back on:
    $ uhubctl -l 1-1 -a on

Configuring OctoPrint

If you are using the OctoPrint-Tasmota Plugin you can skip to the next section.
  1. Back to the OctoPi's terminal, let's add to the end of the config.yaml file:
    $ vi .octoprint/config.yaml
    events
     enabled: true
     subscriptions:
     - command: uhubctl -l 1-1 -a off
       event: Disconnected
       type: system
     - command: uhubctl -l 1-1 -a on
       event: Connecting
       type: system
  2. Reboot the OctoPi server:
    $ sudo reboot

Now, next time you click on Connect on OctoPrint's interface, it will turn on the USB hub ports. And, whenever it disconnects from the printer, it will turn off the USB hub ports.

Configuring OctoPrint with the OctoPrint Tasmota Plugin

  1. Go to OctoPrint Settings (click on the wrench in the toolbar).
  2. Go to the Tasmota plugin settings.
  3. On your existing plug, click on the pencil to edit it.
  4. Check Run System Command After On, and add:
    uhubctl -l 1-1 -a on
  5. Check Run System Command Before Off, and add:
    uhubctl -l 1-1 -a off
  6. Click on Close, then Save, and finally, Close again.

Now, next time you click on the Tasmota's lightning icon, on OctoPrint's interface, it will turn on the printer and the USB hub ports.

References