The MC4 is my forth generation of MIDI foot controller for the Fractal Axefx products. It's based around the Raspberry Pi 3 single board computer connected to a custom PCB to expand the IO functionality. On board is a custom C++ application that displays status information on the touch screen, manages the MIDI to and from the Axefx device and interacts with the user's input. There is also a desktop version of the software that can mimic all the hardware on screen.

Features: Touch screen display. 14 configurable buttons, along with RGB LEDs. 2 infinite rotation knobs with RGB LED ring value display: These are not encoders but potentiometers with better resolution and feel. 7 pin MIDI connection. 2 expression pedal inputs. Support for Axefx Tuner and Tempo messages. Displays the patch name and number, with the right display offset. Buttons can be configured to: Turn blocks on/off. Change scene. Change preset. Change bank up or down. Mode switch to a bank selection page. Toggle the tuner. Tap tempo. Change the parameters the knob inputs map to. Have a custom colour for the LED. Built on the cross platform C++ library LGI using the SDL port on Linux.

Hardware:

• Raspberry Pi 3
• Custom PCB Data Files
  
• Screen
• LED rings and NeoPixels
• Analog Input break out board
• Infinite turn pots
• Photos:
  

  

Software:

• Dependencies:
  • Lgi on SDL generally needs:
    

    sudo apt-get install build-essential libmagic-dev libgstreamer1.0-dev \
        libappindicator3-dev libssh-dev libsdl2-2.0-0

    But you may need to add libgtk3.0-dev if you want to run the IDE to update the makefiles.
    And you might add mercurial if you want to pull the latest source.
    That said it's been a long time since I created the initial dev environment on the Rpi. This list is just a starting point. You may need to add more packages as needed.
• Rpi Source and Binaries:
  • Lgi binary: Code/lgi/trunk/Debug/liblgi-gtk3d.so
    This needs to be in the LD_LIBRARY_PATH.
  • Mc4 binary: Code/MidiHw/mc4/linux-rpi/mc4
    Run command 'sudo ./mc4'.
• Architecture:
  • Gui thread: Handles display of all windows and user interaction.
    • Mc4Ui class in Code/MidiHw/mc4/src/mc4ui.cpp
  • Hardware thread: Handles talking to the hardware for everything AND sending and receiving MIDI to the Axefx device.
    • Mc4Logic class in Code/MidiHw/mc4/src/mc4logic.cpp
    • HardwarePriv class in Code/MidiHw/mc4/src/HardwarePi.cpp
  • Windows desktop version:
    • See Code/MidiHw/mc4/windows/mc4.sln
      Visual Studio 2015
• Screenshots:
  

  

• Notes:
  • To work on the software I generally connect using sshfs to the Rpi to mount the home folder. And then use an IDE on the desktop to edit the code. Before building via an ssh. To run the software I vnc into the MC4 and use a terminal on the device's actual screen. This avoids issues with the X servers DISPLAY setting. You can run the mc4 binary from the ssh connection but it takes extra setup steps.
  • The user interface resources are editable in LgiRes. The actual dialog definitions and string resources are in Code/MidiHw/mc4/resources/mc4.lr8.