You will only need a computer and a USB cable to update firmware contained in Matrix Ctrlr MCU board based on arduino.
To upload .hex file on the MCU, you can either download the raw compiled file from Alpes Machines website or compile your own from the sources available on GitHub.
Update from raw .hex file :
Using a free third party software like XLoader on Windows and Hex Uploader on Mac. Choose your serial port according to USB port connecting to the arduino.
You have to select the Matrix_Ctrlr_vXXX.ino.with_bootloader_mega.hex in your Loader or HexUpLoader software, select ATMEGA2560 and set the rate to 115200 and the appropriate COM port (check the number inside your Windows/Mac hardware configuration).
App for Windows :
alternative to using xLoader with Windows 8.1 (french)
App for Mac :
Hint : upload the version with boot loader if you want to make future updates using arduino IDE. Set baud rate to 115200.
Update from Sources :
You can compile the sources and libraries available on GitHub to create your own firmware using a USB cable and arduino free software IDE (1.6.8 at least). It works on Linux, OS X and Windows.
You will notice a lot of option in the sources and the possibility to extend the features of the Matrix Ctrlr. Experiment, test, do what you like, all is free and open source 🙂