He reckons it cost him about $5 to build each of his cheap USB MIDI adapters which receive notes and pedal data from the keyboard’s MIDI OUT and transmit them to a computer Besides the Pro ...

[TheSpodShed] decided to whip up a USB MIDI interface for the chip, with the help of the Arduino Pro Micro. The Arduino Pro Micro is a Sparkfun creation, using the ATmega32U4 microcontroller.