A downloadable tool for macOS

Mio simplifies serial communication as a trigger for key presses and MIDI communication. It relies on specific commands (eg. a0 87) being sent by a device (eg. Arduino). The command will be parsed, leaving only the integer.


If you want to make changes to the source and build your own visit https://github.com/jonasjohansson/mio and follow the instructions.

Configuring Mio

Mio has a raw interface that uses the default services of the operative system. It is a deliberate decision that encourages ownership, transparency and education.

Press  ⌘ Cmd+, to open the preferences in your default text editor. 


Mio has two modes; Simple (default) and Advanced (toggled by setting Advanced Mode under File).


Does no evaluation of the forwarded values, instead it triggers keypresses and Midi.


Listens to pins defined in its preferences. For successful communication these pins must be identical on both ends. In this example, Arduino is printing lines with the commands "a1" and "d2", followed by a space, and an integer value.

Add an IO

Click the "+" icon to add a new IO block.

Remove an IO

Highlight a block starting from any open curly bracket to the next closed curly bracket, delete and save.


⌘ Cmd+s will save all the IOs to the Preferences, so that on your next open all settings will be remembered.


There are a few ways to reset Homie in case the preferences have become messed up. Either go to Help and Reset or manually delete all text in the preferences file, save and restart Mio.

For validating Midi communication, use MIDI Monitor.

Updated 3 hours ago
Published 10 days ago
StatusIn development
AuthorJonas Johansson


Mio-1.0.3.app 93 MB