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    Control Surface
     
   1.1.0
   MIDI Control Surface library for Arduino 
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This examples shows how to use a button matrix to read many switches.
Connect a 4 × 3 matrix of buttons with the rows to pins 2, 3, 4 and 5, and the columns to pins 6, 7 and 8.
Pull-up resistors are not necessary, because the internal ones will be used.
If you want to be able to press multiple buttons at once, add a diode in series with each button: 
 
When you press one of the buttons, a note on event for the corresponding note is sent, when you release it, a note off event is sent.
The note numbers are specified in the addresses array. Map accordingly in your DAW or DJ software.
Written by Pieter P, 24/09/2017 
 https://github.com/tttapa/Control-Surface
 1.8.16