2) Sending MIDI Notes
To send MIDI commands we need a 5 pin DIN jack, like for the MIDI-in, but without a galvanic decoupling. The jack has to be connected to +5V, the serial output (TX) and to ground (via a 220 Ohm resitor).
-2 x Resistor 220 Ohm
-1 x Resistor 100 kOhm
-1 x Diode
-1 x opto coupler IC GNY17-2
-2 x 5-pole DIN female connector (180°)
-1 x MIDI cable
-1 x MIDI sync master (here: Roland TR-505)
-1 x MIDI sync slave (here: DIY synthesizer with MIDI-input)
-1 x Arduino (here: Arduino Mega. For this demo also Arduinos with less input and output channels will work)
The following code can reveive MIDI clock and send synchronous MIDI notes.