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Simple MIDI Synthesiser


Simple Monophonic MIDI Synthesiser

This design is a simple Monophonic MIDI Synthesiser which produces a synthesised audio 5 volt peak-to-peak squarewave waveform, from Digital Pin D8, corresponding to the pitch/frequency to the received MIDI signal.




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MIDI Simple Synthesiser


PRICE:  €50.00






The Simple MIDI Synthesiser unit utilizes:


  • An assembled, built and tested MIDI and Arduino board including a suitable pre-programmed Atmega microcontroller,
  • A 2.1mm power socket, and associated LED, 
  • A MIDI detection LED,
  • A 4-way DIP switch, which selects the MIDI channel at power-on, shown in table 1
  • A 150mm wired MIDI 5-pin DIN input socket,
  • A 150mm wired MIDI 5-pin DIN output socket, 
  • The complete circuit schematic is available,
  • The MIDI IN/OUT circuit schematic is also available.



The  Simple MIDI Synthesiser requires:

  • A 9 Volt battery or equivalent 9 Volt DC external power source.
  • Output connection direct to piezo speaker or connection to audio amplifier via a potentiometer








     *Click to Enlarge*

The MIDI IN and OUT connectors use  5-Pin 180 degree DIN sockets. Note that the MIDI IN/OUT wiring is polarised and the correct pins should be used.





This design detects incoming MIDI data and if it is a MIDI Note On message, on the correct MIDI Channel (1 to 16), then it produces a synthesised audio squarewave waveform of the corresponding pitch/frequency, of 5 volt peak-to-peak squarewave waveform, from Digital Pin D8.


When the unit detects incoming MIDI Note Off data, it switches off the squarewave waveform. 


Note that the 5 volt peak-to-peak squarewave output waveform may have to be reduced using a potentiometer when fed to the input of some audio amplifiers.


If any System Common, Realtime or Exclusive events are detected they are passed directly from the input to the output. System Exclusive messages will be sent until the End of System Exclusive message is received. However if a system realtime message is received during a System Exclusive message it is also passed to the output.



Power Supply:

The  MIDI Arduino can be powered via the USB connection or with an external power supply. The power source is selected automatically.


External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. A low dropout regulator provides improved energy efficiency.


The board can operate on an external supply of 7 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.



MIDI Specification: 

 The Monophonic MIDI Synthesiser is channel (1-16) dependent. The system will also work with MIDI running status. Here are details of the various MIDI Messages.



DIP Switch Selections



4 3 2 1
on on on on 1
on on on off 2
on  on  off on 3
on on off off 4
on off on on 5
on off on off 6
on off off on 7
on off off off 8
off on on on 9
off on on off 10
off on  off on 11
off on off off 12
off off on on 13
off off on off 14
off off off on 15
off off off off 16

Table 1 MIDI Channel