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MIDI/USB Bass Pedal Arduino Encoder



The MIDI Bass Pedal circuit is capable of encoding any number of momentary action, push to make, single pole single throw (SPST), switches from 1 up to 25 to produce the equivalent MIDI note-on/note-off data commands. The encoded switches are wired via IN4148 diodes. The keys are arranged in a matrix for use with pedalboards with up to 25 switches. Any unrequired switches can be left unconnected.


The  MIDI start Note  is set to  C2 (Note 36), but any different start note can be pre-programmed if required. The MIDI channel (1 to 16) is set using the 4-way DIP switch, see Table. The encoded switches are wired via IN4148 diodes, see switches schematic.


This unit can work in standard MIDI mode and via the USB connection. It defaults to standard MIDI Baud rate of 31250. By replacing the original firmware on Mega8u2/16U2, the Arduino Uno will act as USB-MIDI device (Standard Midi Class), you don’t need to install additional device drivers on Windows, MaxOSX, and Linux, as the firmware acts as a device of Standard Midi Class. It will automatically install on the system as an Audio USB Device.


This unit can be connected to new bass pedals or it can be used with an older non-MIDI bass pedals by using magnetic/reed switches to isolate the old and new scanning circuits. This will allow the older bass pedal synthesizer to continue to operate as normal while also providing a MIDI output.







PRICE:  €50.00




The MIDI/USB Bass Pedal Arduino Unit consists of:

  • An assembled Arduino Board,
  • An assembled  MIDI IN & OUT circuit,
  • A MIDI 5-pin DIN output socket,
  • A MIDI 5-pin DIN input socket,
  • 2 Male Headers x6,
  • 1 Male Header x8,
  • A power-on LED,
  • A 4-way DIP switch which selects the MIDI channel at power-on, see Table 1
  • The velocity byte is preset to the maximum value,
  • The start Note of the keyboard encoder is preset to C2 (Note 36), but may be programmed to any value on request,
  • A 2.1mm power socket, and associated LED.



The  MIDI/USB Bass Pedal Arduino unit requires:

  • a 9v battery or equivalent DC power source,
  • Suitable key-switches or magnetic reed switches and associated IN4148 diodes,


Switching Circuit Schematic:

A circuit schematic of the MIDI/USB Bass Pedal Encoder shows the switch connections. 






Power Supply:

The  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 Wiring:

A circuit schematic of the MIDI IN and OUT circuit shows the Input/Output connections. 




     *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.




MIDI Bass Pedal Wiring:

The switches are organized in a 6 x 5 matrix (30 switches) arrangement.  Note if less than 30 switches are required, then ONLY the switches required need to be wired. The switch keys are wired as shown in the switches circuit schematic diagram.

The lowest note  is switch 1 wired via diode D1 between Pins D8 and A1 (D15) of the Arduino.
Pin D8 is also wired to the Anode of diode D7 and via SW7 to Pin A2 (D16) of the Arduino. 
Pin D8 is also wired to the Anode of diode D13 and via SW13 to Pin A3 (D17) of the Arduino.
Pin D8 is also wired to the Anode of diode D19 and via SW19 to Pin A4 (D18) of the Arduino.


Arduino pin terminal connected to A1 ( D15)  is wired to one side of the 6 key switches SW1 to SW6, and the wire can be looped from one key switch to the next.


Arduino pin terminal connected to A2 ( D16)  is wired to one side of the 6 key switches SW7 to SW12.


Arduino pin terminal connected to A3 ( D17)  is wired to one side of the 6 key switches SW13 to SW18. 


Arduino pin terminal connected to A4 ( D18)  is wired to one side of the 6 key switches SW19 to SW24.  


Each of the other side of these switches SW1 to SW6 is wired to a diode on the Cathode (K) side (end of diode with stripe).

The other side of each of these diodes is looped to 4 other diodes. For example Anode (A) of diode D1 is looped to D7 then to D13 then to D19. 


The rest of the wiring is done in a similar manner.


Wiring Example:

 This is a wiring example from musician Allen Talbot. A breadboard is fixed over the pedal's pins before carrying out any soldering and used solid core wire, yellow for pins A1-A3 and white for pins D8-D12 and A0 to clearly show which side of the pedal switches they represented.


Photographs of the bass pedal wiring:
bass_pedal_wiring_1.jpg (248316 bytes) bass_pedal_wiring_2.jpg (314412 bytes)
bass_pedal_wiring_3.jpg (306801 bytes) bass_pedal_wiring_4.jpg (293465 bytes)


White wiring side:
The diodes were fed into the breadboard and then soldered to one side of the pins and the diodes then to the loops of wire (1-7-13), (2-8), (3-9), (4-10), (5-11), (6-16). I then soldered on wires from the starting loops of pedal 1, 2, 3, 4, 5, and 6 and push fitted them into the Arduino board.

Yelllow wiring side:
The other side of the pedals was pretty much the same, but soldered directly to the pin on each pedal creating loops (1-6) (7-12) and then soldering 1, 7 and 13 and then push fitted them into the Arduino board.


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 Channels




Pedalboard Sizes:

There are many different sizes of pedalboards available today. But generally pedalboards range in size from 13 notes on small organs designed for in-home use (an octave, conventionally C2–C3) to 32 notes (two and a half octaves, C2–G4) on church or concert organs. Modern pipe organs typically have 30-note or 32-note pedalboards, while some electronic organs and many older pipe organs have 25-note pedalboards.
Exact design specifications for pedalboards are published in Great Britain by the Royal College of Organists (RCO), in the United States by the American Guild of Organists (AGO) (which requires a design similar to the RCO's), and in Germany by the  Bund Deutscher Orgelbaumeister (BDO) (which allows both 30-note and 32-note pedalboards, of both concave/radiating and concave/parallel varieties).


Here is an interesting link to Building a pedalboard.






Below is an example of a finished Bass Pedal Unit. NOTE I am selling the MIDI electronic kit only and NOT the Pedals.