This design is a single board MIDI encoder capable of encoding three 61-Note keyboards, one 32-Note Bass pedal, 40 Thumb Piston switch inputs and 3 Expression pedal encoders unit. The keyboards operate on MIDI Channels 1, 2 and 3. The Bass pedal unit operates on MIDI Channel 6. The Thumb Piston Switch Inputs operates on MIDI Channel 9. The Expression Pedal Inputs operates on MIDI Channel 12.
The three keyboard units can work with any number of momentary action, normally open, push to make, single pole single throw (SPST), switches from 1 up to 61 to produce the equivalent MIDI note-on/note-off data commands. The Bass pedal encoder can work with any number of pedal switches up to 32. The Thumb Piston Switch Inputs encoder can work with any number of switches up to 40. The unit can operate with any number of Expression pedals up to 3. The 3 Expression pedals use MIDI Control Change (CC) numbers CC7, CC8 and CC9.
Note: The analog inputs for the expression pedals should be connected to the Ground (GND) Pin if unused. Otherwise random MIDI Expression values will be produced, due to noise/interference pickup on the inputs.
The encoded switches are wired via IN4148 diodes. Any unused keys/notes can be left unconnected.
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 do not 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.Operation:
This unit can be connected to new keyboards or it can be used with an older non-MIDI keyboard by using magnetic/reed switches to isolate the old and new scanning circuits. This will allow the older keyboard synthesizer to continue to operate as normal while also providing a MIDI output.MIDI Encoder Switch Wiring:
The three keyboard switches are organized in a 8 x 8 matrix (up to 61 switches) arrangement. Note if less than 61 switches are required, then ONLY the switches required need to be wired
Note: The row INPUT PINS 23, 25, 27, 29, 31, 33, 35 and 37 have an internal Pullup Resistor. However when using three keyboards you may need an external Pullup resistor connected to each of these pins to provide more current. Connect separate resistors of a value 3.3k ohm between each of these pins and the +5 Volt pin.
The Bass pedalboard switches are organized in a 8 x 4 matrix (up to 32 switches) arrangement. Note if less than 32 switches are required, then ONLY the switches required need to be wired
The Thumb Piston switches are organized in a 8 x 5 matrix (up to 40 switches) arrangement. Note if less than 40 switches are required, then ONLY the switches required need to be wiredExpression Pedals Jack Socket Wiring:
Variable potentiometer pedals can use a MONO or STEREO jack socket. So either a standard 6.3mm style switched 2-pole MONO jack socket with 2-poles switched upon insertion of the jack plug, with switched normally closed contacts available in 2-pole or a standard 6.3mm style switched 3-pole STEREO jack socket with 3-poles switched upon insertion of the jack plug are required.Power Supply:
External power can come either from an AC-to-DC adapter or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack.
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.