This MIDI Bass Pedal Encoder circuit, arranged in an 8x4 matrix, is capable of encoding 32 momentary action, push to make, single pole single throw (SPST), switches to produce the equivalent MIDI note-on/note-off data commands. There are also Octave Up and and Octave Down switch inputs and MIDI Channel Up and Down switch inputs. The MIDI Channel is stored into non-volatile EEPROM memory. So when the unit is powerd up the previous MIDI Channel that was used is restored. Note that if the MIDI Octave or MIDI Channel switches are not required, they can be left unconnected.
The encoded switches are wired via IN4148 diodes. The keys are arranged in a matrix for use with pedalboards with up to 32 switches. Any unrequired switches can be left unconnected.
The MIDI start Note is set to C2 (MIDI Note 36), which is connected to switch SW1, then the switches follow continuously to the last switch SW32, which is G4 (MIDI Note 67). But any different start note can be pre-programmed if required.Operation:
This unit can work in standard MIDI mode and via the USB connection, at the same time. It defaults to standard MIDI Baud rate of 31250. By replacing the original firmware on Mega8u2/16U2, the Arduino 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.
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.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. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector.
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.