MIDI Keyboard Encoder 

 

The keyboard encoder is capable of encoding any number of momentary action, push to make, single pole single throw (SPST), switches from 1 up to 72 to produce the equivalent MIDI note-on/note-off data commands. The keys are arranged in an 8 x 9 (72 keys) matrix.

 

The encoded switches are wired via IN4148 diodes, see switches schematic. Also there is a wiring diagram available.

 

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 8x9 Keyboard ITEM#: MIDI8x9KEYS PRICE:  €35.00

 

 

The Keyboard Encoder to MIDI Unit consists of:   The MIDI channel is preset to channel 1  The velocity byte is preset to the maximum value. Keyboard ranges from MIDI note 24 (C1) to MIDI note 95 (B6), Other MIDI channel, velocity and start Note can be programmed on request, A wiring diagram is available. A Miduino kit including a suitable pre-programmed Atmega168, A 2.1mm power socket, and associated LED, , A MIDI 5-pin DIN output socket, The circuit schematic is available, The switches schematic is available     The Keyboard Encoder to MIDI unit requires: a 9v battery or equivalent DC power source Suitable key-switches or magnetic reed switches and associated IN4148 diodes

 

Circuit Schematic:

A circuit schematic of the MIDI 72 note keyboard shows the switch connections. Note that for this project the 4-way DIL switch is not required. The circuit schematic for the Miduino , and a wiring diagram  are also available.

     

Assembly:

The kit includes all parts necessary, the assembly is straightforward and well documented. This design does not include a USB chip, it is designed to use a FTDI USB 232-TTL cable to program the microcontroller.  However since the cable plugs directly into the Miduino, you can use one cable for multiple Miduinos.

   

MIDI Wiring:

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

 

MIDI Keyboard Wiring:

The switches are organized in a 8 x 9 matrix (72 switches) arrangement. The switch keys are wired as shown in the  Wiring diagram.

 

Note that the red dotted lines implies the extra switches and diodes. For example, at the top, switches and diodes 0, 6 and 7 are shown but the circuit is also wired in a loop to switches and diodes 1 2,3,4 and 5. Also the other sides of these switches/diodes are connected down to Miduino contacts D2 to D9.

 

So, for example, terminal connected to D10  is wired to one side of the 8 key switches SW 0 to SW7 and the wire can be looped from one key switch to the next.

 

Each of the other side of these switches SW0 to SW7 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 7 other diodes. For example Anode (A) of diode DO is looped to D8 then to D16 then to D24 etc. down to D64 and finally to digital terminal D2 on the Miduino.

 

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