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Page history last edited by Noah Vawter 12 months ago


This circuit board accelerates adding synth knobs and controls to instruments.  Knobs_SM refers to "Knobs, Smart."

 This newly developed knob multiplexer allows up to 64 knobs to be daisy-chained into one analog input.

This neatens and simplifies wiring.  It also allows a proper number of controls to be used on digital musical instruments.


It is based on the 4051 multiplexer, the 4040 counter chip and the 74138 1-of-8 selector.  It consumes only three GPIO pins:

1 analog and two digital controls.






The pinout/wiring is like this:

SV3 and SV4 are identical.  Note that labels on pins 1 and 6 are difficult to find on the boards.

1 = reset ( D0 )

2 = clock ( D1 )

3 = analog_out ( to A0 on arduino )

4 = unused (antenna to parallel spirit dimension...)

5 = GND

6 = V+, 3.3V


C defines, such as in an Arduino sketch, typically look like this:

#define SIG_RESET      ( D0 )
#define SIG_CLOCK      ( D1 )
#define KNOB_MUX_INPUT ( A0 )


There are some test Arduino sketches in the Bitbucket archive.  They are called KnobMux_01, _02 and _03.


Each knob mux board holds 5 knobs and has 3 additional pins for analog inputs.  Each board must be jumpered to set its ID:

Remember to solder one pin from JP1 to pin 1-8 of SV2 to set the ID! 




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