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.
Top:
Bottom:
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!