Adding Extra Switches

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The All-In-One circuit can be tweaked for having 4 extra switches that can be used for a sustain pedal, MIDI switches (very useful for SooperLooper!), or for sending some specific MIDI message (program change, etc.).

The unused pins in the MCP23017 are:

pin 27 (GPA6) pin 28 (GPA7) pin 7 (GPB6) pin 8 (GPB7) The first 2 are bound to INTA and the other 2 to INTB.

You can check the schematic: 8

the UI active layer’s MIDI channel will be used.

So, the only things you have to do is:

  • update your zynthian
  • solder a 5 row-pin connector to your AllInOne circuit
  • connect some kind of switch between pin1-4 and pin5 (GND)
  • from the webconf tool, configure your wiring layout accordingly to the used pins: ZYNTHIAN_WIRING_SWITCHES’: “100,103,108,111,106,107,114”

Here are the default pin assignments:

pin 1 => GND
pin 2 => WiringPi GPIO 106
pin 3 => WiringPi GPIO 107
pin 4 => WiringPi GPIO 114
pin 5 => WiringPi GPIO 115

And the current hardcoded configuration is like this:

PANIC switch (6th zynswitch) => pin 2 (106)
short => All Notes Off
bold => All Sounds Off)
Unused (6th zynswitch) => pin 3 (107)
Unused (7th zynswitch) => pin 4 (114)
MIDI CC64 (Sustain Pedal) (8th zynswitch) => pin 5 (115)

Switches are normally open, closing to pin 1 (GND).