Adding Extra Switches
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:
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 press => All Notes Off bold (long) press => 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).