Custom Zynthian Main Board with all multiplexers localized

[infinitymodular]

Hi,

I’m designing a custom main board for my zynthian eurorack project. I want to move all MCP23017’s to the main board. Essentially I want to pack all the logic onto the main board and have “dumb” modules that plug in for button-pad, rotaries, CVs and Gates… I’m looking to replicate Zynface, ZynaptikV3 and ControlV5 all onto the main board.

From the schematics for the above, it would seem like the MCP23017’s SPI addressing is such that the Zynaptik SPI-Addr is the same as the Control board MCP23017 that handles button pads 1 through 16. Was the intended use for Zynaptik to extend a basic ZynBox that doesn’t have the buttonPad?

In simple terms, it looks like the modular architecture of Zynthian handles only 3 Multiplexers on 0x20, 0x21 and 0x22 … If I want button_pad + lights, 4 Rotary encoders and CV/Gate I/O, I would need a fourth MCP23017.

I would like to not evolve away from the main branch of the software and what it currently supports, if I can help it.

[infinitymodular]

Ah… I think I’ve resolved my confusion… the V5_control_rack schematic Multiplexer replaces the zynaptik multiplexer. So I can run buttons and encoders off 0x20 and 0x21, while the zynface adds a third multiplexer for handling the cv_gate I/O, and an extra 8 GPIOs. So I wouldn’t need the additional multiplexer from the zynaptik schematic.

Is this correct?

And then I’d choose the wiring layout of “MCP23017 Zynaptik-3 Zynface” e.g.

Essentially I want to build this User Interface … but with a consolidated main board and break out boards just for the control hardware.