Here is a rough block diagram for the ISHIZENO i8. From left to right, the 16 faceplate knobs will be connected to the Raspberry Pi 2 through its GPIO pins. From there, we will use the Pi’s SPI bus to drive 4 AD5263 quad digital potentiometers on every submodule section, which will require a total of 33 pins on the submodule bay (16 inputs, 16 outputs, 1 ground).
For their parts, the 128 ports (16 per polyphonic channel) will be routed straight to the submodule sections and will be directly fed to 2 AD7606 analog-to-digital converters per submodule and to the AD75019 crosspoint switches (1 or 2 per submodule). The converters are necessary now that we have gotten rid of the Arduinos, and will be used to power 16 oscilloscopes per channel (128 in total).
The crosspoint switches will be connected to the crosspoint bus, which will have 16 or 32 analog ports, depending on the number of crosspoint switches installed on every submodule section, with one by default, and an optional second one. This will require another set of 17 pins on the submodule bay (16 ports, 1 ground).
By default, ports 16 on every channel will be used as output. This will allow us to feed them directly to a mixing section located on the faceplate PCB. This section will be powered by 9 LM833-N operational amplifiers and 9 AD5263 digital potentiometers.