This project is inspired by the iPod Classic, so we want a nice round capacitive sense wheel for user input. (Plus it looks wanky).

Looking into the original iPod Classic (I own a 6th generation one that's sort of broken to play with), It uses a dedicated IC to decode the touch wheel input and transmit this to the host processor.

For the design of Silence, a separate MCU is required to drive the GUI for the user as the raspberry pi does not have any SPI peripherals left over to talk to the screen. We can utilize this processor to also read the capacitive sensor inputs and allow feeding this data back to the raspberry pi.

The common IC around appears to be the MPR121 (as used in the Tricorder project). This looks like a nice IC, however it requires an extra I2C connection and it's in a non-hobby friendly package (Still quite doable though).

Most Microcontrollers seem to have some form of touch sensing built into them now, and I have been meaning to learn the PSoC 4 series from Cypress as my next target to learn (And the reconfigurability looks awesome on paper).

So for this initial version of the unit I will attempt to use the PSoC 4245 as the graphical processor as well as the touch input wheel for the unit.