As there is already a SPI device in the original design (MCP4922 DAC) I want to add a 10k digital potentiometer(MCP41010) to replace the resonance poti. This would allow MIDI automation, patch memory or different response (lin/log) while only using one additional pin for the slave select.
Speaking of pins:
Since the TI Launpad is running at 3.3V, but the audio circuit is powered by 5V, some sort of level conversion should be done. Luckily, this is not only easy, but also well documented by - for example - sparkfun.
SDA and SCL need to be bi-directional, SCK and the chip select lines on the other hand can be protected by a simple voltage divider.
I will try to finalize the schematics tonight and provide a git repo, so you can see what I am talking about.