I am interested in adding a PGA2320 volume control chip to my RPi. My initial thought would be to create a .exe file that runs on the RPi and generates the necessary SPI signals via the GPIO pins to change the volume register of the PGA2320 chip. The .exe would receive a command line argument that defines the new volume setting. This .exe would be called each time the volume is changed on the web UI.
I don't know if this is the "best" approach or not, but it would work. I have the ability to write the .exe without any trouble. However, If somebody could please point me in the right direction as to where in the Voumio code UI volume control events are processed, so I can add the needed "hooks" to talk to the .exe, that would be most helpful.