This is a small add-on PCB that allows for new triggers to be sent from the 218r on each consecutive note without lifting a finger. It converts the changes in the v/oct output into triggers and adds them to the pulse output.
There's no need to change any components on the 218r. The "key" and "pulse" inputs just go to the pads above their respective banana jacks. "out" goes directly to the pulse out bananas. Use a bolt standoff to install it above the STM32.