This is the repo containing only the protocol used in https://github.com/agra-uni-bremen/virtual-breadboard and https://github.com/agra-uni-bremen/riscv-vp. It is not RISC-V specific and can be used to connect any GPIO peripheral, as long as it is modelled in C++.
It is partly described in this paper.
Tests can be built with the usual cmake pattern mkdir build && cd build && cmake .. && make.