That protocol is available in the
DIY-Multiprotocol project
. That file should be the starting point because the implementation is similar to deviation protocols, though the DIY project handles configuration and telemetry differently.
The best guide is to look at an existing protocol to get familiar with the implementation (pick one with a smaller file size). The main concerns are chip initialization, building packets, and the protocol state machine. The state machine is implemented in the callback function. The interface to the rest of the code is in the <protocol>_cmds function usually located at the bottom of the protocol source file.
This
is a recent pull request that added a protocol and shows which files are affected.
Ask questions as needed