How should one controll a BSMCE04U-pp on the fly?

Greetings!

I'm a 3rd year undergraduate Engineering student and part of my final project is to get a CNC machine I've inherited from a previous project working with a custom controller as a scanner.

The students how made the CNC machine are not available and I need to figure out how to communicate with the "brain", a BSMCE04U-pp. So far in researching I've only found some guides on how to set this up using DrufelCNC and Mach3 but neither of these programs seem to have a natural programming interface to send, for example, custom g-code on-the-fly according to the output of some sensors.

Where should I start reading about these types of CNC controllers? Is it possible to write my own way to communicate with this board so I don't have to use DrufelCNC and some hacky AutoHotKey script to send g-code to the machine?

Thanks in advance.