Download or clone the whole firmware and navigate to the keyboards/DeltaSplit75 directory. Once your dev env is setup, you'll be able to generate the default .hex using:
```
$ make V2
make V2
or
$ make ProtoSplit (if you have one of the prototype PCBs)
make ProtoSplit-ProtoSplit (if you have one of the prototype PCBs)
```
You will see a lot of output and if everything worked correctly you will see the built hex files: