Re:XC8 Conflicting Declarations For Variable
I have read your code, and you just need to add #include "msspi2c.h" in your msspi2c.c file.
You error is common.
Look, your main knows about msspi2c.h, your main file knows about the functions, but he don't see the functions with body. Your main file only sees the header functions in your msspi2c.h file. The compiler looks for all the files that includes msspi2c.h file, trying to look for a match functions with code. For this reason you need to include msspi2c.h file in your msspi2c.c file.
Now your main knows about the headers and the functions with code.