MavROS without PX4

I have a question please. I have Mavros Code But I do not know How to begin
In our Project we want to implement Mavlink Protocol using Zedboard FPGA and After that we want to Connect it with a Respaberry pi 3 (which it has Ros ).
my Work is to adapt the Code of Mavros to work correctly in Our System.
we do not have Px4 or any thing else.
please Advice me from where could i begin.