How to perform hardware in loop testing?

i want to perform hardware in loop testing for satellite attitude determination and control. i have already created a plant model for the satellite in simulink. now using xPC target toolbox the plant model is executed on a real time target machine (desktop PC). but instead of having the controller on simulink, i want to run the controller an an actual hardware micro-controller (MSP430F5438A) and interface it with the plant model running on the real-time target machine. but as of now no such drivers exist for an interface of this type. so i want to know how i can do the interfacing, if possible?