Unless you can find a custom Simulink driver blocks library for your hardware (see Hardware Support), you will need to figure out the C-driver code for the hardware and create a Simulink block using the Legacy Code Tool. In addition, you might also need to create some Custom Target infrastructure in order for Simulink to apply a custom tool-chain that is used for your custom hardware, etc.
Alternatively, if you need like you cannot invest in this process, you can manually integrate the driver code into the code generated by Simulink.
