Dear Leonardo Mariga; could you please help me solve this problem? I want to send variables from Simulink to Arduino (for example 7 variables) each variable has a value varying from [0 to 255] Then, ...

Generally debugs messages in Arduino is done by Serial.print*, and show in this monitor serial, or another serial tool, as screen, pyserial, coolterm, etc. The Arduino official IDE, not have debugger.