How about debug console? See file fsl_debug_console.h/.c
Search function DbgConsole_Init() globally in SDK to see examples of how to use it. For example, check demo_apps\hello_world project, which does only a serial in/out.
Alternatively, you can check the project private_profile_client. And the usage of Serial_Print().
But in this case we need to define a print_buffer[], and use sprintf() if we want to print parameters via Serial_Print().