It looks like it might be a file name issue. Try changing "ADK.H" to "adk.h". If that doesn't work, check your "hardware/arduino/sam/libraries/USBHost/" directory. If the "adk.h" exists, something else might be wrong.
It looks like it might be a file name issue. Try changing "ADK.H" to "adk.h". If that doesn't work, check your "hardware/arduino/sam/libraries/USBHost/" directory. If the "adk.h" exists, something else might be wrong.