@DrHidayu , Sorry for the delayed response! Just checking in to see if you solved this problem. Did you make sure to include the header file #include <CoDrone.h> ? If you did, you probably do not have the latest version of the CoDrone library. Go to Sketch>>Include Libraries>>Manage Libraries. Search for CoDrone and make sure you update to the latest version. Close Arduino and then try your code again. This should solve the problem!