:0: error: (500) undefined symbols: _IdleI2C(dist/default/production\01_Hello_world.X.production.obj) _OpenI2C(dist/default/production\01_Hello_world.X.production.obj) _WriteI2C(dist/default/production\01_Hello_world.X.production.obj) (908) exit status = 1 nbproject/Makefile-default.mk:131: recipe for target 'dist/default/production/01_Hello_world.X.production.hex' failed make[2]: Leaving directory 'C:/ProgettiXC18/01_Hello_world.X' nbproject/Makefile-default.mk:90: recipe for target '.build-conf' failed make[1]: Leaving directory 'C:/ProgettiXC18/01_Hello_world.X' nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed make[2]: *** [dist/default/production/01_Hello_world.X.production.hex] Error 1 make[1]: *** [.build-conf] Error 2 make: *** [.build-impl] Error 2 BUILD FAILED (exit value 2, total time: 3s)