I am using MCUXpresso to build an MK10 project. The startup file, startup_mk10d10.cpp, cannot find functions in other modules, for example interrupt service routines or utilities. The IDE gives , as an example, an undefined reference to `PIT1_DriverIRQHandler' error, although it is defined in an other file and a definition line is included. It links only main(). Clearly I have set something wrong! How should I define routines in other modules? Please note that all other files link properly.