I would like to experiment with arduino interrupt handlers.
The reason is because i need real time RS485 communication.
The lag in the main loop is too long, i would like to modify the interrupt handlers and, in the long term, build an extension library (software profibus DP).
My main problem is that i am unable to save modified files to the avr/cores/arduino directory.
Does somebody know how to change the rights on this automatically installed directory so i can change these files. (OS=Windows 7)