i am working on my graduation project with arduino mega 2560 and i have problem while uploading my sketch to the board, the unusual thing is that when i verify the sketch the software gives me DONE COMPILING!! which i guess means everything is okay but for the uploading to board it shows this error message:
Arduino: 1.6.7 (Windows 7), Board: "Arduino/Genuino Mega or Mega 2560, ATmega2560 (Mega 2560)"
Sketch uses 7,568 bytes (2%) of program storage space. Maximum is 253,952 bytes.
Global variables use 350 bytes (4%) of dynamic memory, leaving 7,842 bytes for local variables. Maximum is 8,192 bytes.
avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.
avrdude: ser_drain(): read error: The handle is invalid.
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.
This report would have more information with
"Show verbose output during compilation"
enabled in File > Preferences.
i would appreciate your help