I made a simple project. Everything was working well. Then i have just added "Serial.begin(9600);" in void setup (). And when i tried to compile it, it gave that error:
collect2.exe: error: ld returned 5 exit status exit status 1 Error compiling for board Arduino/Genuino Uno.
When i replace "Serial.begin(9600);", it works well again. But i need to see serial monitor.
Sorry for my writing mistakes.