I used my arduino uno on COM 4 before and it worked well, however when I tried to interface my 16*2 LCD to arduino using the example hello world, the following happened:
-The LCD showed light but no words
-The arduino orange light did light up as usual
-I received a message in the arduino compiler that says "COM4 is currently in use"
I unplugged ardunio from the usb port and plugged it in again and clicked upload..the following happened:
-The port didn't appear in tools > serial port menu.
-I received a message from the compiler that says :"COM 4 is not found" !!
what is happening, any help?
I am using windows 7, arduino is detected by the computer, I checked the control panel.