Hello I need an arduino mega card but in our project we only use few pins of arduino so we want to make arduino ourself .So which pins I need to connect for running arduino.Like if I didn't connect CLKO is there any problem. I want to learn minmum connection for using arduino(power connections,usb connection,etc.)
If you only need a few pins, why are you using a Mega, which has lots of pins ?
have a look at this