I have custom 5V 16MHz Arduino that runs grbl and I was hoping to use one of the HC-05 bluetooth modules to control it wirelessly. This Arduino can be connected to a USB port through a FTDI chip. I'd like this to work with either of them and not both of them. This works for the most part and here is the 'truth table' I've experienced:
USB Bluetooth Works over Works over ON ON USB? Bluetooth? --- --------- ---------- ---------- Y Y N Y Y N Y N N Y N Y
I'm guessing when both are ON the USB does not work because they both share the same RX and TX lines of the Arduino and it seems priority is being given to the bluetooth connection. Is there a way such that when the USB cable is plugged in to the host PC the bluetooth module cannot be used and priority is given to the wired connection?