Clarification of "blown" - by that term I mean that when the Nano is connected to the USB cable, it will not upload the code to the Nano - the IDE fails to load the code, with sync errors. The RxTx lights do not blink as they do during a normal upload.The USB does send data from the Nano to my PC! (I have a serial output of various data, that can be checked, etc)
I am a bit curious as to what the connections to the right of your diagram are?Those go to a brushless DC motor - they are windings and hall sensors in the motor.It would be relevant to know what is supplying each of the power connections on your diagram.All the power comes from a 12 to 14 volt battery, the Nano is powered at its VIN pin, and the other device (the DC motor controller) gets the same voltage on its pin 4.I am using the +5V from the Nano to power pull-up and an encoder.And a photo might give some hints.The "attachment" system is not working properly (if at all) on this forum at present, much preferable if diagrams and pictures are uploaded to imgur and linked as such in the text. So the USB port is in fact entirely functional, but something else is happening. I note you illustrate a pull-up resistor on the reset terminal. Why?