Just to add that many Ard Nano are clones which use CH340G /Prolific and other cheap chips which all have the same problem - They do not have a unique serial number so if you have 2 or more chips of the same type it is impossible (other than position) to write Udev rules for such devices. You can see this if you do a lsusb linux.die.net/man/8/lsusb . However as Eric has said this is something "not for the faint hearted" and i would suggest you the changes on a copy of your SD card (or take a backup first) and takes a little time to get your head around. Of course after doing the "udev by position" you will ALWAYS have to plug the device into the same port/hub.

Simpler way,if this is the problem, buy an genuine FDTI chiped device that has a unique serial number - for the Ard Nano the code will of course not need to be altered but most likely you will need the Autoreset /cap trick - I did and the problem went totally away

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