Update: I now recommend using /dev/serial/by-id, which has stable names in it for the all of the Simple Motor Controller COM ports. See this thread for more info.
Hello.
Each controller does have a unique serial number and it reports to the computer it in the standard way with a USB string descriptor. You can see the serial numbers with our software and probably also with the lsusb command. There might be a way to write a rule in /etc/udev/rules.d/ that assigns the Simple Motor Controller’s virtual COM port correctly depending on what the serial number of the device is (thanks for the idea, jwatte). Searching for “udev rules serial number” on Google yielded a result where someone wrote ATTRS{serial}==“50E6920B000AE8” in their rules file. I’m not sure how well this will work with composite devices like the Simple Motor Controller though, because the serial number is more a property of the device as a whole, not the virtual COM port.
–David