USB Serial Communication to Astar w/o Vbus from Computer


I am currently using an Astar mini sv to control a multi axis stepper driven test fixture. I have the stepper drivers and the Astar powered from a 24V supply going to Batt + and -. I will have a computer (NUC) in close proximity to log output values over serial communication from the Astar. I would like to have the Astar not be powered even though the usb cable to the computer will be connected. Could I connect a 5V line from the Astar back to the vbus and isolate the vbus line from the computer usb? I attempted to use a usb cable with the vbus line disconnected, but the computer did not recognize a com port connected. I would also like the ability to continue to use the computer to program the Astar over the connected usb cable. Is this possible?

Thanks in advance


Why do you want to remove the VBUS connection between your A-Star and computer? If you do not already know, there is a power selection circuit on the A-Stars that allows both USB and VIN to be connected at the same time. The power selection circuit is configured to draw from VIN unless the regulator output falls below ~4.5V. You can find that information under the “Power” heading in the “A-Star 32U4 Mini” section of the A-Star 32U4 User’s Guide.

- Amanda