USB16 controller problems

I’m having some mysterious problems with my USB16 servo controller.

I’ve got two motors hooked up to it and have, for the most part, had no problems controlling them from MATLAB.

However, I’m occasionally finding that the USB16 cannot be accessed. It’s unclear what’s triggering the behavior. What is really odd is that when I unplug the cable to the controller and reattach it, Windows XP (SP 2) doesn’t detect the controller: COM7 (the typical port for the USB16) is gone and doesn’t come back. I have to reboot the machine and then it works ok, at least until it fails again.

The robot I’ve built has the motor controller and a USB camera connected to a USB hub that then runs to the computer. Not sure if this is a problem or not.

Any suggestions/tips appreciated!

Many thanks,

What other USB devices do you have plugged into your control computer?

I use a Pololu USB-to-Serial adapter paired with a micro serial servo controller, which is effectively the same setup as your USB servo controller (same USB to TTL serial chip and driver). I experience exactly the same problem you’re describing when I also plug a certain USB memory stick into my computer. I have several other USB devices plugged in all the time (mouse, wireless adapter, sim license key) but only this one particular memory stick causes the problem. I suspect it has something to do with the drivers, but I just don’t use that key and my robot at the same time and I’m happy!


Interesting. Here’s what I have attached to the computer:

  • USB16 pololu controller
  • Logitech USB Web cam
  • FTDI USB controller (USB->serial controller, used to control a 24 channel -> 144 channel multiplexer)

The USB16 and the webcam are attached to a USB hub, as they are both on the pan/tilt robot. The camera is needed to see where the robot is oriented.

I can move the webcam onto a separate USB jack using an extension cable to see if that is the problem.

I am also exploring using some other hardware to generate the pulse codes for controlling the servo motors, in which case the USB16 would not be used. Other alternative would be to use a different computer to view the camera output.


Oh, I’ve also got the keyboard and mouse on USB.