Com ports

I’m on Window7x64. Trying the cross platform c code in 5.h of the manual I get a Permission denied response. Looking at the manual I see:

“Secondly, the Maestro shows up as two virtual serial ports on a computer if it is connected via USB. One of these ports is called the Command Port and the other is called the TTL port.”

When I installed the software and plugged in the controller, these don’t show under Ports (COM & LPT) in device manager as would be expected. “Pololu Micro Maestro 6-Servo Controller” does show under Pololu USB Devices in device manager, and the Pololu Maestro Control Center software moves servos as expected. Do I need to try and manually install the com ports? Any help would be appreciated.


The permission denied error could be caused by trying to open a port that is already opened by another application. Since the two virtual COM ports (Command Port & TTL Port) are not listed in your Device Manager, I suspect that you tried to run the program as is without modifying the name for the COM port device in the main function. By default, the code uses “\\.\USBSER000” for the COM port device name, which could be occupied by some other device.

Can you try unplugging and plugging your Maestro into your computer to see if the virtual COM ports are visible under “Ports (COM & LPT)” in your Device Manager? Alternatively, you could try rebooting your computer. If you are still unable to see the two virtual ports, can you try re-downloading and re-installing the Maestro drivers to see if that changes anything? Can you try using a different computer?

- Amanda