Hello, Frank.
I am sorry that you are having trouble with the Maestro. When you say that the virtual COM port disappears, does that mean that it is no longer visible in your Device Manager? When you say that the controller powers down, what indications make you think so?
The next time it happens, please let me know:
- What entries for the Maestro are still visible in your Device Manager?
- What are the Maestro’s three LEDs doing?
- If you temporarily short the Maestro’s RST pin to the GND pin, does that solve the problem?
- If not, does unplugging and replugging the USB cable solve the problem?
We have encountered this general type of problem before, but we do not have a great idea of what causes it or how to solve it. Our best idea is that there is some kind of electrical noise that is getting caused by something in the system, and the USB port is shutting down in order to protect itself from damage.
Sometimes the USB host will just stop sending packets on the USB data lines, which tells the Maestro that it should go into USB suspend mode and conserve power. You can see if this has happened by probing either the D+ or D- line with an oscilloscope, and seeing if there is a digital signal there. There should be at least one packet per millisecond under normal operation. There is an option to make the Maestro ignore USB suspend in the configuration utility, and you could try enabling it, but that won’t actually fix the underlying problem that caused the USB data to shut off.
Sometimes the USB host will shut off power to the USB VBUS line as well. You can probe the pins of the USB connector with a multimeter to see if this has happened.
In one case the problem was solved by changing to a better power supply. Could you describe how everything is connected to the Maestro, and what kind of power supply you are using? Some pictures might help too.
–David