Daktronics

"Cannot open Com" TeraTerm; Venus fails to connect immediately

Potential Symptoms

  • Cannot connect in Venus; Connection fails instantly.
  • Cannot connect in M2Config; Connection fails instantly.
  • Device manger says the adapter is working correctly.
  • May have tried another adapter.
  • The new adapter worked when initially setup.
  • When attempting a loopback in Tera Term, the error "Cannot open Com#" comes up.

Environment

  • Moxa USB to Serial adapter
  • Prolific USB to Serial adapter
  • Galaxy 3160, Serial RS232

Cause

  • Another program is using the com port. Is the serial adapter used for any other program? Check in the system tray and running programs and services in the task manager for programs that could be using the com port.

Resolution

  • Stop any service or program that uses the com port. If the program is not used, uninstall it. If the program is used often, get another USB to serial adapter or make sure the other program is stopped before trying to connect to the display.

Work Around

  • Stop the other program before trying to connect to the display.
  • Or, restart the computer and try Tera Term first. 

For Temporary Operation

  • Change the COM port to a unused / available port than reboot computer.
  • Device Manager > USB to Serial adapter properties > Port Settings tab > Advanced.

KB ID: DD2399679

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