com port missing & red cross sign in MAX (device in unknown state?offline)

[NIFan9]

Hi Everyone,

I have three serial ports on our lab computer, one is the default serial port on the motherboard, and two others are usb to serial connectors. The problem is the default serial port com1 has a cross sign in MAX and the other two serial ports are missing. All serial ports shown correctly in the device manager of windows XP, and in the registry too. The labview version is 8.5.1 with NI visa 4.4. See pictures attached.

I have search many hours and haven't find a clue. Please help me.

Thank you!

Eric

[Arham-H · Accepted solution]

Hi,

Have you tried clicking on the troubleshoot button in the Device Status section? Is this the first time you have connected these devices to your computer and can you see the virtual com ports on another computer in the lab?

Regards,

[NIFan9]

Thank you Arham. I updated NI visa, and the serial ports are in MAX now.

Eric