Determining the Serial port number

[muks]

I need to test my board on 3 PCs randomly.Each time i connect the board the serial port number like "com 18" is getting changed.Now the comport number i am using is 40.Though i dont any other USB connection.Though i refresh i still get  the data only if i define the port number as 40.Is there anyway to determine the port number.Also can someone tell me why this is happening?

[Eugen_Graf · Accepted solution]

I think you have USB 1.0, it will always take a new port number if you install a new one. (:unsure)

To find the right COM-Port of your device you can do following:

1) send anything on each port and wait a little for the right answer, if OK,than take this port for communication.

or 2) you can get the description string of all ports installed from the device manager. If your USB-Serial-converter have a unique description string, you cann compare all descriptions with your one, and if it conforms, thank take this port for communication.