Hi Olav,
first you could try the MAX-explorer, go to "devices and interfaces" (or sth. similar, mine is german), then "ports", then on your COM. there you can define port settings and open a test-panel.
The other way would be to try the "basic serial read&write.vi" from the "find examples"-window. There you can define a string to send to your device and afterwards it reads the response.
Hope this helps,
greets, Dave
Greets, Dave