I also have a MKS 651C pressure controller that I have been programming via LabVIEW. It was a little tricky to get all the serial port settings right, but I was able to do it. I created 2 basic VI's for the two types of communication with the 651 - commands and requests. I have attached my VI's for Command and Request. I have also created some others like Read Pressure, Change Set Point, Activate Set Point, Open Valve, etc, to do specific functions. They all use either the Command or the Request VI's that I created. I can send you those if you need them. Just email me at jay.mathews at asu.edu.
