Help, so frustrated, visa write vi working, but serial port write vi doesn't

[wendong]

I was using labview6i to control MKS647C mass flow controller by RS232 serial communcation before. All programs were written by Serial Compatibility VIs, but a week ago the computer crashed and I reintalled the labview and all the drivers. Because I couldn't find the exact verison of labview, I installed labview 6.1. In Max the COM1 interface looks fine,and NI-VISA 4.4, NI-Serial 3.4 are visible.

The problem is: all my old programs using serial compatibility VIs can not communicate with the instrument, but if I rewrite the program using Visa VIs, the communication is fine. I don't want to rewrite everthying, hope some experts can help me out.

[Dennis_Knutson]

I think it was with 6.1 that the old serial driver was made obsolete and not installed. The calling VIs are actually wrappers around VISA calls. You should see this when you look at the block diagrams. I don't understand why one VISA Write would work and not another. What error code do you get?

[wendong]

Thank you for your answer. You are aright, initially NI-Serial driver was not installed, later I installed Ni-serial 3.4 driver manually and I can see the serial port VIs under Instrument IO->IO compatiblity-> Serial Compatiblity after that. But the problem is still there. The error code is 37.  Thanks a lot.

[wendong · Accepted solution]

Problem solved.

It may sounds simple.

Because I restarted the instument once, the parity setting went to ODD by default. But in my old program, I am still using parity NONE, that's why it failed!