Hi moho,
The following thread discusses the error that you are seeing with logging data:
Cannot write to measurement file
As for your timing issue, how long are you seeing each read operation take? How long is the expected duration? How else have you tested your system? Are you sure the device itself isn't taking this amount of time to return to your cRIO?
Lowering the read byte count was a good first step. Have you verified the configuration of your VISA Configure Serial Port VI?
Regards,
Nadine H.
Applications Engineer
National Instruments
