How to get a signal from the serial port to start a labview program?

I need to synchronize the data obtained from a program (which is not in Labview)with the data collected with Labview on a different computer. I can send some data strings to the serial port of the computer running the Labview program when the other program starts. However, I need to be able to read the trigger in my Labview program. Do you know what I should do? Thanks.

If you don't have any other programs listening on the COM port, you need to let a LV program run BEFORE the signal comes, otherwise you won't be able to read it. You can have the program wait in a slow timed loop so that it doesn't use up too much CPU time, and when the required "trigger" comes, to move into the main part of the program.
You basically need a while loop waiting for a certain string in the serial buffer. Once the string is found the while loop is exited, and the data acqquisition or whatever else you require from the progam can be performed.
In the example attached the program wait for ANY text to be sent to the COM port. Please note that you need to configure the VISA resource before using it. Once there is something at the COM port, the loop will exit and the rest of the program will be executed.
Hope this helps
Shane
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)
Attachments:
Wait for serisl message.vi ‏17 KB

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