Wait on Event causes serial communication errors

Hi,
I've been trying to to create a VI that can send and receive text data to a device via RS-232. I started out with the Basic Serial Read and Write.vi that comes as an example with LabView and that works. However, all it does is wait for specified amount of time before trying to read incoming data. I thought to make that example more robust by polling the serial port for incoming characters. I did some Googling and I came upon this page:
http://digital.ni.com/public.nsf/allkb/179E61F87CF8B340862571EA0037CFA3
Preventing LabVIEW from Continuously Polling the Serial Port.
When I modified the Basic ... VI to include this however, I get all manner of errors. Sometimes, I don't get any response at all. Sometimes, I get response data from a previous request (but not all of it), and sometimes the device I'm communicating with tells me it's seeing a framing error. I don't think I've ever actually received a correct response. Can someone tell me if I've implemented this incorrectly? Does the page above ONLY apply to PXI controllers or can I use this for RS-232 communication? Do I need to be waiting on a different event?
Thanks,
Jason Mazzotta

Seems like your expected string is actually terminated by a linefeed character. VISA supports character terminated reads and even enables that for serial ports by default.
The entire loop in the middle and the "wait for event "can be simply replaced by a single VISA Read when you let VISA use read termination mode. It even uses line feed by default as termination character but you can easily modify that at the VISA Serial Init function.
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

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Solved!
Go to Solution.
Attachments:
laberror.JPG ‏85 KB

Is that mean permission from NI? it was working fine, once i terminated the labview application abruptly when not responding since then i have this problem.
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KevinO,
From everything that I can see in your code, it looks like you are programming correctly. Your code is also very neat and easy to read, thank you!
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Visa error handling in serial communication

Greetings,
I have a problem with the serial communication in my Labview program.
I have made an application that reads from serial port, searches for beggining characters, and later counts data after that beggining characters into variables in Labview program.
Everything work fine, but problem starts when I unplug the device from computer.
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Attachments:
find_start.vi ‏12 KB

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Wait on Event causes serial communication errors

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