Having issues with simple serial communication.

Question

 I followed a tutorial online to start learning basic serial communication. The tutorial involved shorting pins 1 and 3 on the Comm 1 port, and writing a simple program (attached). I edited the program a little, to show the varied results that I get when trying to write and read a simple phrase via serial port. 
Could someone explain what causes the kind of result shown in "Serial Comm Example.png"? I believe it has to do with timing. Why would only parts of the phrase be transmitted?
Thanks,
Sarah
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Attachments:
Serial Comm Example.vi ‏30 KB
Serial Comm Example.png ‏139 KB

Answer 1

sarahzig wrote:
The tutorial involved shorting pins 1 and 3 on the Comm 1 port
Shouldn't that be pins 2 and 3?  On a standard DB-9 serial port, pin 2 is the Recieve and pin 3 is the Transmit.
Now for your code...
1. Move the Configure Serial Port to be before the loop.  You only need to configure the port once.
2. Close the port after the loop.
3. Handle your error after the close.
4. Stop your loop on an error or the stop button was pressed.  You will need an OR in there.
5. No need for the Flush Buffer function.  Remove it.
6. Using the Bytes At Port is a dangerous thing.  It introduces all kinds of interesting race conditions.  Instead, tell the VISA Read to read the number of bytes you expect to read.
6a. Alternatively, be sure to send an End Of Line character at the end of your sent data and set the number of bytes to read to something a lot more than you would ever expect to read.  The VISA Read will stop reading when it a) sees the number of bytes it was told to read, b) sees the termination character (currently enabled and set to a Line Feed, which is part of the End Of Line), or c) the timeout happens.  Whichever happens first.
7. With 6, the wait is no longer needed.
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