Visa Read error

[ssmith490D]

I am polling a serial instrument once per second that communicates at 115200bps. It runs fine for 2-3 days and then I get an error in Visa Read -1073807252. Can anyone identify the cause of this error?? Thanks in advance for the help.

ssmith@bnl.gov

[smercurio_fc]

When you right-click on an error cluster you can select "Explain Error". For that code you get: " An overrun error occurred during transfer. A character was not read from the hardware before the next character arrived." Sounds to me like you have a timing issue in that you are not reading the data out of the serial port fast enough.

[ssmith490D]

smercurio--

               I have attached a jpeg of the read section of my vi where the error is occurring. As you can see I poll the instrument with the "RALL" command. Then I wait 50ms for the response. Then the VISA Read reads the number of bytes that are present in the buffer and the program moves on. If there is less than 62 bytes then I go back to the Read case and query the instrument again. The baud rate for this device is 115200bps so it should only take about 5ms for the reponse to come in and I'm allowing 50ms. So I don't understand how that error would apply. What am I missing?? Thanks for the help.

ssmith@bnl.gov

[smercurio_fc]

At the rate of communication that you have are you using flow control? You probably should. Overrun errors are tricky to nail down sometimes because the problem may not even be with the software. See this thread, for example. There is also a KB article talking about this issue.

[ssmith490D]

Thanks a lot. I will check these out and let you know what happens.

ssmith

[stevem181]

Just a minor point:

steve