Error -107380724​6 when trying to control a circulator in Labview via RS-232

Question

Hi, I'm trying to control an F32 refrigeration/heating circulator through LabView via an RS-232 cable but am having trouble. I keep getting the error - 1073807246 at property node (arg1) in VISA configure serial port. What does this error mean and how can I correct it? I have already specified the values for Baudrate (4800), parity (even), handshake (RTS/CTS), data bits (7), and stop bit (1).
Thank you,
Hung

Answer 1

It is rare to get a timeout when writing. I usually get this when I am reading a port. What value did you use for the timeout when you configured the port? I think the default is 10,000 ms, i.e. 10 seconds. If it were timing out, you would notice the code hanging for 10 seconds as the serial I/O function tries to run to completion.
To avoid timeouts, check the following in your code.
1) Make sure the configured timeout is long enough to handle the data stream sent on your write. If you are sending a long stream of data, you should test the time it takes and make sure the timeout is larger than the longest time for your longest data stream.
2) When you are reading a port, make sure the number of bytes you request is equal to or smaller than the number of bytes being sent from your serial device hanging on the other end of the cable. Otherwise, it will always use the entire alotted time (the timeout value) attempting to read the data.
3) Verify that the response time of your device is not abnormally slow. Some devices don't interrupt processes very quickly. In fact, some devices put a very low priority on the serial port and may not respond at all while executing certain functions. You need to set the timeout value to be long enough to account for the device's response time when reading a response from your device.
If you don't know what to use as a timeout value, always start with a long one and try to handle timing variations in your code, e.g. read or write the data in chunks perform sanity checks as you go. Long delays in the response of your code will point you to a bug in the handling of serial port communications. You will get a long delay everytime the serial command cannot complete due to an unreasonable request, e.g. telling it to read 100 bytes when the device can only return 16 bytes for the requested command.
You can use the NumberOfBytesAtPort property to help you determine when data is available for reading. Also, in a loop that may be used to poll a serial port, try to use a wait (the wristwatch timing function). This keeps you from pummeling the serial port to hard with futile requests.
Another good way to avoid serial timeouts is to use a termination character. If your device always expects a as the last character in a command, or if it always sends a as the last character in a response, then configure your port to terminate a transmission automatically upon receiving the character. I think the default termination character is (linefeed character) it you elect to enable this feature in your configuration.
jc
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