LabVIEW
Serial overrun error -1073807252 even after a flush and bytes at port less than buffer limit
I have a device that continuously sends data over the serial port and a VI that records that data for a period then stops when commanded. When i start a new data collection run i want to clear whatever is in the read buffer before collecting the new data.
However, I can't find a way to avoid the buffer overrun error other than to watch for it and clear it, which seems like a work around not a clean way to do things. This must be a fairly common usage of serial communication so i'm hoping there is a technique i'm missing.
I've tried several things but among them is using flush at the start of each data collection run which seems to work fine itself, but then the read will throw an overrun anyway even though there is nowhere near a buffer overrun and no error from previous blocks. It's also odd that there is still several hundred bytes available immediately following a flush.
I'm attaching the the VI which is actually much bigger and more complicated than what i'm positing but i pulled out all the stuff that isn't serial related. You won't be able to run it because you won't have the right serial device with the right packets, but perhaps someone will see something obvious in my serial setup or read that might solve this problem.
the Bytes at Port Start is what was seen at the port before the flush
the Bytes at Port for Read is then what is available for the data i want to keep.
Yes, from when you checked the Bytes At Port to the Flush Buffer, your port received enough data to overrun the buffer.
1. Move your reading of the port to another loop that runs in parallel with your main loop. This way the port can be constantly read without interfering with your main loop.
2. You really should not use the Bytes At Port. Use the protocol of the serial data. It looks like you are dealing with binary data (not ASCII), so do make sure you have the termination character turned off. Now the next question is "What is the structure of the data being sent?" Binary data typically has a structure that includes a start byte, a command code and/or message length, data, and some kind of checksum. So what is the exact protocol your device is sending data to you?
Just another note on the buffer overrun after I've flushed it, I've counted the bytes and it does not exceed the buffer limit however it still gives an overrun error originating from the post flush read attempt. Maybe that error is still propagating from the original overrun, but seems odd. See in the picture below that the buffer was indeed overrun before the flush with 4065 bytes, but the next read only had 641 bytes, less than the max buffer size, and the error starts after that 2nd read. This is the behavior that didn't make sense and was the impetus for my original question. Though now is a bit moot as I've taken the suggestions to open and close the port. I will also look at using a separate loop to run serial in the future.
