Hi folks, Sorry in advance for the wall of text, I just want to give as much information as I think is warranted. I've been struggling with a custom serial communication scheme for a while now, and I'm ready to ask for help and advice. I believe the client device is not responding to commands every now and then (which I believe I've satisfactorily proven using a polling of bytes at port), but the VISA Wait on Event vi is throwing errors that I cannot explain. I have it configured to wait for Serial Character events analogous to the "Detect Serial Break Event" example VI, with my event type enabled and flushed on startup, then VISA Wait on Event called with a 1000 ms timeout in a read loop until the program ends. The gist of the communication interface is to write a few bytes to the client device and wait for a response packet using VISA Wait on Event. As soon as the event is detected, a single byte is read which contains a payload byte count. That number of bytes is then read and passed out for processing through a user event queue. All seems to work pretty well most of the time, even with the device periodically forgetting to respond, but VISA Wait on Event is, according to NI I/O Trace, throwing timeout expired events much faster than once per second, but intermittently. Looking at the details of the calls in NI I/O Trace, it appears to sometimes be called with a 0 ms timeout, resulting in a flood of timeout errors (as one might expect). These error calls also show 2 additional input parameters: outEventType=NULL and outContext=NULL. I am only calling this VI in one place, and the timeout is wired with a 1000 ms constant. Is there some weird internal behavior in this VI? How can it ever be called with a 0 ms timeout if I don't code it that way? Is this somehow related to receiving multiple bytes between wait on event instances? I've attached an nitrace log so you can see traffic and errors. Note that when I first start the trace, I can get up to a few hundred of these wait errors before it seems to "hook into" the traffic properly. Perhaps the errors are entirely fictitious? I noted that the 0 ms timeout errors don't show up in the Desktop Execution Trace Toolkit, while the 1000 ms timeouts do. Thank you in advance for your time.

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Hi there,

Have you tried to set a slower baud rate to your code?

Every time that you have this error, the timeout LED turns ON? or you only see it in I/O trace

Regards

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