IO.Ports.SerialPort Mysterious Delay in port.write

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I have a vb.net app (.net 4) which writes serial data (no more than 10 bytes, via System.IO.Ports.SerialPort) and there seems to be a delay in the send. An external device tells me to do something. It takes my program about 15ms to process this request and send the result back to the host. The host is timing me to see how long it takes. I can guarantee that I am sending the serial string within the 15ms, but the host doesn’t get it for 80ms and some times as much as 150ms! What external force is causing this delay? I was original using a USB to serial adapter but have since switched to a PCIe card and am getting the same results.

Posted 19-Nov-15 18:26pm

Member 8153852

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[no name] 20-Nov-15 0:42am

That's life: http://www.codeproject.com/Articles/110670/Improving-the-Performance-of-Serial-Ports-Using-C

Member 8153852 20-Nov-15 11:06am

Thanks. That was an insightful link. However, it would seem as if the "blame" is put on the "receiving" side of the equation. Here is a bit more to my scenario...I only have control over my app (sender). The receiving app does not have this problem with other applications (which I have no knowledge of) so the burden is on me (the sender) to fix. I also tried my app on Windows Embedded with not change what so ever. Should I be using something other than .net's system.io? Is that my problem, or is it a Windows thing?

[no name] 24-Dec-15 13:18pm

Look for delays on receiving serial data. There are serial port options for (a) defining an event character and (b) defining timeouts for how long to wait for successive bytes.

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