Author Topic: .NET COM port baud rate limited to 115kbps?  (Read 10418 times)


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.NET COM port baud rate limited to 115kbps?
« on: February 03, 2017, 04:58:00 am »
I've run into a strange issue with the RS232 port on my PC (COM1). Using the .NET Serial port class, I'm unable to open it with a baud rate greater than 115kbps. A WinIOException is thrown with the string "Parameter is incorrect". However if the baud is set to 115kbps, I'm able to open the port and everything works fine. Virtual COM Ports on my machine also work fine with baudrate as high as 912600kbps, using the same C# code. To confirm that it's not an issue with my code, I tried to use the COM port terminal application available on this website -, and I get the same error.

Is this a known issue with some known workaround? I see some other posts on the internet alluding to it ( but I dont have an issue with USB serial ports. I'm running a Windows 7 64bit box and using .NET framework 4.5.

Jan Axelson

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Re: .NET COM port baud rate limited to 115kbps?
« Reply #1 on: February 03, 2017, 11:18:20 am »
If you are saying that you can ignore the error and use the desired baud rate, I would suggest doing just that.

It is likely a limitation built into the SerialPort class.

Virtual serial ports don't use baud rates except possibly on the downstream end (not connected to the PC), so the baud rate has no function for PC communications.