Cannot Change Configuration of COM Port - No Changes Accepted

Aug 28, 2018
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Windows 10 laptop
Keyspan USA-19HS USB to Serial Port adapter

I cannot get the system to accept any changes I make to the COM port configuration. I go to the command prompt and type "MODE". It shows that COM3 is set up with 9600 baud, 8bits, 2 stop bits, no parity.

I go into Device Manager and change this to 9600 baud, 8bits, 1 stop bit, Even parity. It accepts this.
At the command prompt, when I type "MODE", I see that the change in the Device manager is not reflected.
At the command prompt, I enter: MODE COM3:96,8,1,E. It accepts this and then displays the current setting of the COM3 port AND NOTHING HAS CHANGED -- IT IS STILL 9600,8,2,N.
I go back into Device Manager and it still shows to have the settings I want, but the command prompt "MODE" query shows it to be wrong. As proof that it's wrong, data transmission doesn't work correctly.

I can do nothing to change the COM3 port configuration. The CNC router that it is hooked up to will accept the programs I send to it, but the toolpath is incorrect. If I unplug this serial cable from my W10 machine and USB-serial adapter, then connect it to my XP machine, it accepts the toolpath program and runs flawlessly.

How do I change the configuration of the stop bits and parity? I have contacted Tripp-Lite (manufacturer of the Keyspan adapter) and they do not have an answer on this.


Sep 26, 2017
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Can't say if it's the same but back a-ways I had a similar issue with a USB to Parallel Port adapter and an HP Deskjet 970 printer, seemed to be the HP software couldn't recognize the adapter.

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