Question

Stop bit problem: USB to Serial Converter attached to motion controller, unable to set for 7-E-2

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I have three different USB to Serial converters, one of them an isolated converter from B&B. One brand of motion controller I work on uses EVEN parity / 7 data bits / 2 stop bits as its default. I find that none of my converters will work on the controller in this configuration.

If I borrow a PC with a fixed serial port and change the comm setup to use 1 stop bit, I can then connect using my USB converters.

What is there about the 2 stop bit setup that prevents my USB converters from working?
I acknowledge 2 stop bits is rare, but TRIO Motion Technology uses it as their standard default (don't know why). This has meant that every time I've been called to work on one of them, I've had to borrow a laptop with a fixed port.

I've never attempted configuring my PC for E-7-1 while leaving the motion controller at E-7-2. I'll try that the next time.

I'm curious as to why PC's with fixed serial ports handle the 2 stop bits OK, but the USB ports don't. Any idea?

This may seem like a silly response, but since the 7-E-2 setting is the default, can it be changed? While I find dealing with serial communications on PLCs to be a pain in the butt, I've never had to deal with odd settings like that one.

Good luck!