Paul  wrote:
>
> If you still lose characters drop baud rate to 4800 then 2400 until you
> get success.
>

Contrary to expectation, lowering the baudrate makes the problem worse.
Raising it to 115200 actually seems to fix the problem. The loopback
works for at least a screenful of characters, which is all I've had the
patience to type using autorepeat.

Unfortunately, the plotter is limited to 9600 baud. Hardware flow control
isn't required, Xon/Xoff is good enough.

Dmesg now reports
63695.621538] usb 1-1.5: new full-speed USB device number 50 using dwc_otg
[363695.656491] usb 1-1.5: New USB device found, idVendor=067b, idProduct=2303
[363695.656511] usb 1-1.5: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[363695.656520] usb 1-1.5: Product: USB-Serial Controller
[363695.656528] usb 1-1.5: Manufacturer: Prolific Technology Inc.
[363695.657965] pl2303 1-1.5:1.0: pl2303 converter detected
[363695.663613] usb 1-1.5: pl2303 converter now attached to ttyUSB0
[363706.314462] pl2303 ttyUSB0: pl2303_get_line_request - failed: -32
[363706.315696] pl2303 ttyUSB0: pl2303_get_line_request - failed: -32

but the error seems nonfatal. The screen session is still running and
characters are still being returned.

I'm stumped on what to try next.

Thanks for reading,

bob prohaska

--- SoupGate-Win32 v1.05