Can't get CW keying via RTS to work

[PE1MR]

Hi everyone, very happy with my (tr)uSDX (fw 2.00t).
Setup: 13.8V powering via DC-connector, Micro B USB to laptop.

Successfully made some CW qsos with my paddle connected, that is working just fine. I wanted to try to send CW by keying the RTS line (e.g. with FLdigi), but it just won't work. The (tr)uSDX resets when the DTR goes high, so that's working as expected But when the RTS goes high, nothing happens. CAT is working just fine. I have paid attention that there is no conflict with a program (flrig, etc.) claiming that particular serial port.

[PE1MR]

Fixed! It seems that you need to open the virtual serial port and start CAT with, for example, flrig and then key the RTS line (flrig -> keyer -> config). Just keying the RTS line from a random programme / terminal won't work. Correct me if I'm wrong.