Reported on a Xiegu G90. With the blue programming cable — three wires, no
modem lines — CAT works perfectly. Behind a DE-19, which carries audio, CAT and
PTT, the radio went into transmit the moment OpsLog connected and stayed there.
Windows raises DTR and RTS when a serial port is opened, and the DE-19 reads
them as PTT; Xiegu's own documentation asks for both low. The CI-V backend has
dropped them since it was written, for the same reason on Icom rigs with USB
SEND mapped to a line. Xiegu, Yaesu and Kenwood did not. They do now.
The second half of the report: WSJT-X through OpsLog's rigctld decoded fine and
never transmitted. Nothing was broken in that chain — set_ptt reaches the
backend, which sends the CI-V PTT command, which a G90 ignores. That is why
Xiegu keys on a hardware line instead. The backend can now do that: Settings →
CAT → Xiegu → how the rig is keyed (CI-V / RTS / DTR).
Untested here — no G90 in reach. The operator who reported it offered to try.