FT-450D: enabling rig activates PTT

[jaymot123]

Rig: Yaesu FT-450D
OS: Linux Mint 21 Wilma
Rig to computer interface: Digirig Mobile RS-232 version with Digirig's TS-480 cables which are also for the FT-450 series radios, also Digirig's coiled, shielded and choked USB A to C cable.
Hamlib version: 4.7-git.2025-09-18T16:08:14Z SHA-D44011 64-bit
QLog version: 0.46.1 built and installed from GitHub
Problem: whenever I connect QLog to the rig, PTT activates. WSJT-X is working normally and only transmits when I tell it to by clicking tune or calling or answering a CQ. When I change bands in WSJT-X it passes that over to QLog via multicast, and confirming a QSO in WSJT-X also logs it in QLog.

It's probably just something wrong in my rig settings in QLog but I haven't been able to figure it out. I've duplicated the radio configuration in WSJT-X as closely as possible: 8 data bits, 1 stop bit, 38400 baud, no flow control, PTT method = CAT, but WSJT-X has a provision for forcing DTR and RTS high or low which QLog's settings lack. When configuring WSJT-X these both had to be forced low to get CAT control to work correctly. I don't know if it matters for QLog though. It's been decades since I last had to configure a serial port so I'm pretty stuck here. :) I just want QLog to read the band, frequency and mode from the radio when I'm in LSB or USB (with wsjts not running) so I have fewer things to manually change, in preparation for the upcoming CQ Worldwide SSB contest this weekend.

My QLog settings for the rig are: interface=Hamlib; enabled rig fearures=mode, freq, power, CS keyer speed, VFO, QSY wiping and PTT state; port type=serial; port= /dev/serial/by=id/usb-Silicon_Labs_CP2102N_USB_to_UART_Bridge_Controller (and some gobbledegook at the end) which is what appears in /dev when I connect the Digirig's USB cable to the computer; baudrate: 38400; data bits 8; stop bits 1; flow control none; parity no; PTT type CAT (I've also tried setting PTT to none.)

Radio settings are CAT RTS none, CAT TOT 3000, CATRATE 38400. If anyone's gotten their 450D to work with QLog, please share your configuration settings.

[jaymot123]

I solved it by forcing DTR and RTS low in the settings for the rig in QLog.