I've got a persistent problem with my TNC-X connected to a Raspberry Pi 4 running APRX. The TNC-X decodes packets fine (yellow LED lights up) and works perfectly under APRSISCE32 on Windows, but the Pi isn't capturing the RF data. Checked /dev/ttyUSB0, tried multiple baud rates (1200, 9600, 19200), and verified UART settings. The beacon_postpoll() continues running but no packets show up in logs or get gated to APRS-IS. Has anyone else solved this specific Pi/TNC-X combo issue?

Check your APRX config file baud rate setting against the actual TNC-X jumper position. I had the exact same problem - jumper was still at factory default 1200 baud but I was trying higher speeds in the config. Simple ID-10-T error but took me hours to figure out!

Also verify your aprx.conf serial device path is correct and you have proper permissions. Try running 'dmesg' after plugging in the TNC-X to confirm the USB enumeration. USB voltage issues are uncommon but worth checking if nothing else works.

Had similar grief with my TNC-Pi setup. Consider trying APRS TNC Web for a lighter interface - it's a Docker-based solution that might bypass whatever's causing your APRX issues. Sometimes a different software stack reveals the actual problem.