Omnibus F4 V3 pro -> uart6 tramp issues

After trying to forget the usb troubles i started with testing the final setup. Go into the OSD Menü (left stick: left, right stick up) and tried to change the Tramp transmitting frequency under features -> TR.  Normally should be there depending on t he settings Band “Fatshark” instead there was “Boscam A”. It was kind strange but lets try it, after confirming new channel with set nothing happens! Normally you should get white noise in your FPV goggles because the channel should change.

Confirmed soldering to the right uart pin, must be the TX pin, because its a half duplex protocol. Also the right serial was set in betaflight to IRC Tramp -> Serial6. Also the cli option vtx_halfduplex was set to “ON” like its default.

Okay lets go deeper and measure the signal:

Looks like betaflight trys every second a communication to the tramp
Something is blocking the Bus, the 3V3 voltage step shows clearly there is something wrong

Lets try uart1 as reference, worked with first try:

Capture signal on uart1 tx

Lets take a look to betaflight wiki: On OMNIBUS F4 V3 and later, serial RX is UART6, not UART1.

So conclusion is that Uart6 TX Pin is not mapped directly to the uart6 tx pin, i assume there must be some hardware inverter used to receive sbus signals which is blocking the signal.

Its still pita, without schematic we have to believe what we get and debugging is hell, hopefully we will get a open schematic flight controller with a F4 like the old CC3D. As workaround i use now Uart1 TX Pin, luckily i have one uart left.

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