1. Three different signal types
VIDEO / CAM / VIN / VOUT
Traditional analog FPV cameras output CVBS composite video. It is a continuous analog waveform containing image and synchronization information. It does not use baud rate, UART ports or serial protocols.
UART TX/RX
UART is a digital communication interface used for GPS, receivers, telemetry and other data devices. It transfers binary data using configured baud rates and protocols.
SmartAudio / IRC Tramp
These protocols allow the flight controller to change VTX settings such as channel, frequency and power. They do not carry the camera video.
2. Correct analog video path
The normal analog FPV OSD path is:
Camera VIDEO → FC VIDEO IN → OSD overlay → FC VIDEO OUT / VTX → VTX VIDEO IN
The flight controller does not send the video through UART. The video remains an analog signal while the OSD information is added by the video circuit.
3. Common mistakes
- VTX VIDEO connected to TX/RX: Wrong. UART cannot process analog video.
- Camera VIDEO connected to RX: Wrong. Connect it to CAM/VIN/VIDEO IN.
- VIDEO OUT connected to SmartAudio: Wrong. SmartAudio is only for VTX control.
4. Important note about the VTX label
Many flight controllers label the analog video output pad as VTX. In this case VTX means “video output to the video transmitter”, not a UART port. Always check the board pinout before wiring.
5. OSD visible but no camera image?
If you can see OSD text but the camera image is black, the VTX output path is probably working. Check the camera power, camera VIDEO wire and FC CAM/VIDEO IN connection first. Changing UART or SERIAL settings will not fix an analog video input problem.
6. Quick summary
- VIDEO / CAM / VIN / VOUT: image signal.
- UART TX/RX: digital data.
- SmartAudio / Tramp: VTX control.
- Analog FPV: Camera → FC → VTX.
When you see VIDEO, CAM, VIN or VOUT, do not look for a UART. They are video interfaces, not serial ports.