OpenVTX

Open-source 5.8GHz analog video transmitter with software-defined OSD, based on OpenOSD-X firmware.

Early stage: parts are selected and project-local libraries are in place. Schematic and layout are not started yet. The full design reference lives in hardware/DESIGN.md.

Planned Features

RF

• RTC6705 5.8GHz FM synthesizer: 40+ channels (A/B/E/F/R bands)
• SKY85743-21 FEM: PA with integrated power detector, ~500mW CW output
• IPEX/u.FL antenna connector

OSD

• Software-defined analog OSD via STM32G4 OPAMP/DAC/DMA, no MAX7456 needed
• SD (30x13/16) and HD (45x26/32) character modes
• NTSC/PAL auto-detection

MCU

• STM32G431KBU6: ARM Cortex-M4F @ 170MHz, QFN-32
• MSP DisplayPort protocol (Betaflight native)
• SmartAudio V2.1 fallback for legacy FCs

Power

• 2S-6S direct input (7-36V) via LMR51420 buck to 5V
• 5V regulated output for camera
• 3.3V LDO (TLV757, low-noise) for MCU and RF synth
• Reverse polarity protection
• TVS input transient protection

Safety

• NTC thermistor on PA for thermal auto-throttle
• Boot-to-pit-mode
• VPD closed-loop power control with logarithmic detector

Repository Structure

OpenVTX/
├── README.md
├── hardware/
│   ├── DESIGN.md           ← Full design document (BOM, pinouts, RF chain, PCB specs)
│   ├── OpenVTX.kicad_pro
│   ├── lib.kicad_sym       ← 14 symbols (project-local)
│   ├── lib.pretty/         ← 14 footprints (project-local)
│   ├── lib.3dshapes/       ← 3D models
│   └── tools/              ← Python scripts
└── reference/
    ├── 043_OpenOSD-X_REFERENCE.pdf
    ├── vpd_table.pdf
    ├── Connection.png
    └── datasheets/         ← Component datasheets

User Interface

Pad/Connector	Function
+BATT / GND	Battery input (2-6S)
5V / GND	5V output for camera
VIN / GND	Video input (CVBS)
TX / RX	UART to FC (MSP DisplayPort)
SA	SmartAudio (single-wire fallback)
IPEX	Antenna (5.8GHz via pigtail)
BTN	Channel/power cycle button
LED	WS2812 status indicator
SWD	Debug test points (SWDIO, SWCLK, NRST)

Key ICs

IC	Part	LCSC	Package
MCU	STM32G431KBU6	C529358	QFN-32 5x5mm
RF Synth	RTC6705	C913074	QFN-40 6x6mm
FEM	SKY85743-21	C5348950	LGA-24 3x5mm
Buck	LMR51420YDDCR	C5383002	SOT-23-6
LDO	TLV75733PDRVR	C2868428	WSON-6 2x2mm

License

Licensed under CERN-OHL-S-2.0.