Perfectum OSD
Stage 1
Video signal detector using 3 Resistors and ADC Watchdog
Connections:
3V3 ---| | | | | R1=560 OMh | | | PA0 ---+ | | | | | R2=75 OMh | | | +---------------> Camera Video | | | | | R3=75 OMh | | | GND ---+---------------> Camera GND
Output to USART1 at 115200 After detecting write PAL/NTSC and lines count
You can try different R1 and R2 combinations. Algorithm can detect right video sync level.