’QY4 MCU Pin number PVCC Usage
IRQ 9 Video horizontal sync (start of video scan line)
PTA3 8 Interface DS1820 1-Wire bus temperature sensor
OSC1 4 32-MHz External oscillator input for OSD Active mode
PTA4 5 Change enable output
AD1 12 Analog input to measure battery voltage
PTA0 13 Communications with user’s PC during Configuration mode
CdS photocell light sensor input (AD0) during Charge mode
PTB0 15 Video vertical sync detection (start of new video frame)
PTB1 14 Output to enable/disable external oscillator
PTB2 11 Auxiliary loads to on/off control output
PTB3 10 Configuration mode request jumper
PTB4–6 7, 6, 3 LED status indicator outputs
PTB7 2 Overlay text output signal (added to video signal)
	
Table 1—Every I/O signal is used here. Port PTA0/AD0 pulls double duty, serving as the serial link in Configuration mode and the light sensor input in Charge mode.