USB to Dual Serial Port Learning Board - Mini Version

1. The schematic is based on the official website. I used the STC8H2K32U chip. To accommodate the screen while maintaining a compact size, I used a 0402 package, which presented some soldering challenges.
2. The OLED screen was replaced with a 0.91-inch 12832 SSD (1306). 
3. The MCU's ADC reference voltage uses a TL431. Without the TL431, the ADC reference voltage is the MCU voltage.
4. An INA199 power input current sensor was added.
5. The output header should have been a dual serial port 8-pin connector, but since the MCU had an empty pin, I used a 10-pin ADC connector. The header is supposed to be 2.0mm pitch, but I didn't have any on hand, so I used 2.5mm pitch instead – a very tight fit.
6. Two LED indicators were added
. 7. Current detection was added to monitor the target board current during downloading. It's just a rough estimate, uncalibrated, and the current cannot be too high.
8. Screen usage can be added as needed.