ESP8266 Minimum System Board V3

The key features of this minimum system board are:
        compatibility with I2C communication devices (such as OLED, magnetic encoders, etc.); compatibility with SPI communication devices (such as e-ink screens, OLED, TFT); compatibility with UART serial communication (such as GPS modules, communication between two ESP8266s); compatibility with WS2812 LED strips; and compatibility with ultrasonic modules. All I/O ports are brought out as pin headers, and a 3.3V to 5V switching function is added (by changing the jumper cap position).      
       It supports charging and program downloading via both Type-C and Android. I designed a two-stage switch: when switched to US5V, it powers the USB and charges the development board; when switched to ET5V, it powers the lithium battery (see schematic for detailed circuit diagram). All I/O ports are brought out as pin headers, and considering the different power requirements of 3.3V and 5V when connecting sensors, jumper caps are added to switch the power supply voltage. For the charging chip, I used the ET9640, which can not only charge the lithium battery but also output 5V.