ESP8266_BOOTLOADER_STM32 ESP8266_BOOTLOADER_STM32 /* ESP8266/8285 Pin STM32 MCU NodeMCU Pin(ESP8266 based) RXD PA9 RXD TXD PA10 TXD Pin4 BOOT0 D2 Pin5 RST D1 Vcc 3.3V 3.3V GND GND GND En -> 10K -> 3.3V */