Features:Compared to old version, the upgraded version has altered pin position and can be compatible for nodemcu. Use BRT (Bias Resistor Transistor), easier to enter flash mode. Optimized circuit makes the system more stable. The new version D1 R2 module meets ESP8266 WiFi. The board is based on the for ESP-8266EX. It has 11 Digital I/O pins, 1 Analog Input pin. OTA -- Wireless Upload(Program). On board switching power supply -- Max 24V input, 5V 1A output. Specification: Size: 70*55*10mm / 2.8*2.2*0.4in Weight: 23g / 0.8oz (approx.) PinPin Function for ESP-8266 PinTX TXD TXDRX RXD RXDA0 Analog input, max 3.3V input A0D0 IO GPIO16D1 IO, SCL GPIO5D2 IO, SDA GPIO4D3 IO, 10k Pull-up GPIO0D4 IO, 10k Pull-up, BUILTIN_LED GPIO2D5 IO, SCK GPIO14D6 IO, MISO GPIO12D7 IO, MOSI GPIO13D8 IO, 10k Pull-down, SS GPIO15G Ground GND5V 5V -3V3 3.3V 3.3VRST Reset RSTAll of the IO pins have interrupt/pwm/I2C/one-wire support except D0ProgrammingThe D1 R2 has a micro USB for auto programming.You can also program it using OTA.Warnings: All of the IO pins run at 3.3V. Package list:1 * Module 1 * Pin Header