ARDUINO与esp8266连接测试
ESP8266是3.3V供电的
arduino的D3、D2分别为软串口的RX与TX。
arduino的D3（RX）连接ESP8266的TX。
arduino的D2（TX）连接ESP8266的RX。(ARDUINO and esp8266 connection test
ESP8266 is 3.3V power supply
The D3 and D2 of Arduino are RX and TX of the soft serial port, respectively.
The D3 (RX) of the Arduino connects to the TX of the ESP8266.
The D2 (TX) of the Arduino connects to the RX of the ESP8266.)