4Pcs ESP8266 Serial Wifi Module ESP01 Updated Wireless Transceiver Board 33V for Arduino

ESP8266 is a highly integrated chip designed for the needs of a new connected world. It offers a complete and self-contained Wi-Fi networking solution, allowing it to either host the application or to offload all Wi-Fi networking functions from another application processor. Specifications: Serial/UART baud rate: 115200 bps Input power: 3.3V I/O voltage tolerance: 3.6V Max Flash Memory Size: 1MB (8Mbit) WiFi security modes: WPA, WPA2 Package Including 4 * ESP8266 Wifi Transceiver Module     Version II---How to use?? Version II(All IO serial port version) Note:The power supply should be 3.3v!! about this version II,if you want to enter into AT command by FLASH boot,just need connect CH-PD pin with VCC pin or pull up resistor to keep high-level.(Sometimes without pulling up the resistor,there's no data on the serial port) The other three pins don't need to connect anything,if you connect them with VCC pin and failed restart,you shouldn't connect them.When GPIO0 is high-level,it means FLASH booting. When GPIO0 is low-level,it means upgrading the system.At this moment,you can upgrade the internal firmware by serial port. And RST(GPIO16)can be used to reset the external hardware. P.S.Different test systems may use different connecting ways,so you need choose the best connecting ways by yourself. Hereby we recommend one connecting way to connect esp01 module with serial port TTL tools.:After welding a 4.7k resistance between CH-PD pin and VCC pin. it needs connect UTXD,GND,VCC and URXD pin with USB-TTL(TXD and RXD need keep cross-linking)to test.