VCC = Regulated 3.3V or 5V supply input of atleast 200mA current capacity.
GND = Ground level of power supply. Must be common ground with microcontroller.
RXD = Receive Input: Input serial data of 3 to 5V logic level, Usually connected to TXD pin of microcontrollers UART
TXD = Transmit Output: Output serial data of 3 to 5V logic level, Usually connected to RXD pin of microcontrollers UART
SET = Setting Mode (Internally Pulled High) – Leave floating(High) is normal mode. To enter config mode pull the pin low either from switch or external MCU and send AT commands to configure.
