Feature:1. FUNCTION: Expanding a single USB to 4 UART serial ports, this serial port module can achieve simultaneous communication.2. 4 WAY TTL PORT: All the 4 serial ports are using XH2.54 port, and the 4 way UART all have TX or RX indicator to show statue.3. EASY SWITCHING: VCC, TX and RX can switch among 5V, 3.3V, 2.5V and 1.8V, and the switching is very quick and easy as well.4. WIDE APPLICATION: Allows for flexible application on electronic equipments and automation equipments, powerful and useful.5. GOOD WORKMANSHIP: Adopting excellent workmanship, the serial port module is not prone to cold joints, simple to install.How to Use:1. Use a USB cable to connect the Micro USB interface on the computer and board. After the computer is installed with the driver, you can see 4 COM ports appear. Use the short circuit cap to select the preferred VCC/TX/RX voltage on the TTL power selection interface, and it will output the corresponding voltage. 2. The smallest value of the COM port corresponds to the first TTL interface, and the largest value corresponds to the fourth TTL interface (the value of the COM port is not fixed). 3. For simple test, you can short circuit TX/RX, and then use the host computer to send information to see if there is any data feedback.