User's Manual

L720 EVB User Manual

5 Application interface

5.1 UART DB9 Interface

There is a DB9 COM port on the L720 development board, and its signal pin is consistent with the

signal on the L720 module. The serial interface as the main serial port can support complete 9 -

line RS232. The COMS 1.8v level on the L720 module is converted to the standard RS232 level

via serial port level conversion chip SP3238. Users can connect to PC or other terminal devices

through DB9 serial port cable provided for serial port communication. Main serial port (this

function has not been opened yet) supports hardware flow control for AT instruction, data

transmission, etc. When using, you need to dial the switch S4 to the right as shown in the arrow

direction below.

Figure5-1: L720 RS232 (DB9) Port

Note: .About the serial port baud rate associated Settings, please refer to L720 software

user manual.

5.2 USB（AT UART）Interface

In addition to the DB9 serial port described in 5.1 for AT communication, L506_EVB_V3 also

provides a set of USB virtual serial ports with exactly the same functions as DB9 serial ports for

AT instruction and data transmission. In use, also need to wave switch S4 to the right. DB9 serial

port function is turned off after USB cable is plugged in. AT instruction and other functions can

only be completed through this serial port.