The system uses LCD1602 displays the distance and temperature, LCD1602 is a character type display, can display 2 lines, 16 characters per line, Characters in the form of ASCII code are shown, therefore need to convert the displayed characters to ASCII code[6]. LCD1602 connected with MCU is shown below Fig.5, data lines DB0~DB7 connected with MCU P0, Data and instruction selection control terminal RS connected with MCU P2.6 pin, read and write control terminal R/W connected with MCU P2.5 pin, data read and write operations control bit E connected with MCU P2.7 pin, the bit sends a pulse to LCD, a data exchange between LCD module and MCU.