51 MCU Experiment 1 - Serial Communication (TX/RX)

The simulation circuit diagram is as follows:

code show as below:

#include "reg51.h"

#define uint unsigned int 

#define uchar unsigned char

uint code segcode[16]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D, 0x07, 0x7F,0x6F,0x77,0x7C,0x39,0x5E,0x79,0x71}; 

uchar code weicode[4]={0x0e,0x0d,0x0b,0x07};  

uchar disbuf[4]={0,0,0,0}; //Define and initialize the digital tube data buffer

void delayms(uint x) //delay 1ms function

{

                          uchar i;

                          while(x--)

                          {

                            for(i=0;i<125;i++);

                           }

}

void usart_Init() //Serial interrupt initialization routine

{

                         TMOD=0x20;     

                         TH1=0xfa;

                         TL1=0xfa; //Configure the serial port baud rate to 9600

                         SCON=0x50; //Set the serial port to work in mode 1, 8 data bits

                         PCON=0x80; //Configure baud rate multiplication

                         IE=0x90; // Enable interrupt

                         TR1=1; // Start the timer/counter

}

void segdisplay() //digital tube display function

{

                            uchar i;

                            for(i=0;i<4;i++)

                            {

                              P1=weicode[i];

                              P0=segcode[disbuf[i]];  

                              delayms(1);

                              P0=0x00;

                            }

}

void main() //Main function

{

                             usart_Init() ; //Serial port initialization

                             while(1) { segdisplay(); } //CPU loops to execute display function

}

void usart_Int() interrupt 4 //Serial interrupt service routine

{

                             if(RI==1) //Judge whether it is a receive interrupt

                             {

                               uint temp; //Temporarily open up a memory space to store the received data

                               RI=0; //Set RI to 0 in time to prevent data loss 

                           temp=SBUF; //Read the contents of the receive data buffer into the specified memory space

                           SBUF=temp; //Resend the input data to the host computer and echo it

                           while(TI==0);

                           TI=0; //Wait for sending to complete and reset TI

                           disbuf[3]=disbuf[1];

                           disbuf[2]=disbuf[0];

                           disbuf[1]=temp/0x10;

                           disbuf[0]=temp%0x10; //Modify the display buffer

                            }

}

After running the simulation, input the character '1', and the digital tube displays "31", as shown below:

Entering other characters in sequence will display their ASCII codes accordingly. When you enter the second character '2', the digital tube displays "3132"; when you enter the third character '5', the digital tube displays "3235" (the previous 31 is removed), and so on after entering characters continuously.