Serial port programming

Serial port programming

Before the serial port works, it should be initialized, mainly to set the timer 1 that generates the baud rate, serial port control and interrupt control. The specific steps are as follows:

Determine the working mode of T1 (program the TMOD register), calculate the initial value of T1, and load TH1 and TL1;

Start T1 (program the TR1 bit in TCON). Determine the serial port control (program the SCON register);

When the serial port works in interrupt mode, interrupt settings must be performed (programming the EIP register).

#include "reg52.h" //This file defines some special function registers of the microcontroller

typedef unsigned int u16;   //declare and define the data type

typedef unsigned char u8;

/***********************************************************************************

* Function name: UsartInit()

* Function    : Set the serial port

* Input : None

* Output          : None

***********************************************************************************/

void UsartInit()

{

SCON=0X50; //Set to work mode 1

TMOD=0X20; //Set the counter working mode 2

PCON=0X80; //Double the baud rate

TH1=0XF3; //Set the initial value of the counter, note that the baud rate is 4800

TL1=0XF3;

ES=1; //Open receive interrupt

EA=1; //Open the general interrupt

TR1=1; //Open the counter

}

/***********************************************************************************

* Function name: main

* Function : Main function

* Input: None

* Output    : None

***********************************************************************************/

void main()

{

UsartInit(); // Serial port initialization

while(1);

}

/***********************************************************************************

* Function name: Usart() interrupt 4

* Function   : Serial communication interrupt function

* Input : None

* Output          : None

***********************************************************************************/

void Usart() interrupt 4

{

u8 receiveData;

receiveData=SBUF; //Output received data

RI = 0; // Clear the receive interrupt flag

SBUF=receiveData; //Put the received data into the send register

while(!TI); //Wait for sending data to complete

TI=0; //Clear the send completion flag

}