Preparing for the Blue Bridge Cup Day11__ Basic operation of serial port communication

One , Serial port communication

There are many kinds of serial communication. Here we choose UART,UART It's a full duplex , Asynchronous serial communication , What are full duplex and asynchronous ？

 

        What we use here is asynchrony. We need to agree on the same communication rate , This communication rate is called baud rate , Refers to the number of bits per second of data transmission , As we often use it 9600 Baud rate refers to the transmission per second 9600 position . So we need to specify a baud rate , The baud rate is determined by the timer 1 To produce , So we turn on the timer 1, By giving TH1,TL1 The initial value determines the baud rate . How many values need to be assigned can be used STC-isp To calculate . The transmitted or received data is placed in SUBF.

Two , Code section

#include "reg52.h"
void Send(unsigned char t);
sfr AUXR=0X8E;
void Uart()
{
	TMOD=0X20;
	TL1=0XFD;
	TH1=0XFD;
	TR1=1;
	AUXR=0X00;
	SCON=0X50;
	EA=1;
	ES=1;
	
}
unsigned char urdat;
void ServiceUart() interrupt 4
{
	if(RI==1)
	{
		urdat=SBUF;
		RI=0;
		Send(urdat+1);
	}
}
void Send(unsigned char dat)
{
	SBUF=dat;
	while(TI==0);
	TI=0;
}
void main()
{ 
	Uart();
	Send(0x5a);
	Send(0xa5);
	while(1);
}

At the beginning, we need to configure the additional auxiliary registers of the Blue Bridge Cup SCM ,AUXR The address is 0x8e. In the interrupt function, we enable the timer 1 Perform baud rate conventions , Need to be right TOMD Register each port by a certain knowledge

Here we use auto reload 8 Bit timer , therefore TMOD=0x20,TR1=1, Start timer . Then on AUXR Carry out a cleaning 0. Another register bit is required to enable serial communication SCON.

Then there is the writing of service functions ,interrput It should be followed by 4,  The following rules .

The topic requires that the receiving adopts the interrupt mode , So we need to use yo... In the service function if Function to check whether the completion data is received （ After receiving the complete data RI I'll set 1, And it needs to be initialized manually ,TI Empathy ） So after receiving, the data is stored in SBUF We use it inside urdat Go ahead SBUF Take the data out of it , Yes RI Set up 0, Add... To the received data 1 after , adopt Send The function is sent to the upper computer . that Send It is necessary to realize the function of sending data to the upper computer , Put the data to be sent into SBUF Inside , use while Function to check whether the sending is completed , After sending, it is necessary to TI Set up 0.