Multi-machine communication based on RS-485 of 51 single-chip microcomputer

//-----------------------Function declaration, variable definition---------------------

#include

sbit RE_DE=P1^0;

#define COUNT 10 // Define the receive buffer size

#define Slaver_NUM 10

 

unsigned char bdata flag; //define a flag variable in bit addressable

sbit time_over_flag = flag^0; //Receive timeout flag

 

unsigned char buffer[COUNT]; //define buffer

unsigned char point; //Define buffer position indication

 

unsigned char Slave_AD[Slaver_NUM]; //Define the effective address storage area

unsigned char ADD_num; //Number of valid addresses

 

unsigned char idata count_10ms; //Used to indicate how many 10ms interrupts there are

 

unsigned char idata send_data[7]={

0x31,0x32,0x33,0x34,0x35,0x36,0x37}; //Define the data to be sent, a total of 7 bits

 

void UART_init(); //Serial port initialization function

void COM_send(void); //Serial port receiving function

unsigned char CLU_checkdata(void); //Calculate check digit function

 

//------------------------------------------------ ---------------

// Function name: UART_init() serial port initialization function

// Function: When the system clock is 11.059MHZ, set the serial port baud rate to 9600bit/s

// Enable serial port receive interrupt, disable send interrupt, set timer interrupt to enable

//------------------------------------------------ ---------------

void UART_init()

{

// Initialize serial settings

SCON =0x58; //Select serial port working mode 1, open receiving permission, TB8=1

TMOD = 0x21; //Timer 1 works in mode 2, timer 0 works in mode 1

TR1 =1; //Start timer T1

ES=1; //Enable serial port interrupt

PS=1; //Design serial port interrupt priority

// Initialize timer 1

TH1 = 0xfd; //Achieve baud rate 9600 (system clock 11.0592MHZ)

ET1 =0; //Timer 1 interrupt disabled

}

//------------------------------------------------ ---------------

// Function name: timer0_init() Initialize timer 0

// Function: Set the working mode of timer0

//------------------------------------------------ ---------------

void timer0_init()

{

time_over_flag=0;

count_10ms=0;

ADD_num=0;

TL0=0x0F0; //T0 is used to generate a 10ms interrupt

TH0=0x0D8; //50 T0 interrupts generate 1 timeout overflow

ET0=1; //Enable timer 0 interrupt

}

//------------------------------------------------ ---------------

// Function name: system_init() system initialization

// Function: Call the serial port and timer initialization functions to complete system initialization

//------------------------------------------------ ---------------

void system_init(void)

{

//System overall settings

UART_init();

timer0_init();

EA =1; //MCU interrupt is enabled

}

//------------------------------------------------ ---------------

// Function name: com_interrup() serial port receive interrupt processing function

// Function: Receive ten bits of data including the start bit "S" into the data buffer

//------------------------------------------------ ---------------

com_interrupt(void) interrupt 4 using 3

{

unsigned char RECEIVR_buffer;

if(RI) //Handle receive interrupt

{RI=0; // Clear the interrupt flag

RECEIVR_buffer=SBUF; //Receive serial port data

if(point==0) //If the start bit has not been received

{

if(RECEIVR_buffer==0xFE) //Judge whether it is the start flag

{

buffer[point++]=RECEIVR_buffer; //Put the received data into the receiving buffer

}

else

point=0; //No, continue waiting for the start position

}

else if(point>0&&point<10) //Judge whether ten bits of data are received

buffer[point++]=RECEIVR_buffer; //Not enough, put the received data into the receiving buffer

else if(point==10)

{

if(RECEIVR_buffer==0xEF) //Judge whether the end flag is correct

{

buffer[point]=RECEIVR_buffer; //Put the received data into the receiving buffer

Slave_AD[ADD_num++]=buffer[2]; //Put the received address into the address memory

//Indicates that there is a valid device at this address

}

else

point=0; //No, continue waiting for the start position

}

else point=0; //The buffer is full, clear the data in the buffer and receive again

}

if(TI) //Serial port sending interrupt

{

TI=0; // Clear transmit interrupt

}

}

//------------------------------------------------ ---------------

// Function name: timer0_interrup()

// Function: Timer T0 interrupt service routine

// Function description: T0 interrupts once every 10ms, and sets time_over_flag=1 for 50 consecutive interrupts;

//------------------------------------------------ ---------------

timer0_interrupt(void) interrupt 1 using 2

{

count_10ms++;

if(count_10ms==50)

{

ET0=0; //Disable timer T0 interrupt

TR0=0; //Stop timer T0

time_over_flag=1; //Set the receive timeout flag

count_10ms=0x00; //10ms counter reset

}

else

{

TL0=0x0F0; //Reload timer initial value

TH0=0x0D8;

}

}

 

//------------------------------------------------ ---------------

// Function name: COM_send() serial port sending function

// Function: Send out the ten-bit data in the data buffer

//------------------------------------------------ ---------------

void COM_send(void)

{

RE_DE=1; //Set MAX483 to the sending state

for(point=0;point=10,TI=1;point++) //Continuously send ten bits of data

//Send all the data in the buffer to the serial port

{

SBUF=buffer[point];

TI=0;

}

RE_DE=0; //Set MAX483 to receive state

 

}

//------------------------------------------------ ---------------

// Function name: write_buffer()

// Function: Write ten bits of data to the send buffer

//------------------------------------------------ ---------------

void write_buffer(unsigned char slaver_add)

{

unsigned char i;

TB8=1; //Open multi-machine communication mode

buffer[0]=0xFE;

buffer[1]=slaver_add;

for(i=2;i<9;i++) //Continuously send ten bits of data

//Send all the data in the buffer to the serial port

{

buffer[i]=send_data[i-2];

}

buffer[9]=0xEF;

}

 

//------------------------------------------------ ---------------

// Function name: Main function

// Function: Schedule a sub-function to complete the communication process

//------------------------------------------------ ---------------

void main(void)

{

unsigned char i=0;

system_init(); //System initialization

do{ //Check if there is any corresponding device for addresses 0 to 10

write_buffer(i++); //Write and query the sending information of device No. i

COM_send(); //Call the sending function to complete the sending

timer0_init(); //Complete a query, re-initialize timer 0, and prepare for the next query

}

while(time_over_flag&&i<10);

}