winreg2.c

使用C++实现将Modbus协议封装在DLL中的源代码

#include <time.h>
#include <ctype.h>
#include <windows.h>
#include <winbase.h>
#include <stdlib.h>
#include <stdio.h>

#include "Comm32.h"


#define WINAPI __stdcall  


int __stdcall read_hold_reg(int reg_num,int slave,int port,int baud,int parity)
{
  time_t start,finish;
  double diff_time;
  int bytes_required = 7;
  int bytes_received = 0;
  int rx_char = -1;
  int timeout = 5;
  unsigned int temp,n;
  int function = 3;
  int offset = reg_num -1;
  int offset_hi = offset >> 8;
  int offset_lo = offset & 0x00FF;
  int numreg_hi = 0;
  int numreg_lo = 1;
  unsigned char crc_lo = 0;
  unsigned char crc_hi = 0;
  int reg_contents;
   
  static unsigned char mess[8];
  static unsigned char recv[20];
  HANDLE ComHandle;
  DWORD  BytesRead;


  mess[0] = slave;
  mess[1] = function;
  mess[2] = offset_hi;
  mess[3] = offset_lo;
  mess[4] = numreg_hi;
  mess[5] = numreg_lo;

 
  
  /****************************** open comport *********************/
   ComHandle = Open_Comport (port,baud,parity);  /* setup for no parity */
   if(ComHandle == 0)
   {
     /* failed to open port */
     return 1;
   }

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


  temp = crc(mess,0,6);
 
  crc_hi = temp >> 8 ;
  crc_lo = temp & 0x00FF;

  mess[6] = crc_hi;
  mess[7] = crc_lo;
  mess[8] = NULL;


  /********************** purge input buffer ************************/ 


  /********************* start timeout timer ************************/ 

     time(&start);		     /*  save the time the message was sent */

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


   


  /*************************** send packet to plc **************************/

   Write_Comport(ComHandle,8,mess); 

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



 


  while(bytes_received < bytes_required)
  {
    
   /******************************** read a byte from plc **********************/ 
    
    Read_Comport(ComHandle,&BytesRead,1,&rx_char);   
      
   /****************************************************************************/
   
   if (BytesRead != 0 )
    {
      recv[bytes_received] = rx_char;
      bytes_received++;
    }

      time(&finish);

      diff_time = difftime(finish,start);

      if(diff_time > timeout)
      {
        /* message box timeout */
        printf("timeout");
	break;
      }
  }


  temp = recv[3];
  temp = temp << 8;
  temp = temp | recv[4];
  reg_contents = temp;

  recv[7] = NULL;





/*************************     Close Comport    **************************/

  Close_Comport(ComHandle);

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

  return temp;
  
}



/*
*****************************************************************************
***************************** [  BEGIN:  crc ] ******************************
*****************************************************************************
INPUTS:
   buf   ->  Array containing message to be sent to controller.
   start ->  Start of loop in crc counter, usually 0.
   cnt   ->  Amount of bytes in message being sent to controller/
OUTPUTS:
   temp  ->  Returns crc byte for message.
COMMENTS:
   This routine receives the data message to be sent down to the controller
and calculates the crc high and low byte of that message.
*****************************************************************************
*/
unsigned int crc(unsigned char buf[],int start,int cnt)
{
   int      i,j;
   unsigned temp,temp2,flag;

   temp=0xFFFF;

   for (i=start; i<cnt; i++){
      temp=temp ^ buf[i];

      for (j=1; j<=8; j++){
	 flag=temp & 0x0001;
	 temp=temp >> 1;
	 if (flag) temp=temp ^ 0xA001;
      }
   }

   /*
   ** Reverse byte order.
   */
   temp2=temp >> 8;
   temp=(temp << 8) | temp2;
   return(temp);
}
/*
************************** [ END:  crc ] ************************************
*/