modbus ascii 开发2.txt

用C编写的MODBUS协议程序,通讯方式为ASCII模式.

Modbus ASCII 开发2-基于Scilab得SCADA system开发手记7 
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#define READ_COIL     01
#define READ_DI       02
#define READ_HLD_REG  03
#define READ_AI       04
#define SET_COIL      05
#define SET_HLD_REG   06
#define READ_FIFO     24
#define PROTOCOL_EXCEPTION 0x81
#define PROTOCOL_ERR  1
#define FRM_ERR       2
const unsigned char auchCRCHi[] = {
0x00, 0xC1, 0x81, 0x40, 
} ;
const unsigned  char auchCRCLo[] = {
0x00, 0xC0, 0xC1, 0x01, 
};
const unsigned char char_tab[128]=
{
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                       
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                      
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                       
    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0,                      
    0, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0, 0, 0, 0, 0, 0, 0, 0, 0,    
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,                      
    0, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0, 0, 0, 0, 0, 0, 0, 0, 0,    
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0                        
};
const unsigned char tab_char[16]=
{ 
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
};
/*const unsigned int bit_tab[]=
{
    BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7, 
    BIT8, BIT9, BITA, BITB, BITC, BITD, BITE, BITF
};
*/
unsigned short crc(unsigned char *puchMsg , unsigned short usDataLen)
{    unsigned char uchCRCHi = 0xFF ; /* high byte of CRC initialized */
    unsigned char uchCRCLo = 0xFF ; /* low byte of CRC initialized */
    unsigned uIndex ;  /* will index into CRC lookup table */
     while (usDataLen--) /* pass through message buffer */
    {
     uIndex = uchCRCHi ^ *puchMsg++ ; /* calculate the CRC */
     uchCRCHi = uchCRCLo ^ auchCRCHi[uIndex];
     uchCRCLo = auchCRCLo[uIndex] ;
    }
    return (uchCRCHi << 8 | uchCRCLo) ;
}
unsigned char a2toh(unsigned char *str)
{
    unsigned char tmp;
    tmp = 0;
    tmp = char_tab[*str];
    str++;
    tmp = tmp*16 + char_tab[* str];
    return tmp;
}
void htoa(  char *str, unsigned char num)/*10进制转16进制*/
{
    unsigned char tmp;
    tmp = num; 
    tmp = tmp & 0xf0;
    tmp >>= 4;
    *str = tab_char [ tmp];
    str++;
    *str = tab_char [ num & 0x0f];
}
unsigned char HI(int num_16)
{
       unsigned char tt;
       tt=num_16 & 0xff00;
       tt >>= 8;
       return tt;
}
unsigned char LOW(int num_16)
{
       unsigned char tt;
       tt=num_16 & 0x00ff;
       return tt;
}
 int  asctortu( unsigned char *dest, unsigned char *source)
{
    unsigned char *tmp;
    unsigned char i;
    i=0;
    tmp = dest;
     if( *source !=':') return 0;
    source ++;
    while ( *source != 0x0d)
    {
       *tmp = a2toh( source);
       tmp ++;
       source ++;
       source ++;
       i++;
    }
    source ++;
    if ( *source != 0x0a) return 0;
    else
   {
       return i;
    }
}
void rtutoascii( unsigned char *dest, unsigned char *source, int lenth)
{
    dest ++;
    for ( ; lenth>0; lenth--)
    { 
       htoa( dest, *source);
       dest++;
       dest++;
       source++;
    }   
}
void rtutoasc( unsigned char *dest, unsigned char *source, int lenth)
{
    dest ++;
    for ( ; lenth>0; lenth--)
    { 
       htoa( dest, *source);
       dest++;
       dest++;
       source++;
     }   

}
unsigned char lrc(unsigned char *str,int lenth)
{
    unsigned char tmp;
    tmp = 0;
    while (lenth-- )
    {
       tmp += *str++;
    }
    return ((unsigned char)(-((char)tmp)));
}