这个是MODBUS控制电磁阀的一个程序。其中还有AD采集的部分。对CRC校验用查表的方法。至于怎样把校验的结果拆分成高低位字节，再发送，看程序吧。
#include"reg51.h"
#include"intrins.h"
#define uchar unsigned char
#define uint unsigned int
#define Pressure P0
////////////////
/////////////////////
uchar addr
uchar Pressure_updata
uchar Pressure_lowdata
/////////////////
sbit Dcf_open=P1^0//电磁阀开启
sbit Dcf_close=P1^1//电磁阀关闭
bit dr
bit Dcf_state=1
bit Halfsecond=0
bit Onesecond=0
//////////////////////////////
sbit Mydress_set=P2^5
sbit P_uplimite =P2^6
sbit P_lowlimite=P2^7
sbit Stor=P3^2
sbit myint=P3^3
sbit ADC_wr =P3^6
sbit ADC_rd =P3^7
sbit xuantong =P1^7
sbit addrset=P1^2
sbit upset=P1^3
sbit lowset=P1^4
/////////////////////////
uchar code Myreturnstateopen[3] ={0x01,0x01,0x00}
uchar code Myreturnstateclose[3]={0x01,0x01,0x01}
uchar code Myreturnopen[3] ={0x01,0x01,0x10}
uchar code Myreturnclose[3]={0x01,0x01,0x20}
uchar receive_count=0
uchar mysend[6],aq[8]
uchar Adc_value
unsigned long Mycount=0
uchar jishi=0 //定时一秒计数
uint crc=0,myaw=0
uint crc16(unsigned char *puchMsg, unsigned int usDataLen)
bit yifasong=0
void Beginsend( uchar Me )
bit check_modbus()
void Open_dcf()
void Close_dcf()
void timer0()
void uart_init(void)
void delay(uint z)
void Read_adc()
void Tosend()
/////////
/*************延时*****************/
void delay(uint z)
{
uchar y
while(z--)
for(y=113y>0y--)
}
/************串口初始化*****************/
void uart_init(void) interrupt 4 using 1
{
if(RI)
{
aq[receive_count]=SBUF
RI=0
receive_count++
if(0==receive_count%8)
{
yifasong=0
receive_count=0
}
RI=0
}
}
/**************定时器0初始化**************/
void timer0() interrupt 1 using 1
{
TH0=0x4b
TL0=0x63
jishi++
if (0==jishi%10) {
Halfsecond=1
aq[0]=0aq[1]=0aq[2]=0aq[3]=0aq[4]=0aq[5]=0aq[6]=0aq[7]=0receive_count=0
}
}
void Read_adc()
{
ADC_rd=1
ADC_wr=1
_nop_()
_nop_()
_nop_()
_nop_()
myint=1
P0=0xff
ADC_wr=0
_nop_()
_nop_()
_nop_()
_nop_()
ADC_wr=1
while( myint==1)
ADC_rd=0
_nop_()
_nop_()
_nop_()
_nop_()
_nop_()
Adc_value=P0 //读出的数据赋与addate
ADC_rd=1
}
void Open_dcf()
{
Dcf_open=0 delay(1200)Dcf_open=1 Dcf_state=1
}
void Close_dcf()
{
Dcf_close=0 delay(1200)Dcf_close=1Dcf_state=0
}
void Read_Pressure()
{
Read_adc()
if (Dcf_state)
{
if((Adc_value<Pressure_lowdata)|| (Adc_value>Pressure_updata))
{
delay(1200)
if((Adc_value<Pressure_lowdata)|| (Adc_value>Pressure_updata)) { Close_dcf()}
}
else
{ }
}
else
{
if((Adc_value>Pressure_lowdata)&&(Adc_value<Pressure_updata))
{ delay(1200)
if((Adc_value>Pressure_lowdata)&&(Adc_value<Pressure_updata)) { Open_dcf()}
}
else
}
}
void initialize()
{
TMOD=0x20
SCON=0x50//串口通讯方式1
TH1=0xfd//波特率9600
TL1=0xfd
TH0=0x4b
TL0=0x63
TI=0//发送中断标志位清零
RI=0//接收中断标志位清零
Mydress_set=1P_lowlimite=1P_uplimite=1xuantong=1
Mydress_set=0delay(20)addrset=1delay(20)addr=P0
delay(20)
addrset=0Mydress_set=1delay(200)P0=0xff
P_lowlimite=0delay(20)lowset=1delay(20)Pressure_lowdata=P0
delay(20)
lowset=0P_lowlimite=1P0=0xff
P_uplimite=0delay(20)upset=1Pressure_updata=P0delay(20)upset=0P_uplimite=1P0=0xff
xuantong=0
}
void main(void)
{
IE=0x92
TR0=1TR1=1
// WDTRST=0x1E
// WDTRST=0xE1//初始化看门狗
initialize()
Stor=0
for() { // WDTRST=0x1E
//WDTRST=0xE1//喂狗指令
if (Halfsecond==1) {
Halfsecond=0
Read_Pressure()
}
//够一秒开始转换
if(receive_count==0&&(yifasong==0))
{ Stor=0
dr= check_modbus()
if (dr&&addr==aq[0])
{ if(aq[1]==0x05)
switch ( aq[3])
{
case 0x00 :
if(!Dcf_state) Open_dcf()
Beginsend(0) break
case 0x01 :
if(Dcf_state) Close_dcf()
Beginsend(1)
break
default :
}
else if(aq[1]==0x01)
{
if(Dcf_state)
{ Beginsend(2)
}
else
{ Beginsend(3)
}
}
else
}
else
}
}
}
void Beginsend(uchar Me )
{
uchar i
ES=0Stor=1
TI=0
mysend[0]=addr
switch(Me)
{
case 0:
{ for(i=1i<4i++)
{
mysend[i] = Myreturnopen[i-1]
}
i=0
}break
case 1:
{for(i=1i<4i++)
{
mysend[i] = Myreturnclose[i-1]
} i=0}break
case 2:
{ for(i=1i<4i++)
{
mysend[i] = Myreturnstateopen[i-1]
} i=0}break
case 3:
{for(i=1i<4i++)
{
mysend[i] = Myreturnstateclose[i-1]
}i=0}break
default : }
myaw=crc16(mysend,4)
mysend[4] =myaw&0x00ff
mysend[5] =(myaw>>8)&0x00ff
for(i=0i<6i++)
{
SBUF=mysend[i]
while(TI!=1)
TI=0
}
Stor=0
ES=1
yifasong=1
}
bit check_modbus()
{
uchar m,n
crc=crc16(aq,6)
m=crcn=crc>>8&0x00ff
if(aq[6]==m&&aq[7]==n)
return 1
else
return 0
}
uint crc16(uchar *puchMsg, uint usDataLen)
{
uchar uchCRCHi = 0xFF //* 高CRC字节初始化
uchar uchCRCLo = 0xFF //* 低CRC 字节初始化
unsigned long uIndex // CRC循环中的索引
while (usDataLen--) // 传输消息缓冲区
{
uIndex = uchCRCHi ^ *puchMsg++ // 计算CRC
uchCRCHi = uchCRCLo ^ auchCRCHi[uIndex]
uchCRCLo = auchCRCLo[uIndex]
}
return (uchCRCHi | uchCRCLo<<8)
}
/***********************CRC校验*************************/
// CRC 高位字节值表
#ifdef MODBUS//
//******************************************************************************
// CRC 16 Data Table
// *****************
const unsigned int crc_tbl[256]={
0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
0x7800, 0xB8C1, 0xb981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040}
//#pragma end_abs_address
//******************************************************************************
//
#define DEFAULT_ADDRESS 1// all slaves start with this Modbus address
// communication commands:
//#define CHOOSE_SLOT0x80
//#define POLL_SLOT0x81
//#define POLL_ACK0x82
// positions in a Modbus packet
#define ADDR0
#define FCN 1
#define REGHI 2
#define REGLO3
#define NUMREGSHI 4
#define NUMREGSLO 5
#define OUTBYTES 2
// Modbus exception codes
#define FCN_NOT_SUPPORTED1// a Modbus function code we can't
handle
#define BAD_ADDR_OR_CMD2// a Modbus "register"
(command or address to us) we don't know
#define BAD_COUNT3// num regs != num bytes
* 2
#define CMD_NOT_COMPLETE4// command didn't complete
successfully
// other defines
#define IN0
#define OUT1
//
// SLOT_NUMBER is the 2 byte device configuration
// the first byte is the ID
// the second byte is the transmission mode coded as follows:
//bit 0x01: 0=19200, 1=9600 baud
//bit 0x02: 0=even parity, 1=odd parity
//bit 0x04: 0=parity, 1=no parity
//bit 0x08: 0=1 stop bit, 1=2 stop bits
//if bit 0x04 is set and bit 0x08 is not set then it's 8
bit mode (vs 9 bit mode)
//
//unsigned char receiveBuffer[32] = {0} // Reserve 32 bytes for packet.
unsigned char device_addr = DEFAULT_ADDRESS// assigned device address - start
with disconnected
//unsigned char timeout_counter = 10
//unsigned char timeout_duration = 10 // seconds, default
//unsigned char pkt_index = 0
// return number of bytes in packet, not including crc
unsigned char MDB_get_length(unsigned char in_out, unsigned char* ptr)
{
if(comControlByte &0x20)
return 6
switch(*(ptr+FCN))
{
case 0x06: // write single reg
return 6
case 0x03:// read multiple regs
if (in_out == IN) // incoming packet
return 6
else
return *(ptr+OUTBYTES) + 3
case 0x10:// write multiple regs
return (*(ptr+NUMREGSLO) <<1) + 7
default:// assume error packet
return 3
}
}
// calculate CRC16 on a packet
unsigned int MDB_crc_calc(unsigned char in_out, unsigned char* ptr)
{
unsigned char c1, c2
unsigned int crc = 0xffff
// initial value
unsigned char* ptr_pkt_hdr = ptr
c2 = MDB_get_length(in_out,ptr)
for(c1=0c1<c2c1++)
crc = ((crc >>8) &0xFF) ^ crc_tbl[(crc ^ *ptr_pkt_hdr++) &0xFF]
return crc
}
// check crc on an incoming packet
unsigned char MDB_crc_check(unsigned char* ptr)
{
unsigned int i1
unsigned char c1, c2, c3
i1 = MDB_crc_calc(IN, ptr)
c1 = *(ptr+MDB_get_length(IN,ptr)+1) // msb of incoming crc
c2 = *(ptr+MDB_get_length(IN,ptr)) // lsb of
incoming crc
c3 = (i1 >>8)
// msb of calculated crc
if((c2 == (i1 &0x00FF)) &&(c1 == c3))// compare msb
&lsb
return 1
else
return 0
}
// send Modbus packets
void MDB_pkt_sender(unsigned char* ptr)
{
unsigned char idx, pkt_len
unsigned int i1
// append crc, lsb 1st
i1 = MDB_crc_calc(OUT,ptr)
pkt_len = MDB_get_length(OUT,ptr)
*(ptr+pkt_len++) = (unsigned char)i1 // lsb
*(ptr+pkt_len++) = (i1 >>8) // msb
//SCI1C2 = 0x08 // transmit enable
//comLedOn()
PTGD |= 0x80
for (idx = 0idx <pkt_lenidx++)
{
while(!(SCI1S1 &0x80)) // wait for tdre=1
i1 = SCI1S1
SCI1D = *(ptr+idx)
}
while(!(SCI1S1 &0x80))
while(!(SCI1S1 &0x40))
//comLedOff()
PTGD &= 0x7f
//SCI1C2 = 0x2c // back to receive mode
}
// return a Modbus error packet
void MDB_error(unsigned char exp_code, unsigned char* ptr)
{
*(ptr+FCN) |= 0x80 // set error code
*(ptr+FCN+1) = exp_code // set exception code
MDB_pkt_sender(ptr)
}
//
void MDB_read_data(unsigned char* ptr)
{
if(get_data((ptr+2), *(ptr+3)))
{
// get_data() sticks the length of the data in
receiveBuffer[2]
// receiveBuffer[3] &on will have actual data
// receiveBuffer[0] &receiveBuffer[1] unchanged
MDB_pkt_sender(ptr) // appends CRC before sending
}
else
MDB_error(BAD_ADDR_OR_CMD, ptr)
}
// handle data writes
void MDB_write_data(unsigned char* ptr)
{
if((*(ptr+5)<<1) == *(ptr+6))
{
switch(*(ptr+3))//receiveBuffer[3])
{
//case 0x18:// new timeout value
//timeout_duration = receiveBuffer[7]
//MDB_pkt_sender() // echo
received command
//break
//case 0x63:// lamp test
//clampTest = 40
//MDB_pkt_sender() // echo
received command
//break
case ADDRESS:
//if(receiveBuffer[8] &&
(receiveBuffer[8] <248))// valid addresses
if(*(ptr+8) &&(*(ptr+8) <248))
{
//device_addr = *
(ptr+8)// not until reset
nonvolatile[0] = *(ptr+8)
// device ID
nonvolatile[1] = *(ptr+7)
// transmission mode
nonvolatile[2] =
~nonvolatile[0]
nonvolatile[3] =
~nonvolatile[1]
writeToNonvolatile
(SLOT_NUMBER, &nonvolatile[0])
comControlByte |= 0x20
MDB_pkt_sender(ptr)
comControlByte &= 0xdf
}
else
MDB_error
(BAD_ADDR_OR_CMD, ptr)
break
case INSTALLATION_DATE:// installation
date
readFromNonvolatile(DATE_DATA,
&nonvolatile[0])
nonvolatile[4] = *
(ptr+7)//receiveBuffer[7]
nonvolatile[5] = *
(ptr+8)//receiveBuffer[8]
nonvolatile[6] = *
(ptr+9)//receiveBuffer[9]
nonvolatile[7] = *
(ptr+10)//receiveBuffer[10]
nonvolatile[12] = ~nonvolatile[4]
nonvolatile[13] = ~nonvolatile[5]
nonvolatile[14] = ~nonvolatile[6]
nonvolatile[15] = ~nonvolatile[7]
writeToNonvolatile(DATE_DATA,
&nonvolatile[0])
comControlByte |= 0x20
MDB_pkt_sender(ptr) // echo
received command
comControlByte &= 0xdf
break
default:
MDB_error(BAD_ADDR_OR_CMD, ptr)
break
}
}
else
MDB_error(BAD_COUNT, ptr)
}
//
void MDB_parse(char *bufPtr)
{
unsigned char i = 0
if(MDB_crc_check(bufPtr))
{
if(*(bufPtr+ADDR) == device_addr)
{
switch(*(bufPtr+FCN))
{
case 0x03: // modbus read multiple
regs
MDB_read_data(bufPtr)
break
case 0x10:// modbus write multiple
regs
MDB_write_data(bufPtr)
break
default:// modbus function not
supported
MDB_error
(FCN_NOT_SUPPORTED, bufPtr)
break
}
}
}
}
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