Modbus协议最初由Modicon公司开发出来,在1979年末该公司成为施耐德自动化(Schneider Automation)部门的一部分,现在Modbus已经是工业领域全球最流行的协议。此协议支持传统的RS-232、RS-422、RS-485和以太网设备。许多工业设备,包括PLC,DCS,智能仪表等都在使用Modbus协议作为他们之间的通讯标准。有了它,不同厂商生产的控制设备可以连成工业网络,进行集中监控。
当在网络上通信时,Modbus协议决定了每个控制器须要知道它们的设备地址,识别按地址发来的消息,决定要产生何种行动。如果需要回应,控制器将生成应答并使用Modbus协议发送给询问方。
Modbus 协议包括ASCII、RTU、TCP等,并没有规定物理层。此协议定义了控制器能够认识和使用的消息结构,而不管它们是经过何种网络进行通信的。标准的 Modicon控制器使用RS232C实现串行的Modbus。Modbus的ASCII、RTU协议规定了消息、数据的结构、命令和就答的方式,数据通讯采用Maser/Slave方式,Master端发出数据请求消息,Slave端接收到正确消息后就可以发送数据到Master端以响应请求; Master端也可以直接发消息修改Slave端的数据,实现双向读写。
Modbus 协议需要对数据进行校验,串行协议中除有奇偶校验外,ASCII模式采用LRC校验,RTU模式采用16位CRC校验,但TCP模式没有额外规定校验,因为TCP协议是一个面向连接的可靠协议。另外,Modbus采用主从方式定时收发数据,在实际使用中如果某Slave站点断开后(如故障或关机), Master端可以诊断出来,而当故障修复后,网络又可自动接通。因此,Modbus协议的可靠性较好。
下面我来简单的给大家介绍一下,对于Modbus的ASCII、RTU和TCP协议来说,其中TCP和RTU协议非常类似,我们只要把RTU协议的两个字节的校验码去掉,然后在RTU协议的开始加上5个0和一个6并通过TCP/IP网络协议发送出去即可。所以在这里我仅介绍一下Modbus的ASCII和 RTU协议。
- #include "main.h"
- //字地址 0 - 255 (只取低8位)
- //位地址 0 - 255 (只取低8位)
- /* CRC 高位字节值表 */
- const uint8 code auchCRCHi[] = {
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
- 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
- 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
- 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
- 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
- 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
- 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
- 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
- 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
- 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
- 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
- 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
- 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
- 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
- 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40
- } ;
- /* CRC低位字节值表*/
- const uint8 code auchCRCLo[] = {
- 0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,
- 0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
- 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
- 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,
- 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,
- 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
- 0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
- 0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,
- 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
- 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,
- 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,
- 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
- 0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,
- 0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
- 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
- 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
- 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,
- 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
- 0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,
- 0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,
- 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
- 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,
- 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
- 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
- 0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,
- 0x43, 0x83, 0x41, 0x81, 0x80, 0x40
- } ;
- uint8 testCoil; //用于测试 位地址1
- uint16 testRegister; //用于测试 字址址16
- uint8 localAddr = 1; //单片机控制板的地址
- uint8 sendCount; //发送字节个数
- uint8 receCount; //接收到的字节个数
- uint8 sendPosi; //发送位置
- uint16 crc16(uint8 *puchMsg, uint16 usDataLen)
- {
- uint8 uchCRCHi = 0xFF ; /* 高CRC字节初始化 */
- uint8 uchCRCLo = 0xFF ; /* 低CRC 字节初始化 */
- uint32 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 << 8 | uchCRCLo) ;
- }//uint16 crc16(uint8 *puchMsg, uint16 usDataLen)
- //开始发送
- void beginSend(void)
- {
- b485Send = 1; //设为发送
- sendPosi = 0;
- if(sendCount > 1)
- sendCount--;
- ACC = sendBuf[0];
- TB8 = P;
- SBUF = sendBuf[0];
- }//void beginSend(void)
- //读线圈状态
- void readCoil(void)
- {
- uint8 addr;
- uint8 tempAddr;
- uint8 byteCount;
- uint8 bitCount;
- uint16 crcData;
- uint8 position;
- uint8 i,k;
- uint8 result;
- uint16 tempData;
- uint8 exit = 0;
- //addr = (receBuf[2]<<8) + receBuf[3];
- //tempAddr = addr & 0xfff;
- addr = receBuf[3];
- tempAddr = addr;
- //bitCount = (receBuf[4]<<8) + receBuf[5]; //读取的位个数
- bitCount = receBuf[5];
- byteCount = bitCount / 8; //字节个数
- if(bitCount%8 != 0)
- byteCount++;
-
- for(k=0;k<byteCount;k++)
- {//字节位置
- position = k + 3;
- sendBuf[position] = 0;
- for(i=0;i<8;i++)
- {
- getCoilVal(tempAddr,&tempData);
-
- sendBuf[position] |= tempData << i;
- tempAddr++;
- if(tempAddr >= addr+bitCount)
- { //读完
- exit = 1;
- break;
- }
- }
- if(exit == 1)
- break;
- }
- sendBuf[0] = localAddr;
- sendBuf[1] = 0x01;
- sendBuf[2] = byteCount;
- byteCount += 3;
- crcData = crc16(sendBuf,byteCount);
- sendBuf[byteCount] = crcData >> 8;
- byteCount++;
- sendBuf[byteCount] = crcData & 0xff;
- sendCount = byteCount + 1;
- beginSend();
- }//void readCoil(void)
- //读寄存器
- void readRegisters(void)
- {
- uint8 addr;
- uint8 tempAddr;
- uint16 result;
- uint16 crcData;
- uint8 readCount;
- uint8 byteCount;
- uint8 finsh; //1完成 0出错
- uint16 i;
- uint16 tempData = 0;
- //addr = (receBuf[2]<<8) + receBuf[3];
- //tempAddr = addr & 0xfff;
- addr = receBuf[3];
- tempAddr = addr;
- //readCount = (receBuf[4]<<8) + receBuf[5]; //要读的个数
- readCount = receBuf[5];
- byteCount = readCount * 2;
- for(i=0;i<byteCount;i+=2,tempAddr++)
- {
- getRegisterVal(tempAddr,&tempData);
- sendBuf[i+3] = tempData >> 8;
- sendBuf[i+4] = tempData & 0xff;
- }
- sendBuf[0] = localAddr;
- sendBuf[1] = 3;
- sendBuf[2] = byteCount;
- byteCount += 3;
- crcData = crc16(sendBuf,byteCount);
- sendBuf[byteCount] = crcData >> 8;
- byteCount++;
- sendBuf[byteCount] = crcData & 0xff;
- sendCount = byteCount + 1;
- beginSend();
- }//void readRegisters(void)
- //强制单个线圈
- void forceSingleCoil(void)
- {
- uint8 addr;
- uint8 tempAddr;
- uint16 tempData;
- uint8 onOff;
- uint8 i;
- //addr = (receBuf[2]<<8) + receBuf[3];
- //tempAddr = addr & 0xfff;
- addr = receBuf[3];
- tempAddr = addr;
- //onOff = (receBuf[4]<<8) + receBuf[5];
- onOff = receBuf[4];
- //if(onOff == 0xff00)
- if(onOff == 0xff)
- { //设为ON
- tempData = 1;
- }
- //else if(onOff == 0x0000)
- else if(onOff == 0x00)
- { //设为OFF
- tempData = 0;
- }
- setCoilVal(tempAddr,tempData);
- for(i=0;i<receCount;i++)
- {
- sendBuf = receBuf;
- }
- sendCount = receCount;
- beginSend();
- }//void forceSingleCoil(void)
- //设置多个寄存器
- void presetMultipleRegisters(void)
- {
- uint8 addr;
- uint8 tempAddr;
- uint8 byteCount;
- uint8 setCount;
- uint16 crcData;
- uint16 tempData;
- uint8 finsh; //为1时完成 为0时出错
- uint8 i;
- //addr = (receBuf[2]<<8) + receBuf[3];
- //tempAddr = addr & 0xfff;
- addr = receBuf[3];
- tempAddr = addr & 0xff;
- //setCount = (receBuf[4]<<8) + receBuf[5];
- setCount = receBuf[5];
- byteCount = receBuf[6];
- for(i=0;i<setCount;i++,tempAddr++)
- {
- tempData = (receBuf[i*2+7]<<8) + receBuf[i*2+8];
- setRegisterVal(tempAddr,tempData);
- }
- sendBuf[0] = localAddr;
- sendBuf[1] = 16;
- sendBuf[2] = addr >> 8;
- sendBuf[3] = addr & 0xff;
- sendBuf[4] = setCount >> 8;
- sendBuf[5] = setCount & 0xff;
- crcData = crc16(sendBuf,6);
- sendBuf[6] = crcData >> 8;
- sendBuf[7] = crcData & 0xff;
- sendCount = 8;
- beginSend();
- }//void presetMultipleRegisters(void)
- //检查uart0数据
- void checkComm0Modbus(void)
- {
- uint16 crcData;
- uint16 tempData;
- if(receCount > 4)
- {
- switch(receBuf[1])
- {
- case 1://读取线圈状态(读取点 16位以内)
- case 3://读取保持寄存器(一个或多个)
- case 5://强制单个线圈
- case 6://设置单个寄存器
- if(receCount >= 8)
- {//接收完成一组数据
- //应该关闭接收中断
-
- if(receBuf[0]==localAddr && checkoutError==0)
- {
- crcData = crc16(receBuf,6);
- if(crcData == receBuf[7]+(receBuf[6]<<8))
- {//校验正确
- if(receBuf[1] == 1)
- {//读取线圈状态(读取点 16位以内)
- readCoil();
- }
- else if(receBuf[1] == 3)
- {//读取保持寄存器(一个或多个)
- readRegisters();
- }
- else if(receBuf[1] == 5)
- {//强制单个线圈
- forceSingleCoil();
- }
- else if(receBuf[1] == 6)
- {
- //presetSingleRegister();
- }
- }
- }
- receCount = 0;
- checkoutError = 0;
- }
- break;
-
- case 15://设置多个线圈
- tempData = receBuf[6];
- tempData += 9; //数据个数
- if(receCount >= tempData)
- {
- if(receBuf[0]==localAddr && checkoutError==0)
- {
- crcData = crc16(receBuf,tempData-2);
- if(crcData == (receBuf[tempData-2]<<8)+ receBuf[tempData-1])
- {
- //forceMultipleCoils();
- }
- }
- receCount = 0;
- checkoutError = 0;
- }
- break;
-
- case 16://设置多个寄存器
- tempData = (receBuf[4]<<8) + receBuf[5];
- tempData = tempData * 2; //数据个数
- tempData += 9;
- if(receCount >= tempData)
- {
- if(receBuf[0]==localAddr && checkoutError==0)
- {
- crcData = crc16(receBuf,tempData-2);
- if(crcData == (receBuf[tempData-2]<<8)+ receBuf[tempData-1])
- {
- presetMultipleRegisters();
- }
- }
- receCount = 0;
- checkoutError = 0;
- }
- break;
-
- default:
- break;
- }
- }
- }//void checkComm0(void)
- //取线圈状态 返回0表示成功
- uint16 getCoilVal(uint16 addr,uint16 *tempData)
- {
- uint16 result = 0;
- uint16 tempAddr;
- tempAddr = addr & 0xfff;
- //只取低8位地址
- switch(tempAddr & 0xff)
- {
- case 0:
- break;
- case 1:
- *tempData = testCoil;
- break;
- case 2:
- break;
- case 3:
- break;
- case 4:
- break;
- case 5:
- break;
- case 6:
- break;
- case 7:
- break;
- case 8:
- break;
- case 9:
- break;
- case 10:
- break;
- case 11:
- break;
- case 12:
- break;
- case 13:
- break;
- case 14:
- break;
- case 15:
- break;
- case 16:
- break;
- default:
- break;
- }
- return result;
- }//uint16 getCoilVal(uint16 addr,uint16 *data)
- //设定线圈状态 返回0表示成功
- uint16 setCoilVal(uint16 addr,uint16 tempData)
- {
- uint16 result = 0;
- uint16 tempAddr;
- tempAddr = addr & 0xfff;
-
- switch(tempAddr & 0xff)
- {
- case 0:
- break;
- case 1:
- testCoil = tempData;
- break;
- case 2:
- break;
- case 3:
- break;
- case 4:
- break;
- case 5:
- break;
- case 6:
- break;
- case 7:
- break;
- case 8:
- break;
- case 9:
- break;
- case 10:
- break;
- case 11:
- break;
- case 12:
- break;
- case 13:
- break;
- case 14:
- break;
- case 15:
- break;
- case 16:
- break;
- default:
- break;
- }
- return result;
- }//uint16 setCoilVal(uint16 addr,uint16 data)
- //取寄存器值 返回0表示成功
- uint16 getRegisterVal(uint16 addr,uint16 *tempData)
- {
- uint16 result = 0;
- uint16 tempAddr;
- tempAddr = addr & 0xfff;
- switch(tempAddr & 0xff)
- {
- case 0:
- break;
- case 1:
- break;
- case 2:
- break;
- case 3:
- break;
- case 4:
- break;
- case 5:
- break;
- case 6:
- break;
- case 7:
- break;
- case 8:
- break;
- case 9:
- break;
- case 10:
- break;
- case 11:
- break;
- case 12:
- break;
- case 13:
- break;
- case 14:
- break;
- case 15:
- break;
- case 16:
- *tempData = testRegister;
- break;
- default:
- break;
- }
- return result;
- }//uint16 getRegisterVal(uint16 addr,uint16 &data)
- //设置寄存器值 返回0表示成功
- uint16 setRegisterVal(uint16 addr,uint16 tempData)
- {
- uint16 result = 0;
- uint16 tempAddr;
- tempAddr = addr & 0xfff;
- switch(tempAddr & 0xff)
- {
- case 0:
- break;
- case 1:
- break;
- case 2:
- break;
- case 3:
- break;
- case 4:
- break;
- case 5:
- break;
- case 6:
- break;
- case 7:
- break;
- case 8:
- break;
- case 9:
- break;
- case 10:
- break;
- case 11:
- break;
- case 12:
- break;
- case 13:
- break;
- case 14:
- break;
- case 15:
- break;
- case 16:
- testRegister = tempData;
- break;
- default:
- break;
- }
- return result;
- }//uint8 setRegisterVal(uint16 addr,uint16 data)
复制代码
|