Modbus協議最初由Modicon公司開發出來,在1979年末該公司成為施耐德自動化(Schneider Automation)部門的一部分,現在Modbus已經是工業領域全球最流行的協議。此協議支持傳統的RS-232、RS-422、RS-485和以太網設備。許多工業設備,包括PLC,DCS,智能儀表等都在使用Modbus協議作為他們之間的通訊標準。有了它,不同廠商生產的控制設備可以連成工業網絡,進行集中監控。
當在網絡上通信時,Modbus協議決定了每個控制器須要知道它們的設備地址,識別按地址發來的消息,決定要產生何種行動。如果需要回應,控制器將生成應答并使用Modbus協議發送給詢問方。
Modbus 協議包括ASCII、RTU、TCP等,并沒有規定物理層。此協議定義了控制器能夠認識和使用的消息結構,而不管它們是經過何種網絡進行通信的。標準的 Modicon控制器使用RS232C實現串行的Modbus。Modbus的ASCII、RTU協議規定了消息、數據的結構、命令和就答的方式,數據通訊采用Maser/Slave方式,Master端發出數據請求消息,Slave端接收到正確消息后就可以發送數據到Master端以響應請求; Master端也可以直接發消息修改Slave端的數據,實現雙向讀寫。
Modbus 協議需要對數據進行校驗,串行協議中除有奇偶校驗外,ASCII模式采用LRC校驗,RTU模式采用16位CRC校驗,但TCP模式沒有額外規定校驗,因為TCP協議是一個面向連接的可靠協議。另外,Modbus采用主從方式定時收發數據,在實際使用中如果某Slave站點斷開后(如故障或關機), Master端可以診斷出來,而當故障修復后,網絡又可自動接通。因此,Modbus協議的可靠性較好。
下面我來簡單的給大家介紹一下,對于Modbus的ASCII、RTU和TCP協議來說,其中TCP和RTU協議非常類似,我們只要把RTU協議的兩個字節的校驗碼去掉,然后在RTU協議的開始加上5個0和一個6并通過TCP/IP網絡協議發送出去即可。所以在這里我僅介紹一下Modbus的ASCII和 RTU協議。
- #include "main.h"
- //字地址 0 - 255 (只取低8位)
- //位地址 0 - 255 (只取低8位)
- /* CRC 高位字節值表 */
- 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低位字節值表*/
- 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; //用于測試 位地址1
- uint16 testRegister; //用于測試 字址址16
- uint8 localAddr = 1; //單片機控制板的地址
- uint8 sendCount; //發送字節個數
- uint8 receCount; //接收到的字節個數
- uint8 sendPosi; //發送位置
- uint16 crc16(uint8 *puchMsg, uint16 usDataLen)
- {
- uint8 uchCRCHi = 0xFF ; /* 高CRC字節初始化 */
- uint8 uchCRCLo = 0xFF ; /* 低CRC 字節初始化 */
- uint32 uIndex ; /* CRC循環中的索引 */
- while (usDataLen--) /* 傳輸消息緩沖區 */
- {
- uIndex = uchCRCHi ^ *puchMsg++ ; /* 計算CRC */
- uchCRCHi = uchCRCLo ^ auchCRCHi[uIndex] ;
- uchCRCLo = auchCRCLo[uIndex] ;
- }
- return (uchCRCHi << 8 | uchCRCLo) ;
- }//uint16 crc16(uint8 *puchMsg, uint16 usDataLen)
- //開始發送
- void beginSend(void)
- {
- b485Send = 1; //設為發送
- sendPosi = 0;
- if(sendCount > 1)
- sendCount--;
- ACC = sendBuf[0];
- TB8 = P;
- SBUF = sendBuf[0];
- }//void beginSend(void)
- //讀線圈狀態
- 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]; //讀取的位個數
- bitCount = receBuf[5];
- byteCount = bitCount / 8; //字節個數
- if(bitCount%8 != 0)
- byteCount++;
-
- for(k=0;k<byteCount;k++)
- {//字節位置
- position = k + 3;
- sendBuf[position] = 0;
- for(i=0;i<8;i++)
- {
- getCoilVal(tempAddr,&tempData);
-
- sendBuf[position] |= tempData << i;
- tempAddr++;
- if(tempAddr >= addr+bitCount)
- { //讀完
- 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)
- //讀寄存器
- void readRegisters(void)
- {
- uint8 addr;
- uint8 tempAddr;
- uint16 result;
- uint16 crcData;
- uint8 readCount;
- uint8 byteCount;
- uint8 finsh; //1完成 0出錯
- 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]; //要讀的個數
- 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)
- //強制單個線圈
- 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)
- { //設為ON
- tempData = 1;
- }
- //else if(onOff == 0x0000)
- else if(onOff == 0x00)
- { //設為OFF
- tempData = 0;
- }
- setCoilVal(tempAddr,tempData);
- for(i=0;i<receCount;i++)
- {
- sendBuf = receBuf;
- }
- sendCount = receCount;
- beginSend();
- }//void forceSingleCoil(void)
- //設置多個寄存器
- void presetMultipleRegisters(void)
- {
- uint8 addr;
- uint8 tempAddr;
- uint8 byteCount;
- uint8 setCount;
- uint16 crcData;
- uint16 tempData;
- uint8 finsh; //為1時完成 為0時出錯
- 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)
- //檢查uart0數據
- void checkComm0Modbus(void)
- {
- uint16 crcData;
- uint16 tempData;
- if(receCount > 4)
- {
- switch(receBuf[1])
- {
- case 1://讀取線圈狀態(讀取點 16位以內)
- case 3://讀取保持寄存器(一個或多個)
- case 5://強制單個線圈
- case 6://設置單個寄存器
- if(receCount >= 8)
- {//接收完成一組數據
- //應該關閉接收中斷
-
- if(receBuf[0]==localAddr && checkoutError==0)
- {
- crcData = crc16(receBuf,6);
- if(crcData == receBuf[7]+(receBuf[6]<<8))
- {//校驗正確
- if(receBuf[1] == 1)
- {//讀取線圈狀態(讀取點 16位以內)
- readCoil();
- }
- else if(receBuf[1] == 3)
- {//讀取保持寄存器(一個或多個)
- readRegisters();
- }
- else if(receBuf[1] == 5)
- {//強制單個線圈
- forceSingleCoil();
- }
- else if(receBuf[1] == 6)
- {
- //presetSingleRegister();
- }
- }
- }
- receCount = 0;
- checkoutError = 0;
- }
- break;
-
- case 15://設置多個線圈
- tempData = receBuf[6];
- tempData += 9; //數據個數
- 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://設置多個寄存器
- tempData = (receBuf[4]<<8) + receBuf[5];
- tempData = tempData * 2; //數據個數
- 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)
- //取線圈狀態 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)
- //設定線圈狀態 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)
- //設置寄存器值 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)
復制代碼
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