在工業(yè)自動化領域，ModBus協(xié)議作為一種通用通信標準，被廣泛應用于設備之間的數(shù)據(jù)交換。它主要包含ModBus RTU（用于串行通信）和ModBus TCP（用于以太網(wǎng)通信）兩種協(xié)議。在一些應用場景中，需要將ModBus TCP數(shù)據(jù)轉換為ModBus RTU格式或者是將ModBus RTU格式轉換為ModBus TCP數(shù)據(jù)。本文將詳細介紹如何使用Node-RED來實現(xiàn)ModBus TCP到RTU的協(xié)議互轉。

Node-RED簡介

Node-RED是一個基于Node.js的開源編程工具，它通過圖形化界面，讓用戶能夠通過拖拽節(jié)點來實現(xiàn)復雜的邏輯流處理。Node-RED支持多種協(xié)議，包括HTTP、MQTT、TCP/UDP等，同時也支持通過安裝額外的節(jié)點來擴展其功能，如ModBus協(xié)議的支持。這使得Node-RED成為快速搭建物聯(lián)網(wǎng)應用的理想選擇。

Node-RED節(jié)點添加

添加一個TCP客戶端，連接至對應服務器。

添加一個函數(shù)計算節(jié)點，輸入如下函數(shù)：

var arr1=[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];

// ModBus crc計算

function CRC16(arr,num){
var crc16=0xFFFF; var temp=null; for(var i=0;i""> { temp=crc16&0xFF; crc16=((crc16>>8)^arr1[(temp^arr[i])&0XFF]); } return crc16;}global.set("firstByte",msg.payload[0]);global.set("secondByte",msg.payload[1]);if(msg.payload[5] == msg.payload.length - 6){ var arr = []; for (var i = 0; i < msg.payload.length - 6; i++) { ? ? ? ?arr.push(msg.payload[i + 6]); ? ?} ? ? ? ?var crc16Value = CRC16(arr, arr.length); ? ?arr.push(crc16Value&0x00ff); ? ?arr.push(crc16Value >> 8); return {payload:Buffer(arr)};
}

添加一個串口節(jié)點，串口連接設備，選擇對應串口設備，這樣就實現(xiàn)了ModBus TCP到RTU的數(shù)據(jù)轉換，如果需要實現(xiàn)ModBus RTU到TCP的數(shù)據(jù)轉換，同樣添加一個函數(shù)計算節(jié)點，輸入如下函數(shù)：

var arr1=[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];

// ModBus crc計算

function CRC16(arr,num){
var crc16=0xFFFF; var temp=null; for(var i=0;i-2;++i)< div=""> { temp=crc16&0xFF; crc16=((crc16>>8)^arr1[(temp^arr[i])&0XFF]); } return crc16;}var crc16Value = CRC16(msg.payload,msg.payload.length);if((msg.payload[msg.payload.length-1] == (crc16Value>>8))&&(msg.payload[msg.payload.length-2] == (crc16Value&0x00ff))){ var arr=[]; arr.push(global.get('firstByte'),global.get('secondByte'),0,0,0,msg.payload.length-2); for(var i=0;i-2;i++)< div=""> { arr.push(msg.payload[i]); } return {payload:Buffer(arr)};
}

這樣就能實現(xiàn)ModBus RTU到TCP的轉換。

最后添加一個TCP客戶端節(jié)點，連接到對應服務器，這樣就能實現(xiàn)數(shù)據(jù)轉換。

注意事項

? 串口連接需要選擇對應串口參數(shù)，如波特率、數(shù)據(jù)位等。

? TCP連接需要連接對應服務器。

總結

通過上述步驟，我們利用Node-RED實現(xiàn)了ModBus TCP到RTU以及ModBus RTU到TCP的協(xié)議轉換。

億佰特串口服務器推薦

億佰特串口服務器產(chǎn)品涵蓋單串口服務器、多串口服務器、Wi-Fi串口服務器以及串口服務器模組等，可提供串口轉網(wǎng)絡功能，能夠將串口數(shù)據(jù)轉換成TCP/IP協(xié)議數(shù)據(jù)，實現(xiàn)串口與網(wǎng)絡的雙向透明傳輸。被廣泛應用于考勤系統(tǒng)、機房監(jiān)控、電力監(jiān)控等場景。