modbus-tcp | 易学教程

modbus rtu over tcp (modbus tcp gateway)

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问题 Is it possible to build a modbus-RTU ethernet gateway using a linux box or arduino? I have plc slaves linked together using modbus RTU, and I want to connect one of them over TCP with my pc as master. I wonder if I can use a linux box (rasbery pi/raspbian) connected to a router, as a modbus-to-tcp converter by piping the usb port to my local ip on some port, as one plc will be connected in modbus rtu to the linux box`s usb port. Piping command will be something Like this: nc -l 5626 > /dev

Can you keep a CRC in a Modbus TCP message?

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问题 Another modbus question here, I've been learning Modbus RTU and feel that I have a pretty good grasp on it and am now writing code to convert RTU to TCP. A question that was brought up to me today was, when you are converting from RTU to TCP, can you leave the CRC on the end? I know that the TCP structure does not contain a CRC but I'm not sure why? Any insight to this would be quite helpful :) 回答1: The CRC is not necessary mainly because TCP/IP is running on top of protocols that already

Communication in ASP.NET Core

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问题 Situation: I need to create some kind of controlling part of the communication over Modbus TCP/IP in my ASP.NET Core project. Communication is working correctly with Modbus, but I need to read some Modbus addresses pernamently and I need to set them interval. I have such structure for this in db. I have now singleton called CommunicationRepository, which is such controller for this protocol and have methods to read from the module, write to module, have structure for data from modules, etc.

Unexpected number when reading PLC using pymodbus

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问题 I am using pymodbus to read a register on a Wago 750-881 PLC. I am also reading the same register on the Modbus Poll utility, as well as, an HMI. The Modbus Poll and HMI are reading correctly, but the pymodbus program is not. Here is the code: from pymodbus.client.sync import ModbusTcpClient c = ModbusTcpClient(host="192.168.1.20") chk = c.read_holding_registers(257, 1, unit = 1) response = c.execute(chk) print response.getRegister(0) Here is the response from running the code: >>> runfile('C

i am trying to read the register values from modbus simulator but unvailable to do

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问题 the connection has been established to modbus simulator but I am trying to read the register values from simulator and write it on console but not able to do. this code creates the connection successfully to modbus simulator but contains the syntax of readind the register values i.e requesting for register values and also response about the same but unable to fetch the register values. below is the code i tried. package com.jamodapp; import java.net.InetAddress; import net.wimpi.modbus.Modbus

Qt/C++ communication with CMMO-ST-C5-1-LKP Festo controller over Modbus TCP

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问题 I am trying to commicate with a motor controller via modbus with Qt/C++. I connect to it using this code that I took mainly from Qt SerialBus adueditor example: void Stepper::connect_device(){ if (ui.pb_connect->text() == "Connect"){ m_device = device;device->setParameters(0, 0x0000, 0x0000, 0x000F, 0x0000); m_device->setConnectionParameter(QModbusDevice::NetworkAddressParameter, ui.tcpAddressEdit->text()); m_device->setConnectionParameter(QModbusDevice::NetworkPortParameter, ui.tcpPortEdit-

Pymodbus read holding registers

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问题 I was assigned to perform the task without any documentation. I have a problem with reading data from MODBUS. This is the script that I was able to create: from pymodbus.constants import Endian from pymodbus.payload import BinaryPayloadDecoder from pymodbus.payload import BinaryPayloadBuilder from pymodbus.client.sync import ModbusTcpClient client = ModbusTcpClient('X.X.X.X') connection = client.connect() request = client.read_holding_registers(12606,2) result = request.registers decoder =

pymodbus: request creation and response receiving

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Can anyone explain how to create the request and get the response in right way using pymodbus via Modbus TCP/IP? I have the PLC wich I want to use as slave and PC - as master. I trying to do it in such way: from pymodbus.client.sync import ModbusTcpClient host = '192.168.56.9' port = 502 client = ModbusTcpClient(host, port) client.connect() #Register address 0x102A (4138dec) with a word count of 1 #Value - MODBUS/TCP Connections #Access - Read #Description - Number of TCP connections request = client.read_holding_registers(4138, 1) response = client.execute(request) print response >>>