Questions tagged [modbus]
Modbus is a serial communications protocol commonly used by PLCs (programmable logic controllers) and other industrial control systems. While originally based on traditional serial communication, many extensions exist to allow communication over other networks such as TCP/IP.
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Can I connect ten RS485 modbus kWh meters to one RJ45 modbus server? [closed]
If I have a fusebox with about ten/fifteen eastron sdm630 and Orno OR-WE-515 kWh meters with RS485 modbus, can I daisy chain ...
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Hardware advice for communicating data between two different MODBUS protocols using RS-485
I am trying to build a small device that will act as translator between two devices having two different RS-485 MODBUS protocols. This device will store 4 different values from "Device 1" ...
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How to debug modbus rtu address space problems? [closed]
I have an "Ewon Flexy server" and an "IMO SD1 Inverter" connected via Modbus RTU RS485.
I can change some of the parameters with Flexy interface and observe the change in the ...
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Can USB-to-SERIAL dongle be used to drive an RS-485 transceiver?
Pictured below is a simple arrangement used to read the Temperature sensor from the PC. Standard/Protocol is MODBUS RTU RS-485 Half-Duplex.
I've used this arrangement with both modpoll.exe and ...
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Modbus receiving same message as sent
I am having a problem when communicating with a Modbus slave.
I have made a circuit with the translator shown in the picture. UART2_RXD and ...
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Modbus ASCII messages delimiter
I need to implement Modbus messages reception over UART. For RTU it's easy because UART on my uC has configurable idle receive line detection. However, for ASCII the task is tricky - the delimiter is ...
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MODBUS TCP Read response query - second opinion required
I am having an interoperability problem between a Modbus/TCP driver from one company and a Modbus/TCP device from another.
The Modbus driver I am using seems to be able to correctly read all but four ...
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Modbus RTU on ESP8266 to control VFD
Hoping to get some help on setting up a NodeMCU (esp8266) with this 1 arduino library to control a Variable Frequency Drive (VFD).
I'm afraid to say that I almost need help from square one, as I'm ...
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Communicating with 6 TTL devices that support the Modbus protocol
I am working on project using Hukseflux SR05-D2A2 thermal sensors. These sensors support Modbus communication through a TTL interface. The objective is to read the value at a specific address in the ...
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Datexel DAT3024 4-Ch Digital to Analog Converter (0-10V and 0-20mA): Voltage Output Titles Not Responding
Issue:
I was attempting to perform the calibration procedure for the DAT3024 when all 4 output channels stopped responding to modbus commands to set their respective voltages. This occurred after ...
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Modbus TCP illegal packet (CRC) time-out problem in gateway
I am connecting a Modbus gateway to an RTU acquisition system. I am using a MOXA Gateway MB3480 with a RS485 (2 wires) connector. The thing is that I can't read the data all the time; I receive a time-...
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How to read MOXA gate Modbus RTU to Modbus TCP in Python?
I have got some MOXA devices. One of them is an Mgate MB3180. I want to code in a program in Python to read the data using TCP.
I don't know if I have to use a regular "TCP reading" or an &...
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Modbus Based Current Sensor Development Environment
We are looking to use a WattNode WNC-3Y-480-MB power meter. What is the suggested development environment setup to power and test this unit? Ideally, we would need a very lower power 480V 3 phase ...
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Same holding register address for different purposes in Modbus?
I have a device which is supposed to support the Modbus protocol. By Function-3, I can read an input status at address-1000, but the same address-1000 is used as an output so I can write the value to ...
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Can I test if a MODBUS server device is active?
We have a device which has a RS485 Modbus connection. This device supposedly acts as a server on the bus.
We are in a position where it is not clear if the Modbus feature is even turned on or active. ...
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Modbus gateway and VCOM configuration using Linux
I am connecting a Modbus Gateway (USER-TCP232) to a Linux PC. The thing is that it does not use MODBUS TCP, it just packs the RTU data frame over TCP, so I cannot use MODBUS TCP in the PC, I must use ...
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Project setup help: Siemens S7-1200 with Modbus and OPC UA
I'm currently planning a PLC project but I'm not sure how to put the components together.
About my setup:
I want to integrate a Siemens S7-1200 as master PLC.
The PLC should control a subordinate ...
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VFD speed reference command: Will MODBUS/TCP have better resolution than 4.0 ~ 20.0 mA
I need help to understand the difference between tranditional 4.0~20.0 mA and digital communication (for example MODBUS/TCP)
Assume: a PLC communicates with a VFD to control a variable speed pump from ...
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Microcontroller requirements for multiple Modbus controllers
I am in the process of trying to design a circuit that will have four RS485 RTU Modbus ports, two acting as clients and two acting as servers, on which I will connect up to fifteen sensors. I am ...
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SIM7080 UART Noise interfacing with PIC18F4550
I'm working on a project where I read data over Modbus line and send it in the cloud service through a SIM7080 CATM modem. I'm using PIC18F4550 as MCU.
As that PIC18F has just one UART module, I'm ...
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Modbus over RS485 - no response from device
I am trying to connect to Epever Tracer AN Solar Charge controller from ESP32 using below Max485 module but I can't get any repsonse from device.
I was trying to use exactly the same setup mentioned ...
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Is it advisable to make communication re attempts in modbus?
In my system, I know that the approximate response time between master-slave is 10ms, if the slave does not receive communication during those 10ms then it detects an error and the motors turn off.
Is ...
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Maxim MAX3485ESA+T vs SP3485EN-L/TR
I have a question about the MAX3485ESA+T RS485 Transceiver.
I ordered a PCB with a MAX3485ESA+T and the project doesn't work. The previous design was with a SP3485EN-L/TR and it worked well, but I had ...
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How to identify Modbus device speed rate?
In particular how to identify it without causing device misbehaving.
Either new device is being connected, and master has no idea what baud rate the device is configured with (assume it knows about 8/...
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RS485 MODBUS ARDUINO: Print multiple response data frame from soil sensor
Hi everyone. I'm guiding myself from tutorial https://how2electronics.com/measure-soil-nutrient-using-arduino-soil-npk-sensor/
I'm using...
Hardware components:
RS485
Arduino uno
Charger 9V (Only for ...
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How to connect a slave device to an RS-485 network without a signal ground reference terminal?
I want to connect a flow meter and a variable frequency drive (VFD) to the same modbus network but the absence of a signal ground reference terminal on the flow meter is causing me some confusion with ...
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Rs485 A & B Labels being used inconsistently
I would like to know if there is an official standard with regards to rs-485 terminals being labelled A & B.
I have always believed:
A=> + (positive)
and
B=> - (negative)
however, I have ...
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Can MAX485 TTL-to-RS-485 module be used as UART-to-RS485 module?
I'm trying to make a bridge from Modbus til Home Assistant using an ESP8266 (as outlined here), which uses an UART-to-RS485 module.
I have this MAX485 TTL to RS-485 Interface Module.
I'm not competent ...
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Need Help Connecting Arduino to PC via RS485 with Max485 breakout board
I am currently attempting to connect an arduino to a PC via the RS485 communication protocol using a max485 to convert the RS485 to serial. It does not however appear to be receiving any data at all. ...
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PC to MCU ModBus Communication Problem
Im trying to create a communication between PC to MCU with ModBus, so i used pyserial at PC side and used freemodbus at MCU side. But it did not worked. I tested PC code with Modbus program and its ok,...
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Want to use SPI sensor in RS485 modbus
I want to use multiple ICM20948 over SPI to RS485 with esp32 . is there anyway to do it and also is there have any other IMU which support rs485?
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Modbus Vs CANopen - Which one should I choose?
Modbus Vs CANopen - Which one should I choose if I want:
Broadcast to all units
Talk to specific units
Robust
Send lots of data
Implement for embedded systems
Easy to use
Using in new projects with ...
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Half duplex connection with a full duplex cevice
I have a sensor that I want to use with Modbus RTU and am not sure if I can use half duplex or if I need to use full duplex.
I would also like to get some suggestions how to read from it with my ...
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Good idea to use UART in half-duplex mode when using RS485 transceiver?
Most 2-wire RS485 implementations I have seen use both UART RX and TX pins which works of course. And I have done so.
But I was wondering whether using UART in half-duplex mode is a good alternative ...
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RS-485 Modbus keeps sending set timeouts. Is it normal?
I try to monitor RS-485 communication between Toyo motor drivers and an IPC control program. I monitor with a third-party software Device monitoring studio. The program is written by us. However, I ...
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How to record RS-485 Modbus communication at PC?
I am working on a system with an IPC, RS-485 Modbus communication, and 15 Toyo step motors and drivers. A motor frequently moves without IPC intentionally sending moving instruction and causes a ...
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RS485 UART Rx Receive Event Handler not fired for all Tx Commands sent [closed]
I am using (1)Azure Sphere MT3620 Starter Kit and (2)RS485 CLICK 5V and (3)Geovan Board
Here is the setup (I don't have latest picture, so #2 is swapped to first slot in the MT3620)
My MT3620 is ...
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Cable selection and wiring for RS485 communication
I'm designing a sensor system where each sensor communicates via RS485 MODBUS in a high-density environment. Each line consists of 18 sensors which then goes to a gateway (Elfin EE11) that converts ...
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Modbus acquisition timings
Part 1
What is the standard timing method for bits acquisition for a receiver using Modbus RTU?
For example, for UART: "Communicating UARTs have no shared timing system apart from the ...
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MODBUS RTU reading on Jetson Nano over RS485
I'm trying to implement Modbus reading on Jetson Nano (Linux - Ubuntu operation system).System include 3 part:
-MODBUS device which I would like to achieve input registers. --> Krohne Signal ...
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Wired sensor bus technology
I am working on a project which requires a dozen VL53l0X I2C-TOF sensors to be polled by one master MCU over a few meters of cable.
Thus, I decided to accompany each TOF by an Atmega8 acting as a ...
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Bus communication scheme for large number of devices (255+ nodes)?
I'm trying to figure out the feasibility of setting up some type of differential bus communication for up to 400 devices outdoors. The main constraints are mainly power consumption, complexity, wire ...
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Turn Node MCU into a PLC which is integrated Lora module for IoT application
I've built a PLC that supports Lorawan and Modbus protocol using Node MCU. I managed to make it possible with Modbus by using OpenPLC. Everything worked well apart from its limitation in the distance ...
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RS485 communication issue
I have used PIC18F45k40 device for RS485 communication. I have 2 ckts one is isolated and another non isolated RS485 design. I have schematic & placement for reference. I have connected multiple ...
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RS485 USB converter driver polarity
I have an RS485 USB converter connected with a temperature controller in the controller's datasheet it says that the 12 is (+) and 11 is (-) and in my USB converter there is A and B
Am not sure the D+...
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Isolating an existing RS485 tranceiver
I have a heat pump with an RS485 interface. Via a simple RS485 chip. No isolated interface, no isolated power supply to it.
I want to add a power meter at 400+ meter to it and want to properly isolate ...
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modbus register address vs. register number; absolute address vs. offset
I'm developing a Modbus Server device, and I'm having a little trouble understanding how to name or address my registers.
Let's say I have 2 Discrete Inputs and 2 Input registers. From Modicon ...
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Is there any limit of how many commands it can be sent to modbus controller relay?
I have modbus controlled relay hooked to raspberry pi (using node-red) which depending on the condition sends "on" or "off" command every 5 seconds (24h/365d). I know that relays in general have its ...
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Exactly what is an RTU (Remote Terminal Unit)?
I find the Wikipedia article and other sources ambiguous and I find that the definitions are so broad that I don't know how and when to use the term "RTU". I would like to figure this out because I ...
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How to increase data through put of RS485 RTU?
I am using 20 sensor nodes, each has mpu9250 i2c, Arduino atmega328 MCU 8MHz and max485 chip in it,
each server has a unique id program.
I have Arduino due as Modbus client with max485 chip,
I hope to ...
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