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 communications many extensions exist to allow communication over other networks such as TCP/IP.

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551 views

Standard cables for modbus protocol

What are the standard cables I can use for modbus protocol? lease add the price details if anybody knows
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1answer
55 views

Does FT232RLMG support RS-485?

I have the FT232RLMG device and a device that uses the RS-485 connection standard. I would like to know if I can connect the TX and RX pins of the FT232RLMG to the device that uses RS-485 directly or ...
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689 views

watchdog timer on PLC

I've currently set my PLC as a modbus slave, and written some python code which connect to it and act as a modbus client. I am having some problems with the modbus server sometime terminating the ...
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7k views

How to connect RS485 Device to computer in Modbus RTU

How to physically connect a voltage monitoring meter device(ND20) with RS485 out, to a computer with Modbus RTU? Should I use a converter to RS232 and connect to serial COM port of computer? Should I ...
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290 views

Is the information in MODBUS function code 16 redundant?

MODBUS function code 16 is "Write Holding Registers". The function command structure is: ...
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1answer
196 views

Get line to line values from line to neutral reading

My device can provide reading of Line to neutral values through Modbus , I'm requested to provide Line to Line readings which is not available in our Modbus table for the device. Is it possible to get ...
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Termination resistor creating communication problem in RS485 MODBUS/TCP

In RS485 communication, what is the role of termination resisotor. Is it mandatory? I have been working on a project with MODBUS/TCP over RS485 where upto 32 slaves are there in some links, out of ...
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3k views

Difficulty in reading values Modbus application in Python(Pyserial) On Energy meter (EM6400)

I am trying to read energy meter(EM6400) voltage values in python by using modbus protocol. But there are issues when I am reading values. I think the issue is with,...
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2k views

How to connect Arduino Uno to an energy meter

How do I connect an energy meter, such as the L&T (Larsen & Toubro) Quasar Intelligent meter (datasheet,) which uses Modbus RTU protocol with RS485 communication to an Arduino Uno? I am ...
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363 views

Modbus and the Sunny Boy

I am using libmodbus to connect to the a SunnyBoy 2.5 inverter. I make the connection as follows: ...
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2answers
958 views

Microcontroller Interface with Modbus Serial [closed]

I'm a beginner and I'm trying to acquire data from a microcontroller with Modbus serial protocol in order to create an interface with LabVIEW. I'm using a Prolific Technology USB-RS232 converter and ...
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2answers
440 views

Put firewall hardware with ethernet ports between serial ports

I want to put a firewall hardware product between a RTU and PLC to block some Modbus function codes (e.g. write coil, read coil). (This firewall product is able to do deep packet inspection on Modbus ...
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506 views

Modbus raw data COM capture file example?

I'm attempting to use a RS232 tap to sniff a serial connection between two devices that are communicating using Modbus RTU. I'm looking for any capture files taken from sniffing a COM connection or ...
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1answer
419 views

RS485 not working in pic24fj128ga202

I would like to send and receive data between two PIC24F microcontrollers via RS485. Here i'm using SP3485 IC. I've set one microcontroller as transmitter and another one has receiver. My ...
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3answers
727 views

RxTx communication with multiple slaves using a RaspberryPi

I am a programmer trying to build a circuit with limited EE knowledge. With so many options(at least being new to this), just want to make sure I am going down the right path. What I am trying to ...
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1answer
922 views

Modbus RS485 - Voltage greater than 12V?

I have a boiler (Immergas Eolo Star) which has 2 pins where you can connect either a normal thermostat or a "remote control unit" which can also give more detailed information (self-diagnosis) about ...
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3answers
3k views

Struggling with serial communication over RS 485 using modbus protocol

I have around 60-70 inverters that I want to talk to using arduino over RS-485. The connection that I am making with arduino is according to the attached image. Now I think that my connection part ...
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1answer
902 views

Modbus Rs-485 serial communication and polling with reference to manual

I have connected my slave and RS-485 using serial connection and using my computer as master device. I'm able to poll but I cant figure out which registers I'm polling as shown in image 1. I tried to ...
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2answers
2k views

modbus_read_registers - ERROR connection timed out

We are using libmodbus library to read register values from energy meter EM6400 which supports Modbus over RTU. We are facing the following two issues. 1) We are facing issue with ...
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3answers
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Serial, RS232, Modbus, UART and TCP

I want clearly know this, Serial is protocol right? Then what is the Modbus? Is it under serial. And what are RS232 and RS485? What is UART and serial and UART same? What about TCP? TCP and serial ...
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2answers
1k views

RS-485 Modbus device to MCU

I have a device (an energy meter) that sends data via RS-485 (Modbus protocol). And I want to collect it with MCU. The important thing is that I'm trying to design a board and I want it to be scalable....
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1answer
4k views

libmodbus trouble with reading from slave

I have the following code for connection to a temperature sensor as my slave using the libmodbus library in C, ...
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3answers
926 views

Arduino: RS232 Level Shifter or RS2323 Breakout needed? [closed]

I am trying to establish communications between an Arduino Mega2560 (Master) and a customised controller (Slave) via a Master-Slave RS232 link using Modbus RTU. The communication should be bi-...
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2answers
4k views

Connectors for a RS485 multipoint bus

I need to connect a bunch of Mass Flow Controllers on a RS485 (TIA-485-A) multipoint bus. I will use Modbus protocol to communicate with the devices. As specified on modbus.org (Specification and ...
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313 views

Modbus compile error Arduino

I have Code for Mod bus Library as below. I have Gone through lots of forum. How to assign device ID, slave address, length using below library function: ...
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1answer
4k views

atmega32 communicating using rs-485 modbus protocol

I am trying to read values from a meter (WDM303FDWA1) through ATmega32. The communication to the meter has to be done by RS-485 modbus protocol. I would like to know what IC do I have to use to ...
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3answers
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Holding register in microcontroller for Modbus RTU

I'm very noob in microcntroller modbus. I want to do Modbus RTU slave device using RS232. I read modbus documentation from modbus.org site. But still I'm not clear about few things. How to define the ...
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Modbus TCP/IP slave - functions

I'm developing a slave modbus TCP/IP application on the PIC32 platform. Do you have any idea about the the role of the ...
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445 views

Handling register updates in Modbus systems

I am currently developing a Modbus RTU enabled system that consists of DSP and a microprocessor that handles the Modbus communications. The DSP is sending data to the microprocessor and the ...
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3answers
35k views

Arduino as modbus master with MAX485 doesn't get any response

I'm having some troubles trying to query a modbus slave with an Arduino through RS485. I've already succeeded in querying a software modbus slave running on my PC through the USB/COM port using the ...
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2answers
527 views

What is a conventional way to set a Modbus device address and baudrate?

What's a conventional way to set an address and baud-rate/parity on a Modbus device? Is this supposed to be done using hardware switches or can be done through a software? If done through a ...
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3answers
4k views

Best way to poll for Modbus RTU slaves through a Modbus TCP gateway

I'm using a number of Modbus RTU devices connected to my PC through a Modbus TCP gateway. I'd like to poll all the available slave addresses to check which ones are available through my program. What ...
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2answers
341 views

FOSS ModBus libraries/VCl?

I'm looking for FOSS (for commercial use) VCL components for Delphi or libraries for Visual Basic/C/C++/C# ... basically, just something to abstract the h/w for development, although a h/w simulator ...
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1answer
7k views

Reading MODBUS RTU slave device Registers via RS485

i have a panel multimeter that i use for my whole house that has RS485, Modbus RTU comunication. I know what registers to read in order to get currents, voltages, power factor etc How can i use this ...

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