• Modbus Tcp/ip Testing Software
• Modbus Tcp/ip Library Arduino
• Allen Bradley Modbus Tcp Ip
• Modbus Tcp Server
• Modbus Tcp/ip

Jan 19, 2018  Dear, I am working on a project in which I seek to collect information from a similar input and then send the data via Modbus TCP / IP. For which I am using an Arduino MEGA together with an Ethernet Shield W5100, I. Modbus TCP/IP on Arduino. Ask Question. Up vote 1 down vote favorite. I am trying to implement Modbus TCP on arduino uno + ethernet shield using the following code. I am using a modbus slave simulator on a pc to check the following code. However, the code doesn't seem to be working.

Modbus TCP/IP on Arduino. Is it possible to have two Modbus map in one PLC? Modbus TCP - Arduino. FTP client on ethernet shield arduino. It uses the SPI and Ethernet Arduino libraries (first two lines) and the Mudbus libraries (for the modbus TCP). In the setup () function, apart from setting Ethernet parameters like mac, ip, gateway and subnet mask, I set to zero the first four registers of the modbus. What you will need to make sure is that the gateway will only send packets directed to port 502 to the arduino (502 is the Modbus TCP port) as it is possible other IP traffic could cause some drama for the modbus slave.

This library allows your Arduino to communicate via Modbus protocol. The Modbus is a master-slave protocolused in industrial automation and can be used in other areas, such as home automation.

The Modbus generally uses serial RS-232 or RS-485 as physical layer (then called Modbus Serial) andTCP/IP via Ethernet or WiFi (Modbus IP).

In the current version the library allows the Arduino operate as a slave, supporting Modbus Serial andModbus over IP. For more information about Modbus see:

Author's note (motivation and thanks):

It all started when I found the Modbus RTU Arduino library of Juan Pablo Zometa. I had extend thelibrary to support other Modbus functions.

After researching several other Modbus libraries I realized strengths and weaknesses in all of them.I also thought it would be cool have a base library for Modbus and derive it for each type of physical layer used.

I appreciate the work of all the authors of the other libraries, of which I used several ideas to compose the modbus-arduino.At the end of this document is a list of libraries and their authors.

• Operates as a slave (master mode in development)
• Supports Modbus Serial (RS-232 or RS485) and Modbus IP (TCP)
• Reply exception messages for all supported functions
• Modbus functions supported:
• 0x01 - Read Coils
• 0x02 - Read Input Status (Read Discrete Inputs)
• 0x03 - Read Holding Registers
• 0x04 - Read Input Registers
• 0x05 - Write Single Coil
• 0x06 - Write Single Register
• 0x0F - Write Multiple Coils
• 0x10 - Write Multiple Registers

Notes:

1. When using Modbus IP the transport protocol is TCP (port 502) and, by default, the connection is terminated to each transmitted message, that is, is not a keep-alive type connection. If you need a TCP keep-alive connection you have to remove comments of this line in ModbusIP.h header (or ModbusIP_* headers):

2. The offsets for registers are 0-based. So be careful when setting your supervisory system or your testing software. For example, in ScadaBR (http://www.scadabr.com.br)offsets are 0-based, then, a register configured as 100 in the library is set to 100 in ScadaBR. On the other hand, in the CAS Modbus Scanner(http://www.chipkin.com/products/software/modbus-software/cas-modbus-scanner/) offsets are 1-based, so a register configured as 100 in library should be 101 in this software.

3. Early in the library Modbus.h file there is an option to limit the operationto the functions of Holding Registers, saving space in the program memory.Just comment out the following line:

Thus, only the following functions are supported:

• 0x03 - Read Holding Registers
• 0x06 - Write Single Register
• 0x10 - Write Multiple Registers

4. When using Modbus Serial is possible to choose between Hardware Serial(default) or Software Serial. In thiscase you must edit the ModbusSerial.h file and comment out the following line:

Now, You can build your main program putting all necessary includes:

And in the setup() function:

There are five classes corresponding to five headers that may be used:

• Modbus - Base Library
• ModbusSerial - Modbus Serial Library (RS-232 and RS-485)
• ModbusIP - Modbus IP Library (standard Ethernet Shield)
• ModbusIP_ENC28J60 - Modbus IP Library (for ENC28J60 chip)
• ModbusIP_ESP8266AT - Modbus IP Library (for ESP8266 chip with AT firmware)

If you want to use Modbus in ESP8266 without the Arduino, I have news:http://www.github.com/andresarmento/modbus-esp8266

Modbus Jargon

In this library was decided to use the terms used in Modbus to the methods names, then is important clarify the names ofregister types:

Notes:

1. Input Status is sometimes called Discrete Input.
2. Holding Register or just Register is also used to store values in the slave.
3. Examples of use: A Coil can be used to drive a lamp or LED. A Holding Register tostore a counter or drive a Servo Motor. A Input Status can be used with a reed switchin a door sensor and a Input Register with a temperature sensor.

Modbus Serial

There are four examples that can be accessed from the Arduino interface, once you have installed the library.Let's look at the example Lamp.ino (only the parts concerning Modbus will be commented):

Inclusion of the necessary libraries.

Sets the Modbus register to represent a lamp or LED. This value is the offset (0-based) to be placed in its supervisory or testing software.Note that if your software uses offsets 1-based the set value there should be 101, for this example.

Create the mb instance (ModbusSerial) to be used.

Sets the serial port and the slave Id. Note that the serial port is passed as reference, which permits the use of other serial ports in other Arduino models.The bitrate and byte format (8N1) is being set. If you are using RS-485 the configuration of another pin to control transmission/reception is required.This is done as follows:

In this case, the pin 2 will be used to control TX/RX.

Adds the register type Coil (digital output) that will be responsible for activating the LED or lamp and verify their status.The library allows you to set an initial value for the register:

In this case the register is added and set to true. If you use the first form the default value is false.

This method makes all magic, answering requests and changing the registers if necessary, it should be called only once, early in the loop.

Finally the value of LAMP1_COIL register is used to drive the lamp or LED.

In much the same way, the other examples show the use of other methods available in the library:

Adds registers and configures initial value if specified.

Sets a value to the register.

Returns the value of a register.

Modbus IP

There are four examples that can be accessed from the Arduino interface, once you have installed the library.Let's look at the example Switch.ino (only the parts concerning Modbus will be commented):

Inclusion of the necessary libraries.

Sets the Modbus register to represent the switch. This value is the offset (0-based) to be placed in its supervisory or testing software.Note that if your software uses offsets 1-based the set value there should be 101, for this example.

Create the mb instance (ModbusIP) to be used.

Sets the Ethernet shield. The values ​​of the MAC Address and the IP are passed by the config() method.The syntax is equal to Arduino Ethernet class, and supports the following formats:

Then we have:

Adds the register type Input Status (digital input) that is responsible for detecting if a switch is in state on or off.The library allows you to set an initial value for the register:

In this case the register is added and set to true. If you use the first form the default value is false.

This method makes all magic, answering requests and changing the registers if necessary, it should be called only once, early in the loop.

Finally the value of SWITCH_ISTS register changes as the state of the selected digital input.

Modbus IP(ENC28J60)

The Arduino standard Ethernet shield is based on chip WIZnet W5100, therefore the IDE comeswith this library installed. If you have a shield based on ENC28J60 from Microchip you must installanother Ethernet library. Among several available we chose EtherCard.

Download the EtherCard in https://github.com/jcw/ethercard and install it in your IDE.Use the following includes in your sketches:

Done! The use of Modbus functions is identical to the ModbusIP library described above.

Notes:

1. EtherCard is configured to use the pins 10, 11, 12 and 13.

2. The voltage for shields based on ENC28J60 is generally 3.3V.

3. Another alternative is to use the ENC28J60 UIPEthernet library, available fromhttps://github.com/ntruchsess/arduino_uip. This library was made so thatmimics the same standard Ethernet library functions, whose work is done byWiznet W5100 chip. As the ENC28J60 not have all the features of the other chip, the libraryUIPEthernet uses a lot of memory, as it has to do in software what in the shield Wiznetis made in hardware. If for some reason you need to use this library, just changethe file ModbusIP.h and your sketches, changing the lines:

by

Then, you can use the ModbusIP library (not the ModbusIP_ENC28J60).In fact it allows any library or skecth, made forWiznet shield be used in shield ENC28J60. The big problem with this approach(and why we chose EtherCard) is that UIPEthernet library + ModbusIP uses about 60%arduino program memory, whereas with Ethercard + ModbusIP_ENC28J60this value drops to 30%!

Modbus IP (ESP8266 AT)

Modules based on ESP8266 are quite successful and cheap. With firmware thatresponds to AT commands (standard on many modules) you can use them as asimple wireless network interface to the Arduino.

The firmware used in the module (at_v0.20_on_SDKv0.9.3) is available at:http://www.electrodragon.com/w/ESP8266_AT-command_firmware

(Other AT firmwares compatible with ITEAD WeeESP8266 Library should work)

Warning: Firmware such as NodeMCU and MicroPython does not work because librariesused here depend on a firmware that responds to AT commands via serial interface.The firmware mentioned are used when you want to use ESP8266 modules without the Arduino.

You will need the WeeESP8266 library (ITEAD) for the Arduino. Download from:

https://github.com/itead/ITEADLIB_Arduino_WeeESP8266 and install in your IDE.

Notes:

1. The ESP8266 library can be used with a serial interface by hardware (HardwareSerial) orby software (SoftwareSerial). By default it will use HardwareSerial, to change edit the fileESP8266.h removing the comments from line:

2. Remember that the power of ESP8266 module is 3.3V.

For Modbus IP (ESP8266 AT) there is four examples that can be accessed from the Arduino interface.Let's look at the example Lamp.ino (only the parts concerning Modbus will be commented):

Inclusion of the necessary libraries.

Creates the serial interface via software using pins 2 (RX) and 3 (TX). So it can usehardware for the serial communication with the PC (e.g. for debugging purposes) in Arduino models that have only one serial (Ex .: Arduino UNO).

Create the wifi object (ESP8266) specifying the rate in bps.Warning: If you use SoftwareSerial do not specify a baud rate of 115200bps or more for the serial because it will not function. Some firmware / modules comes with 115200bps by default. You will have to change the module via AT command:

Continuing with our example:

Modbus Tcp/ip Testing Software

Sets the Modbus register to represent a lamp or LED. This value is the offset (0-based) to be placed in its supervisory or testing software.Note that if your software uses offsets 1-based the set value there should be 101, for this example.

Create the mb instance (ModbusSerial) to be used.

Configure ESP8266 module. The values quoted correspond to the network name (SSID) and security key.By default IP configuration is received via DHCP. See the end of the section how to have an Static IP(important so you do not need to change the master / supervisor if the IP changes).

Folowing, we have:

Adds the register type Coil (digital output) that will be responsible for activating the LED or lamp and verify their status.The library allows you to set an initial value for the register:

In this case the register is added and set to true. If you use the first form the default value is false.

This method makes all magic, answering requests and changing the registers if necessary, it should be called only once, early in the loop.

Finally the value of LAMP1_COIL register is used to drive the lamp or LED.

Quite similarly to other examples show the use of other methods available in the library.

Using a static IP on the ESP8266 module

We are aware today of two options:

Modbus Tcp/ip Library Arduino

1. In your router configure the MAC address of the module so that the IP address provided byDHCP is always the same (Most routers have this feature).

2. In your code, include two lines to change the IP address after the module configuration:

Allen Bradley Modbus Tcp Ip

Note .: For the module to receive IP via DHCP again you will need to remove the linesand run (at least once) the command: AT + CWDHCP = 1.1 via direct connection to the module, either:

Arduino Modbus RTU
Author: Juan Pablo Zometa, Samuel and Marco Andras Tucsni
Year: 2010
Website: https://sites.google.com/site/jpmzometa/

Simple Modbus
Author: Bester.J
Year: 2013 Website: https://code.google.com/p/simple-modbus/

Arduino-Modbus slave
Jason Vreeland [CodeRage]
Year: 2010
Website: http://code.google.com/p/arduino-modbus-slave/

Mudbus (Modbus TCP)
Author: Dee Wykoff
Year: 2011
Website: http://code.google.com/p/mudbus/

ModbusMaster Library for Arduino
Author: Doc Walker
Year: 2012
Website: https://github.com/4-20ma/ModbusMaster
Website: http://playground.arduino.cc/Code/ModbusMaster

Modbus Tcp Server

http://github.com/andresarmento/modbus-arduino
prof (at) andresarmento (dot) com

Modbus Tcp/ip

The code in this repo is licensed under the BSD New License. See LICENSE.txt for more info.