How to Program an Arduino as a Modbus RS485 Master & Slave
If you work in the Automation Industry, you will know that automation equipment is very expensive. And many a time, especially for small applications, you simply cannot justify the use of very expensive equipment.
This is where the Arduino comes in!
The Arduino development board allows you to create very simple, but very powerful, Modbus master or slave devices through the use of relatively simple “C” programming. With the Arduino, you have full custom control over the program design allowing you to create very lean and very efficient devices for very specific purposes.
Put simply, mastering Modbus on the Arduino is going to take your skill level and value in the Automation Industry to a whole new level.
That is what this course is going to do. At the end of the course, you will know how to:
1. Choose the appropriate Arduino hardware.
2. Interconnect Arduino hardware with other add-on hardware.
3. Write “C” applications to implement Modbus master and slave functionality.
4. Use software and hardware to test each application that you write.
All of the programs written in the course are freely downloadable and give you a perfect starting point for further development. At the end of the course, you will have the knowledge to create your own products, your own custom Modbus master and slave hardware.
Looking forward to seeing you on the inside!
The Hardware We Will Be Using
The hardware that is used in the course is listed and their purpose given.
An overview of the Arduino Uno.
An overview of the RS485 shield for Arduino Uno.
An overview of the LCD display and Interconnecting Hardware.
An overview of the USB-to-RS485 converter as well as the basic connection of the hardware.
A look at the physical hardware set up.
The Software We Will Be Using
This lecture shows where to go on the web to download and install the free Arduino programming software.
Modbus Libraries are used to simplify the implementation of the Modbus protocol on the Arduino.
Modsim32 is a Modbus slave simulation application. It will be used to provide data values that will be read by the Windows Modbus Master application.
Quick Start - Creating our First Arduino Modbus Master Application
The Arduino IDE is briefly introduced.
A built in application is used as the first application and also to test the LCD display.
The code is modified to display the value of a variable on the LCD display.
Additional LCD code is added to update the LCD display only on data changes.
Using the laptop with Modsim32 as a Modbus Slave, the Arduino application is run and tested.
Extending the Arduino Modbus Master Application
Quite a bit of coding was done very quickly in the last section. This lecture reviews all of the code so as to solidify the function of the various commands.
Code is added and the application updated to be able to read a holding register.
Code is added and the application updated to be able to read an input status.
Code is added and the application updated to be able to read a coil.
Configuring the Arduino to Read/Display Data from a Modbus Temperature Sensor
An overview of the details of the section.
We have a look at the website from which the sensor was purchased.
We look at the datasheet for the sensor to determine the communication details.
Configuring the Arduino to Write Modbus Data to the Slave
Code is added to an existing Arduino program to write to a Modbus Coil based on the value in an Input Register.
The new code added in the previous video is testing using Modim32 as the Modbus Slave.
Configuring the Arduino as a Modbus Slave Device
The previously downloaded Modbus Slave Library is installed into the Arduino IDE.
Code is written to implement the Modbus Slave in the Arduino and then Modscan32 is used to read Modbus data.
The code from the previous lecture is modified to test the write functionality of the slave. Modscan32 is used to write to the Arduino slave.
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