Arduino Modbus Connection

Abstract

This article provides an overview for the basic configuration and operation of the Modbus serial communication between an Arduino Uno, which acts as a slave device that receives and executes commands, and CODESYS 3.5 whose function is that of a master device that initiates and controls the communication. This configuration requires certain parameters that must be taken into account to establish an optimal connection from the physical part with the assignment of the serial port for the Arduino, as well as the synchronization in the transmission speed, data bits, parity and other parameters that match what is specified in the type of RS-232, RS-485 interface of CODESYS 3.5. The above with the purpose of reading or writing data in the Arduino Uno by using functions such as "Read Holding Registers" to obtain information from the slave device, and "Write Single Register" to send the information, tests which are done preliminarily with the use of the "Modbus Poll" software to ensure the transmission.