We recommend you to read the following posts in order to understand the program of this blog. We used the following blog posts to do this example:

• How to program our industrial PLC with Arduino IDE: Installing the Industrial Shields's boards in the Arduino ID

In order to work with RS-485 protocol, you will need any of our industrial PLC controllers for industrial automation:

• Industrial Shields controllers: Wifi & Bluetooth Controller Family, Ethernet Controller Family, GPRS / GSM Controller Family or 20IOs Controller Arduino Family

The first step is downloading the  Arduino based PLC boards for Arduino IDE.
After making the hardware configuration, we need to continue with the software configuration and also how we use it. To begin this process, it is necessary to include the library RS485.h  founded in our website. After this, in the function setup, please take care to do the right implementation of your communication

For all families:

Software configuration

#include <RS485.h>

To check the RS-485 activation you only have to use the serial monitor from the Arduino IDE using the right sentence inside the setup() function.

Serial.begin(9600); 

It is also important to implement the initialization on the setup() function.

RS485.begin(38400);

IMPORTANT : CHECK THE SPEED OF TRANSMISSION OF PLC-LAPTOP AND PLC-DEVICES .

Basic example of writing in the RS-485: 

// Include Industrial Shields libraries
#include <RS485.h>

//// IMPORTANT: check switches configuration

////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
  // Begin serial port
  Serial.begin(9600);

  // Begin RS485 port
  RS485.begin(38400);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
  // Wait bytes in the serial port
  if (Serial.available()) {
    byte tx = Serial.read();

    // Echo the byte to the serial port again
    Serial.write(tx);

    // And send it to the RS-485 port
    RS485.write(tx);
  }
}

Basic example of reading of the RS-485: 

// Include Industrial Shields libraries
#include <RS485.h>

//// IMPORTANT: check switches configuration

////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
  // Begin serial port
  Serial.begin(9600);

  // Begin RS485 port
  RS485.begin(38400);
}
////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
  // Print received byte when available
  if (RS485.available()) {
    byte rx = RS485.read();

    // Hexadecimal representation
    Serial.print("HEX: ");
    Serial.print(rx, HEX);

    // Decimal representation
    Serial.print(", DEC: ");
    Serial.println(rx, DEC);
  }
}

Basic Full-duplex example of RS-485: 

Before start the test, connect A,B (receivers) to the Y, X (transmitters).

// Include Industrial Shields libraries
#include <RS485.h>
//// IMPORTANT: check switches configuration
//// IMPORTANT: Full duplex mode is only available when device supports it
////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
  // Begin serial port
  Serial.begin(9600);
  // Begin RS485 port
  RS485.begin(38400, FULLDUPLEX);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
  // Wait bytes from the RS-485
  if (RS485.available()) {
    byte tx = RS485.read();
    // In full-duplex mode it is possible to send and receive data
    // at the same time in a secure way
    RS485.write(tx);
    // Echo the byte to the serial port
    Serial.write(tx);
  }
}