Serial Communication Standard

RS-232 protocol formally defines the signals connecting between DTE (Data Terminal Equipment) such as a computer terminal, and DCE (Data Circuit-terminating Equipment or Data Communication Equipment), such as a modem.

Our Arduino Based PLCs incorporate the integrated circuit MAX232.

MAX232 converts signals from to TIA-232 (RS-232) serial port to signals suitable for use in TTL-compatible digital logic circuits. The MAX232 is a dual transmitter / dual receiver that is used to convert the RX, TX, CTS, RTS signals.

MAX232 Pin Configuration and Typical Operating Circuit

Hardware

Check the LoRa Family products now!

IMPORTANT: Make sure that your Ethernet PLC is powered (12-24Vdc).

Switch configuration 

For the RS-232 communication protocol there isn't any switch that affects it. So it does not matter the configuration of the switches to implement a RS-232 communication.

Used pins

For RS-232 communication protocol the defined Arduino Mega pins are showed in the chart below:

M-Duino Ethernet PLC pinout	Arduino Mega pinout
TX	16 (Serial2 TX)
RX	17 (Serial2 RX)

You can access easily to RS-232 pins in our Ethernet PLCs, you can see their position in the following image:

Connections

Software

IMPORTANT: Make sure to download the Arduino based PLC boards for Arduino IDE.

RS232.begin(baud); //sets the baud rate for RS232 data transmision
RS232.read(); //reads incoming RS232 data
RS232.write(byteToSend); //write binary data to RS232 port
RS232.write(dataToSend, dataLength); //write binary data to RS232 port
RS232.available() //returns the number of bytes available for reading on RS232 port

// Include Industrial Shields libraries
#include <RS232.h>

//// IMPORTANT: check switches configuration

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

  // Begin RS232 port
  RS232.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-232 port
    RS232.write(tx);
  }
}

 Basic RS-232 read example:

// Include Industrial Shields libraries
#include <RS232.h>

//// IMPORTANT: check switches configuration

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

  // Begin RS232 port
  RS232.begin(38400);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
  // Print received byte when available
  if (RS232.available()) {
    byte rx = RS232.read();

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

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

By following these steps carefully, you will be able to achieve the use of the RS-232 protocol using the Industrial Shields equipments.