Industrial Arduino DHT library for use in programming. In this case, we are using the Adafruit library that you can download for free here.

(https://github.com/adafruit/DHT-sensor-library)

With this library, you can easily read both sensors and not worry about the communication protocol between the PLC Arduino and those sensors.

With the already imported library, we can start programming.

This example show you how to read humidity and temperature (Celsius and Fahrenheit).

#include "DHT.h" #define DHTPIN 2     //Pin where is the sensor connecte

#define DHTTYPE DHT22   // Sensor DHT22

DHT dht(DHTPIN, DHTTYPE);

void setup() {
Serial.begin(9600);
Serial.println("Loading...");
dht.begin(); 
}

void loop() {
delay(2000);
float h = dht.readHumidity(); //Reading the humidity 
float t = dht.readTemperature(); //Reading the temperature in Celsius degree 
float f = dht.readTemperature(true); //Reading the temperature in Fahrenheit degrees 

//--------Sending the reading through Serial port------------- 

Serial.print("Humidity ");
Serial.print(h);
Serial.print(" %t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.print(" *C ");
Serial.print(f);
Serial.println(" *F");
}

The following code has the function of communicating the Master and the Slave by sending the instruction to activate the relay to turn on a water pump.

An example of Simplecomm Master communication:

#include <RS485.h>
#include <SimpleComm.h>

// Create SimplePacket for sending and receiving data
SimplePacket packet;

// Define master address
uint8_t masterAddress = 0;

// Define slave address to communicate with
uint8_t slaveAddress = 1;

// Value to send as packet data
int value = 5;

////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
	Serial.begin(9600L);

  // Start RS485
  RS485.begin(19200L);
  RS485.setTimeout(20);

  // Start SimpleComm
  SimpleComm.begin(masterAddress);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
  static unsigned long lastSent = millis();

  // Send packet periodically: once per second
  if (millis() - lastSent >= 10000) {
    // Set request packet data
    packet.setData(value);

    // Send request to slave
    if (SimpleComm.send(RS485, packet, slaveAddress)) {
      lastSent = millis();

      Serial.print("Sent value: ");
      Serial.println(value);
    }
  }

  // Get responses
  if (SimpleComm.receive(RS485, packet)) {
    // Update value from the response
    value = packet.getInt();

    Serial.print("Received value: ");
    Serial.println(value);
  }
}

An example of Simplecomm Slave communication:

#include <RS485.h>
#include <SimpleComm.h>

// Create SimplePacket for sending and receiving data
SimplePacket request;
SimplePacket response;

// Define slave address to communicate with
uint8_t slaveAddress = 1;

////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
	Serial.begin(9600L);

  // Start RS485
  RS485.begin(19200L);
  RS485.setTimeout(20);

  // Start SimpleComm
  SimpleComm.begin(slaveAddress);
}

////////////////////////////////////////////////////////////////////////////////////////////////////
void loop() {
  // Get requests
  if (SimpleComm.receive(RS485, request)) {
    int value = request.getInt();

    Serial.print("Received value: ");
    Serial.println(value);
if ( value==5){
  digitalWrite(R0_8,HIGH);
  delay(5000);
  digitalWrite(R0_8,LOW);
  
}
    // Process value
    //value++;

    // Send response to the request packet source
    response.setData(value);
    if (SimpleComm.send(RS485, response, request.getSource())) {
      Serial.print("Sent value: ");
      Serial.println(value);
    }
  }
}