[Arduino source code for KC868-A2]-05 RS485 modbus temperature humidity sensor

Code:
/*

  RS485 Modbus Temperature and Humidity Sensor Reader

  Made by KinCony: https://www.kincony.com

  

  This program reads temperature and humidity data from a Modbus RS485 sensor

  and prints the values via the Serial monitor.



  Hardware configuration:

  - RS485 communication using GPIO TX (32) and RX (35)

  - Modbus RTU protocol

  - Temperature and humidity values are stored in separate registers



  You must install the ModbusMaster library in Arduino IDE.

*/



#include <ModbusMaster.h>  // Include the ModbusMaster library for Modbus communication



// Define GPIO pins for RS485 communication (TX and RX)

#define TXD_PIN 32  // Transmit pin for RS485

#define RXD_PIN 35  // Receive pin for RS485



// Define the Modbus slave ID (this should match the sensor's address)

#define SLAVE_ID 1



// Create a ModbusMaster object to handle Modbus communication

ModbusMaster node;



/*

  This function is called before starting a Modbus transmission.

  If your hardware needs control of RS485 DE/RE pins, configure them here.

*/

void preTransmission()

{

  // Optional: Control DE/RE pins for RS485 if necessary

}



/*

  This function is called after completing a Modbus transmission.

  If your hardware needs to reset DE/RE pins, configure them here.

*/

void postTransmission()

{

  // Optional: Control DE/RE pins for RS485 if necessary

}



void setup()

{

  // Start the Serial communication for debugging at 9600 baud rate

  Serial.begin(9600);

  

  // Start Serial2 for RS485 communication using GPIO 32 (TX) and GPIO 35 (RX) at 9600 baud rate

  Serial2.begin(9600, SERIAL_8N1, RXD_PIN, TXD_PIN);



  // Initialize the Modbus communication with the slave ID and associate it with Serial2

  node.begin(SLAVE_ID, Serial2);



  // Set the pre- and post-transmission handlers for controlling RS485 hardware if needed

  node.preTransmission(preTransmission);

  node.postTransmission(postTransmission);



  // Print an initial message to Serial monitor

  Serial.println("RS485 Modbus Sensor Example - Reading Temperature and Humidity");

}



void loop()

{

  uint8_t result;  // Variable to store the result of Modbus operations

  uint16_t data[2];  // Array to store the raw temperature and humidity data from the sensor



  // Read two input registers starting from address 0x0000, where temperature and humidity are stored

  result = node.readInputRegisters(0x0000, 2);  // Read 2 registers (temperature and humidity)



  // Check if the read operation was successful

  if (result == node.ku8MBSuccess)

  {

    // Retrieve raw temperature and humidity data from Modbus response buffer

    uint16_t temperatureRaw = node.getResponseBuffer(0);  // Temperature is in the first register

    uint16_t humidityRaw = node.getResponseBuffer(1);     // Humidity is in the second register



    // Parse temperature value

    float temperature;

    if (temperatureRaw < 10000)  // Check if the value represents a positive temperature

      temperature = temperatureRaw * 0.1;  // Positive temperature

    else

      temperature = -1 * (temperatureRaw - 10000) * 0.1;  // Negative temperature



    // Parse humidity value (always positive)

    float humidity = humidityRaw * 0.1;



    // Print the parsed temperature value to the Serial monitor

    Serial.print("Temperature: ");

    Serial.print(temperature);

    Serial.println(" °C");



    // Print the parsed humidity value to the Serial monitor

    Serial.print("Humidity: ");

    Serial.print(humidity);

    Serial.println(" %RH");

  }

  else

  {

    // If the read operation failed, print the error code to the Serial monitor

    Serial.print("Failed to read from sensor, error: ");

    Serial.println(result);

  }



  // Wait for 5 seconds before reading the sensor again

  delay(5000);

}