Development v12

Warning - Product Update

All the resources present on this section belong to Waspmote v12, Waspmote Plug & Sense! v12 and Meshlium v3.8.

If you have a Waspmote v15, Waspmote Plug & Sense! v15 or Meshlium v4.0 please go to the new Development Section.

Check what is your version and what are the differences between the old and the new one in this document.

» RS-232 05: Modbus Read Coils (v12)

This sketch shows the use of the Modbus communication protocol over RS-232 standard, and the use of the main functions of the library. Modbus allows for communication between many devices connected to the same network.

Required Materials

1 x Waspmote
1 x Battery
1 x RS-232

Notes

- This example shows how to configure the Waspmote as a Modbus master device. The Waspmote read the ACC values and the battery level from a Modbus slave.
- There are many variants of Modbus protocols, but Waspmote implements the RTU format. Modbus RTU is the most common implementation available for Modbus.
- This example can be executed in Waspmote v12

Code

/*   
 *  ------ [RS-232_05] Modbus Read Coils -------- 
 *   
 *  This sketch shows the use of the Modbus communication protocol over 
 *  RS-232 standard, and the use of the main functions of the library.
 *. Modbus allows for communication between many devices connected
 *  to the same network. There are many variants of Modbus protocols, 
 *  but Waspmote implements the RTU format. Modbus RTU is the most 
 *  common implementation available for Modbus. 
 *  
 *  This example shows the use of the function readCoils. This function 
 *  requests the ON/OFF status of discrete coils from the slave device.
 * 
 *  Copyright (C) 2014 Libelium Comunicaciones Distribuidas S.L. 
 *  http://www.libelium.com 
 *   
 *  This program is free software: you can redistribute it and/or modify 
 *  it under the terms of the GNU General Public License as published by 
 *  the Free Software Foundation, either version 2 of the License, or 
 *  (at your option) any later version. 
 *   
 *  This program is distributed in the hope that it will be useful, 
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of 
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 *  GNU General Public License for more details. 
 *   
 *  You should have received a copy of the GNU General Public License 
 *  along with this program. If not, see <http://www.gnu.org/licenses/>. 
 *   
 *  Version:          0.1 
 *  Design:           David Gascon 
 *  Implementation:   Ahmad Saad
 */

// Include these libraries for using the RS-232 and Modbus functions
#include <Wasp232.h>
#include <ModbusMaster232.h>

// Instantiate ModbusMaster object as slave ID 1
ModbusMaster232 node(1);

// Define one address for reading
#define address 1 

// Define the number of bits to read
#define bitQty 1

void setup()
{
  // Power on the USB for viewing data in the serial monitor
  USB.ON();

  // Initialize Modbus communication baud rate
  node.begin(9600, SOCKET0);

  // Print hello message
  USB.println("Modbus communication over RS-232");
  delay(100);
}


void loop()
{
  // This variable will store the result of the communication
  // result = 0 : no errors
  // result = 1 : error occurred
  int result =  node.readCoils(address,bitQty);

  if (result != 0) {
    // If no response from the slave, print an error message
    USB.println("Communication error");
    delay(1000);
  } 
  else { 

    // If all ok
    USB.print("Read value: ");

    // Print the read data from the slave 
    USB.print(node.getResponseBuffer(0));
    delay(1000);
  }

  USB.print("\n");
  delay(1000);

  // Clear the response buffer
  node.clearResponseBuffer();

}

Output

E#
Modbus communication over RS-232
Read value: 234a

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