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Communication / RS-485:

» RS-485 09: Modbus Slave Mode

This sketch shows the use of the Modbus communication protocol over RS-485 standard, and the use of the main functions of the library. This example shows the use of the Waspmote RS-485 in slave mode.

Required Materials

1 x Waspmote
1 x Battery
1 x RS-485

Notes

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.

Code

/*   
 *  ------ [RS-485_09] Modbus Slave Mode -------- 
 *   
 *  This sketch shows the use of the Modbus communication protocol over 
 *  RS-485 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 Waspmote RS-485 in slave mode. 
 * 
 *  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 
 *  Implementation:   Ahmad Saad
 */

// Include these libraries for using the RS-485 and Modbus functions
#include <Wasp485.h>
#include <ModbusSlave485.h>

// Create new mbs instance 
ModbusSlave485 mbs;

// Slave registers
enum {        
  MB_0,   // Register 0 
  MB_1,   // Register 1 
  MB_2,   // Register 2 
  MB_3,   // Register 3    
  MB_4,   // Register 4     
  MB_REGS // dummy register. using 0 offset to keep size of array
};

int regs[MB_REGS];

void setup(){

  // Power on the USB for viewing data in the serial monitor. 
  USB.ON();  
  
  // Modbus slave configuration parameters   
  // SlaveId 
  const unsigned char SLAVE = 2;   
  // Baud rate
  const long BAUD = 9600;    
  // Configure msb
  mbs.configure(SLAVE, BAUD);
}

void loop()
{
  // pass current register values to mbs
  mbs.update(regs, MB_REGS);

  // Read all the analog Inputs, and store the values in 
  // the Modbus registers
  regs[MB_0] = analogRead(ANALOG1);  
  regs[MB_1] = analogRead(ANALOG2); 
  regs[MB_2] = analogRead(ANALOG3);  
  regs[MB_3] = analogRead(ANALOG4); 
  regs[MB_4] = analogRead(ANALOG5);  
  
  delay(10);

}

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