How to add or assign modbusSlave ID more than one

Using Arduino Programming Questions
1

Hi, I m Hermanto from indonesia.

here I have a problem adding ID to the modbusSlave program arduino. arduino uno as slave and using RS 485 converter. Please Help me.

#include <modbus.h>
#include <modbusDevice.h>
#include <modbusRegBank.h>
#include <modbusSlave.h>
modbusDevice regBank;
modbusSlave slave;

#define RS485TxEnablePin 2
#define RS485Baud 9600
#define RS485Format SERIAL_8E1


#define LED1 11
#define LED2 12

void setup()
{
  //Assign the modbus device ID.
  regBank.setId(1);
  /*
    modbus registers follow the following format
    00001-09999  Digital Outputs, A master device can read and write to these registers
    10001-19999  Digital Inputs, A master device can only read the values from these registers
    30001-39999  Analog Inputs, A master device can only read the values from these registers
    40001-49999  Analog Outputs, A master device can read and write to these registers

    Analog values are 16 bit unsigned words stored with a range of 0-32767
    Digital values are stored as bytes, a zero value is OFF and any nonzer value is ON

  */

  //Add Analog Input registers to the register bank
  regBank.add(30001);
  regBank.add(30003);


  //Add Analog Output registers to the register bank
  regBank.add(40001);
  regBank.add(40002);

  slave._device = &regBank;

  slave.setBaud(&Serial, RS485Baud, RS485Format, RS485TxEnablePin);
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
}

void loop()
{
  digitalWrite(LED1, regBank.get(40001));
  digitalWrite(LED2, regBank.get(40002));
  regBank.set(30001, (word) analogRead(A0)); //from 0 - 1023
  regBank.set(30003, (word) analogRead(A1)); //from 0 - 1023

  slave.run();
}
2

You shouldn't use the ArduinoModbus library on AVR Arduinos as it's designed for MKR Arduinos (which have a lot more RAM).

This is only a convention used by some PLC vendors. It's not part of the Modbus standard you can use any address for any type of register. Unfortunately some PLC vendors even don't use the higher register numbers but use the range only to select the type of register, so that 30001 effectively is input register 1.

3

Thank a lot Sir.
so, how about an example of making an arduino modbusSlave program? I have tried several programs, but I always fail. I want to make three analog inputs with three different addresses for the outputs. I use RS485 for output conversion.

4

Most libraries offer example code. Just one example.

5

okay sir. I will try it. Thank you very much for your response.

6

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