Communication Modbus and Arduino

[ssaienko]

Hi Everyone, I am trying to read holding register of a electromagnetic flowmeter Proline Promag P 300 via RS485 using Modbus RTU but unable to do. I am new to Arduino and getting so much confused by different library e.g. ModbusMaster.h and SimpleModbusMaster.h etc.

I am using RS-485 toTTL to module and also have 1 arduino mega.
This is register addres:

For more information use this link about Promag 300:

BA01395DEN_0116.pdf

My code:

#include <ModbusMaster.h>
#include <SoftwareSerial.h>

SoftwareSerial mySerial(5, 3); // RX, TX
ModbusMaster node;

void setup() {
  Serial.begin(9600);
  mySerial.begin(9600);
  node.begin(1, mySerial);
}

void loop() {
  uint8_t result;
  uint16_t data;

  result = node.readHoldingRegisters(5050, 1);
  if (result == node.ku8MBSuccess) {
    data = node.getResponseBuffer(0);
    Serial.print("Register 5051 value: ");
    Serial.println(data);
  } else {
    Serial.println("Error reading from register 5051.");
  }

  delay(1000);
}

and module what i use:

Please help me out and thanks in advance.

And please let me know if any other information I need to provide.

[b707]

And what is result of calling your code? Do you see any output in the console?

[ssaienko]

this is result in console

[ruilviana]

@ssaienko

result = node.readHoldingRegisters(5050, 1);

use the debug function, printing the read value in HEX:

Ex:
After the line:
result = node.readHoldingRegisters(5050, 1);
use:
Serial.println(result,HEX);

And say what you printed.

[qubits-us]

Did you change the parameters, address defaults to 247, baud defaults to 19,200??
per your pdf anyways..

good luck.. ~q