Question

I am trying to ping a Socomec meter using the Modbus protocol, having researched, I found NModbus, a C# library. I have never used libraries or C# before (normally Java), but I have to dive right in.

I set myself up with Visual Studio Express for C# and installed .Net. I have copied then contents of the NModbus file into my project folder and added the references to the two main DLLs. Its didn’t work with .Net 4, but I retargeted to 3.5 (and removed the Microsoft.Csharp reference) and things seemed to compile.

I am using this sample, below, to attempt to connect to the slave device. When I run this, and set the startAdress variable to the desired one (found in Socomec documentation) however all I get is a blank console window.

In short, am I using the correct method/parameters, is my setup/code incorrect? How do I connect to this meter?

My code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO.Ports;
using Modbus.Data;
using Modbus.Device;
using Modbus.Utility;


namespace NModbus
{
    class SerialMaster
    {
        static void Main(string[] args)
        {
            ModbusSerialAsciiMasterReadRegisters();
        }

        public static void ModbusSerialAsciiMasterReadRegisters()
        {
            using (SerialPort port = new SerialPort("COM1"))
            {
                // configure serial port
                port.BaudRate = 9600;
                port.DataBits = 8;
                port.Parity = Parity.None;
                port.StopBits = StopBits.One;
                port.Open();

                // create modbus master
                IModbusSerialMaster master = ModbusSerialMaster.CreateAscii(port);

                byte slaveId = 1;
                ushort startAddress = 50536;
                ushort numRegisters = 5;

                // read five registers       
                ushort[] registers = master.ReadHoldingRegisters(slaveId, startAddress, numRegisters);

                for (int i = 0; i < numRegisters; i++)
                    Console.WriteLine("Register {0}={1}", startAddress + i, registers[i]);
                    Console.ReadLine();
            }

            // output:
            // Register 1=0
            // Register 2=0
            // Register 3=0
            // Register 4=0
            // Register 5=0
        }
    }
}

Answer 1

Why don’t you use some Java MODBUS library when you are already familiar with Java? I haven’t worked with Socomec meters, but in general for MODBUS devices you need to know the protocol and addresses you are interested in. Then try to read tags from the device with some tool that you know is working well, like MODPOLL. Then when you get usable values as expected, you go to programming the polling connection in any language you like. Otherwise, you risk to loose a lot of time wondering what’s going on.
One hint… From your code I see that you are acting as MODBUS ASCII serial master. Although such devices exist, 95% of RS232/RS485 devices I worked with were MODBUS RTU. Read specification if you don’t know the difference.