I would like to explore the idea of using Ethernet I/O modules to bring in non-critical signals from remote instrumentation. Searching the internet returns an overwhelming list of options. The problem is that most all of the Ethernet I/O modules that I've looked at communicate using complex protocols such as MODBUS etc...

I'd like to use a simple Telnet connection or WinSock to do read/writes to the I/O's IP, Port and I/O address. It seems that this should be all that's required. Using protocols such as MODBUS will require that I purchase a MODBUS ActiveX or use some other commercial software package to handle the communication... or God forbid, code the MODBUS protocol into my applications. This seems like complete overkill and needless complexity. Is there a simple Ethernet I/O module on the market? I'd prefer that It be DIN rail mountable and have a rugged enclosure vs an open circuit board.

 

Actually,
Modbus TCP is a very simple protocol in comparison to others (EtherNet/IP, Profinet, EtherCat, etc.). There are several free drivers and controls for using Modbus TCP.

Advanced HMI is free and has several drivers and example source code. This would allow you to choose from several protocols:
http://advancedhmi.com/Drivers/default.html
YouTube video:

lowcostio has, well, low cost I/O; and they include drivers and source code examples.
http://lowcostio.com/

Advantech also has Ethernet I/O at a good price. They also provide .Net drivers and example source:
http://www.advantech.com/products/Ethernet-I-O-Modules-ADAM-6000/sub_GF-5197.aspx

Personally, I think one of these, or one of many other manufactures would be much simpler than using I/O that has a generic WinSock connection.

CH

 

Have you investigated the offerings from National Instruments (www.ni.com) or Measurement Computing (www.mccdaq.com)? At first glance, NI's stuff is geared towards LabView, but there may be some DLLs available that you can call from your application.

The first hit on MC's site is this:
http://www.mccdaq.com/ethernet-data-acquisition/E-PDISO16.aspx

It shows a universal library "...for Windows® Visual Studio® programming languages, and others."

 

As it happens, Modbus/TCP is trivial to implement. I did it in an afternoon. Later, I hired a recent college grad. To introduce him to what we do and get a feel for his abilities, I had him get some Wago I/O working on Modbus/TCP. From a standing start, at his first real job, he had it working in 3 days. Modbus/TCP is easy. There are even free versions of the Modbus/TCP library, but seriously, you don't need them.

Nevertheless, I will give you another option. Elexol makes a board that has very simple control over generic TCP/IP.
http://www.elexol.com/IO_Modules/Ether_IO24_PIC_R.php

Hope that helps.

-James Ingraham
Sage Automation, Inc.

 

I think you are correct not to want to buy a third party active X tool or OPC server magic. They tend to take over your application in weird ways and can be slow. I havent' coded it myself, but in the reading I've done it seems that Modbus TCP is a simple application level protocol on top of a standard TCP/IP connection. I am pretty sure there is .NET source code out there in the public domain (Do a search on this site or google). If you want to write it yourself the spec is online but you probably only have to implement a few commands in that spec if you are tying into instrumentation (word reads, word writes, and read/write words ... ). You may also need to read some bits on the device for status depending on how they implement the instrument.

The problem with finding vendors that talk over a raw TCP connection (or telnet) is that they will have their own proprietary protocol (usually simple ASCII human readable), but each device brand will be different. This could be a maintenance nightmare long term. Worst case on the Modbus is that you have to remap word/bit addresses and rewrite a portion of your application to handle slightly different behavior of the device if you change to another vendor.

KEJR

 

Our ET-7000 series does use Modbus TCP protocol but has a built in web HMI for viewing I/O status and configuration

http://www.icpdas-usa.com/et7000table.php

See link or email if you have any questions.