RS-232 or USB<->Industrial Protocols


Thread Starter

Willy Smith


My company is trying to make it easier for our distributors and end customers to run test and configuration programs for our valves with bus
interfaces. To this end, we are trying to find less expensive and standard PC interfaces for several different protocols. Right now, we use ISA type cards, which are becoming dinosaurs. I would like to switch to either RS232 or USB type devices, so that access can be afforded with either desktops or laptops. We don't need $1,000 cards! Throughput is not a problem, since it's not for use as a master scanner. Can anyone help me complete this list of interfaces?

Interbus-S: Phoenix contact has a new card called Eco-link, which allows access to an Interbus-S network via an RS-232 line. The only thing I don't
like about it is that it needs an external 5 volt supply. I haven't found any USB interfaces.

Remote I/O: I haven't found anything for this network except an expensive ISA card.

Profibus: Surprisingly, I can only find ISA, PC104, and PCI cards.

CAN: Found a Softing card and also one from These seem fine. If anyone knows any others, I'd still like to hear about them.

I'm surprised that this has been so difficult to find what I'm looking for. If anybody has any pointers, please send links!


Willy Smith
Costa Rica

Curt Wuollet

Hi Willy

Here's a few from the low budget hacker's perspective:

Parallel port with I2C or other "bit banging" protos.
Serial Modbus.
JPS (just plain serial, interaction with a terminal or emulator)
World's smallest www server for a buck.
X10 protocol, talk to the valve through the power connection.

I am surprised that no one has developed custom silicon for this need. All the bus chips I've seen need a host processor. CAN or I2C seem like the best bet.

Cesar Garcia


I think a solution for industrial device is the IRDA protocol, you can see a very good implementation in the low cost power metering from
SquareD ( You can used from a Laptop, Palm or Windows CE device for programming in field.


Maybe I didn't explain myself very well. Sure, we've made custom boards for people with parallel, serial, I2C, and all sorts of bizarre
stuff too. I wish I had a list of all the weird valve drivers we've made over the years! And this certainly points out the fact that things will be easier once Ethernet - TCP/IP gets going; I'll be able to tell any distributor to go to a Circle-K and pick up an Ethernet board for ten bucks, and it won't matter what O/S or anything else!

But what I need NOW are interfaces for our standard products, which include the below-mentioned protocols. The problem is that each
distributor can't afford to buy $10,000 worth of smart ISA or PCI cards just to configure/test/troubleshoot all these different
protocols! Neither can each customer in fact, but usually the typical customer only has to support one protocol for their particular projects or plants. Besides, they usually already have some kind of PLC or interface before they buy our valves, and a commercial software package to run/test/configure the I/O. This is also not an option for the distributors, as buying all that stuff and learning how to use it is quite a hill to climb.

So, I want to buy inexpensive SERIAL interfaces for these protocols, so that the people involved in production, test, configuration, troubleshooting, etc. can install an interface at their PC or laptop, run our test software, and talk to the valve. We can't possibly write the low-level drivers for all the different protocols and all the different cards available, so we have to find a common interface for each protocol. It seems like this would be a fairly common need, as
manufacturers and vendors of any distributed control I/O products have the same type of problem.

I'm content with what I've found for CAN and Interbus-S. But I'm open to other suggestions if someone knows of other products.

The worst one is RIO, as it really is a proprietary protocol and I don't see any options except A-B's (expensive) card. Unfortunately
(from this perspective anyway), it is very popular! So I can't just ignore it.

And doesn't somebody make a serial Profibus adaptor?

What I'd like to end up with is a kit I can put together with all four different interfaces for $1,000 or less; then the disties could each buy one and have 99% of the current mess covered. And we'd only have to write four more drivers.

Anybody have more sources? I've surfed 'til my wrist is sore on these items!

BTW, I am a "low-budget hacker" too, and I'd love to just design 'em and build 'em myself. But they're both non-trivial exercises, and I've
got enough to do! I'd rather be spending my time on Ethernet anyway. As far as I'm concerned, the frustration level I'm experiencing getting this one task done has put the last nail in the coffin on all these open and closed protocols. I'm ready for Ethernet to become THE standard.


Willy Smith
Costa Rica

Johan Bengtsson

A Profibus (DP only?) adapter can be found at Weidmuller We use it ourself to control educational equipment from our programs and it works well most of the time but it can only be run at 9600 and 19200 (but since speed wasn't your concern that should be enough)

I think there are more companies doing similar cables and are interesting in finding them too.

/Johan Bengtsson

P&L, the Academy of Automation
Box 252, S-281 23 H{ssleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
E-mail: [email protected]

Curt Wuollet

Hi Willy

I guess I did misunderstand, I thought you had options on the valve side. The picture looks pretty bleak though. Many of these require
substantial horsepower to operate. That's why the cards have their own processor. And even if that wasn't the case, just the fact that they are proprietary protos means you are gonna pay top dollar for hardware. Even if you design it yourself some of the custom silicon is single sourced and expen$ive. And some require expen$ive
conformance testing and membership in a good old boys club to play. I would buy the cards, stick em in a PC and code a dedicated application that hides all the detail from the user. That way, at least it's easy if not cheap.

Ethernet will be a very, very, good thing if we get it before they finish rendering it useless with 50 incompatible top level protos. The same gang that gave you the eight headed monster standard will do all they can to decommoditize it. Pity......