Ethernet -Serial Converter


Thread Starter


Looking for feedback from anyone who has used either Intelligent Instrumentation brand or DIGI Connectware brand Ethernet-to-RS232 Interfaces for connecting remote devices to Ethernet TCP/IP networks. It looks too easy to be true.
We already work with some device that only have a RS232 Comunication port, we put a Lantronix converter from RS232 to TCP/IP,also there are some others that you can use, depend how you configure your converter you can obtain a
point-multipoint comunication...

Michael R. Batchelor

We've got about a dozen Intelligent Instrumentation EDAS devices scattered around several plants. They work great if you understand how to use them and don't expect them to work magic. All of our control software which actually interfaces directly with the EDAS units is custom written in VB. We've never actually tried to use the "virtual" serial ports because very little industrial control stuff understands ports beyond com4. Frankly, I think of the "virtual" ports as more of a tinker toy than anything else, but YMMV.

So, the summary view is that it really isn't that easy unless you've got a real simple problem. But once you get them going they do work pretty well.

I can't speak to the DIGIboard product.
Michael R. Batchelor - Industrial Informatics & Instrumentation, Inc. Linux is like a wigwam... No windows, no gates. Apache inside.

Bill Hullsiek

I have had good experiences with the lantronix units.
configure them, install the re-director and they work.

however, your actual "mileage" is dependent on the application. Some applications only talk with a "real hardware device" i.e., they don't adhere to the windows api. (Please don't flame me for using windows).

- bill hullsiek
I haven't used those brands, but have found others (e.g., Moxa NPort from B&B Electronics) pretty easy to use. I'd like to find one that used ssh or other effective encryption, however, since by default any access codes and data is in plain text and susceptible to sniffing. A simple Linux PC could be used for this, but I'd like it to be small in size, no moving parts, low power, etc., similar to the ethernet-to-serial devices.

Ken Irving <[email protected]>
One thing I should point out about these devices:
If power is cycled to the converter without cycling power to the PC running the driver which connects to the device, communications is lost (until power is cycled at the PC). At least with the Digi product, closing and reopening the port does NOT help... If you need more than 1-2 ports, check out Comtrol, their products are a bit more industrial and didn't seem to exhibit this problem AFAIK.
Hi Anonymous,

I see a lot of products like these on the market that are designed to bring control systems devices that use only serial communication onto ethernet.

I would stick to those that explicitly state that the serial protocol you are using has been tested with this protocol.

In general, there are some serial protocols that have tight timing restrains and some that do not.

Those that do not have a timing contraint, like Modbus ASCII, will work on just about any terminal server type device.

Of those that do have a timing contraint, some are
byte oriented and some are bit oriented. The byte
oriented ones like Modbus RTU may work ( the manufactured will probably mention this in spec ), but will require software at the host end to make sure the Modbus messages are not fragmented into multple ethernet messages.
If you have a bit oriented protocol, the UART in the terminal server will go bonkers. I have not seen any products to deal with this case. Maybe a Black Box gizmo will work, but get your oscilloscope ready.

Sorry, link was broken to product you mentioned: "":

But it smells like a dumb terminal server, with the above contraints.

Take a look at the products at "": .

Jay Kirsch
We use Ethernet to RS-232 converters to access remote numerical power transmission relays. The key is to have a good software driver for the host
PC. The driver must "trick" the operating systems and applications making to belive that there exist one or more serial ports. When the application of the remote device try to access it the software driver must redirect the bits
stream through the "virtual port", then to ethernet LAN/WAN and then to the Ethernet to RS-232 converter. The propietary of the remote device software must not "feel" the difference between the virtual serial port and physical serial port.

We have did experimens within LAN and got good results. The next step is use that devices in very geografical remote numerial relays within our WAN.

Luis Rios
[email protected]

Patrick Townsend

We've been using the Intelligent Instrumentation EDAS units for several years in our commerical products. We evaluated a number of other products (Lantronics, 3Com, Systech, etc.) but found the EDAS units to be superior in terms of reliability and recovery. They auto-recover from power and network failures, and survive in harsh environments. Great product! (We are not a reseller).

Hi Ken

Yeah, the Linux PC begins to make sense when you need about 8 or 10 ports. I've done it before, but the terminal servers and converters have come down to almost reasonable pricing. What I don't understand is why print servers are somewhat cheaper when they probably are more complex. Of course if you've got the room and an old pc lying around it'll do the job. I did a lot of terminal servers when IBM and HP asynch hardware was around $500.00 a port. Lotsa tiny packets.


Yes, I know the MOXA have much product for conver Ethernet to Serial.
But We need another product like MOXA. Could you please if you have information please e-m to me.