Serial to Ethernet Device Servers - Page 1
Forum section: electronics / projects

author: Throy
author_rank: Regular Contributor
timestamp: July 24, 2015, 09:49:23 am
content: I'm working on a project right now where I have to communicate with UPS via RS-485 using Modbus protocol. The issue is the customer is not willing to ship the UPS here for easy debugging of the software due to its size and issues with sending batteries between countries, and it's not feasible for me to do the debugging on site.My thought to solve this problem was to buy two serial to Ethernet device servers. Set one up here in the office, and the other the customer would have to set up there. The two that I've found so far are:https://www.perle.com/products/iolan-ds-terminal-server.shtmlhttp://www.lantronix.com/device-networking/external-device-servers/uds1100-iap.htmlWhat my question is, has anyone had any experience using these devices and how feasible is it to set something up where the Modbus information between two devices would be transmitted over the Internet?I am not going to be controlling the UPS in anyway, just polling information from it, so there shouldn't be any danger that I accidentally cause some type of device failure remotely. Only problem is they are going to have to have some poor soul that sits next to the UPS to flip switches for me to induce alarms, etc.

author: kaz911
author_rank: Super Contributor
timestamp: July 24, 2015, 10:14:16 am
content: http://www.digi.com/products/serialservers/digioneia

author: Scrts
author_rank: Frequent Contributor
timestamp: July 24, 2015, 10:36:00 am
content: The UPS is probably connected to the PC? Then ask the customer to set up remote desktop. I've always been doing remote desktop stuff and it worked fine.

author: Throy
author_rank: Regular Contributor
timestamp: July 24, 2015, 12:41:21 pm
content: Quote from: Scrts on July 24, 2015, 10:36:00 amMy device is a Modbus master unit that polls the slave devices on the network and displays the data on a TFT-Display and also does data logging. I need my device to be able to send and receive information from the UPS over the internet as if it was directly connected to the UPS. Similar to this diagram:Was just wondering if anyone has done anything like this before and how easy it is to get working.

author: helius
author_rank: Super Contributor
timestamp: July 24, 2015, 01:17:08 pm
content: There were hundreds of models of box to do this, made over the course of decades. They were called terminal servers.Livingston Portmaster, Xylogics Annex, Xyplex, and Cisco each made several models.One thing to consider is that they were mainly designed for interactive use; you would connect to the terminal server and tell it to open a connection to another port. They were only transparent after a connection was established, and normally break signals would not be passed through, but revert control back to the command line. The diagnostic messages they send could be a problem for non-terminal equipment.

author: LabSpokane
author_rank: Super Contributor
timestamp: July 24, 2015, 03:45:02 pm
content: Quote from: Throy on July 24, 2015, 09:49:23 amI've used the Lantronix devices on private networks and they are a good solution. I don't think the device server is going to be the issue as much as the latency the -485 side is going to expect. I expect you'll have to make a persistent TCP connection and then lengthen any timeouts on the 485/Modbus side in order to accommodate the latency between the nodes.I do think that not having the same UPS in front of you you're trying to make the connection to is going to be a major hassle. At least initially, you'll need to be in front of it to configure the device servers to behave reliably.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 24, 2015, 04:25:53 pm
content: Anybus also has devices like that:http://www.anybus.com/

author: pelud
author_rank: Regular Contributor
timestamp: July 24, 2015, 05:39:52 pm
content: I've also used the Lantronix devices for connecting to legacy RS232 devices from a PC application. In fact, I have a UDS2100 in front of me. If your customer has a USB->RS485 converter (or similar), you may be able to just runpiracomon a PC at the remote site and configure the UDS to connect to it.Please be aware that it has no encryption so you may want to go over some sort of VPN link to prevent people from snooping the connection.Also, even though the Lantronix devices say that support RS485, you still may need a media converter as they typically have only RS232 ports on them.You should check the user manual to be sure.Edit: I just double checked the user manual, and it appears that you can put the UDS2100 serial port into RS485 two wire or RS422 four wire mode.

author: ruffy91
author_rank: Regular Contributor
timestamp: July 24, 2015, 05:45:14 pm
content: Also have a look at Moxa. They also do RS485/modbus to ethernet. Altough I only ever used the RS232 variants. But they can do what you want.

author: AG6QR
author_rank: Frequent Contributor
timestamp: July 24, 2015, 06:26:19 pm
content: Yet another supplier of this sort of device is GridConnect:http://gridconnect.com/usb-to-serial/serial-to-ethernet.htmlI've been using a GridConnect Net232+ for a home automation system for about nine years now. The box is in my unheated/uncooled garage, and has worked perfectly over extended temperature ranges with no maintenance or glitches whatsoever. Sounds like you might want the RS485 version. You can get a pair of them and configure them to talk to each other, to effectively give you a virtual serial cable as long as the Internet. Or you can do as I did, and only use one of the devices connected to the hardware that has a serial port, and have your software open a TCP port instead of an RS232 port, and let the software send and receive bytes over TCP.I don't have experience with competing products, so can't offer a comparison, but GridConnect stuff has worked well for me.

author: tomlut
author_rank: Regular Contributor
timestamp: July 25, 2015, 09:32:20 am
content: We've had nothing but trouble with the Perle IOLAN single port devices. Constantly having to power cycle them after they lock up. Also some basic fault finding revealed one device was shipped without one of the RS232 driver voltage doubling caps fitted to the PCB.Global Cache serial to Ethernet bridges have been performing flawlessly.

author: Throy
author_rank: Regular Contributor
timestamp: July 25, 2015, 09:54:26 am
content: Quote from: tomlut on July 25, 2015, 09:32:20 amThanks for the tip. I'll be sure to steer clear of them then.

author: nctnico
author_rank: Super Contributor
timestamp: July 25, 2015, 04:00:40 pm
content: Quote from: Throy on July 24, 2015, 09:49:23 amIsn't there a smaller version of the UPS with the same protocol? If anything else fails I'd start with creating a UPS simulator to test against. I have done many protocol implementations this way: write a simulator first and then test against the real hardware.