Back to back RS232 to Ethernet converters to extend RS232? - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: July 07, 2012, 02:39:02 pm
content: Has anyone been able to use the cheap $25 RS232 to Ethernet converters you find on Ebay in a back to back configuration to extend RS232 over ethernet?If it works then it's a big cost saving over purpose built RS232 entenders.All I need is Tx and Rx to do remote comms with an Arduino.Mike

author: Unknown
author_rank: Unknown
timestamp: July 07, 2012, 03:05:39 pm
content: I believe the cheap ebay converters can only act as a TCP server, they require the other side to establish a TCP connection. One of them would require firmware modification. If they support both client and server mode, then you may be able to get it working. Possible pitfalls are lack of static addressing, an idle timeout that drops the connection until the client side receives data over the serial port, and lack of proper reconnect making the power-up sequence critical.The professional Moxa NPort devices work fine in this configuration, but they are unlikely to be available for $25. They can be configured as client or server, and allow you to change timeouts and reconnect behavior.

author: gxti
author_rank: Frequent Contributor
timestamp: July 07, 2012, 05:03:28 pm
content: If you don't need to interface with any actual Ethernet equipment, you can run RS-422 over Cat-5 for 1000s of feet. There are lots of premade converters out there but they're also trivial to make. Just make sure the differential pairs line up with the twisted pairs in the Cat-5 cable. Also if you can get one with isolation, it'll save you a lot of potential headache later on.

author: PeterG
author_rank: Frequent Contributor
timestamp: July 08, 2012, 05:01:06 am
content: If you want to get a pair of Arduino boards talking over Ethernet, you could use the Arduino Ethernet boards and set up your communication over Ethernet between a pair of these boards. This would also offer greater speed than RS232 as well.Regards

author: digsys
author_rank: Unknown
timestamp: July 08, 2012, 06:30:32 am
content: As been suggested, IF you DON'T actually need Ethernet functionality then -RS232, up to 38K4 Baud will travel 100MetersUse a cheap RS422/485 chip and that extends to 1-2 KM, up to 76K8Use a cheap mutimode fiber, TTL levels, ST or SC connections and go several KMs at 115KB+,I've made 100s of all these and can post ccts if you need.You can also go "radio", like the garage door kits, ~2400B, or 900MHz = 76K8 to 20KM.Lots of options

author: Unknown
author_rank: Unknown
timestamp: July 08, 2012, 07:59:49 am
content: I'll concur with those above. Does the path include switches hubs routers etc? if the answer is now and your merely want to utilise Ethernet cables then consider using RS-485 or RS-422 connections would be the simplest option.Alm suggested the Moxa device servers which can be set up point to point and work brilliantly, but they are not in the Arduino price bracket. Lantronix have some device servers that will work but while much cheaper than the Moxa still don't get down to Arduino level prices. Take a look at some of the Xport modules theymay be able to be configured as point to point.

author: e100
author_rank: Frequent Contributor
timestamp: July 08, 2012, 08:23:34 am
content: The particular problem I'm trying to solve is doing a remote firmware upgrade of an Arduino connected via Ethernet/TCPIP carried over mains wiring instead of CAT5. The Arduino is about 50m (150ft) from the nearest CAT5 cable and 70m (210ft) from the nearest computer with a number of solid brick walls in between.The current Arduino bootloader only works with a serial connection so I need some of way piping serial data over TCPIP and turning it back into serial data at the Arduino end.From cheapest to most expensive my options appear to be:- Use two Xbee 60mW radios. I need the power because of the brick walls.- Buy a TCPIP to RS232 converter ($150) for use at the Arduino end and install a virtual com port driver on the PC.- Install 50m of CAT5 cable and conduit.- Buy a netbook computer and plug it into the ethernet next to the Arduino, connect a USB cable to the Arduino and remote desktop from the other PC. I know this sounds like madness, but these things can be purchased new for $300 and recycled for other uses once the software development is finished.

author: digsys
author_rank: Unknown
timestamp: July 08, 2012, 08:58:06 am
content: OK, that's a lot more complex scenario than your original question suggested. Needs rethinking.

author: PeterG
author_rank: Frequent Contributor
timestamp: July 08, 2012, 09:03:43 am
content: Thats a whole new can of worms......Sending anything over power is not easy. I am thinking something similar to the old x10 modules.Regards

author: e100
author_rank: Frequent Contributor
timestamp: July 08, 2012, 09:22:32 am
content: Quote from: PeterG on July 08, 2012, 09:03:43 amThe TCPIP over mains is the easy bit as I'm using NETCOMM NP204 mains adaptors for the house networking. I find them to be much more reliable and faster than WIFI. You plug them in, press a few buttons to pair them, then they just start working. They are convection cooled and run warm when active so they would be classed as domestic rather than professional quality units, but so far so good.

author: notsob
author_rank: Frequent Contributor
timestamp: July 08, 2012, 09:29:41 am
content: lots of ethernet over the AC circuit stuff - "powerline" solutionsNetgear make one, TP-Link etchttp://www.ebay.com/itm/PA201-Mini-200M-Powerline-Ethernet-Adapter-Pair-Button-/140596066011

author: jhalar
author_rank: Regular Contributor
timestamp: July 08, 2012, 09:48:24 am
content: Quote from: e100 on July 08, 2012, 08:23:34 amFor accessing serial ports over tcpip I use terminal servers. These devices (depending on the capabilities of a brand) allow tcpip access to remote serial ports. Many available on the market with 1-48 ports. I use them to connect to the serial consoles of remote network devices.

author: Unknown
author_rank: Unknown
timestamp: July 08, 2012, 10:07:15 am
content: Quote from: e100 on July 08, 2012, 08:23:34 amSo much easier to help with a bit more detail provided.QuoteQuoteHave a look at the hope transceivers, the prices are betterthan Xbee and they can be used direct the serial pins. Need a good connection though.QuoteDefinitely will work just make sure they will connect point to point.QuoteRS232 can be pushed a lit further than spec provided the baud rates are kept lowand the route is interference free. Cat5 parallel with your mains cable not such a good idea. For 50m like that you'd want a good screened data cable.QuoteNot silly at all. in fact if the data link isn't required after development, this is the cheapest of all the quoted options.

author: markus_b
author_rank: Regular Contributor
timestamp: July 08, 2012, 11:34:47 am
content: Quote from: e100 on July 08, 2012, 08:23:34 amDon't you or a buddy has some older laptop lying around you can use for this. I just fished a older laptop out of the thrash two days ago, it will probably work fine, like the one I fished three months ago. You may also find one on craigslist or Ebay. (Almost) free PCs can be found, these days.

author: Unknown
author_rank: Unknown
timestamp: July 08, 2012, 11:52:02 am
content: Quote from: Uncle Vernon on July 08, 2012, 10:07:15 amConverting to RS-422 might also be a feasible solution if a dedicated UTP cable is available.Quote from: e100 on July 08, 2012, 08:23:34 amYou could do the same with those $25 ethernet to RS-232 interfaces. Just connect them temporarily, plug in the ethernet cable and load the firmware from a computer connected to the network somewhere.