[time-nuts] rs-422 rs-232 to fast ethernet converter

Wojciech Owczarek wojciech at owczarek.co.uk
Tue Nov 25 03:32:40 EST 2014

Ser2net is the way to go for me. 

A hardware solution I have been using for this purpose for quite a while are those tiny USB-powered SoC-based "3G / 4G portable routers" from vendors like TP-Link (good little case designs - TL-MR3020 for instance which I currently use). The "3G" models don't actually have cellular modems, they just have a single USB port - and a Fast Ethernet port, and 802.11. They (can) run Linux.

The newer ones have 4M onboard flash and you can flash them instantly with OpenWRT. You can drop the web UI to trim down flash usage if you want, but out of the box they will fit USB-serial drivers and ser2net. Just add a USB to serial cable (or even go wild and buy a quad one with an USB hub built in) and you are still below the price of a Raspberry Pi, nevermind a dedicated serial to Ethernet box. You can also add a mini USB hub, stick a mini USB key in and use it as storage overlay. OpenWRT has all the tools you need available in the package repositories.

I paired mine with a 12Ah portable USB power bank, clipped on using 3M Command(tm) hook-and-loop straps. It ran on it for 48 hours straight. This setup has proven an invaluable tool in data centre work for emergencies and upgrades. I can hang it in a rack or keep it in my pocket, connect to kit using serial or Ethernet, and work from my smartphone over wifi. File transfers, firmware upgrades, whatever you want. Not sure if ser2net supports X/Zmodem somehow (it's probably down to the telnet client here) but for the times you need it, there's minicom. Naturally, USB-RSxxxx converters are not always the way to go, but the RPi needs one as well, it can only do TTL natively.

With some DYI you can put the router board, USB hub and battery in a neat little box as well and add an antenna, for improved usability.


Wojciech Owczarek

-----Original Message-----
From: Paul Alfille <paul.alfille at gmail.com>
Sender: "time-nuts" <time-nuts-bounces at febo.com>Date: Mon, 24 Nov 2014 22:38:04 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
 <time-nuts at febo.com>
Subject: Re: [time-nuts] rs-422 rs-232 to fast ethernet converter

There is a protocol for ending serial commands over telnet (tcp): RFC2217

See http://tools.ietf.org/html/rfc2217

A number of command line tools, like ser2net and netcat use the protocol.
Some of the small serial servers support it and it can make using serial
remotely tunneled over tcp seamless.

On Mon, Nov 24, 2014 at 6:23 PM, Graham <planophore at aei.ca> wrote:

> I have done a bit of searching and found that what I want to do is nothing
> really new and their are several off the shelf applications which will work
> just fine - linux and Windows based hence the mention of the Raspberry PI
> and Beaglebone Black. Some of the higher end Arduinos (i.e. Yu) are capable
> of running linux and Windows as well but it would be entirely possible to
> roll you own using the lower end Arduinos as well.
> I found some answers rather quickly after I started searching for the
> right things, for example Serial to Network Proxy.
> On Windows you could use a virtual serial port to do the redirecting from
> com port to network and on linux there are several the one I found often
> mentioned is socat.
> The little serial to fast ethernet boxes which I was finding would work in
> the situations where you don't have a computer near the device you are
> trying to connect to, they act as the Serial to Network Proxy. In my case,
> I have a computer nearby which runs linux and is my GPS disciplined NTP
> server. I have purchased a RS422 to USB interface cable which will connect
> the KS-24631 to my linux box. Now I just have to sort through all of the
> information I have found and figure out just which app I need on the linux
> box (likely socat) and which one on any of the other computers on my
> network with which I may want to connect to the KS-24631. And of course,
> how to configure them.
> cheers, Graham ve3gtc
> On 2014-11-24 08:42, Jim Lux wrote:
>> On 11/24/14, 2:20 AM, Graham wrote:
>>> Interesting.
>>> I have also been thinking that it might not be too difficult to
>>> implement using Beaglebone Black, Raspberry PI, or even one or another
>>> flavour of Arduino. Lots of possibilities from simple to not so simple.
>> The challenge is always trying to figure out what sort of protocol to use
>> for encapsulating serial data in the Ethernet Stream.  Do you send each
>> character in its own UDP or TCP datagram? Do you batch them together and
>> send a message every TBD milliseconds.
>> Ideally, you'd like the protocol to match some commonly available client
>> on the other end.  Sure, things like telnet exist, but does software that
>> expects an actual serial port know how to use telnet instead?
>> That said, there's plenty of example code out there for, example, the
>> Arduino Ethernet.  There's a telnet server that could easily be modified.
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