I you are really really dead set on building your own there are lots of
chips available with varying levels of external parts needed.
An economical and versatile solution is to use one of the digi TS-One or
portserver TS terminal servers. They are a little pricey new, but, last time
I needed some there were several on the 'Bay. I bought 5 for $75 last time.
That was an incredible steal.
A few positives for using them:
1. several of the models have jumper selection of rs232/rs422 so you don't
need an extrernal level converter.
2. They have excellent and currently maintained support software for past
and current OS's which among other things provides a 'virtual com
port' driver which makes the ports on the remote terminal server appear as
normal serial ports to the OS.
3. 2nd generation models provide the capability to use SSH and SSL to
encrypt control and data streams for security.
4. You don't need to do any development work to start using them. you can
start working on the more interesting aspects of your project instead of
reinventing the wheel for several hours while you figure out the arcana of
serial transmission. (been there, done that)
digi also makes board level product for integration in customer products,
but, I have not seen any for sale on the used market.
Netburner makes pretty economical board level stuff too. don't know if
they have any rs422/485 functionality.
I generally avoid using wifi for anything where failure/unreliability would
cost me time/money.
having said that there are also several wifi and bluetooth modules that
might serve your needs.
the bluetooth serial modules I bought from seeed studios were cheap and seem
to work well. they also have the advantage of maintained OS support of
'virtual com ports' so apps don't need any special knowledge of the serial
hardware.
Also, you shouldn't really need a fast ethernet port on the terminal
server. A fast ethernet switch when connected to a stone-age 'regular'
10Mbps port should (after failing auto-negotiation) fall back to 10Mbps half
duplex which is likely sufficient for a single or even several serial
streams.
Hope this is helpful to someone.
Dale NV8U
-----Original Message-----
From: Jim Lux
Sent: Monday, November 24, 2014 8:42 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] rs-422 rs-232 to fast ethernet converter
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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