[Elecraft] KPA500 serial interfaces

Sat Feb 16 19:29:54 EST 2019

I always worry about what I don't know with this kind of discussion that
seems to dive into entrenched positions of pedantic certainty. Since I love
my KX3 and other Elecraft products, as well as various microcontrollers, I
was concerned that I'd missed something about RS232 which I've used for
decades. So I did a little research. And let me tell you there is so much
information out there that a pedant can basically shut down any discussion
as being inaccurate! Don't dare talk about DB9 connectors on equipment
because you probably mean DE-9P!

Reading the RS232 standard(s), it is clear that any multi-point
implementations are not technically RS232 compliant and require
non-standard wiring and/or software and hardware support that is not in the
specification. Directly connecting standard's compliant equipment will be
hit and miss and could damage some devices - strict compliance to RS232 is
short-circuit protected between pin pairs, but many devices are "sort-of"
compliant. But if you control all sides, then proprietary implementations
could be easily done. Again, that would not technically comply with the
standard. On the other hand, RS232 and RS423 support a multi-drop (multiple
listeners, one sender) format in some cases, which only allows 1 bus driver
and up to 10 receivers.

BUT. There have been many variations over the years, along with
similar-seeming RS485 which is multi-drop. RS485 is wired in a similar way
but is a current loop interface instead of voltage based.  I also found
RS422 which is a long distance "drop-in-replacement" for RS232 and that has
a multi-drop version, but there seem to be so many different flavors of
wiring, it may as well be proprietary at that point.

I've found and reviewed a few dozen of the many, many specifications for
serial communications that are similar to RS232 and can find none that fit
the impression some of the earlier posts gave of having multiple devices
communicating back-and-forth on the same physical RS232 connection. The
talk of sharing connections with boxes that multiplex over an RS232
connection led me to find the products that speak SDLC to a device that
then communicates with a set of RS232 devices. I hardly think that is the
same thing, since although a single RS232 is required on the computer, it
is not speaking directly to the devices on the other end.

I looked up the Bisync protocol as well as the Uniscope equipment. It looks
like although they did use what is called RS232 connectors and wiring, they
did not follow the specification, so standards complient RS232 devices
wouldn't work in a multi-drop setting.

In summary, it seems that a degree of liberty in the use of the terms and
standards results in confusion and folks arguing across each other. There
is a large difference between what might be possible over wiring that
otherwise conforms to RS232 but is unrelated to the standard which is a
point-to-point standard for linking two devices. Then if you overlay
proprietary protocols as used by Uniscope, IBM, et.al along with the many
almost RS232 standards and we get the situation where some insist that
RS232 supports multi-point networking while others claim it doesn't. I
think the bottom line is that any fancy connections (beyond what Elecraft
specifies) between Elecraft devices will need additional software and/or
hardware to support.

Some of the references I used:

   - RS232 connectors and wiring
   <http://www.zytrax.com/tech/layer_1/cables/tech_rs232.htm>
   - IIT course on Serial Communications
   <https://nptel.ac.in/courses/Webcourse-contents/IIT%20Kharagpur/Embedded%20systems/Pdf/Lesson-25.pdf>
   - Blackbox RS232 connection sharing devices
   <https://az849230.vo.msecnd.net/resources/10920_20100.pdf>
   - IBM SDLC protocol concepts
   <http://www.textfiles.com/bitsavers/pdf/ibm/datacomm/GA27-3093-3_SDLC_Concepts_Jun86.pdf>
   - IBM SDLC communications adapter manual
   <http://minuszerodegrees.net/oa/OA%20-%20IBM%20SDLC%20Adapter.pdf>
   - List of some Network Bus standards
   <https://en.wikipedia.org/wiki/List_of_network_buses>
   - EIA RS232 V24 standard
   <https://www.electronics-notes.com/articles/connectivity/serial-data-communications/rs232-eia-v24-standard.php>

With a hurting brain,
73 - Brendon
KK6AYI

On Mon, Feb 11, 2019 at 2:51 PM Michael Blake via Elecraft <
elecraft at mailman.qth.net> wrote:

> Andy, in support of your comments I was an active Bell System DATEC
> representative back in the 70s and 80s and multipoint polled RS-232 was
> very common here in the colonies :)
>
> Michael Blake
> k9jri at mac.com <mailto:k9jri at icloud.com>
>
>
>
>
>
>
> > On Feb 11, 2019, at 4:54 PM, Andy McMullin <Andy at rickham.net> wrote:
> >
> > Not wishing to get into an argument but consider Binary-Synch, Uniscope
> or UTS400 protocols. They are poll and response, RS232c communications
> systems. Used from mainframe to (dumb) terminal. They are synchronous RS232
> of course rather than asynch and so use the clock and other signals ignored
> by the [IBM PC] cut down implementation of the RS232 connector. RS232 of
> course only defining the names and voltages on the connector.
> >
> > From memory a Uniscope (U100) “poll” from the mainframe would be the
> characters: sync, sync, sync, sync, SOH, RID, SID, DID, STX, text, ETX,
> BCC.
> >
> > Now that was dug out of the 1970’s if nothing was!
> >
> > Andy, G8TQH
> >
> >> On 11 Feb 2019, at 21:35, Don Wilhelm <donwilh at embarqmail.com <mailto:
> donwilh at embarqmail.com>> wrote:
> >>
> >> Andy,
> >>
> >> "Polling" normally refers to a situation like Ethernet and others where
> a response from a particular *addressed* device is requested.
> >> For RS-232, it is "handshaking" (if implemented) telling the DTE when
> it is OK to send data - since there is only one transmitter on an RS-232
> signalling line, there is no need for addressing. The transmitting device
> expects to communicate to only one receiving device on the other end
> (although other receivers can 'listen in'.
> >>
> >> I have worked with RS-232 for over 35 years both professionally (both
> modems and DCEs for 20 years) and with ham radio gear and PCs after
> retirement from that life.
> >>
> >> If we wish for clear communication, the terms used are important. Ham
> Radio "speak" often confuses the proper engineering terms. You hear of ham
> radio software that "polls" the radio - in reality, it is simply issuing a
> command to the radio and expects a response to that command.  That is a
> command/response scenerio, and is not really polling.
> >>
> >> Don W3FPR
> >>
> >> On 2/11/2019 3:55 PM, Andy Durbin wrote:
> >>> "I have no idea how your "polling" device works, but with RS-232,
> thereis no polling, "
> >>>
> >>> Point 1 is true. Point 2 is, in my opinion, not true.
> >>>
> >>> A poll is a request for information. The device issuing the
> poll/request is the polling device.   For example, sending IF; to a TS-590
> is a data request, or poll, for the current IF status.  The TS-590 responds
> with the full IF word.
> >>>
> >>> Andy, k3wyc
> >>>
> >>>
> >>
> >> ______________________________________________________________
> >> Elecraft mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:Elecraft at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >> Message delivered to andy at rickham.net <mailto:andy at rickham.net>
> >
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft <
> http://mailman.qth.net/mailman/listinfo/elecraft>
> > Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm
> >
> > Post: mailto:Elecraft at mailman.qth.net <mailto:Elecraft at mailman.qth.net>
> >
> > This list hosted by: http://www.qsl.net <http://www.qsl.net/>
> > Please help support this email list: http://www.qsl.net/donate.html <
> http://www.qsl.net/donate.html>
> > Message delivered to k9jri at mac.com <mailto:k9jri at mac.com>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to brendon at whateley.com