[Elecraft] KPA500 serial interfaces

Sat Feb 16 22:30:55 EST 2019

As is often the case on reflectors, things often drift of the main topic. RS232, 422. , and RS485 are among a number of electrical specifications that permits the transmission of serial data. While each has certain inherent limitations due to the electrical specification, it is really how the software involved implements the interface can be utilized. 

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> On Feb 16, 2019, at 7:29 PM, Brendon Whateley <brendon at whateley.com> wrote:
> 
> 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
>>>> 
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