Is anyone using a Hardware Data Switch instead of LP Bridge?

[Elecraft mailing list]

While LP Bridge does serve the purpose I was wondering if anyone was usinga pure hardware solution to share the K3's serial port across applications.
If so how are you doing it?
Thank you

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[Don Wilhelm-4]

Harry,

RS-232 is a point to point protocol, so no hardware sharing - some
hardware devices get away with connecting into the data stream by *only*
listening to the traffic - SteppIR controllers are one example.  
Multiple transmitters on the same connection will corrupt the data.

However, if you run only one application at a time, you *could* use an
A/B/C/D switch with 4 serial ports on your computer after telling each
application to use a different com port.
BUT --
The easier solution is to simply close any conflicting application and
open a new one, each using the same com port.  The only problem with
that is that there are some ham applications that do not clean up their
'dirty footprints' and will leave the com port open when the application
has closed, and that condition can only be solved by re-booting the
computer.

A software virtual com port sharing solution like LP-Bridge is the best
solution if you want to run multiple applications at once.

73,
Don W3FPR

On 1/5/2015 5:26 PM, Harry Yingst via Elecraft wrote:
> While LP Bridge does serve the purpose I was wondering if anyone was usinga pure hardware solution to share the K3's serial port across applications.
> If so how are you doing it?
>

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[Jim Rhodes-3]

I have somewhere an old "Omniport" device that had multiple ports that
could be set to switch all sorts of ways. But if memory serves it was a 1
to 1 setup. Would have to look for the docs on it.
On Jan 5, 2015 8:18 PM, "Don Wilhelm" <[hidden email]> wrote:

> Harry,
>
> RS-232 is a point to point protocol, so no hardware sharing - some
> hardware devices get away with connecting into the data stream by *only*
> listening to the traffic - SteppIR controllers are one example.  Multiple
> transmitters on the same connection will corrupt the data.
>
> However, if you run only one application at a time, you *could* use an
> A/B/C/D switch with 4 serial ports on your computer after telling each
> application to use a different com port.
> BUT --
> The easier solution is to simply close any conflicting application and
> open a new one, each using the same com port.  The only problem with that
> is that there are some ham applications that do not clean up their 'dirty
> footprints' and will leave the com port open when the application has
> closed, and that condition can only be solved by re-booting the computer.
>
> A software virtual com port sharing solution like LP-Bridge is the best
> solution if you want to run multiple applications at once.
>
> 73,
> Don W3FPR
>
> On 1/5/2015 5:26 PM, Harry Yingst via Elecraft wrote:
>
>> While LP Bridge does serve the purpose I was wondering if anyone was
>> usinga pure hardware solution to share the K3's serial port across
>> applications.
>> If so how are you doing it?
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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>

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[Elecraft mailing list]

Actually I was looking at this Pricey but it is a possibility


Serial Data Switches | RS232 Switch Box - B&B Electronics

|   |
|   |  |   |   |   |   |   |
| Serial Data Switches | RS232 Switch Box - B&B Electronic...Our user-friendly serial data switches are versatile, intelligent, and allow for seamless communication between your PC and multiple RS-232 devices. |
|  |
| View on www.bb-elec.com | Preview by Yahoo |
|  |
|   |

  
      From: Don Wilhelm <[hidden email]>
 To: Harry Yingst <[hidden email]>; Elecraft Reflector <[hidden email]>
 Sent: Monday, January 5, 2015 9:17 PM
 Subject: Re: [Elecraft] Is anyone using a Hardware Data Switch instead of LP Bridge?
   
Harry,

RS-232 is a point to point protocol, so no hardware sharing - some
hardware devices get away with connecting into the data stream by *only*
listening to the traffic - SteppIR controllers are one example. 
Multiple transmitters on the same connection will corrupt the data.

However, if you run only one application at a time, you *could* use an
A/B/C/D switch with 4 serial ports on your computer after telling each
application to use a different com port.
BUT --
The easier solution is to simply close any conflicting application and
open a new one, each using the same com port.  The only problem with
that is that there are some ham applications that do not clean up their
'dirty footprints' and will leave the com port open when the application
has closed, and that condition can only be solved by re-booting the
computer.

A software virtual com port sharing solution like LP-Bridge is the best
solution if you want to run multiple applications at once.

73,
Don W3FPR



On 1/5/2015 5:26 PM, Harry Yingst via Elecraft wrote:
> While LP Bridge does serve the purpose I was wondering if anyone was usinga pure hardware solution to share the K3's serial port across applications.
> If so how are you doing it?
>



 
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[George Danner]

Harry,
Years ago we used 8 devices controlled from one PC com port on one RS-232
data link.
All of the devices bridged the receive line and were wire or'd for transmit.
The devices were polled by the PC and only allowed to transmit when polled.
This worked well with no conflicts for many years.
So it is possible to use one RS232 port for multiple devices -but- the
devices must be made to play nice in all circumstances and have special
hardware interfaces.
My best memory is we spent about 20 man hours developing the hardware
solution and another 100 hours writing & debugging software. BTW this was in
DOS days!

73 George AI4VZ
--------------------------------------------------------------------------
-----Original Message-----
From: Harry Yingst via Elecraft
While LP Bridge does serve the purpose I was wondering if anyone was usinga
pure hardware solution to share the K3's serial port across applications.
If so how are you doing it?

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[Don Wilhelm-4]

George,

Since RS-232 is a point-to-point protocol, multiple TX drivers cannot
exist together.
Yes, tri-state RS-232 drivers can be constructed (and were likely used
in your particular arrangement), but only one driver can be allowed to
be active at one time.  The fact that you say the drivers (transmitters)
were "wire or'd" means that the inactive drivers would have to present a
high impedance.  That is not the normal case for RS-232 drivers.  The
fact that you state it took 20 man-hours to develop the hardware
indicates that these are not normal RS-232 drivers.

I repeat - RS-232 is a point to point protocol, and the hardware
reflects that situation.  One cannot have two active drivers on the same
line at a time.  The voltages for RS-232 are up to -25 volts for the
'mark' level, and up to +25 volts for the 'space' level (the idle
condition or logic zero).  Now think about connecting two active RS-232
drivers together, one trying to send a logic '1' (-25 volts), while the
other is idling (at +25 volts).  The combination of the two drivers
equals zero volts at the receiving end, and zero volts is in the RS-232
undefined area, so the voltage level should be undefined and ignored.

Further complicating the situation is that some PC serial ports and many
"almost RS-232" devices have strayed from the normal spec, and will
respond to zero volts as a logic '1' and any positive voltage as a logic
'0'.  Normal RS-232 levels would ignore anything between -3 volts and +3
volts as 'noise'.  But recent psuedo RS-232 receivers will respond to
that zero volt level as a logic 1 (mark) and receive it as such.

The above situation works for very short 'RS-232' lines as usually
encountered in PC and ham equipment situations. but will not work well
with compliant RS-232 receivers that will ignore levels between -3 and
+3 volts.

In summary, multiple RS-232 drivers on a single line will conflict with
one another unless special enabling circuits are built into the driver
and a means of controlling which driver has control of the line are
present - not a trivial task.  In other words, do not "wire OR" multiple
RS-232 drivers together unless those drivers are specifically designed
to allow only one at a time to be active. That means a total system
control must exist, and that can only happen in specific controlled
situations.

That is why George's example took 20 hours of hardware design, but
required 100 hours of writing and debugging software.  This was a
specific system design and cannot be expanded to "wire or'd" RS-232
drivers in general - that will not work.

73,
Don W3FPR

On 1/5/2015 10:43 PM, George Danner wrote:

> Harry,
> Years ago we used 8 devices controlled from one PC com port on one RS-232
> data link.
> All of the devices bridged the receive line and were wire or'd for transmit.
> The devices were polled by the PC and only allowed to transmit when polled.
> This worked well with no conflicts for many years.
> So it is possible to use one RS232 port for multiple devices -but- the
> devices must be made to play nice in all circumstances and have special
> hardware interfaces.
> My best memory is we spent about 20 man hours developing the hardware
> solution and another 100 hours writing & debugging software. BTW this was in
> DOS days!
>
>

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[Lynn W. Taylor, WB6UUT]

Don,

In the relatively early days of Packet Radio there were more than a few
multi-port NET-ROM nodes that were assembled by tying three (or more)
TNC-2s together with a relatively simple diode combiner.

I may even still have the diagram for combiner.  It wasn't powered,
didn't have anything more complex than diodes.

The TNC-2 used normal 1488/1489 chips for receivers and drivers, and
took slight advantage of the fact that the receiver didn't strictly
"need" RS-232 levels (that 0v was as good as -3v).

Serial errors did occur when two or more ports tried to talk at once,
but NET-ROM ran AX-25 on the serial port and the errors got handled that
way.

73 -- Lynn

On 1/5/2015 8:59 PM, Don Wilhelm wrote:
> Since RS-232 is a point-to-point protocol, multiple TX drivers cannot
> exist together.

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[Lynn W. Taylor, WB6UUT]

P.S. the big secret is that you can't run pure ASCII with no other
protocol and pull this off.  All of the devices have to know when to
talk, and when to shut up.

On 1/5/2015 9:34 PM, Lynn W. Taylor, WB6UUT wrote:

> Don,
>
> In the relatively early days of Packet Radio there were more than a
> few multi-port NET-ROM nodes that were assembled by tying three (or
> more) TNC-2s together with a relatively simple diode combiner.
>
> I may even still have the diagram for combiner.  It wasn't powered,
> didn't have anything more complex than diodes.
>
> The TNC-2 used normal 1488/1489 chips for receivers and drivers, and
> took slight advantage of the fact that the receiver didn't strictly
> "need" RS-232 levels (that 0v was as good as -3v).
>
> Serial errors did occur when two or more ports tried to talk at once,
> but NET-ROM ran AX-25 on the serial port and the errors got handled
> that way.
>
> 73 -- Lynn
>
> On 1/5/2015 8:59 PM, Don Wilhelm wrote:
>> Since RS-232 is a point-to-point protocol, multiple TX drivers cannot
>> exist together.
>

\
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[Joel Black-2]

I’m not sure why I didn’t think of this before. How about the MS-3 from BlackBox? It has one DTE port and three DCE ports on it (or is it the other way around?). BlackBox also makes a larger box with eight ports but I’m not sure if it’s an “MS-8” or they call it something different.

We use these at work for SCADA.

They also make a smaller version of the MS-3 where they use RJ-48s instead of DB-25s.

Before you ask, they do work for two-way communications, but on the MS-3, you’ve got to make sure what kind of device you’re hooking up. It only works one way but it does allow bi-directional communications.

73,
Joel - W4JBB

> On Jan 5, 2015, at 9:43 PM, George Danner <[hidden email]> wrote:
>
> Harry,
> Years ago we used 8 devices controlled from one PC com port on one RS-232
> data link.
> All of the devices bridged the receive line and were wire or'd for transmit.
> The devices were polled by the PC and only allowed to transmit when polled.
> This worked well with no conflicts for many years.
> So it is possible to use one RS232 port for multiple devices -but- the
> devices must be made to play nice in all circumstances and have special
> hardware interfaces.
> My best memory is we spent about 20 man hours developing the hardware
> solution and another 100 hours writing & debugging software. BTW this was in
> DOS days!
>
> 73 George AI4VZ
> --------------------------------------------------------------------------
> -----Original Message-----
> From: Harry Yingst via Elecraft
> While LP Bridge does serve the purpose I was wondering if anyone was usinga
> pure hardware solution to share the K3's serial port across applications.
> If so how are you doing it?
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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[Don Wilhelm-4]

And that is why it will not work with multiple computer applications -
they run independently and 'talk' whenever they want to.
LP-Bridge solves that problem by buffering the individual requests. Plus
it also buffers some K3 information so it can respond to some of the
application requests without directly communicating with the K3.

73,
Don W3FPR

On 1/6/2015 12:42 AM, Lynn W. Taylor, WB6UUT wrote:
> P.S. the big secret is that you can't run pure ASCII with no other
> protocol and pull this off.  All of the devices have to know when to
> talk, and when to shut up.
>

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[Wes (N7WS)]

LP-Bridge is great.  I connect the K3 to my general logging program (DXBase),
RTTY program (AXETTY, a DXBase specific version of MMTTY), N1MM and SpectraVue
(SDR-IQ panadapter).  They all talk to each other without conflict.  I have it
set up to create the virtual ports and start the connected programs automatically.

Wes  N7WS


On 1/6/2015 5:57 AM, Don Wilhelm wrote:

> And that is why it will not work with multiple computer applications - they
> run independently and 'talk' whenever they want to.
> LP-Bridge solves that problem by buffering the individual requests. Plus it
> also buffers some K3 information so it can respond to some of the application
> requests without directly communicating with the K3.
>
> 73,
> Don W3FPR
>
>

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