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K2 interface with steppIR and computer

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John's email

K2 interface with steppIR and computer

I built my serial cable for the K2 to talk to my SteppIR controller from the Elecraft manual. Works just fine. It also talks to my computer for HRD, N1MM etc. So I decided to work on having the two interfaces work together like they did with my IC 746 Pro. However, building a Y cable doesn't seem to be working out the way I want! Each device works fine when I have it plugged into the Y cable by itself but when I plug in both at the same time, One or the other will freeze up. I am simply using pins 2, 3 and 5 from the K2 serial port wired straight through to the female DB 9s at the device end and have 7 and 8 jumpered at the external device end. What am I doing wrong?

My KPA500 arrives on Monday so I'd like to get this resolved before my next project!

John KE4D
K2 #7231

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Joe Subich, W4TV-4

Re: K2 interface with steppIR and computer

John,

I am sending you the schematic for SteppIR's Y cable. Pay attention as
pin 5 is not connected between the SteppIR and rig. The jumper on the
SteppIR end is between 7 and 9 (not 7 and 8).

You can not parallel pin 3 (Transmit Data) on two RS-232 devices.
the device that is not sending data will load the transmit line
so that no data can be sent. Doing a full parallel connection
requires a special diode matrix connection with external pull-up
(or pull down - can't remember without tracking down the old device)
resistors, etc.

73,

... Joe, W4TV

On 1/7/2012 10:08 AM, [hidden email] wrote:
> I built my serial cable for the K2 to talk to my SteppIR controller
from the Elecraft manual. Works just fine. It also talks to my computer
for HRD, N1MM etc. So I decided to work on having the two interfaces
work together like they did with my IC 746 Pro. However, building a Y
cable doesn't seem to be working out the way I want! Each device works
fine when I have it plugged into the Y cable by itself but when I plug
in both at the same time, One or the other will freeze up. I am simply
using pins 2, 3 and 5 from the K2 serial port wired straight through to
the female DB 9s at the device end and have 7 and 8 jumpered at the
external device end. What am I doing wrong?

>
> My KPA500 arrives on Monday so I'd like to get this resolved before my next project!
>
> John KE4D
> K2 #7231
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
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Don Wilhelm-4

Re: K2 interface with steppIR and computer

In reply to this post by John's email

John,

You said you were "building a Y cable". I do not know the configuration
of your cable, but it sounds like you may have the transmit data
connected from both the SteppIR Controller and from the computer - the
transmit data from the two sources will "fight" and communications will
cease.

The SteppIR Y cable does not connect transmit data from the SteppIR
Controller - it depends on the logging application to poll for the
transmit frequency, and the SteppIR Controller just listens in on that
information transfer.

So, if you have connected both TXD and RXD on both sides of the Y cable,
that is your problem - RS-232 cannot have multiple drivers on any
connection, although multiple receivers will work.

73,
Don W3FPR

On 1/7/2012 10:08 AM, [hidden email] wrote:

> I built my serial cable for the K2 to talk to my SteppIR controller from the Elecraft manual. Works just fine. It also talks to my computer for HRD, N1MM etc. So I decided to work on having the two interfaces work together like they did with my IC 746 Pro. However, building a Y cable doesn't seem to be working out the way I want! Each device works fine when I have it plugged into the Y cable by itself but when I plug in both at the same time, One or the other will freeze up. I am simply using pins 2, 3 and 5 from the K2 serial port wired straight through to the female DB 9s at the device end and have 7 and 8 jumpered at the external device end. What am I doing wrong?
>
> My KPA500 arrives on Monday so I'd like to get this resolved before my next project!
>
> John KE4D
> K2 #7231
>
> ______________________________________________________________
> 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
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ke4d

Re: K2 interface with steppIR and computer

In reply to this post by John's email

Got it! It didn't make sense to me but once I inserted the "S13" cable from the K2 to the Y cable, removed the TXD from the SteppIr DB9 and changed the jumper from pin 8 to pin 9 per SteppIR and Don, it all worked. Whew! Ok, only the S13 cable didn't make sense but it works so I guess it doesn't have to make sense to me.

John KE4D

Don Wilhelm-4

Re: K2 interface with steppIR and computer

John,

What needs to "make sense" is that you can only have one driver on an
RS-232 line. It is not a matter of "making sense", but is a technical
requirement. If you have two devices trying to send stuff at the same
time, the result at the receiving end is garbage. In "HamSpeak" we call
that QRM.

73,
Don W3FPR

On 1/7/2012 5:44 PM, ke4d wrote:

> Got it! It didn't make sense to me but once I inserted the "S13" cable from
> the K2 to the Y cable, removed the TXD from the SteppIr DB9 and changed the
> jumper from pin 8 to pin 9 per SteppIR and Don, it all worked. Whew! Ok,
> only the S13 cable didn't make sense but it works so I guess it doesn't have
> to make sense to me.
>
> John KE4D
>
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