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Pull-up Question

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Corboy - Poteet

Pull-up Question

I've a question on the pull-up resistor mod for the KIO3 board: is this addition being done to support "legacy devices" or is it the wave-of-the-future (or none of the above)? If current interface "standards" don't require the pull-up capability and the outlook for the future is the same, I think I will take a pass on doing the mod. Otherwise I shall take the K3 apart again and add the resistors (I skipped that mod when doing the K3 upgrades but have decided it might be best to be sure).

Mike W5FTD
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w0mu

Re: Pull-up Question

It is to support a myriad of devices that use ttl levels such as band
decoders that drive antenna switches, bandpass filters, etc.

"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Corboy-Poteet
Sent: Saturday, March 07, 2009 10:44 AM
To: [hidden email]
Subject: [Elecraft] [K3] Pull-up Question

I've a question on the pull-up resistor mod for the KIO3 board: is this
addition being done to support "legacy devices" or is it the
wave-of-the-future (or none of the above)? If current interface "standards"
don't require the pull-up capability and the outlook for the future is the
same, I think I will take a pass on doing the mod. Otherwise I shall take
the K3 apart again and add the resistors (I skipped that mod when doing the
K3 upgrades but have decided it might be best to be sure).

Mike W5FTD
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K8RS

Re: Pull-up question

In reply to this post by Corboy - Poteet

Mike Fatchett,
OK, but what happens when you use them with devices that already work without them,e.g. Array Solutions 6 Pack and early band decoders?
Roger K8RS

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w0mu

Re: Pull-up question

>From what I understand the 6 pack would require a band decoder and proper
switching levels to switch the 6 pack. I do not believe that you can switch
the 6 pack with the levels off any rig. There needs to be some type of
interface between the switches and the radio.

I would send a note to Array Solutions. W5OV have been very helpful with my
questions and has a K3.

Mike W0MU

"A slip of the foot you may soon recover, but a slip of the tongue you may
never get over." Ben Franklin
-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Roger
Sent: Saturday, March 07, 2009 12:04 PM
To: elecraft
Subject: Re: [Elecraft] [K3] Pull-up question

Mike Fatchett,
OK, but what happens when you use them with devices
that already work without them,e.g. Array Solutions 6 Pack and early band
decoders?
Roger K8RS

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Jack Brindle

Re: Pull-up question

The six-pack needs +14 volt drive to enable its relays. Power is
applied to each antenna relay to be selected. This is usually provided
by the Six-pack switch or an external decoder/driver such as the
Elecraft KRC2. The K3 alone will not be able to provide the drive - it
definitely needs the external band decoder.

Of course we suggest the KRC2 for this function, it performs the
service quite well.

-Jack Brindle, W6FB
Elecraft Engineering
=======================================================================

On Mar 7, 2009, at 11:10 AM, W0MU Mike Fatchett wrote:

>> From what I understand the 6 pack would require a band decoder and
>> proper
> switching levels to switch the 6 pack. I do not believe that you
> can switch
> the 6 pack with the levels off any rig. There needs to be some type
> of
> interface between the switches and the radio.
>
> I would send a note to Array Solutions. W5OV have been very helpful
> with my
> questions and has a K3.
>
> Mike W0MU
>
>
> "A slip of the foot you may soon recover, but a slip of the tongue
> you may
> never get over." Ben Franklin
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Roger
> Sent: Saturday, March 07, 2009 12:04 PM
> To: elecraft
> Subject: Re: [Elecraft] [K3] Pull-up question
>
> Mike Fatchett,
> OK, but what happens when you use them with
> devices
> that already work without them,e.g. Array Solutions 6 Pack and early
> band
> decoders?
> Roger K8RS
>
>
> ______________________________________________________________
> 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
>
> ______________________________________________________________
> 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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Don Wilhelm-4

Re: Pull-up question

In reply to this post by K8RS

Roger,

That is where the situation gets 'sticky'. It all depends on what the
circuits at the end away from the K3 have implemented. You have two
pullup resistors on each line and 2 separate voltage sources.

1) If the voltage to the pullup resistors in the internal device do not
match the voltage to the pullup resistors in the K3, there will be a
continuous flow of current through both pullups on any one line when the
drivers are at their open, non-conducting state). If the voltages are
close to the same value, this may not cause a problem, but if they are
quite different (say one is 12 volts and the other is 5 volts), that
could create a big problem.
2) The drivers in the K3 (when at the low level) must carry the current
provided by both pullup resistors. Whether that is a problem or not
depends on the value of the pullup resistors and the current capability
of the drivers.

In my view of a good design, open collector (or open drain) drivers are
the only thing to use. The terminating device can determine what
voltage is needed for reliable switching at its input and that device
controls the high level by providing its own pullup resistors.
Secondly, the pullup values can be sized according to the high level
input current required by that device and can control its immunity to
noise by controlling its input conditions. All is under the control of
the external device designer. Unfortunately, much of the ham gear
available uses bare, open inputs and depends on the driving device to
provide the voltage and levels it needs at its inputs.

73,
Don W3FPR

73,
Don W3FPR

Roger wrote:
> Mike Fatchett,
> OK, but what happens when you use them with devices that already work without them,e.g. Array Solutions 6 Pack and early band decoders?
> Roger K8RS
>
>
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Joe Subich, W4TV-4

Re: Pull-up question

> Unfortunately, much of the ham gear available uses bare, open
> inputs and depends on the driving device to provide the voltage
> and levels it needs at its inputs.

Let's see ... that would apply to the KRC2 in the "parallel input
mode" along with the W9XT BCD-10 and the Yaesu Quadra for starters.
On the other hand the TopTen Systems BD-Y, the original microHAM
Band Decoder, the Yaesu FL-7000, and Tokyo High Power HL-1.5Kfx,
have internal pull-up resistors.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Don Wilhelm
> Sent: Saturday, March 07, 2009 2:56 PM
> To: Roger
> Cc: elecraft
> Subject: Re: [Elecraft] [K3] Pull-up question
>
>
> Roger,
>
> That is where the situation gets 'sticky'. It all depends on
> what the
> circuits at the end away from the K3 have implemented. You have two
> pullup resistors on each line and 2 separate voltage sources.
>
> 1) If the voltage to the pullup resistors in the internal
> device do not
> match the voltage to the pullup resistors in the K3, there will be a
> continuous flow of current through both pullups on any one
> line when the
> drivers are at their open, non-conducting state). If the
> voltages are
> close to the same value, this may not cause a problem, but if
> they are
> quite different (say one is 12 volts and the other is 5 volts), that
> could create a big problem.
> 2) The drivers in the K3 (when at the low level) must carry
> the current
> provided by both pullup resistors. Whether that is a problem or not
> depends on the value of the pullup resistors and the current
> capability
> of the drivers.
>
> In my view of a good design, open collector (or open drain)
> drivers are
> the only thing to use. The terminating device can determine what
> voltage is needed for reliable switching at its input and that device
> controls the high level by providing its own pullup resistors.
> Secondly, the pullup values can be sized according to the high level
> input current required by that device and can control its immunity to
> noise by controlling its input conditions. All is under the
> control of
> the external device designer. Unfortunately, much of the ham gear
> available uses bare, open inputs and depends on the driving device to
> provide the voltage and levels it needs at its inputs.
>
> 73,
> Don W3FPR
>
> 73,
> Don W3FPR
>
> Roger wrote:
> > Mike Fatchett,
> > OK, but what happens when you use
> them with devices that already work without them,e.g. Array
> Solutions 6 Pack and early band decoders?
> > Roger K8RS
> >
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html

Jack Brindle

Re: Pull-up question

The KRC2 has on-chip pullups that handle the task. They are enabled
whenever the
KRC2 is in BCD input mode. Thus external pullups are NOT needed for
the KRC2.

The inputs are resistor-protected in case the driving device does
power the pullups. We spec
those inputs only for the TTL voltage range.

-Jack Brindle, W6FB
=======================================================================

On Mar 7, 2009, at 8:42 PM, Joe Subich, W4TV wrote:

>
>> Unfortunately, much of the ham gear available uses bare, open
>> inputs and depends on the driving device to provide the voltage
>> and levels it needs at its inputs.
>
> Let's see ... that would apply to the KRC2 in the "parallel input
> mode" along with the W9XT BCD-10 and the Yaesu Quadra for starters.
> On the other hand the TopTen Systems BD-Y, the original microHAM
> Band Decoder, the Yaesu FL-7000, and Tokyo High Power HL-1.5Kfx,
> have internal pull-up resistors.
>
> 73,
>
> ... Joe, W4TV
>
>
>
>
>> -----Original Message-----
>> From: [hidden email]
>> [mailto:[hidden email]] On Behalf Of Don Wilhelm
>> Sent: Saturday, March 07, 2009 2:56 PM
>> To: Roger
>> Cc: elecraft
>> Subject: Re: [Elecraft] [K3] Pull-up question
>>
>>
>> Roger,
>>
>> That is where the situation gets 'sticky'. It all depends on
>> what the
>> circuits at the end away from the K3 have implemented. You have two
>> pullup resistors on each line and 2 separate voltage sources.
>>
>> 1) If the voltage to the pullup resistors in the internal
>> device do not
>> match the voltage to the pullup resistors in the K3, there will be a
>> continuous flow of current through both pullups on any one
>> line when the
>> drivers are at their open, non-conducting state). If the
>> voltages are
>> close to the same value, this may not cause a problem, but if
>> they are
>> quite different (say one is 12 volts and the other is 5 volts), that
>> could create a big problem.
>> 2) The drivers in the K3 (when at the low level) must carry
>> the current
>> provided by both pullup resistors. Whether that is a problem or not
>> depends on the value of the pullup resistors and the current
>> capability
>> of the drivers.
>>
>> In my view of a good design, open collector (or open drain)
>> drivers are
>> the only thing to use. The terminating device can determine what
>> voltage is needed for reliable switching at its input and that device
>> controls the high level by providing its own pullup resistors.
>> Secondly, the pullup values can be sized according to the high level
>> input current required by that device and can control its immunity to
>> noise by controlling its input conditions. All is under the
>> control of
>> the external device designer. Unfortunately, much of the ham gear
>> available uses bare, open inputs and depends on the driving device to
>> provide the voltage and levels it needs at its inputs.
>>
>> 73,
>> Don W3FPR
>>
>> 73,
>> Don W3FPR
>>
>> Roger wrote:
>>> Mike Fatchett,
>>> OK, but what happens when you use
>> them with devices that already work without them,e.g. Array
>> Solutions 6 Pack and early band decoders?
>>> Roger K8RS
>>>
>>>
>> ______________________________________________________________
>> 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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html

Jack Brindle

Re: Pull-up question

In reply to this post by Don Wilhelm-4

To add a bit more to Don's last point, there is a situation that few
folks (especially engineers) realize with respect to interconnect
drive systems. With todays low-power microcontrollers and digital
systems, it is very easy to accidentally power another device from the
driving device. In fact it is a pretty big problem in high-
availability (usually telco) systems where one board is supposed to be
powered off, but is being powered through it's I/O pins from another
board. The two solutions to this are very similar, basically doing as
Don suggests, using open-collector (or open-drain) drivers with
pullups on the receiving board. This eliminates any chance of
accidental power being applied to the receiving system. The second
solution is to use opto-isolators to isolate the two boards, but this
is really the same as #1 in that the receiving board provides the power.

In this case the decoder could actually be powered by the K3 through
its pullups, although they are limited by the high resistance of the
pullups. In radios with true TTL drive there is much more power
available to power a band decoder through its IO lines. We mitigate
this in the KRC2 by providing series limit resistors which effectively
limit the problem. It still exists, but at a much lower probability.

So what is the real problem if this happens? The device will not be
properly powered, so not all circuits will work. Worse, it will try to
function, attempting to provide drive to other circuits even though
not enough current is available. In the end, the poor microcontroller
tends to toast itself.

This is actually a very interesting area of study for systems that has
emerged in the past several years, and as I noted is of great
importance in the telco / high availability systems arena.

-Jack Brindle, W6FB
=======================================================================

On Mar 7, 2009, at 11:56 AM, Don Wilhelm wrote:

> Roger,
>
> That is where the situation gets 'sticky'. It all depends on what the
> circuits at the end away from the K3 have implemented. You have two
> pullup resistors on each line and 2 separate voltage sources.
>
> 1) If the voltage to the pullup resistors in the internal device do
> not
> match the voltage to the pullup resistors in the K3, there will be a
> continuous flow of current through both pullups on any one line when
> the
> drivers are at their open, non-conducting state). If the voltages are
> close to the same value, this may not cause a problem, but if they are
> quite different (say one is 12 volts and the other is 5 volts), that
> could create a big problem.
> 2) The drivers in the K3 (when at the low level) must carry the
> current
> provided by both pullup resistors. Whether that is a problem or not
> depends on the value of the pullup resistors and the current
> capability
> of the drivers.
>
> In my view of a good design, open collector (or open drain) drivers
> are
> the only thing to use. The terminating device can determine what
> voltage is needed for reliable switching at its input and that device
> controls the high level by providing its own pullup resistors.
> Secondly, the pullup values can be sized according to the high level
> input current required by that device and can control its immunity to
> noise by controlling its input conditions. All is under the control
> of
> the external device designer. Unfortunately, much of the ham gear
> available uses bare, open inputs and depends on the driving device to
> provide the voltage and levels it needs at its inputs.
>
> 73,
> Don W3FPR
>
> 73,
> Don W3FPR
>
> Roger wrote:
>> Mike Fatchett,
>> OK, but what happens when you use them with
>> devices that already work without them,e.g. Array Solutions 6 Pack
>> and early band decoders?
>> Roger K8RS
>>
>>
> ______________________________________________________________
> 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

Joe Subich, W4TV-4

Re: Pull-up question

In reply to this post by Jack Brindle

Jack,

> The KRC2 has on-chip pullups that handle the task. They are enabled
> whenever the KRC2 is in BCD input mode. Thus external pullups are
> NOT needed for the KRC2.

Thank you for the clarification. The pull-ups were not visible on
the schematic.

> The inputs are resistor-protected in case the driving device does
> power the pullups.

As is the case when connecting the KRC2 to either a computer LPT
port or the Yaesu "band data" jack. Yaesu in particular sources
+13V on those lines (and the "inhibit" line from the Quadra).

73,

... Joe, W4TV

> -----Original Message-----
> From: Jack Brindle [mailto:[hidden email]]
> Sent: Sunday, March 08, 2009 12:36 AM
> To: [hidden email]
> Cc: [hidden email]; 'elecraft'
> Subject: Re: [Elecraft] [K3] Pull-up question
>
>
> The KRC2 has on-chip pullups that handle the task. They are enabled
> whenever the
> KRC2 is in BCD input mode. Thus external pullups are NOT needed for
> the KRC2.
>
> The inputs are resistor-protected in case the driving device does
> power the pullups. We spec
> those inputs only for the TTL voltage range.
>
> -Jack Brindle, W6FB
> ==============================================================
> =========
>
>
> On Mar 7, 2009, at 8:42 PM, Joe Subich, W4TV wrote:
>
> >
> >> Unfortunately, much of the ham gear available uses bare,
> open inputs
> >> and depends on the driving device to provide the voltage
> and levels
> >> it needs at its inputs.
> >
> > Let's see ... that would apply to the KRC2 in the "parallel input
> > mode" along with the W9XT BCD-10 and the Yaesu Quadra for
> starters. On
> > the other hand the TopTen Systems BD-Y, the original microHAM Band
> > Decoder, the Yaesu FL-7000, and Tokyo High Power HL-1.5Kfx, have
> > internal pull-up resistors.
> >
> > 73,
> >
> > ... Joe, W4TV
> >
> >
> >
> >
> >> -----Original Message-----
> >> From: [hidden email]
> >> [mailto:[hidden email]] On Behalf Of Don Wilhelm
> >> Sent: Saturday, March 07, 2009 2:56 PM
> >> To: Roger
> >> Cc: elecraft
> >> Subject: Re: [Elecraft] [K3] Pull-up question
> >>
> >>
> >> Roger,
> >>
> >> That is where the situation gets 'sticky'. It all depends on what
> >> the circuits at the end away from the K3 have implemented.
> You have
> >> two pullup resistors on each line and 2 separate voltage sources.
> >>
> >> 1) If the voltage to the pullup resistors in the internal
> device do
> >> not match the voltage to the pullup resistors in the K3,
> there will
> >> be a continuous flow of current through both pullups on any one
> >> line when the
> >> drivers are at their open, non-conducting state). If the
> >> voltages are
> >> close to the same value, this may not cause a problem, but if
> >> they are
> >> quite different (say one is 12 volts and the other is 5
> volts), that
> >> could create a big problem.
> >> 2) The drivers in the K3 (when at the low level) must carry
> >> the current
> >> provided by both pullup resistors. Whether that is a
> problem or not
> >> depends on the value of the pullup resistors and the current
> >> capability
> >> of the drivers.
> >>
> >> In my view of a good design, open collector (or open
> drain) drivers
> >> are the only thing to use. The terminating device can
> determine what
> >> voltage is needed for reliable switching at its input and
> that device
> >> controls the high level by providing its own pullup resistors.
> >> Secondly, the pullup values can be sized according to the
> high level
> >> input current required by that device and can control its
> immunity to
> >> noise by controlling its input conditions. All is under the
> >> control of
> >> the external device designer. Unfortunately, much of the ham gear
> >> available uses bare, open inputs and depends on the
> driving device to
> >> provide the voltage and levels it needs at its inputs.
> >>
> >> 73,
> >> Don W3FPR
> >>
> >> 73,
> >> Don W3FPR
> >>
> >> Roger wrote:
> >>> Mike Fatchett,
> >>> OK, but what happens when you use
> >> them with devices that already work without them,e.g.
> Array Solutions
> >> 6 Pack and early band decoders?
> >>> Roger K8RS
> >>>
> >>>
> >> ______________________________________________________________
> >> 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
> >
> > ______________________________________________________________
> > 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
>