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RS-232 and Navworx

 
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saolesen(at)sirentel.net
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PostPosted: Wed Nov 08, 2017 7:28 am    Post subject: RS-232 and Navworx Reply with quote

I am trying to use my GNS480 as the position source for my Navworx unit. The 480 is located at the top of stack and access is very difficult for running new wires. I thought I could use a wire that is already going to my GRT for the position source. The question is: How many RS-232 receivers can one transmitter drive? I am trying to drive 3 receivers from one transmitter. Does distance matter, since the Navworx unit is aft of the baggage bulkhead?

A grounding question: The Navworx unit has 3 or 4 signal ground pins, one of which already goes to the 480, do I need another?

Sheldon Olesen
RV-10 475PV 789hrs

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Tim Olson



Joined: 25 Jan 2007
Posts: 2870

PostPosted: Wed Nov 08, 2017 8:23 am    Post subject: RS-232 and Navworx Reply with quote

I'm not what I'd call an expert, but I think I can answer this one ok.

First, if you're using the 480, make sure that the intended
position source setting is what you need for the NavWorX.
I have not done this myself but it sounds like ADSB+, not
just ADSB. Bob Leffler probably knows best on this, and I'm not
sure if you would need to also be at the latest 480 firmware or not.
Bob, can you chime in and correct me or educate me on this part?

But, assuming it is the same data stream, you should be able to
drive all 3 receivers with no issue, if they are all uni-directional
connections. Distances within the airplane really won't matter,
as they really aren't *that* long. And, if you already have
signal grounds going to other pins, it's unlikely that you would
have a problem if you ignored it for that new additional wire.
You may still want to connect the shield, but the actual
signal ground will probably work just fine. I have a couple of
serial runs on my planes that don't have serial grounds connected,
for things like engine monitor data and such.
Tim

On 11/8/2017 9:27 AM, Sheldon Olesen wrote:
Quote:


I am trying to use my GNS480 as the position source for my Navworx unit. The 480 is located at the top of stack and access is very difficult for running new wires. I thought I could use a wire that is already going to my GRT for the position source. The question is: How many RS-232 receivers can one transmitter drive? I am trying to drive 3 receivers from one transmitter. Does distance matter, since the Navworx unit is aft of the baggage bulkhead?

A grounding question: The Navworx unit has 3 or 4 signal ground pins, one of which already goes to the 480, do I need another?

Sheldon Olesen
RV-10 475PV 789hrs

Sent from my iPad



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Mauledriver(at)nc.rr.com
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PostPosted: Wed Nov 08, 2017 9:18 am    Post subject: RS-232 and Navworx Reply with quote

One issue you may want to carefully look at (in addition to availability
of the ADS-B+ protocol on the 480); All the diagrams in the Navworx
installation manual that show the RS232 connection for the GPS source,
also have you connecting up 1 or 2 "Time Mark" lines. I also noted that
he 480 diagram for GPS source only showed an ARINC connection option.
There wasn't a diagram for an RS232 connection but I'm guessing you've
moved past that already.

 I don't know exactly what the "Time Mark " line does but it's unique
to the GPS source connection for Navworx.

I have a G430w and (3) GRT HX EFISs.  There is already a multi-point
RS232 GPS connection in my installation and it occurred to me to just
link the Navworx box to it just as you are planning.  I agree with Tim
that it would not be a problem.  But following the installation
diagrams. I was forced to go get that Time Mark connection from the back
of the G430, so I got a dedicated RS232-Out connection at the same time.

I would suggest investigating both availability of the  ADS-B+ protocol 
and that Time Mark line.

On 11/8/2017 11:21 AM, Tim Olson wrote:
Quote:


I'm not what I'd call an expert, but I think I can answer this one ok.

First, if you're using the 480, make sure that the intended
position source setting is what you need for the NavWorX.
I have not done this myself but it sounds like ADSB+, not
just ADSB.  Bob Leffler probably knows best on this, and I'm not
sure if you would need to also be at the latest 480 firmware or not.
Bob, can you chime in and correct me or educate me on this part?

But, assuming it is the same data stream, you should be able to
drive all 3 receivers with no issue, if they are all uni-directional
connections.  Distances within the airplane really won't matter,
as they really aren't *that* long.  And, if you already have
signal grounds going to other pins, it's unlikely that you would
have a problem if you ignored it for that new additional wire.
You may still want to connect the shield, but the actual
signal ground will probably work just fine.  I have a couple of
serial runs on my planes that don't have serial grounds connected,
for things like engine monitor data and such.
Tim

On 11/8/2017 9:27 AM, Sheldon Olesen wrote:
>
> <saolesen(at)sirentel.net>
>
> I am trying to use my GNS480 as the position source for my Navworx
> unit.  The 480 is located at the top of stack and access is very
> difficult for running new wires.  I thought I could use a wire that
> is already going to my GRT for the position source. The question is: 
> How many RS-232 receivers can one transmitter drive?  I am trying  to
> drive 3 receivers from one transmitter.   Does distance matter, since
> the Navworx unit is aft of the baggage bulkhead?
>
> A grounding question:  The Navworx unit has 3 or 4 signal ground
> pins, one of which already goes to the 480, do I need another?
>
> Sheldon Olesen
> RV-10  475PV  789hrs
>
> Sent from my iPad
>




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rene(at)felker.com
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PostPosted: Wed Nov 08, 2017 11:01 am    Post subject: RS-232 and Navworx Reply with quote

I tried doing the same thing with my 430. No go. The GRT is using the
"aviation" format and the Navwox is using ADS-B+. I am on a business trip
and do not have everything right now.....but I could not find a way without
running new wires. I think it will take me 2 days just to wire the 430
based on previous experience.

Rene'
801-721-6080

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Kellym



Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

PostPosted: Wed Nov 08, 2017 1:07 pm    Post subject: RS-232 and Navworx Reply with quote

The 430/530 series and the 650/750 series did NOT have ADS-B+ format in
their original software. The original ADSB output had a few deficiencies
in the format to meet the final rule. When Garmin updated the output I
believe the FAA required they change the name of the output, hence
ADS-B+. You have to get the Garmin software update to get that output,
and then select it in the setup. I am familiar, because when I bought my
Dynon/Trig transponder it did not have that output format as a
selection. Had to get update to 650 and to the Trig to get everything to
meed the FAA spec. I expect the 480 also had to have an update to get
that format. I had to install a single wire from the Garmin 232 output
to the Trig position input.

On 11/8/2017 11:59 AM, Rene wrote:
[quote]

I tried doing the same thing with my 430. No go. The GRT is using the
"aviation" format and the Navwox is using ADS-B+. I am on a business trip
and do not have everything right now.....but I could not find a way without
running new wires. I think it will take me 2 days just to wire the 430
based on previous experience.

Rene'
801-721-6080

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Peter(at)sportingaero.com
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PostPosted: Wed Nov 08, 2017 1:12 pm    Post subject: RS-232 and Navworx Reply with quote

Sheldon,

You do need to be slightly careful with terminology, RS232 is more the
physical method to connect boxes together defining connectors, pin-outs,
voltages and bit rates. The interface between them is a software standard -
such as NMEA0183 (usually just called NMEA). The interface standard will
define how the data is transmitted - what each transmitted bit means. A
typical RS232 chip will struggle to drive a cable greater than 50ft due to
capacitance issues, if your installation is approaching that length you may
have to experiment with different cables to find one that works - I have
only ever used cables a few feet long.

A NMEA bus can have several listeners, but must have only one talker - there
is no protocol for more than one box to talk. You should be able to supply 3
listeners. But be aware that strictly NMEA 0183 is not completely compatible
with RS232.

Should all the ground pins be connected together? So, no, you probably don't
need another. A circuit must be made for any databus to work, after all each
bit is only what the chip interprets as high (3v to 15v) or low (between +3v
and -3v) fluctuating at whatever the bit rate is (say 4800 baud - bits per
second). An RS232 bus should have a transmit, receive and ground/common
lines (wires). Whereas NMEA will only use either the Tx or Rx for each
device (so could make do with only 2).

All the details of both are explained pretty well on Wikipedia.

Hope this helps, Peter
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alec(at)alecmyers.com
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PostPosted: Wed Nov 08, 2017 2:42 pm    Post subject: RS-232 and Navworx Reply with quote

Might be worth noting that NMEA0183 uses the EIA-422 (sometimes known as RS-422) not RS-232.

Correct me if I’m mistaken but EIA-422 is +5V for logic 1 and 0v for logic zero, whereas RS-232 is -3 to -12V for logic 1 and +3 to +12V for logic zero, so entirely incompatible.

RS-232 is differentially signalled

On Nov 8, 2017, at 4:10 PM, Peter Pengilly <Peter(at)sportingaero.com> wrote:



Sheldon,

You do need to be slightly careful with terminology, RS232 is more the
physical method to connect boxes together defining connectors, pin-outs,
voltages and bit rates. The interface between them is a software standard -
such as NMEA0183 (usually just called NMEA). The interface standard will
define how the data is transmitted - what each transmitted bit means. A
typical RS232 chip will struggle to drive a cable greater than 50ft due to
capacitance issues, if your installation is approaching that length you may
have to experiment with different cables to find one that works - I have
only ever used cables a few feet long.

A NMEA bus can have several listeners, but must have only one talker - there
is no protocol for more than one box to talk. You should be able to supply 3
listeners. But be aware that strictly NMEA 0183 is not completely compatible
with RS232.

Should all the ground pins be connected together? So, no, you probably don't
need another. A circuit must be made for any databus to work, after all each
bit is only what the chip interprets as high (3v to 15v) or low (between +3v
and -3v) fluctuating at whatever the bit rate is (say 4800 baud - bits per
second). An RS232 bus should have a transmit, receive and ground/common
lines (wires). Whereas NMEA will only use either the Tx or Rx for each
device (so could make do with only 2).

All the details of both are explained pretty well on Wikipedia.

Hope this helps, Peter
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jim(at)PoogieBearRanch.co
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PostPosted: Wed Nov 08, 2017 3:14 pm    Post subject: RS-232 and Navworx Reply with quote

And just in case you haven't already found it, here is the link to an
AOPA page that shows the various approved AMOC for the NavWorx AD:
https://www.aopa.org/go-fly/aircraft-and-ownership/ads-b/navworx-amoc-information

All three of the AMOC described on that page are for Garmin equipment:
GTN6xx/GTN7xx, GNC4xxW/GNC5xxW, and GNS480.

And in somewhat unusual behavior for the FAA, all of them are "AMOCs of
general applicability" so that any affected aircraft owner who meets the
requirements of the AMOC can use it.

Good luck to all the NavWorx purchasers!

Jim Parker

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PostPosted: Wed Nov 08, 2017 6:30 pm    Post subject: RS-232 and Navworx Reply with quote

Thanks to all who replied. It looks like I need a 480 software update, some more wires run, and a contortionist friend or a box of money.

I checked up and under the panel with a borescope and there are a lot of wires directly in the way of the connectors I need to use, and then, there is the distance problem of the 480 being on the top of the stack. This going to take some serious time to complete.
Sheldon Olesen
Sent from my iPad

[quote] On Nov 8, 2017, at 5:12 PM, <jim(at)poogiebearranch.com> <jim(at)poogiebearranch.com> wrote:



And just in case you haven't already found it, here is the link to an
AOPA page that shows the various approved AMOC for the NavWorx AD:
https://www.aopa.org/go-fly/aircraft-and-ownership/ads-b/navworx-amoc-information

All three of the AMOC described on that page are for Garmin equipment:
GTN6xx/GTN7xx, GNC4xxW/GNC5xxW, and GNS480.

And in somewhat unusual behavior for the FAA, all of them are "AMOCs of
general applicability" so that any affected aircraft owner who meets the
requirements of the AMOC can use it.

Good luck to all the NavWorx purchasers!

Jim Parker



------


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Kellym



Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

PostPosted: Wed Nov 08, 2017 8:57 pm    Post subject: RS-232 and Navworx Reply with quote

Many avionics trays allow the rear of the tray to be removed, or the
connectors removed, so that you can get them out to add/remove wires.
You do not want to make the connection with the connector in its normal
position.
Once I got the rear connectors removed from my GTN650, it was relatively
easy to insert the one additional wire I needed.

On 11/8/2017 7:28 PM, Sheldon Olesen wrote:
[quote]

Thanks to all who replied. It looks like I need a 480 software update, some more wires run, and a contortionist friend or a box of money.

I checked up and under the panel with a borescope and there are a lot of wires directly in the way of the connectors I need to use, and then, there is the distance problem of the 480 being on the top of the stack. This going to take some serious time to complete.


Sheldon Olesen


Sent from my iPad

> On Nov 8, 2017, at 5:12 PM, <jim(at)poogiebearranch.com> <jim(at)poogiebearranch.com> wrote:
>
>
>
> And just in case you haven't already found it, here is the link to an
> AOPA page that shows the various approved AMOC for the NavWorx AD:
> https://www.aopa.org/go-fly/aircraft-and-ownership/ads-b/navworx-amoc-information
>
> All three of the AMOC described on that page are for Garmin equipment:
> GTN6xx/GTN7xx, GNC4xxW/GNC5xxW, and GNS480.
>
> And in somewhat unusual behavior for the FAA, all of them are "AMOCs of
> general applicability" so that any affected aircraft owner who meets the
> requirements of the AMOC can use it.
>
> Good luck to all the NavWorx purchasers!
>
> Jim Parker
>
> ------


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PostPosted: Fri Nov 10, 2017 6:27 am    Post subject: RS-232 and Navworx Reply with quote

At 04:39 PM 11/8/2017, you wrote:
Quote:
--> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com>

Might be worth noting that NMEA0183 uses the EIA-422 (sometimes known as RS-422) not RS-232.

NMEA0183 is a digital language that can be conveyed
on RS232, 422, 485, fiber optics or even bluetooth.

The "RS" conventions speak to voltage levels, and
transmission lines and are totally independent
of 'language'.

RS232 is a single wire signal operating against ground
that swings above and below ground to represent "1"
or "0". That voltage may be as high as +/-12 volts
but I've built systems that ran quite happily on
+/-5v. I had one project that ran +5/=12 . . .
the exact voltage is not critical, it's he
transition from + to = and vise versa that carries
the information.

RS422 is a balanced pair of wires where the signal
polarities alternate between the two wires. RS422
transceivers generally operated in the 5v world so
the voltage between the two lines is generally 5v
with data being carried on polarity reversals.

There are integrated circuits designed to translate
422>232 or 232>422 . . . either convention can
carry NMEA0183 messages . . . or any other
protocol.


Bob . . .


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