Connecting D-100 and GPS 251 -> missing wind data

[Ludger]

I got the following problem with my Dynon:

In my CTLS (2010) from Flight Design I had installed: Dynon EFIS D 100 & Dynon EMS D 120 & GPS Garmin 695.
The GPS Garmin 695 was replaced by an iPad mini and for the Dynon we built in the Dynon GPS 251. Following the instructions the 4 wires of the GPS were connected this way:

GPS wire color gray/orange (GPS-251 Tx) -> EFIS D 100  DB25 pin 22
GPS wire color gray/violet (GPS-251 Rx) -> EFIS D 100  DB25 pin 10
GPS wire color black (GPS-251 Ground) -> EFIS D 100  DB25 pin   9
GPS wire color orange (GPS-251 Power) -> EFIS D 100  DB25 pin 12

Normaly located in the lower right corner of the EFIS page, the winds aloft arrow indicates the wind direction relative to the current direction of flight and the number indicates the current absolute wind speed. Before replacing the Garmin by the GPS 251 this has always worked.

Now neither the wind aloft arrow nor the number (windspeed) is displayed at any time.
The Dynon GPS 251 is connected to the Dynon D 100 in the discribed way. And the Dynon is connected to the OAT probe (never was disconnected).

So, where to search for the mistake?

Ludger (Germany)

 

[Dynon]

There are a few things to check. First, is the OAT still displaying? Next, is the baud rate for the serial port on the Dynon set to 9600 (or auto)? When you change the D100 to display the HSI page, what do you see above the HSI in terms of text? Is there a GPS ground speed displayed on this page? Does it say waiting for gps, or something else? Do you definitely have a GPS-251? There's a sticker that identifies the product, and the SV-GPS-250 and GPS-251 are not interchangable.

Also, where was your former 695 connected? To the EFIS or EMS?

 

[Ludger]

Today we checked for the answers:
First, is the OAT still displaying? -> YES
Next, is the baud rate for the serial port on the Dynon set to 9600 (or auto)? -> YES (I tested both)
When you change the D100 to display the HSI page, what do you see above the HSI in terms of text? -> In Yellow: BUG 078° (and at the bottom: TAS ...)
Is there a GPS ground speed displayed on this page? -> NO
Does it say waiting for gps, or something else? -> NO
Do you definitely have a GPS-251? There's a sticker that identifies the product, and the SV-GPS-250 and GPS-251 are not interchangable. -> I definitely orderd a GPS-251, because I knew, that 250 and 251 were not interchangable. It was bought from aircraftspruce.com, date 09/06/16: "10-06240 DYNON GPS-251".
Also, where was your former 695 connected? To the EFIS or EMS? -> As far as we do remember it, it was connected to the EFIS.

In the setup menu of the EFIS the GPS is not recognized.

 

[Dynon]

So everything sounds correct there. The only last thing I'd double-check is that the GPS thinks it's a GPS-251. I don't know that I've heard of any dealers shipping the wrong part, but they look the same other than the box and product markings. You'll want to look at the actual sticker on the product, which is on the wires just below the actual puck. Or, if that's not too accessible, check the sticker on the Dynon box.

And of course, if any of the power, serial tx, or ground wires aren't going where they should be, that would also cause the GPS to not work. So double-check the wiring. One other thing you can check is that there's voltage across pins 9/12 on the EDC?

 

[Ludger]

Today I checked:
1.
Between
GPS wire color black (GPS-251 Ground)  <->  EFIS D 100  DB25 pin 9
and
GPS wire color orange (GPS-251 Power) <->  EFIS D 100  DB25 pin 12
I measured 11.86 Volt (while at the battery poles are 13.6 Volt)

2.
Further: there is a sticker at the wires of the GPS that says "Dynon Avionics GPS-251 LOT: 3016 www.dynonavionics.com" (and on the backside: "DO NOT REMOVE")

So tomorrow I will double-check the wiring from the GPS to the pins of the DB25 (by measuring the electrical resistance and therefore open the insulation near the GPS).

What is left to be checked when it turns out that the connections are correct?

Might it be than a missing or non-synchronized update causes the problem?

The last update was done by the local Dynon dealer in September 2016 in order to set up the Dynon autopilot. But perhaps the EMS did not get an update. (I don't know how to check that.)

 

[Dynon]

Not an update thing. If you were using a GPS previously, the GPS-251 should work. The voltage is what we expect to see there (and is good, it shouldn't match the battery).

Next step would be to get in touch with our support team at 425-402-0433 or support at dynonavionics dot com, and we might do an RMA to figure things out. We're also double-checking the testing records on our end based on your lot code.

 

[Ludger]

Today checked all 4 connections (GPS-251 <-> DB25 at EFIS):
The wires are ok and certainly connected as discribed above.

 

[Dynon]

Actually, on further review, I think your TX and RX wires are flipped. The instructions we wrote with EAA have the best description of this connection - see https://www.eaa.org/en/eaa/aviation-communities-and-interests/pilot-resources/eaa-stc-low-cost-avionics . Where did you get your wiring instruction from? I'm wondering if we have it wrong somewhere.

 

[Ludger]

Now the CT is on tour for one week, so I can't check if TX and RX wires are flipped.

Where did I get the in my first post discribed wiring instruction from? It was "Table 2-1 Pin Assignment for Female 25-Pin Harness" page 2-4 from document "Dynon EFIS-D10A/D100  STC SA04075CH - Installation Manual; Document Number: TJJ-MAN-02 Rev. A; Date: 2 August, 2016  EAA STC, LLC 3000 Poberezny Road\ Oshkosh, WI 54902":  https://m.aircraftspruce.com/catalog/pdf/EFIS-DYNON-DA10A.pdf

Female DB25 Pin #       Dynon Harness Wire Color       Function                         Details 
           1                 Red                       Master Power (10-30 volts)       Page 3-1 
           3                 Black                     Master Ground                    Page 3-1 
           [b]9[/b]                 Black                     [b]GPS-251-GND[/b]                      Page 3-3 
          [b][color=#ff0000]10[/color][/b]                 Orange                    [b][color=#ff0000]GPS-251-TX[/color][/b]                       Page 3-3 
          11                 White/Orange              EDC-D10A Data B                  Page 3-4 
          [b]12[/b]                 White/Blue                EDC-D10A and [b]GPS-251 Power (12V)[/b] Page 3-3 Page 3-4 
          16                 Black                     Audio Ground                     Page 3- 153-13 
          18                 Green                     Audio out                        Page 3-15 
          [b][color=#ff0000]22[/color][/b]                 Yellow                    [b][color=#ff0000]GPS-251-RX[/color][/b]                       Page 3-3 
          23                 White/Green               EDC-D10A Data A                  Page 3-4 
          24                 White                     EDC-D10A GND                     Page 3-4

And "Table 3-2 Pin Assignment for GPS-251 connector" page 3-3 from the same document:
EFIS DB25 pin# GPS-251 DB9 pin# Function              Wire color
       22                 2                       GPS-251 Tx       Gray/Orange
       10                 3                       GPS-251 Rx       Gray/Violet
         9                 5                       GPS-251 Ground       Black
       12                 9                       GPS-251 Power    Orange

Probably my interpretation of the given information was wrong and thusby I flipped TX and RX wires (that sounds pretty reasonable). My understanding was that "the text from the one side must be read on the other side", meaning TX connects to RX (which, as I guess now, is wrong). Anyway it seems to be the only possible mistake to be left which causes the missing GPS-connection and thusby causes the missing wind aloft arrow.
I check on 18th of July and let You know.
For the installation instruction, a small supplementary drawing might help to understand easier the correct wiring for the GPS or the connection of GPS and EFIS. For if the installation instructions were misunderstood and TX and RX were interchanged, after the repair of this error the question remains which of the two data connections (Gray/Orange or Gray/Violet) should be disconnected for an update. I guess the Gray/Orange one - correct?
Thank You!
Ludger (Germany)

 

[Dynon]

So re-rereading your first post, I think you're right. Pin 22 is the serial RX pin on the EFIS, and the gray/orange is the tx on the GPS. TX from the GPS does go to the RX on the EFIS, so your understanding is correct. Double-check to be sure.

 

[Dynon]

And funny enough, I fell into the same trap you did while re-reviewing: The (outdated) Rev A document that is hosted on Aircraft Spruce's site had an error. The updated version hosted on EAA's site (they're the source of the documents for this project) has and update. So, to double back again, I think it's the data wires. And do make sure to get the latest docs directly from the EAA site.

 

[Ludger]

Today I checked the wires again. Switching the data wires seems not to be the solution. Yet I was only on the ground, not in the air. Is it right that there's no winds aloft displayed when on the ground? HSI screen: no change.
Also checked the setup for the HSI and there the GPS was not recognized. (I tried both opportunities of data wire connections.) So I still am not sure, that it might be necessary to get an update like I had to have for the installation of the autopilot.
After I now tried different connections and made sure, that the wires itself are ok and well connected, I guess, that either the GPS-251 is not ok or the D-100 needs an update or special setup. (Remember, before installing the GPS-251 a Garmin 695 was connected to the D-100.)
Does anybody else have this combination of D-100 and GPS-251 running successfully? Did You double-check the testing records on Your end based on my lot code (3016)? Would You be so kind to give me the direct link to the docs on the EAA site?
Next I will try it all "in the air" and there also "change of wires" plus "change of baud rates".

 

[Ludger]

Meanwhile I found the script from September 2016 an there the Table 3-2 Pin Assignment for GPS-251 connector:
GPS wire color gray/orange (GPS-251 Rx)      ->      EFIS D 100  DB25 pin 10
GPS wire color gray/violet (GPS-251 Tx)      ->      EFIS D 100  DB25 pin 22
GPS wire color black (GPS-251 Ground)      ->      EFIS D 100  DB25 pin   9
GPS wire color orange (GPS-251 Power)      ->      EFIS D 100  DB25 pin 12

So indeed Rx and Tx have to be connected the other way as I had it before (see first post) - I just have to check it in the air!

 

[Ludger]

Today I tried the connection as described in the script from September 2016 an there in Table 3-2 "Pin Assignment for GPS-251" (see Reply '12), named "Dynon EFIS-D10A/D100   STC SA04075CH - Installation Manual   Document Number: TJJ-MAN-02   Rev. B   Date: 19 September, 2016   EAA STC, LLC   3000 Poberezny Road   Oshkosh, WI 54902" and which can be found here:
https://www.eaa.org/en/eaa/aviation...sts/pilot-resources/eaa-stc-low-cost-avionics
and then -> https://www.eaa.org/~/media/files/e...on-efis-d10a-efis-d100-install-guide-revb.pdf.
It includes: "Corrected error in GPS module wiring table on page 3-3 (Rx and Tx were swapped)."

Also I checked the corresponding setup for the HSI and choosed "NMEA" and "9600 baud". Thusby the GPS was recognized and on the screen in the lower right corner of the EFIS page first the "--" appeared and in the air the wind aloft arrow and the number (windspeed) was displayed.
And on the HSI screen above the HSI the GPS-data were displayed in magenta - just the way it should be.
So finally: IT WORKS!
Thanks for the help!

So it turns out, than first I was following a wrong description on page 3-3 ("Table 3-2 Pin Assignment for GPS-251 connector") of the document:"Dynon EFIS-D10A/D100  STC SA04075CH - Installation Manual; Document Number: TJJ-MAN-02 Rev. A; Date: 2 August, 2016  EAA STC, LLC 3000 Poberezny Road\ Oshkosh, WI 54902" - corresponding link: https://m.aircraftspruce.com/catalog/pdf/EFIS-DYNON-DA10A.pdf 

Why don't You put a link on Your website to the actual Installation Manual? It is the place where most people would search first.

Ludger (Germany)

 

[Dynon]

On the installation tab of this page - http://www.dynonavionics.com/eaa-stc-documentation.php - we have a link to the EAA page. The EAA is the official source for the installation documentation, so we point there for those.

 

[Ludger]

Thank You for the hint - i didn't find it on Your website before. Sorry.