Connecting a JPI EDM-930 and Garmin GPS 175 help, please

[bcg-63M20C]

I put a JPI EDM-930 into my plane at my last annual and have been unable to get it to talk to my GPS 175. I'm at a loss as to what to try next and would appreciate any suggestions. Here's what I've done so far -

Pin 8 on the GPS 175 is connected to GPS In on the EDM
Pin 30 is connected to GPS out on the EDM
I would expect these to put the EDM 930 on RS 232 #2

On the EDM, baud rate is set to 9600 and I've tried the all of the Output fomats, including #6 GNS 430/530-WP and #7 GNS 430/530-DST with no success. On the input side, I've tried all the setting, including #3 AVIATION/BENDIX with the Output from the GPS 175 set to Aviation 1, Aviation 2 and Shadin, again with no success.

I don't see a way to set the RS 232 Input format on the GPS 175, only the Output format.
I've got 2 other devices connected to the other RS 232 ports, a G5 on #1 and my Transponder on #3, both of which work fine. Prior to the installation of the EDM, the G5 was on #1 and the Transponder was on #2, I had the entire harness redone and that's how the Transponder got moved.

I'm stuck at this point and don't know what else to try. I've contacted JPI and Garmin, JPI gave me some settings to try that didn't work so I sent them another email asking for next steps. I haven't heard anything from Garmin yet but, given that the GPS works with the other devices and #2 was previously connected to the Transponder without issue, I don't really think the problem is on the GPS side.

If anyone has any ideas, I'd love to hear them. Thanks!

 

[asicer]

From the GPS175 configuration mode menu, you should be able to tap on "Setup", "Interfaces" and then "RS232" and get this screen. What does yours show?


Also from the configuration mode menu, you should be able to tap on "Diagnostics", "Serial" and get this. What does yours show?

 

[bcg-63M20C]

From the GPS175 configuration mode menu, you should be able to tap on "Setup", "Interfaces" and then "RS232" and get this screen. What does yours show?
View attachment 130823

Also from the configuration mode menu, you should be able to tap on "Diagnostics", "Serial" and get this. What does yours show?
View attachment 130824

On the RS232 page, I've tried Aviation Output 1, Aviation Output 2, Fuel Format 1, Fuel Format 2. None of those have worked.

Diagnostic>Serial shows Not Receiving on all ports. 1 and 3 are Output only though, so I expect those to be that way, 2 should be receiving something.

I disconnected the units and tested the wires, they ohm out at 0 pin to pin and are wired correctly.

Sent from my Pixel 6a using Tapatalk

 

[asicer]

On the RS232 page, I've tried Aviation Output 1, Aviation Output 2, Fuel Format 1, Fuel Format 2. None of those have worked.

Diagnostic>Serial shows Not Receiving on all ports. 1 and 3 are Output only though, so I expect those to be that way, 2 should be receiving something.

I disconnected the units and tested the wires, they ohm out at 0 pin to pin and are wired correctly.

Sent from my Pixel 6a using Tapatalk

If you disconnect the EDM and short the wires (form a loopback), does the diagnostic page show "Receiving"?
(I don't remember if "Receiving" just means that it's seeing something RS232 or if the protocol also needs to be correct)

 

[bcg-63M20C]

If you disconnect the EDM and short the wires (form a loopback), does the diagnostic page show "Receiving"?
(I don't remember if "Receiving" just means that it's seeing something RS232 or if the protocol also needs to be correct)

I hadn't thought of trying that. It seemed like an interesting idea so I did, it still says Not Receiving.

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[Chip Sylverne]

Not sure what you're trying to get the 175 to do. According to the 175 manual, the fuel range and fuel to destination on the 175 are calculated from user inputs, and aren't generated by data input from an EDM.

In order for the EDM to generate fuel data, the 175 must be on an active flight plan. I have an 830 connected to a 175, and the combo works great, but fuel range information comes via the 830.

 

[bcg-63M20C]

Not sure what you're trying to get the 175 to do. According to the 175 manual, the fuel range and fuel to destination on the 175 are calculated from user inputs, and aren't generated by data input from an EDM.

In order for the EDM to generate fuel data, the 175 must be on an active flight plan.

I would expect the marked fields to show up regardless when use Sensor Data is active and for the EDM to record GPS position in the flight logs. Neither of these happens. Nothing is communicated between them.

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[Chip Sylverne]

Check page 4-6 of your 175 Pilot's Guide. Use Sensor Data refers only to GPS ground speed. The rest is user input.

 

[asicer]

Check page 4-6 of your 275 Pilot's Guide. Use Sensor Data refers only to GPS ground speed. The rest is user input.

I believe software version 3.21 added support for the following RS-232 Fuel formats for fuel data to display on the Fuel Planning Page:

• FADC Format 1
• Fuel Format 1
• Fuel Format 2

(2023) Service Bulletin 23037 Rev B: GPS 175/GNX™ 375/GNC® 355 Main Software Version 3.21 and GNX 375 Transponder Board Software Version 2.80 | Garmin Customer Support

Garmin Support Center is where you will find answers to frequently asked questions and resources to help with all of your Garmin products.

support.garmin.com

 

[Chip Sylverne]

I haven't upgraded the 175 sw, so with that I can't be of any help. That SB mentions compatibility only other Garmin products, so maybe that's the issue. FWIW, I use the 175 tx rs232 aviation data format, which according to JPI is supposed to be automatically detected and determines the format of any fuel data tx from the EDM to another unit.
Sorry can't be of more help.

 

[bcg-63M20C]

I believe software version 3.21 added support for the following RS-232 Fuel formats for fuel data to display on the Fuel Planning Page:

• FADC Format 1
• Fuel Format 1
• Fuel Format 2

(2023) Service Bulletin 23037 Rev B: GPS 175/GNX™ 375/GNC® 355 Main Software Version 3.21 and GNX 375 Transponder Board Software Version 2.80 | Garmin Customer Support

Garmin Support Center is where you will find answers to frequently asked questions and resources to help with all of your Garmin products.

support.garmin.com

I updated the software a couple of months ago and have those 3 options. I've tried them all.

 

[bcg-63M20C]

Check page 4-6 of your 175 Pilot's Guide. Use Sensor Data refers only to GPS ground speed. The rest is user input.

That's dumb. Why would Garmin do that? Surely there's got to be some way to use the RS 232 data to fill those fields with more accurate and real time information.

 

[asicer]

That's dumb. Why would Garmin do that? Surely there's got to be some way to use the RS 232 data to fill those fields with more accurate and real time information.

I think the Pilots Guide is older than the firmware. But I suspect only Garmin knows if it will really work. And even then, the right hand (product support) might not know what the left hand (firmware engineering) is doing.

 

[bcg-63M20C]

Here's what Garmin told me -

Thank You for contacting Garmin International. Garmin has conducted testing with the interface to the EDM 700. The GPS 175 must have software version 3.20 or above. The setting for the GPS 175 serial input (port 1,2 or 3) from the EDM 700 will be Fuel Format 2 ( aka...Shadin Fuel) and the output of that chosen port will automatically be set to Aviation format 1. Please contact JPI directly for information on setting the EDM 930 to Shadin Fuel output and the Aviation output.

Based on that, I think it should work with the EDM set to Shadin out, Aviation in and the GPS set to Fuel Format 2. I've got make a flight today, I'll try it again with an active flight plan and see if my results are any different.