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Minor Upgrade...

Ironflight

VAF Moderator / Line Boy
Mentor
I guess a METAR of 300' Overcast and less than a mile in rain showers is Nature's way of telling you it's a good day to do that wiring upgrade.... :p

After waking up to the best weather in a week (1200 and 10 miles) and getting in a little flight time before it all went back to "lousy", I decided to tackle a minor upgrade to my GRT system that I had been putting off while the flying was good. Pulling the panel only takes about ten minutes, but I hate to break interfaces and then retest everything unless I have to - or I have time on my hands...

I have a little hockey-puck Garmin GPS-18 receiver on my glareshield, wired to an outlet to feed my IpaQ. Unfortunately, my IpaQ has gotten fairly long in the tooth, and I let my AnywhereMap subscription lapse, so the GPS-18 has been underutilized. So today I pulled the panel out of the plane and wired it up to the EFIS as "GPS 2". Both of my Channel 6 Inputs were unused, so that is where I put it on each MDU.

The wiring took about an hour (I hate having to splice into the middle of a bundle!), but when I was done, everything fired right up. I enabled the Channel 6 inputs as "GPS2", and didn't see the counters incrementing - thought I'd screwed something up until I remembered that I had to do a "Save" and then go back into Setup for the changes to take effect. The GPS-18 manual said the default Baud rate was 4800, so that is what I set, but then I noticed that my Transponder and GNS430 had lost their altitude. Since Channel six from one of the MDU's was feeding that, I returned it to the original 9600 rate, and voil? - not only did the altitude data come back, but the GPS 18 data worked as well!

Unfortunately, by the time I got this all done, it was raining hard enough on the hangar roof that I couldn't hear my stereo - much less open the door and put the airplane outside so that the GPS could see some satellites! So a report on how it works will have to wait....I do know that the EFIS is receiving serial data however (as indicated by the counters), and look forward to having this extra source of Nav data where I can get it more easily. The GPS-18 naturally has no display of it's own, but hooking it up to the GRT will give a really nice backup to the 430. And get this....the GPS-18 is WAAS enabled!! Not bad for $70....

Has anyone else used a simple "this is where I am" NMEA GPS as a second GPS yet on their GRT system? I guess it will give the EFIS position, and I can use internal flight planning with it (unlike my main GNS 430 where I do all my flight planning external to the GRT). I'm just a bit curious how it will integrate. SInce both the GNS 430 and the GPS-18 feed both MDU's individually and I have a 396 as well), the overall redundancy is now quite satisfactory... :D

Now if it will ever stop raining, I can go experiment!

Paul
 
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second gps.

Good idea Paul. I've stopped using my palm with its portable gps since I got my Garmin 196. I was going to wire the 196 to the dynon D100 for it HSI input but maybe I'll try the portable gps first since I can just plug that one right in. That would give me a nice back up gps. Maybe I can do that tomorrow and report on that.
 
And Now....it Works!

OK!! I just got back from the hangar, and everything is now working -
this is just TOO COOL!!

I called GRT this afternoon, and in the discussion, was reminded
that there is a GPS Status page buried in Setup under MDU Setup. If
you go there, you'll see a big circle representing the sky, and then
lots of parameters that might or might not be getting shipped in
from the GPS. You can toggle between GPS1 and GPS2 right there, so
it is easy to do compares.

I pulled the airplane half out of the hangar and plugged in external
power, closed the canopy against the wind and started playing. I
left the GNS 430 turned off at first, to make sure that I wasn't
getting fooled by data coming in from there. I had incrementing bit
counters on both MDU's (the GPS 18 was connected to both units as
Channel 6), but when I went to the GPS Status page, I was getting
all "zeroes" for Lat, Long, etc....I then started playing with Baud
rates, and Bingo! When I tried 4800, I had good position data and
the circle started showing the satellite positions. None of the
other rates wanted to work.

Now, this created what I thought to be a small problem, because my
MDU 1 is feeding Altitude data out Channel 6, and the the
transponder would only accept it at 9600. However....and this is the
good part....when I disabled the Channel 6 input to MDU1, the MDU
started receiving GPS2 data across the interlink from MDU2! Victory!!

I spent the next half hour toggling between the two GPS's on both
MDU's, and playing with Internal and External flight plans. You can
select a GPS on either MDU, and the other one follows, so you can't
get them out of sync. I also discovered that if you have one of the
GPS's selected, and then power it off, the EFIS automatically
selects the one that is still there. It's a good thing that there is
an annunciator on the screen to tell you the current source....

This thing just keeps getting better and better! :D

Paul
 
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