Veetail88

Veetail88

Well Known Member
Folks,

I have an AFS 4500 that I'm trying to configure a GPS 18 puck to drive as a secondary GPS source.

I've downloaded the GPS 18 configuration software, hooked it up to a pc and verified that it is set to 4800 baud.

I've configured serial input #3 on the AFS unit for 4800 baud, configured GPS2 to use serial input #3 and hooked up the puck.

I'm getting a "NO GPS" warning in the middle of the attitude screen and a "GPS INTEGRITY" warning in the middle of the map screen. So, you'd think that the units weren't talking, but, when I unplug the puck, the "GPS INTEGRITY" warning on the map switches to "NO GPS".

This tells me they're talking, but something is wrong.

Any ideas? :eek:
 
We send the GPS puck configured for NMEA 9600. If you reconfigured it you most likely messed up more settings.

Call our support phone and ask for Shawn once you have the puck connected to the configuration software.

(503) 263-0037

Rob Hickman
Advanced Flight Systems
 
Thanks

for the response Rob. The puck isn't from you guys. It is a Garmin GPS 18, but it's an older one I grabbed for a song. I used the Garmin utility for it, which is a struggle working through a usb/rs232 patch cable, but you're right, I probably messed more up.

I'll take another shot at configuring the unit before I call. It's a little tough being at the hanger during normal business hours.
 
You need

1. EFIS should be set to AFS GPS

2. Set GPS 18 to output

9600 Baud
GPRMC
GPGGA
 
hi jesse,

i was battling similar problems with the afs-gps (which is just one of the gps18 submodels that comes preconfigured. it looks like it's the GPS18-5Hz submodel.)

i then did some deeper debugging and found out, that the serial connection was just fine / baud rate correct etc... (stream received on laptop, would work on the efis after a while, sometimes only when airborne)
the integrity flag also had the effect of disabling the auto mode switching in the vertical power VP200 with audio callouts "mode manual" and "mode automatic". obviously annoying when not justified. this would also happen when going upside down with the antenna losing direct line of sight of the satellites for only a few seconds.
however, the gps was transmitting an "integrity" flag in the stream, despite most of the times already providing a lat/lon position (which wasn't bad at all).
i then did firmware updates, and tried to tweak all 3d/high accuracy settings to the lowest possible level and put the track prediction/dead reckoning to the max of 30s.

i never completely got rid of the problem with that puck. one observation was, that the problem was more likely to occur when the aircraft was sitting in the hangar for a bit longer than usually. also, the fact that the integrity flag only started to appear after an initial period without any issues left me startling. my theory goes in the direction of the internal battery running low/not properly recharging and therefore the gps taking much longer to rebuild the almanach / acquire a 3d fix with full integrity (and the afs gps/gps18-5Hz won't remove the integrity flag from just a 2d position and some more.).

i then intended to replace it completely with a different chip, favourably a ublox. however, i didn't find a matching unit/case/same pinout and didn't want to start an electronics project ;-)

so i got another GPS-18, but a "GPS 18 PC". cut off the connectors, same pinout, but a few different options in the firmware. now, this edition seems less focussed on the "ultra high reliability / 5 updates per second" aspects and is much more benign regarding aligning to the constellation or losing sight for a few seconds. haven't had an issue since. i can only remember getting the integrity flag once, on the ground, behind a hangar, on an airport in a relatively narrow valley. probably too few satellites or multipath reflections. so for now, i consider the problem fixed.

hope this helps you out.

kind regards,
bernie
 
No joy

Rob, I set the output of the GPS 18 (PC model not 5 Hz) to 9600 baud and the two nmea sentence protocols per your post, disconnected it from the pc and reconnected, read the configuration from the puck and it remained correct (so the internal battery is good I assume). Set Serial 3 to "AFS GPS" and still no joy.

Below is how it's wired. Anything else I can check?

 
Advanced Deck issue

I just went thru this following your post. It worked perfect for me. Did you set the NMEA 2.30 mode to ON in the sensor config program ? Do you have a Nav source set to serial port #3 in the AFS EFIS ?

Gary
 
You have your data lines crossed. Serial 3 TXD should go to RXD on the GPS and vice versa. But it's hard to tell if that is what you meant by the crosses in the diagram.
 
Not crossed

The diagram is from the puck tech sheet. Don't know why thy show them crossing like that, but they do. The puck communicates with my laptop fine for the config software.

I'm pretty sure NMEA 2.30 is on, but I can't verify. I'm 500 miles away from the hanger right now. :(
 
I decided to shorten my AFS GPS today. When looking at the DB9 there was to black wires connected to the ground pin. Imagine my surprise when I cut the cable shorter and found three black wires plus the shield drain.

For those that have done this already, did you connect all three black wires to ground? If not, how do you determine which two black wires go to ground?

Thanks,

Bob
 
rleffler said:
I decided to shorten my AFS GPS today. When looking at the DB9 there was to black wires connected to the ground pin. Imagine my surprise when I cut the cable shorter and found three black wires plus the shield drain.

For those that have done this already, did you connect all three black wires to ground? If not, how do you determine which two black wires go to ground?

Thanks,

Bob
Click to expand...

hi bob,

i will have to look it up at home. but IIRC put all the black wires together and didn't have an issue. shield not so sure any more. yellow can be cut, not needed. green is only for debugging/programming.

i also thought the diagram was wrong. TX/RX need to be crossed between each serial unit, while GND-GND goes together.

good luck!

bernie

p.s. if you are still having issues thereafter, there is a debug page in the maintenance menu. there you can at least see what data if any is coming in on all serial ports. if it's completely scrambled, it's a baud/kbps config issue. if it's clear text and still doesn't work, then it's a gps config (which type of data messages are being sent by the gps) or efis config (the right serial port being set to the right input type) issue.
 
Thanks for the replies folks

Got it working.

After several hours of extremely frustrating tinkering on Saturday I was able to make the GPS puck talk with the AFS 4500.

Having checked and triple checked every wire, programmed and reprogrammed the puck several times I still had no joy.

I had the puck set top output at 9600 baud and had the NMEA sentences set to the two that Rob said I needed and nothing was working.

As I was just about to call it a day, I'd recalled something that was said earlier in the day from a gentleman who stopped by about his having to wait a long time for his Garmin 496 to boot as his battery had died

Light bulb. The gps puck didn't know where it was and had to acquire satellites and download some data, which takes a while. I wasn't waiting for the thing to come to life. Still didn't work the way it was though.

I reprogrammed the puck to output 4800 baud, plugged it back in, reset the serial 3 input to 4800 baud on the AFS unit, waited a minute and VOILA! Success!

Not 100% sure exactly when something became right though. Maybe I had things right several times and without the unit being ready, it didn't work and I shut it off! Cussing of course.:D

Anyway, it works now thank you.

And Bob, I twisted all three black wires from the puck together.
 
Thanks for the feedback Jesse!

How long did it take for the puck to acquire the satellites? Did it need a wide open view or can it be obscured with juat hangar door open?

thanks,

bob
 
Hard to tell

I had it powered up for 20 minutes and it didn't work. Reconfigured the baud rate and AFS settings, hooked it up and it took off in maybe a minute or two.

So, I don't know if it acquired everything it needed during the 20 minute spree and was then ready when it could communicate with the AFS unit or what. I really don't like when something comes alive and I don't know what exactly it was that did it.

Inside the hanger it won't work.

Now that the puck is "aware", it takes off in a minute.

Hope that helps.

BTW, I don't know how old my pucks are or if the internal batteries will last real long. I bought them on e-bay. Five of them for $25. Probably came from some vehicle fleet, but they work.......now.
 
Success

Glad to see you got the antenna working. You have a great looking project going there and looks like it will be in the air soon. That was my son and I that stopped in to see your project.
 
Thanks Don

You were the clue I needed!

Looking forward to first engine start in a couple of months! :D. I think.
 
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