RAK12500 GPS Module, What's Expected?

Support
1

I recently added two RAK12500 GPS module to my RAK19700 base boards. I knew the battery drain was going to be substantial going into it, but I didn’t expect it to take things down from ~30 days of runtime to just 7 days…but I can work with that by wiring in a defeat switch to power the module, so that’s not why I’m writing today.

Performance though, is not great. It takes a good ~5 minutes, under wide-open clear sky, (yes my receiver is the right way up), to get a lock…sometimes. Other times, it’ll spin for hours…overnight even, and never get a lock.

Often I can “force” a lock by rebooting the thing over and over again…it’s to where if it wont grab lock in a few minutes, I know it’s never going to and the best option is to reboot, wait 3-5 minutes…if no lock, reboot again…

Even once it obtains a lock, it’s really inconsistent. Sitting completely motionless, outdoors, with a clear sky picture, and 6+ satellites tracked, I can watch my pin-point on the map “dance” around every time the GPS updates. I’m talking a radius of about 100 meters with a similar change in altitude between any two readings. I do have High Precision enabled for the channel, so that’s not the problem.

All in all, I feel really disappointed by the RAK12500, but I"d be happy to find out I’ve done something wrong in the configuration or set.

FWIW, I’ve tried the 12500 on both ports A and D with equal results on each.

I’ll admit there maybe more going on here than I’m aware and if you folks have had different experiences with the 12500, let me know…but I’ve got the exact same behavior on two independent units now.

Current Firmware: 2.3.8.d490a33

Similar experience on:

Thanks!
Pol

2

Hi @polamnus

Thats quite unfortunate you are seeing those results.

Ive built quite a few units with the 12500 and have had nothing but good results even with the stock antennas in odd positions.

A few recommendations:

  1. Erase the firmware off your units.
  2. Check your bootloader version, latest is 0.4.3.
  3. Try a different antenna. I have a Kyocera helical that gets a lock pretty deep indoors.
3

Hi, Was There Ever An Official Solution To This. I Have The Same Issue Running On Firmware v2.3.15.deb7c27 And Using The Web Flasher. I’ve Never Been Able To Get A Lock To Even A Single Satellite. Even Sitting My Node Outside On A Clear Day With The Antenna Pointing Straight To The Sky.

4

Hi, it’s been better, but not great…let me explain…

I have tried both supported slots on the baseboard, and it doesn’t seem to make a difference…unless there’s something pressing down physically on the module or the baseboard. Every time I took the Rak out of my enclosure to check it in a serial terminal, sure enough it worked fairly well. I’m using a custom enclosure as a case and it was pretty tight in there…re-arranging and making sure nothing was pressing directly down on the board seems to have helped.

It’s pretty solid once it obtains a lock, but I still get a ton of drift when stationary. It seems significantly more accurate while in motion though.

I’d start by hooking up to usb-serial and checking the output in realtime as it boots up…it’s pretty obvious during the boot cycle when it’s initializing the gps, then later as it checks for sats at whatever rate you’ve set, default is 120s. But if it’s not even initializing, then it’ll never get a lock, best to check for that first.

Good luck, I still get cases where it will simply not get a lock without 2-3 reboots, regardless of how long I leave it with clear skies…it’s considerably rarer now, but does still happen from time to time.

Let us know how it goes or if you discover anything noteworthy!

Best,
Pol

1 Like
5

After Much Trial And Error And Getting No Success Still Constant No GPS Lock And No Sats. I Bit The Bullet And Ordered A Cheap Replacement GPS Antenna.

Swapped Out The Default RAK One And Turned On My Node. Within 20 Seconds The Cheap Antenna Picked Up 4 Sats Whilst Indoors And Then More Once Stepped Outside.

Here Is The GPS Antenna I’m Now Using:

RAK12500 Replacement GPS Antenna

MAKE SURE YOU GET THE 15X15 Size.