dGPS not getting sattelites signal


#1

I was recently gifted with dGPS and have the following problems (with EV3):

  1. The first day I tried it it got the signal for an hour or so (blue light + correct position)
  2. It never aquired the sattelite signal again (fixed on this first good position and later, after taking/putting battery fixed on default positions)

I have tried the following to solve the issue:

  1. Replacing CR2032 battery with fresh one
  2. Trying on EV3 firmware
  3. Putting on rooftop with fresh EV3 batteries for 3 hours
  4. Polling with 500 ms, 1000 ms, not polling at all

I was writing driver for ev3dev and have already got most of the functions working. Extended firmware also seemed to be working (correct altitude for the position it got correctly the first time).

The battery is ok (old one and freshly replaced, the UTC time keeps going on).
EV3 power sources tested were rechargable batteries (freshly charged) and EV3 accumulator from edu version (freshly charged).
When writing the driver I might have made some I2C writes I should not but from what I have seen in your forum it shouldn’t affect the firmware.

Any ideas?

Kind regards!


#2

Just to confirm, did the blue light ever come one? Did it ever stay solid? Has it stayed solid since the last time you changed the battery out?

If the GPS fires up normally and gives you a few blinks, but doesn’t have a solid blue light, the issue might be in the amount of sky the gps is seeing. The GPS chip, on it’s first run (or first run since you put the new battery in) needs to download an almanac from the GPS satellite system. This can take some time, and is best done in a pretty open space with as much of the skyline visible. If you’re trying this inside, it won’t work. If you’re in an urban canyon, it will be slow, and might not work.

Can you tell us more about where you are?


#3

Hi John,

Just to confirm, did the blue light ever come one? Did it ever stay solid?

Yes - the first day I was using the device. Light was blue. When outside (rooftop) it stayed solid. In I2C register the signal byte was 1. Then it never came blue again (apart from the moment when powering on EV3 or plugging the cable to EV3). The position was never updated again but the one that was read this time was correct.

Has it stayed solid since the last time you changed the battery out?

No. Only blinks when turning on EV3 or plugging the cable.

If you’re in an urban canyon, it will be slow, and might not work.

Huh, I tried at roof of my house and at roof in my work. 3 hours in the second case. It is kind of urban area but the skyline seems visible from the roof.

It was getting the correct signal the first day. Even some blue blinks inside.

Can you tell us more about where you are?

Europe/Poland/outskirts of Warsaw


#4

So the light on the dGPS is going to go solid only when you have a solid signal from the satellites. Acquiring that first signal from the satellites can be difficult and take some time but not 3 hours, that’s a very long time. On the roof should work well enough, and should take only 15 minutes at most.

Just looking at the old post, you should try to poll every 1 second at most. The GPS chip itself is only updating position once every second. And you shouldn’t be able to destroy the firmwware, so I woulnd’t worry about that. At worst, you can just unplug the GPS and plug it back in.


#5
Just looking at the old post, you should try to poll every 1 second at most.

I know. I tried that. I also tried disabling polling at all.

The only other things I can think about is taking it to the field.

Also the sky was clear (not cloudy) the first day when I got it working but this should affect the signal only very little.


#6

One more question to simplify the test:

Should dGPS get satelite signal with original firmware on EV3 and no program running (EV3 enabled)?


#7

As far as I understand, the firmware on the EV3 should have no effect on the getting the satellite signal. It should not matter what version of Ev3 firmware you’re using, I think. I’m not familiar with the very latest, have they put out a new version of firmware lately?


#8

> It should not matter what version of Ev3 firmware you’re using

I usually use other operating system running on EV3 booted from SD card, so normally I don’t use the original firmware at all.

What I am specifically asking is:

  • on stock EV3 firmware, do I have to use DexterIndustries blocks or should dGPS acquire signal just if it is powered on by EV3, with no program running

This is what I would normally assume but I have trouble with the signal (no signal).


#9

Got it, I think I understand. The solid blue light on the dGPS should go solid, no matter what firmware you’re using (but again, be sure to use full batteries).