Phantom 2 Vision Plus+ new GPS module with no GPS signal

brunoaduarte · Dec 7, 2023

So, as of my previous post, I'm recovering an old P2V+

Rebuilding old Phantom 2 Vision Plus+ recovered from electronics trash

The old GPS module was bad, so I disassembled it and it had a cracked antenna. Even after replacing the antenna I could not get a GPS fix (by manually debugging with the uBlox uCenter software), and also the onboard battery was dead.
So I decided to get a brand new GPS module. Battery OK (~2.5V), antenna OK, and I can get a GPS FIX by manually debugging with the uCenter software, so the new GPS module works perfectly.

Unfortunately in the drone the issue persists, it displays 0 sats like there's no communication between the DJI VISION app and the GPS module.
The strange thing is that I can check the GPS revision and firmware versions when connected to the DJI Assistant 2 software, so it means the connection between the GPS and the flight controller (black box with orange sticker) is good.

What could be the problem in this case ?

Mark The Droner · Dec 8, 2023

Hi -

I saw your post on the other site. There doesn't seem to be an obvious problem. GPS on this drone is usually very simple. In fact, everything on this drone is usually very simple. That's what so cool about the P2. Very simple drone, fun to work on.

Are you sure the compass is okay? A working compass is mandatory. And if you're inside, you have to be hyper-aware that the drone is a good 10 feet away from anything that would interfere with compass. It's important to calibrate the compass outside in an open field away from all ferrous objects including metal hiding in the ground. And you must not be wearing any metal jewelry, rings, bracelets, watches, etc, that might interfere with the compass.

I see you are also showing almost zero power with your range extender and it's showing that you have no SD card in the drone. And it's showing only 27% power for your flight battery.

I would charge up the drone battery to at least 50% (it's a good idea to keep your Li Ion drone battery at 40-60% at all times when not flying), charge up the range extender completely (it takes quite a while, maybe a couple hours, maybe more), and install a formatted SD card in the drone (or format it using the DJI Phantom 2 app if you can). Then check and see if it's showing on the app screen that you have a good SD card and everything else is checking out.

Let me know how it goes...

brunoaduarte · Dec 8, 2023

Mark The Droner said:
Hi -

I saw your post on the other site. There doesn't seem to be an obvious problem. GPS on this drone is usually very simple. In fact, everything on this drone is usually very simple. That's what so cool about the P2. Very simple drone, fun to work on.

Are you sure the compass is okay? A working compass is mandatory. And if you're inside, you have to be hyper-aware that the drone is a good 10 feet away from anything that would interfere with compass. It's important to calibrate the compass outside in an open field away from all ferrous objects including metal hiding in the ground. And you must not be wearing any metal jewelry, rings, bracelets, watches, etc, that might interfere with the compass.

I see you are also showing almost zero power with your range extender and it's showing that you have no SD card in the drone. And it's showing only 27% power for your flight battery.

I would charge up the drone battery to at least 50% (it's a good idea to keep your Li Ion drone battery at 40-60% at all times when not flying), charge up the range extender completely (it takes quite a while, maybe a couple hours, maybe more), and install a formatted SD card in the drone (or format it using the DJI Phantom 2 app if you can). Then check and see if it's showing on the app screen that you have a good SD card and everything else is checking out.

Let me know how it goes...

Hi Mark, so, I've charged the batteries and inserted the sd card. Video was recorded perfectly and everything else works fine.

The compass seems OK as the mod value is in the recommended range and I'm not getting any error related to that.

Only the GPS is still grayed out.

brunoaduarte · Dec 8, 2023

The GPS module connects to the main board thru a 4 wire pin (+5V, RX, TX, GND) and then there's a 3 wire pin connecting the motherboard back to the FCU thru the EXP port, that's known to be GPS related.
Do you know what's the pinout of this 3 pin wire? Maybe one of them is not working. That would be weird of course, as the USB port comes from the FCU and the FCU shows the GPS revision and firmware versions in the DJI Assistant 2. I don't see any reasons for GPS data not to be arriving.

Are there any schematics that detail the GPS portion of the PCB? I have one schematic but the GPS part is incomplete.

Mark The Droner · Dec 9, 2023

Good work.

I don't know of any schematics. DJI doesn't release that stuff, it's up to us to figure it out.

Whenever I've had problems with GPS, which is extremely rare, I simply replace the module and it works.

This drone has had GPS problems where the wifi module just below will interfere with the GPS receiver so that the GPS can only see a few satellites, for example four satellites instead of seven. But this problem is different.

You might want to talk to this guy: crash1sttime

He is a P2 expert from the UK and might have an idea.

brunoaduarte · Dec 13, 2023

Mark The Droner said:
Good work.

I don't know of any schematics. DJI doesn't release that stuff, it's up to us to figure it out.

Whenever I've had problems with GPS, which is extremely rare, I simply replace the module and it works.

This drone has had GPS problems where the wifi module just below will interfere with the GPS receiver so that the GPS can only see a few satellites, for example four satellites instead of seven. But this problem is different.

You might want to talk to this guy: crash1sttime

He is a P2 expert from the UK and might have an idea.

Hi! The issue was related to noise on the GPS module afterall. It seems in my case the wifi module is more noisy than common. I removed the GPS module from the shell and it found a couple of satellites. Put the GPS module back in the case with the aluminum foil trick and It improved a little more. Far from ideal though. I'll test it with full open sky this weekend.

Thanks!

quaddamage · Dec 20, 2023

brunoaduarte said:
Put the GPS module back in the case with the aluminum foil trick and It improved a little more.

Can't remember how the GPS is normally shielded in Ph2, but in Ph3 there is a copper foil sticker under it.
Copper tape is relatively cheap, you may consider it as a solution. Better conductivity than aluminum, and there are tapes with thicker metal than the kitchen foil.

RodPad · Dec 20, 2023

Wow!
I'm lost on your project.

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