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Issues w/ GPS, takes up to 20 mins to pick up sats (UPDATE)

Discussion in 'Phantom 2 Discussion' started by brianh, Feb 9, 2015.

  1. brianh

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    Hey all, have learned a lot from reading through the forums in the past several months and just joined to get some help with my P2 and gps. Looking forward to contributing in the future.

    A little background...have had a P2 (upgraded version) since mid-december. Installed the iOSD mini inside the body and also moved the canbus connector to inside for a clean install. Have an ImmersionRC 600mw tx mounted on the underside of the body. Have the H3-3D carrying a Hero 4 Silver. Installed all of the components before any test flights, so don't have a baseline to compare before these were installed.

    From the first day I have flown, it seems to be taking way too long to pick up satellites if there is any sort of obstructions relatively close (i.e. trees and/or houses). It does seem to pick up quicker if in a wide open field, but I have to think the inability to pick it up near minor obstructions is not normal. A typical backyard test flight goes something like this...turn on Phantom in backyard and monitor FPV monitor for 20+ minutes until it starts to pick up satellites. It seems that once it starts picking up a couple, it goes relatively quick, but it will be stuck at zero for more than 20 mins, but will sometimes hover in the 4-6 range. By this time, my battery is typically in the 8X% range. Once satellites have been picked up, I turn off the unit and then back on to confirm the two sets of green lights. I have gotten as many as 9 satellites in these areas. Once it picks up satellites the first time, it seems to pick up the same number fairly quick (within 1-2 mins) if I power off and back on.

    After a dozen or so flights, I had a crash from critical low battery autoland above some trees. That's a whole other story, but in short the battery went from 65% to 7% in just a couple minutes. H3-3D took a beating but all else seemed okay. Flew a few times after the crash and seemed okay but had the thought in the back of my head that there may be another failure coming as a result of the crash. Contacted DJI and must say that I was impressed with their customer service. They repaired the H3-3D and battery at no cost and I also sent in the whole unit with the request of a "post-crash inspection". DJI indicated that they "replaced the center board due to no GPS output on the Phantom," possibly due to the crash. I indicated that I was able to pick up GPS after the crash (in wide open field) and their response was as follows:

    "When we first test flew your Phantom to drain both batteries to find the flaw that would auto descend, we could not get a GPS lock no matter how long in was in the air, even after replacing the GPS module it still had the same GPS problem. The center board was at fault, even though it registered the GPS firmware and loader in the Phantom assistant software. - Possibly damaged after the crash."

    I am not questioning their response, and in fact think they were seeing the same issue that I have seen since day 1, unrelated to the crash. I received the P2 back last week and just attempted to fly it a couple of days ago for the first time. Let it sit in my backyard for about 25 mins with power on until it got to picking up between 5 and 6 satellites, but nothing more. Did a quick test flight in ATTI mode to confirm stability. I did note that the back H3-3D appeared to be vibrating heavily, but will look into that later once I am able to get in in the air more. Just flew it for a minute or two at ~10 ft above ground.

    I tried it again in backyard this morning and let it sit for 15 mins with zero satellites, gave up and brought her in. Then took it to family's house this evening and tried the same thing. Let it sit outside in a relatively open area with clear view of the sky for ~30 mins while we ate dinner and it never picked up any satellites.

    Note that I have spent a good amount of time familiarizing myself with the Phantom software...have calibrated the IMU multiple times as I am attempting to figure this out. IMU has been calibrated on flat surface away from interference. I also calibrated the compass each time (multiple times at my house and once at family's house) away from cell phone and any electronics. One thing maybe of note, when I picked up the Phantom to move it to a different area in my backyard while powered on, the indicating lights started blinking indicating that I needed to recalibrate compass. I recalibrated successfully. After my short flight, as soon as I landed, the lights started blinking again indicating to recalibrate compass. Too many things going on here that I am uneasy about flying it like I had before the crash.

    Back to the GPS issue...any thoughts/recommendations? Based on DJI's response, I read it as they replaced both the GPS unit and the center board...in my opinion, my issues are related to neither of these. I think the issues that I was having before the crash are the same that DJI saw while they had the unit, and it is still unchanged after they replaced those components. Is it possible that my wiring for FPV inside the body could be interfering with the GPS? Note that I did not send my tx to DJI when they tested, but left the iOSD mini and the wiring inside. I've read plenty about people shielding the GPS with copper tape and am leaning towards this next, but want to make sure I'm not covering up another underlying issue. Most of the copper insulating mods seemed to be geared more towards the vision series...is the P2 non-vision susceptible to the same interference to the GPS?

    I plan on following up with DJI tomorrow but wanted to put this out there to get some input from the you all...thanks in advance!
     
  2. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up satellites

    A few more things to add...running v3.08 and in NAZA-M mode. Also, I have flown several times at our farm property and once at a large park. Each of those times I was able to pick up satellites much faster (a couple mins) and would get 7-9 sats. May have even got to 10 but not sure.

    This is what leads me to believe it has something to do with interference. I seem to be able to pick up okay in wide open spaces, but have significant issues in town where the sky is more obstructed.
     
  3. Mako79

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    Re: Issues w/ GPS, takes up to 20 mins to pick up satellites

    3 things...

    The GPS plug fix.
    viewtopic.php?f=27&t=30912

    And do an EMI Shielding - as known as the foil mod. Make sure you tuck the exposed GPS cable.
    And yes, I know its for the vision plus, but believe me, I did this on my P2nv and I could get sat pickups in narrow areas. You would want all the sats you can get to prevent ATTI switch.
    viewtopic.php?f=27&t=31054&p=313330&hilit=foil+mod#p313330

    The last is extreme - Not really required... its to replace a higher dbi GPS antenna.
    viewtopic.php?f=27&t=32311&p=318661&hilit=digikey#p318661

    I did the first 2 mods and have no issues..
     
  4. Meta4

    Meta4 Moderator
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    Re: Issues w/ GPS, takes up to 20 mins to pick up satellites

    Brian ... it's not clear from your story. Just need eliminate this to work out if the problem is in your Phantom.
    You say that it acquires sats relatively quickly on a farm or large park but not at home.
    This suggests that maybe your sky at home is restricted.
    How much of the sky is visible at home? If you have trees, buildings etc obscuring say half of the sky you will only be able to get about half the sats that are in your part of the sky.
    You can use a GPS app on your phone (like GPS Status on Android) or a handheld GPS to check how many sats are visible in your sky.
     
  5. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up satellites

    Thanks for the input fellas, the more I read the more I think it is a GPS interference issue. Meta4, thanks for the feedback that is what I was looking for…a way to eliminate potential issues and narrow it down to the source. Admittedly, I have not been using a GPS app to confirm satellites in the area but have previously used GPS Status for an older android phone I used to have. Upon downloading it last night, I think it further confirmed my concerns about the Phantom GPS not picking up satellites like it should. I was able to pick up 10 indoors (near a wall/window) and picked up 15 this morning as soon as I walked outside. I understand that available satellites change throughout the day, but I recall never having an issue previously with my phone picking up satellites and confirmed with the app. I will continue to monitor when I try to fly the Phantom.

    There are some obstructions that partially block the sky but in my opinion should by no means prevent the Phantom from picking up ANY satellites. A one story house to the east, a row of trees to the west (about 60 ft high) and a large single tree to the south (about 100 ft high). By no means ideal conditions, but with all of the foliage off the trees and still a good view of the sky to above, to the SE, SW, NE, N and NE I have a hard time believing it is an issue with not enough satellites available. But I do believe that those obstructions are having an impact on the GPS picking up satellites. I have previously tried to fly in my backyard and had issues picking up satellites, then drove a mile down the road to a large open park and it picked up satellites in a couple minutes. I’m rambling now…but thanks for the advice and I will monitor satellites with the app next time I attempt to fly.

    Mako79, thanks for the input on your experience with your P2. I think the foil mod is in order, but I hadn’t seen the plug fix in my searches before. Like many others have noted on the forums, I could not believe how loose that connection was when I opened up my Phantom to install the iOSD mini and wiring. I was planning on adding some electrical tape to it the next time I open it up, but will definitely look into putting a small wedge in there if it seems it will improve/ensure contact.
     
  6. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up satellites

    I have some copper tape on the way, but just finished tucking the GPS cable under the factory foil and doing the plug fix. Phantom has been sitting outside going on 10 mins now and still no satellites picked up. Again, it is not perfectly ideal conditions in my backyard but there is plenty of visible sky. The GPS status app indicates my phone has a fix on 20 of 24 available satellites right next to the Phantom.

    After giving it a full 10 mins with zero satellites, I powered off and unplugged the Zenmuse ribbon cable (at the Zenmuse, not inside the body) and gave it 5 more minutes...still zero satellites verified by FPV. Then I powered off again and unplugged the power and video cables to the ImmersionRC tx and gave it 5 more minutes...still less than 5 satellites verified by one green blink (indicating GPS mode) followed by three red blinks.The only things left inside the body other than the factory components are the iOSD mini and anti-interference board that came with the H3-3D.

    Trying to narrow down the source of the problem...not even sure if it is interference at this point or something else? I plan on doing the full EMI shielding mod when the tape arrives in a couple days and see if that gets many any where. Any other ideas in the meantime?
     
  7. Bill_Burkert

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    The battery on the gps module seems to be not holding a charge. If it is dead then it takes a while to get some charging then the gps has to load satellite info. I suggest you verify the small button battery and make sure it has good contact.
     
  8. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    I'm measuring 1.84v across the battery...what is normal?
     
  9. Bill_Burkert

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    I suspect it is a 3V lithium battery
     
  10. TuT

    TuT

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    Yup, button batteries are 3V. 1.8 is a dead battery. This could be your problem.
     
  11. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    It went up to 2.4v after I plugged it in to Phantom and powered it on for 5 mins but then drained down to lower than 2.

    I've read the forums quite a bit in the past several months and have never seemed this mentioned...is it a common issue?

    Anyone know if they are replaceable...it almost seems to be soldered in at the base and replacing the whole gps would be easier. Still waiting to hear back from DJI since I reopened my previous ticket a couple of days ago.

    Also, I gave it another 20 mins outside this evening and zero satellites. So now I was able to get up to 5 sats after 20 mins a few days after receiving it back from DJI, and have not been able to pick up a single satellite since then.
     
  12. Bill_Burkert

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    I doubt the battery soldered but rather the battery holder, soldering would be way to hot for the battery itself. Maybe post a picture because I haven't had my phantom 2 opened in a while.
     
  13. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    Don’t have a picture handy but will look closer this evening. It may not actually be soldered in, but the battery certainly isn’t moving with a moderate amount of force. I’m not comfortable using any more force. Maybe the coating on the PCB is acting as a glue around the battery? Either way, not sure I will be able to replace it? Any suggestions (still pending DJI’s response)?

    To be sure, I checked voltage again last night and it read 0v. Wasn’t 100% sure that I just wasn’t getting the leads on the battery terminals since they are small and tough to get to cleanly. I plugged the GPS module into the P2 for a few minutes and powered on the P2. Unplugged the GPS module and checked voltage again and got 2.4v. Repeated the same thing this morning. Read 0.2v initially and then I plugged in to P2 and powered it on for a minute or so before unplugging the GPS module and checking voltage again…1.7v.

    Thanks for steering me in the right direction (hopefully) Bill, this may end up being the solution. May have some trouble getting the actual battery out. I don’t want to risk damaging anything but certainly don’t want to send it back to DJI for 3-4 more weeks…suggestions welcome. Anyone else replaced a battery on the GPS module before?
     
  14. Bill_Burkert

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    So I don't think the battery is bad, I think it lost its charge and the gps just can't warm start itself. I suggest you allow the battery to charge and then disconnect the gps while the phantom is powered on and then reconnect the gps module. I think the gps the NAZA times out looking for the gps. If this doesn't work then after the battery has a decent charge turn off the phanton and turn it back on.

    If this doesn't work then I feel the gps lost its configuration and I don't know how to reload or where to the configuration file. It is normally a fddi connection but DJI is a closed system and replacing the gps may be your only option, thanks DJI.
     
  15. N017RW

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    I don't think it's a battery but rather a super-cap.

    Someone check me on this:
    The ephemeris data is updated about every 2 hours and valid for about 4 hrs.. Then there is the time required to download it. So any back-up [data] beyond more than 4 hours old is invalid and you must wait for a update/reload as well as TTF.

    The function of the super-cap is to reduce the TTF by maintaining the ephemeris data from one flight to the next within the super-cap's capability or approx. 4 hrs. which ever comes first.

    As far as minutes to achieve TTF, you have SNR issues due to on-board or local environment noise, atmospheric conditions, etc. or possibly a damaged component on the GPS module.

    My $0.02.
     
  16. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    Thanks for the input. I am going back to DJIs response to the repair work they recently did, pasted below...

    When we first test flew your Phantom to drain both batteries to find the flaw that would auto descend, we could not get a GPS lock no matter how long in was in the air, even after replacing the GPS module it still had the same GPS problem. The center board was at fault, even though it registered the GPS firmware and loader in the Phantom assistant software. - Possibly damaged after the crash.

    Does this shed any more light on the situation? What are they referencing by center board? The NAZA controller or the board that all components are mounted to? Or something else? Whatever it was, I feel like it didn't solve the problem and I am having the same issues that they saw during testing of the unit.
     
  17. N017RW

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    I have to guess it is the main PCB to which the Naza is mounted on top of.

    As to the reason for it's replacement I don't know. But among other things, the GPS, compass, battery data, and Naza plug into it so there could be a routing or buss issue that was corrupting communications or data.

    Just a guess. But from what you're saying it hasn't helped you.

    Have you tried driving to a new location to see if the GPS time-to-fix is improved?

    It would eliminate location as an issue.
     
  18. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    Haven't tried a new location yet but agree that I need to. May be getting a bit ahead of myself until im able to check. Overtime, sick 2 yr old, 8 month pregnant wife, bathroom remodel, house painting and cold weather have limited my testing to backyard only. Ya know, just life haha.

    That being said, what should be expected for gps reception in a "treed" residential area? I've never had an issue with cell phones (cellular and wifi off) or an older Garmin handheld gps. I can see a residential area being more limited on number of sats, but zero??
     
  19. N017RW

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    Sat density for the most part is equal anywhere on the globe.

    Local conditions vary too much to say that you are in a bad area. Trees can reduce signal strength and even that varies by density and the shape of the leaves, etc.

    From an on-line source:
    "The system is designed to ensure that at least four satellites are visible at least 15 degrees above the horizon at any given time anywhere in the world."

    The P2 V+ is known to have some noise from the camera, and related, cause interference with the GPS receiver. Thus the added 'foil mod' so many have done.

    I'm assuming you work outside the home, if so, take it to work and test it there.
     
  20. brianh

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    Re: Issues w/ GPS, takes up to 20 mins to pick up sats (UPDA

    I have verified that there are satellites in the sky directly above with phone app while I have the p2 outside waiting for satellites.

    Back to the GPS module, I'm not all that familiar on how they are supposed to operate....is the battery supposed to maintain a charge or is it normal that it is losing it's charge each time the p2 is powered off for an extended period of time? I would think a battery should hold its charge, and that either the battery is self-draining or their is a short somewhere causing it to drain (maybe more likely?). Am I way off base or is this how they are intended to operate?

    Thanks and sorry for all the questions, just trying to get to the bottom of this so I can get it back up in the sky.

    Brian