Neo M8N and Pixhawk, No GPS fix

Good afternoon everyone.
I recently finished my 3D-Printed X4 frame, and have installed all required (Pixhawk) electronics. Everything is working great, and I have done a successful test flight; But.. The GPS seems to be unwilling to work with the Pixhawk unit.
I am getting the "No GPS Fix" message on Mission Planner, even after leaving the unit outside for nearly an hour in an attempt to acquire GPS satellites. I have followed the manuals instruction, and I am certain I have proper connection between the M8N and the Pixhawk.
In the Mission Planner program terminal, I'm seeing a repeating "Need 3D fix" followed by code. I've also tried connecting via u-Center 8.2 and there is no GPS information whatsoever. I really am lost, and have been researching this since 8AM today. (Almost 12 hours..)
Does anyone have any idea what's going on?
Any help would be greatly appreciated.

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  • That is a counterfeit ublox part.  That is a Chinese knock off.  You have been cheated.  The way to tell is quite simple.

    Each ublox chip has a unique serial number.  Every ONE!  The smart tag on the ublox chip that you have is a QR code.  It is not a digital serial number.  The smart tag on a genuine ublox chip is unique.

    I read the tags on my cell phone.  To do it, I use a close up camera to take a picture of the 'ublox' part.  I put it on a large computer screen.  Then I use the smart tag reader program of my phone to interpret the tags.  The ublox digital tag will match the printed serial number on the label.

    I have 2 dozen units now that are going back to China.

    The fake parts will have something that is not matching the serial number.  Also if you buy more than 1 of the units, from the same supplier, you will find that all the serial numbers are the same.

    Finally I suspect that ublox use a check digit in their serial number.  So generating valid serial numbers for fake parts needs to know the algorithm used to generate the real serial numbers.

    Two pictures attached.

    Note the difference in the smart tags.  One is a digital tag the other a QR tag.  Not the same.

    See picture 2031a has unique digital smart tag unique to each unit.  Picture 2032a has a QR tag.  The QR tag in the picture says NEO-6M.  Yet the part says NEO-M8N.  Also all 3 units have the same serial number.

    I report the vendor of the fake parts to ublox america, with the store number or seller name on ebay, BangGood, AliExpress or Alibaba.

    Ublox take counterfeit parts seriously.


  • I've got the exact same issue-- it's not a bad GPS-- I took my m8n and connected it to an APM and it worked fine. If I rearrange the wires going into the Pixhack, I get "no gps" in Mission Planner - if I get the wires connected in what I *think* is correct, I get "no gps"..."no fix"..."no gps"..."no fix" and so on-- I've done the same things, taken the thing outside for a long time, all that-- there seems to be a problem with the FC itself simply not understanding what the GPS is sending. I got to a point where I simply had to remove the Pixhack from my 680 frame an replaced with an APM for the time being-- I was going to buy a CUAV gps on the assumption that something has been done to the Pixhack that limits its compatibility. 

  • Looking at your pictures the wires appear to be correct. The yellow RX from gps is going to TX on pixhawk and TX from GPS is going to RX on Pixhawk. The other thing you might do with an ohm meter is check that the wires aren't broken somewhere. If everything checks out then start the return process. 

    When you checked the GPS through Ucenter where you running through the pixhawk or a separate FTDI adapter?

    • How were you and Ublox able to determine it was a fake? I've got a bunch of the cheap M8N's and I'm wondering if they are fake.
      • Well, if on a sunny day you get 10+ satellites and a hdop close to 1.0 they are real.

    • Rob,
      I used the Pixhawk Controller as a way to access the GPS in u-Center.
      According to u-Blox, this isn't the best way to do so, but it should still provide data.
      I got off the phone earlier today, for a second time, with u-Blox support.
      It seems the issue is simply that the whole GPS, including the u-Blox processor on the circuit-board, is fake.
      I'm really praying I don't start getting issue with the Pixhawk unit...

      • I would like to know how to tell a fake from a genuine Ublox M8. Anyone have any pointers?

        • The u-Blox support team is extremely helpful.
          I would send them an image of your board, and they will be able to distinguish if it's a genuin u-Blox.

  • I recently got a bad M8N as part of a knock-off pixhawk package from ebay.  It actually worked for a few minutes but then stopped working.  The GPS itself was clearly working since the blue light indicated a signal lock, I even used u-center to check the baud rate which very spottily indicated it was functioning, but then went dead...I figure it was something wrong with the tx circuit but didn't want to waste any more time with it. Seller was unresponsive..pretty frustrating.  I ended up just ordering another one for $25 or so from a different seller that took about a month to arrive (luckily I had other crafts I could cannibalize from in the meantime).  The annoying thing isn't necessarily the cost or even that the seller wouldn't respond (they churn these things out with no quality control - I accept that risk for the price).  The annoying part is just the wasted time troubleshooting it...there's always a billion reasons it may appear to not be working via mission planner (interference, pixhawk problem, wiring problem, firmware incompatibility, etc. etc. etc...) and you don't want to blame it on brand new faulty hardware without checking into those billion other things somehow. :)

    • Yeah, I'm a bit worried about the Pixhawk unit I got too.
      I've flown it quite a bit now, but in alt-hold, it bounces up and down and is UNABLE to "Altitude-Hold"..
      $25 for a GPS, well, fine. But $200 for the GPS, Pixhawk, and a few accessories that may or may not work; That's a bit intimidating seeing as I have less than a week before eBay considers this a "Done Deal"....

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