GPS Shield Weirdness??

Hi Everyone,

I have owned an original IRIS since March of 2014. I just recently got around to installing the IRIS+ upgrade kit. The upgrade kit came with a GPS shield which I installed as part of the upgrade. You should know that I had also updated Mission Planner, the firmware to the latest releases as well as moving the Pixhawk as advised by the Improvement Update. I then recalibrated the radio, Acceleration, ESC, etc. That is when the weirdness started. I couldn't arm and received error messages for NEED GPS FIX, BAD VELOCITY, HIGH GPS HDOP. After reading a number of forums I found that I could not arm without setting the GPS_HDOP_GOOD parameter to 500! After communicating with Alan at 3DR I was cautioned that this value should not exceed 230 (Alan and 3DR support has been great). So I suspected a GPS hardware failure. I opened the shell and removed the GPS shield and traced all the connections. Everything looked good so I reassembled the IRIS+ without the shield. The result was GPS lock in 30 seconds! I dialed back the GPS_HDOP_GOOD parameter to 150, and I am arming and flying around with no problem. So I am wondering if anyone else has had similar experience with the GPS shield. I had a similar issue with my Blade 350QX...in an effort to block the EMI from my GoPro H3+ I applied copper tape to the bottom and sides of the Taoglass antenna (I upgraded this from the original antenna). I was never able to acquire GPS Lock until I removed the copper tape from the sides of the antenna. Should I reinstall the IRIS+ GPS shield or simply ignore it?

Replies

Erik Graham March 21, 2015 at 10:13am

I think you might still have an issue. 30 seconds seems like a long time to get GPS lock. Mine locks in 10 to 15 seconds. Anyway, you definetly need the shield. You might have just inadvertently fixed a loose cable while removing the shield.
- Mark Stanoch > Erik Graham March 21, 2015 at 10:50am
  
  Do you expect a hardware failure? Should the GPS antenna be replaced?
- Erik Graham > Mark Stanoch March 21, 2015 at 12:11pm
  
  Hmmm. Hard to say. 30 seconds isn't that bad and it obviously depends where you are in the world and where the satellites happen to be at that time. I should also say that in new locations my Iris+ does seem to take awhile to get a lock the first time. That could be my imagination - I haven't tested it.
  
  In general though, it locks on very quickly. Surprisingly so compared to my previous drones (DJI models).
  
  I'd put that shielding back in carefully. Make sure nothing conductive is touching any components and then test it out for awhile.
- Mark Stanoch > Erik Graham March 22, 2015 at 5:04am
  
  Well I reapplied the GPS shield this morning and was not able to acquire a GPS lock after 15 minutes. I made sure that the shield was not touching the antenna. So I will try covering the GPS antenna with electrical tape and then reapplying the shield. I hope I don't have to replace the GPS!
- Erik Graham > Mark Stanoch March 22, 2015 at 6:08am
  
  Well that stinks. And your sure all cables are properly connected? If you remove the shield again, does it start working again? If so that obviously implies your somehow installing the shield incorrectly.
- Mark Stanoch > Erik Graham March 22, 2015 at 6:27am
  
  In a flash of brilliance I reinstalled the shield but turned it upside down. Now I acquire GPS lock in10 seconds or less. So I have to conclude that the shield is defective. I did notice a bit of copper protruding beyond the edges. So I will ask 3DR for a replacement but use this one in the meantime.

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