I bought 2 IRIS+, received them last week after waiting 2 weeks before they were shipped.
Both of them are giving yellow flashing. When I plugged one into mission planner I say it was giving a PREARM: GPS HDOP HIGH WARNING. The HDOP is about 2.6 - 3.0.
I am assuming it’s the same issue with the other IRIS+. Both are getting GPS locks according the the telem on the remote controller and droid planner 2.
This happens if you have Fence enabled. Not because of it, but it won’t let you arm until HDOP is below the value expressed by the GPS_HDOP_GOOD parameter if Fence is enabled. The reason is that if it doesn’t have a good fix, it won’t be able to RTL reliably if it hits the fence. So it doesn’t let you fly.
You can either turn GPS Fence off, or increase GPS_HDOP_GOOD to something like 350 (valid range is 100-900). Higher HDOP value will mean it accepts a less-accurate fix before takeoff. Fence off means it won’t RTL if you get too far away.
I had the same issue last December. I increased GPS_HDOP_GOOD to 350 and monitored it. It allows arming sooner, and HDOP improves once you’re flying around.
You will also get the yellow flashing LED when HDOP value is high and you are trying to arm in a GPS-assisted flight mode (e.g. Loiter).
Read more about HDOP and why what you are seeing isn’t actually HDOP here: cloud-surfer.net/2014/09/12 … ying-iris/