3 GNSS on Pixhawk 2.1

Hi All,

Got a query I hope someone may have some experience with. I have just purchased new avionics to upgrade my large octocopter (pixhawk 2.1, 2x Here GNSS, Mauch power system etc.) and I was planning on running 3 GNSS in total on this system.

Ideally GPS1 and GPS2 ports will be used for the the Here GNSS and the third GPS will be a Piksi RTK, which I believe I can plug into the Telemetry 2 port (serial 2). My intention was to run in blended GPS mode for the two HERE GNSS, and just log the Piksi output for later post processing.

Question is, if I use the blended option, will it try to blend all of the different GNSS, or will it only try to blend those conneted to the dedicated GPS1/2 ports (I hope its the later!).

If anyone knows anything about this then please get back to me.



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Hi Simon,

Arducopter has support for only 2 gnss devices, you can use any ports you’d like but I believe only two will work at a time.

I don’t know how you plan to log gnss data, afaik it is only supported on certain ublox devices (logging to pixhawk sd card that is).

Many rtk solutions have onboard storage (sd card, on-board flash etc.) to which they log raw observational data to be used for post processing. The piksi evaluation board looks like it has one. It is probable you just need to supply power for it to start logging.

I am not actually sure what happens if you set more than 2 serial ports to be used for gps, maybe they get id’s by which one connects sooner or something.

What I think you should do is just set serial2 (or whichever one you use for the piksi gnss) unconfigured (-1) and set up the piksi to log on sd card or usb device, here is the how to guide on piksi’s site.
They explain how to log to usb, but it should be able to log to sd though I have never seen or used piksi device.

Still, why not use piksi as the 2nd gnss device, should it not be better than ublox m8n? From what I can see it is a dual frequency device so it is more resistant to interference (less glitches).

Thanks Fr0sst,

Unfortunately I have the older Piksi (L1 only, RTK only, no internal storage logining and has a tendacy to drop its lock a lot!) so I simpley wanted to log its position and status and not use it controlling the UAV at all.

It was only a temporary solution anyway as we will have an EMlid Reach when they start delivering the new ones some point in June, and that will log internally so won’t be connected to the pixhawk at all.

Doing the maiden of the rebuild today (sans piksi) so hopefully it will all work!