Having read that the Quectel EP06 module can contain a GPS I decided to investigate. The purpose of this post is to share info, 'cause while it works there are some mysteries…
First of all, the EP06-A modules I got contain the GPS option: yay! One has to open the router (there are two screws hidden under the label in the back) and connect an antenna to the unused antenna port on the EP06 (there’s a little “G” label next to it).
In the EP06 hardware manual it says:
It is recommended to use a passive GNSS antenna when LTE B13 or B14 is supported, as the use of active antenna may generate harmonics which will affect the GNSS performance.
The first mystery is whether the EP06 provides power for an active antenna or whether one would have to inject power externally. The hardware manual is not clear on this. I ended up using a passive antenna with a 30cm long cable, which seems to be the max available.
To enable the GPS one has to issue an AT+QGPS=1 command on /dev/ttyUSB2 and then one can read the nmea sentences on /dev/ttyUSB1. There are additional commands to configure the GNSS functions, but they’re very limited compared to “regular GNSS chips”. The details can be found in the Quectel EP06&EG06&EM06 GNSS AT Commands Manual. I believe one has to register to download that one.
The second mystery is that I don’t manage to change the configuration of which GNSS systems are enabled and which sentences it outputs after having enabled the GPS. Basically after power-on I can configure and enable, after that even disabling the GPS and changing the config has no effect until the next power-cycle.
The third mystery is whether the GNSS chip supports SBAS augmentation (e.g. WAAS). The docs are silent on that, but it’s hard to believe that a GNSS chip in 2019 doesn’t support it. I’ll have to keep an eye on what the thing outputs after it has had time to download all the GPS info. (Update: after 12 hours the module sees 23 satellites, uses 7 for a fix and none have ID>120, which would indicate WAAS. It reports a “2D fix”.)
As far as I can tell, the actual chip used is from Mediatek, but I haven’t poked further correction: “Qualcomm Location Gen8C Lite” about which there is very little info online. I have also not figured out whether there is a way to get to the PPS for time synchronization.