I was wondering if it is possible to log the data from the rover on the base by sending it back over the radio link. If so, would this work with multiple rovers as well?
Radio in this context is a half-duplex medium, getting multiple devices, synchronized to GPS, talking all at roughly the same time, probably not a good plan.
You’d likely want to given each rover a turn, and cycle between them in the time domain.
Different Radios have different bandwidth and contention algorithms.
Review the documentation for your chosen radio sub-system, and see what configuration and anti-collision/contention methods they provide for.
> I was wondering if it is possible to log the data from the rover on the base by sending it back over the radio link.
Yes. CFG-PRT in the rover. In u-center configuration view (old style, Ctrl+F9) go to PRT (ports), choose UART2 as the target, 1 – NMEA as protocol out (keep RTCM as protocol in) and save. By default the XBees are configured in AT (transparent) mode so the base should start receiving data straight away, this can be read via the base radio’s USB port.
> If so, would this work with multiple rovers as well?
Yes (untested by me as of yet)
However you have no way of knowing which data is coming from which rover (and as Clive1 says, they may end up talking over each other mid-sentence). So what you want here (again, untested so far) is to switch the radios to API mode so that you can get the sender addresses and send each packet to a different queue. For this you will have to decouple the radios from the GPS module and stick a microprocessor in between to push packets in and out of the radio in API mode. It should be possible to do this just on the base station and leave the rovers as they are. But again, I haven’t tested yet.
Note also that zed-f9p has own logging capabilities. Check in the interface description UBX-LOG-CREATE message.
Comments of Clive1 and Ardusimple very helpful. Using multi RF at the same time will cause a conflict bandwidth. However, this problem has been solved on ESPrtk 2.4.1, it has supported the sending of NMEA (multiple Rover) in real time for connecting WIFI (RTK offline) and MQTT or NTRIP (RTK online).
MNEA messages will be placed in Waiting-stacks by agreement on the waiting time after they connect with each other (or to the server), besides that – each message will be assigned an ID for each Rover.This will help the messages can be classified later. You can read more here about Multifunction RTK linking on ESPrtk.
I would like to send my rover position to my base to get it back to my computer.
On the Rover I send the GGA frame on the UART2 but the “GPS=>XBEE” don’t blink.
When I connect the Xbee modem the base on a serial reader , nothing appear.
Is there anything more to do ?
Make sure that UART2 is enabled (it probably is) and that NMEA output on UART2 is enabled (it probably isn’t).