Basic Base / Rover setup with GPS-RTK2 (ZED-F9P)

GPS/GNSS Development Boards
1

I’m having trouble getting 2 ZED-F9Ps to communicate in a base / rover setup, and it’s likely that I’m new to a lot of this and have much to learn so bear with me. I have 2 GPS-RTK2 boards (ZED-F9P boards). I have separate antennas setup on my roof and both work fine as rovers with external NTRIP for RTK, but I want to use one as a base and the other as a rover. My goal is to see how accurate I can get the rover in order to do some simple surveying in real time.

Following SparkFun’s guide (https://learn.sparkfun.com/tutorials/gp … ion-source), I have can get the base unit to display the data to the Arduino serial monitor, but I can’t find any information about how to use this to feed to my rover.

I have tried connection the base and rover with a QWIIC (I2C) cable but can’t get it to work. One would freeze everytime I plugged them together, however I switched the address of one RTK2 board to 0x43 since both were 0x42. This prevented them freezing but the rover never seemed to see the data for RTK.

I have 2 Bluetooth modules that can plug into the boards as well. I also have plenty of jumpers and other cables laying around.

What is the easiest way to get the base and rover communicating for RTK? As this is just a test for now I have no problem having a cable between the two boards sitting on my desk.

Would it be better to setup the base through u-center instead of the Arduino library?

Thanks in advance for any help.

2

Hi cdundorf,

[This section of our Hookup Guide will be the best place to start for sending correction data between your two ZED-F9P RTK2 Modules. I would recommend taking a look at the two links to the Ublox documentation (Setup Guide and Ublox Integration Manual) to get more familiar with how to configure them as you can either use u-center or SparkFun’s Arduino Library. It is probably best to either start with one or the other, but you could use the Arduino Library to set up your base and u-center to monitor the accuracy of your rover as RTCM data begins to be sent to it.

If you want to use the example from the [SparkFun Ublox Arduino Library, you would need to customize the “processRTCM()” function to send the RTCM data over your preferred communication protocol. For testing, you could probably use an unmodified version of ZED-F9P Example 3 “Start RTCM Base” and run jumper wires from the HW UART pins on the Arduino (usually D1 and D0) to the RTCM correction serial port on the rover ZED-F9P. If you have a connection open in u-center to the rover receiving the RTCM data, you should be able to watch the fix accuracy increase if everything is working properly.

To learn more about the “processRTCM()” function in our library, I would recommend taking a look at the cpp source file [here as that will have some helpful notes about the RTCM data and how the Arduino library processes it.

Once you have gotten things working with a wired connection, you could move to a Bluetooth connection with the modules you have by modifying the RTCM Base Example to send the RTCM data via a SoftwareSerial connection similar to what we outline in our [Bluetooth Mate Hookup Guide.

I hope this information helps you get your rover/base testing started and gives you some ideas on how to move forward with it once you have gotten them working properly. Let us know if you have any other questions about the ZED-F9P and we would be happy to help as much as we can.](Using the BlueSMiRF - SparkFun Learn)](SparkFun_Ublox_Arduino_Library/src/SparkFun_Ublox_Arduino_Library.cpp at master · sparkfun/SparkFun_Ublox_Arduino_Library · GitHub)](GitHub - sparkfun/SparkFun_Ublox_Arduino_Library: Library to control UBX binary protocol and NMEA over I2C on Ublox GPS modules)](GPS-RTK2 Hookup Guide - SparkFun Learn)

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Thanks for the reply and for providing the links. We are now able to get the units working on the bench. Our next move is seperate the two ZED-F9P boards from their respoective Windows laptops each by about 100 to 200 feet but since the signal will be going through a building I’m not sure if the Sparkfun Bluetooth Gold modules will work. Could we use RS-485 instead using something like the SparkFun Transceiver Breakout - RS-485 and SparkFun USB to RS-485 Converter over CAT5 cable? Is there a better way? The RS485 board is half duplex, is that ok with the ZED? If RS-485 is a good way to go, what components are needed to go between the ZED and a USB port on the laptop? Starting at the ZED would it be:

  1. Jumper wires

  2. SparkFun Transceiver Breakout - RS-485

  3. RJ-45 jack

  4. 50 to 150 foot LAN cable with RJ-45 plugs

  5. RJ-45 jack

  6. SparkFun Transceiver Breakout - RS-485 and SparkFun USB

  7. USB cable

  8. Laptop

Thanks,

Chris

4

Hi Chris.

We’ve never tried something like what you’re attempting before so we can’t provide much solid advice. All we can say is give it a try and see.

If you have the range, Bluetooth is full duplex where our RS485 breakouts are not. If you need full duplex communication, you may need a different RS485 product than ours ,or you might need two on each end. (one for transmit and the other for receive.) RS485 should give you the distance you’re looking for though.