RTK difficulty using XBee Radios

GPS / RTK / GNSS
1

Hi All, I hoping someone can point me in the right direction. After looking at AgOpenGPS posts as well as other GPS sites and haven’t found a solution. Here’s the scenario. Trying to setup my own base station. Using the AdruSimple units, and Xbee radios to stream RCTM from base to rover. The core issue is the rover’s “No RTK” led is always on solid.

Base Station LEDs
“GPS FIX” LED blinks
“GPS->XBEE” LED blinks

Rover Units LEDs
“GPS FIX” LED blinks
“XBEE->GPS” LED blinks
“No RTK” LED on solid

So according to my understanding the base Xbee radio is transmitting, the rover XBee radio is receiving, but no RTK is happening.

I followed torriem’s instructions here for the configuration of the base station.

Any suggestions on how to troubleshoot this further?

Thanks,
Kyle

2

Really need to open each in u center and see the status of them. They will need a clear view of the same sky. If you can read the output of the rover gps, it will tell you if you are getting corrections and if they are stable enough to get a true fixed status.

3

Thanks Ken. My fix mode is 3D, not float or fix, in U-Center. Both base and receiver are side by side (with more than 20 satellites in view).

I don’t know how to see what is being sent on UART2 (Xbee radio plugged into the ardu unit). I believe it should only be the RCTM msgs according to the config, but maybe I have something messed up in the config.

4

Make sure the baud rates match between everything. Just because the LED blinks doesn’t mean the receiver baud matches the transmitter. Specifically make sure the rover xbee UART baud matches the rover GNSS receiver uart2 baud. Then you can also enable ubx-rtcm message on the rover to see if it’s able to read the rtcm data.

5

Thank you! I am not a hardware guy and I didn’t realize that the xbee had it’s own UART settings. The problem was a mismatch between the Ardu board the XBee module.

For reference for other people with the same problem. The default for the XBee radio is 9600 baud and once I changed the Ardu board configuration for UART2 to 9600 baud for both the base and rover, presto it started working.

6

Have you told us which XBee radios you are using? The arduSimple radios are 115200 by default.

7

I am using the Digi XBee radios model XB-9XR.
This one specifically: [https://www.mouser.ca/ProductDetail/888-XB-9XR-DMST-001]

For others in the same situation, there are two programs from Digi (XCTU and Xbee Studio), available on the Digi website, that can be used to change settings on the radio, like the baud rate. I haven’t done that yet so don’t know the details.