simpleRTK2B+heading not communicating

Q&A forumCategory: QuestionssimpleRTK2B+heading not communicating
Nick Gamroth asked 2 months ago
I’ve got a singleRTK2B+heading unit, but I’m not able to get valid heading readings out of it.  Here’s what I’ve done so far:

  • Upgraded firmware on both units to the latest version available from u-blox (1.32)
  • Applied the 1Hz configuration files as instructed in the Ardupilot tutorial
  • Connected to an Ntrip source in u-center connected to the COM port of the base device (small board)
  • Connected another u-center instance to the rover board to monitor messages

At this point, the base board u-center instance shows 3D/DGNSS/FIXED and what looks like an accurate location.  The rover board only shows 3D/DGNSS.  The “NO RTK” LED on the base board is off, and the “NO RTK” LED on the rover board is solid on.
My guess here is that the two boards are not communicating properly, but I’m not familiar enough with the platform to try and diagnose this myself.
I did check UBX-RXM-RTCM on the rover board, and it says it’s receiving 1077, 1087, 1097, 1230, and 4072.0 but I’m not totally sure what that means.
Is there somewhere in the configuration I should be looking to try and debug this?

replied 2 months ago

If the rover board is receiving the RTCM3 messages, then its clearly communicating.
The communication only needs to occur in a singular direction.

You’d perhaps want to focus on the separation of the antennas and their respective views of the sky.

Nick Gamroth
replied 2 months ago

The antennas are 2.5m apart and mounted on steel plates. I’m testing in a wide open parking lot. I think the view of the sky is OK because I get fixed rtk from both boards if I feed them both ntrip data.
Should I see the no rtk LED turn off on the rover if it’s communicating with the base board? I would expect it to get the same corrections if everything is configured properly.

replied 2 months ago

Well both units should get into RTK Float, and then RTK Fixed.
On my systems, using a pair of the full sized boards, I see the UART2 LEDs blinking, and the TIMEPULSE LEDs blinking in unison.
Can see RTCM3 data acceptance with UBX-RXM-RTCM
Technically the data isn’t corrections, each unit gets different data.
The secondary unit gets observation data from the primary, along with position/velocity about how it’s moving.
The UBX-RXM-RTCM should show count metrics for each message, and these should be counting together. And I think UBX-MON-COMMS will show how data is processed and if some isn’t being decoded as RTCM3.

Staff replied 2 months ago

We don’t have yet the updated configuration files for moving base and firmware v1.32.
Did you update an older fw configuration file?
As clive mentioned, the fact that your rover is receiving those RTCM messages is a good sign and should bring it to RTK float/fix pretty fast (if antenna signals are good).

Nick Gamroth
replied 2 months ago

Very strange, but I left the system alone for a few days and it appears to be working when I came back to it. Not really sure how that’s possible. Maybe I had some unsaved settings that were causing problems.
I’m still using 1.32. Should have mentioned that I ignored the warning about the settings file being for an older version of firmware.

One thing I may be misunderstanding about this device is whether or not I need external RTCM data. When I start the boards up, the rover board “No RTK” LED shuts off after a bit and I start seeing what looks like correct data on UBX-NAV-RELPOSNED. This is without the u-center NTRIP client running or any other NTRIP client connected.

replied 2 months ago

For exact POSITION you’d need external RTCM3 data
For secondary unit to determine it’s relative displacement (direction, distance, attitude) to the primary, NO

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