Setup Tilt Survey using SparkFun GNSS Flex pHAT - ZED-X20P & IM19 IMU

[steve-talent]

Title shows GNSS hardware I'm using for a rover. Here's more detail:

PyGPSClient 1.5.18
X20P Firmware HPG 2.0.2
Raspberry Pi 5 -- 8 GB

I'm running a base station with a similar device, except no IMU, which is running NTRIP CASTER.

The rover is running NTRIP Client connected over my LAN.

I configured the X20P UART1 and UART2 to run at 460800 baud.
I used the Preset UBX Configuration Command: Enable NMEA High Precision

I'm getting a solid RTL fix.

I tried using the TTY Preset Feyman IM19 Tilt Survey Setup. Nothing seems to be happening. I will update the geometry specified in the preset after I get things working.

I read that I need to enable GNGGA, GNRMC, and GNGST, but I don't know how to do that. I see RMC messages, but not the other two. Maybe that's all I'm missing.

How do I enable the required messages?

Are there other UBX configuration items I should set?

Thanks!

[semuadmin]

Hi @steve-talent

I'm a little confused - are you trying to apply tilt compensation on a rover or on a base station? Can you clarify exactly what it is you're trying to achieve and what you're expecting to see?

I read that I need to enable GNGGA, GNRMC, and GNGST,

Where specifically did you read that (link?), and what was the context?

GGA and RMC should be enabled by default. GST is a specialised pseudorange noise statistic message that would need to be explicitly enabled. The Feyman IMU initialisation procedure is fairly convoluted - you're best referring to the manufacturer or retailer for details (Sparkfun have useful tutorials here and here) - but in essence it involves:

1. having an RTK-FIXED status first
2. ensuring the IMU is correctly aligned with the GPS
3. configuring the IMU using the appropriate AT+ commands (see TTY preset panel), based on the alignment in (2)
4. trigger the IMU to enter initialisation mode by vigorously shaking its mount

On the X20P, enabling or disabling specific NMEA or UBX messages is done via the UBX Configuration CFG-VALSET/DEL/GET panel. You have to choose the appropriate port e.g. UART1 or USB, depending on how you're connected to the device, e.g:

If you can clarify your objective here I may be able to provide further guidance.

[steve-talent]

Hi @semuadmin

Sorry, I typed in the names wrong. The messages have a 'GP' prefix, not 'GN'. I found that information here in a box labeled "Abstract".

I think I have everything set up correctly. I suspect my problem is in the Feyman IMU initialization procedure. In the "Tilt Compensation with SparkFun RTK Torch" video, the user listens for beeps. I don't have a speaker on my rover. If I add a speaker, I will need to know when and how to trigger a beep. How is the initialization status sent from the IMU back to the host?

I am testing everything right now using a VNC connection from my desktop computer to the rover's Raspberry Pi where I'm running PyGPSClient. The rover is currently mounted outside on a tripod. I'm showing the IMU Monitor, hoping to see data returned. After sending the Feyman IMU 19 Tilt Survey preset, I go outside and shake the tripod. With no audible feedback, I have no way of knowing if I am triggering the IMU.

Can you explain how I should approach debugging my setup? How can I see messages being sent by the IMU? For example, AT+VERSION and AT+READ_PARA=SYSTEM/ALL should return information. Is it possible to see what is returned in PyGPSClient? If so, how?

My end goal is to be able to do basic surveying while using SW Maps or similar application to record points and tracks.

[semuadmin]

I'm happy to help with general PyGPSClient issues but I'm not really in a position to assist with the Feyman setup - the Sparkfun Community Forum is by far your best resource here (FYI I did work quite closely with Sparkfun product specialists in developing the necessary TTY command and IMU monitoring functionality, so I'm reasonably confident it works but - as I say - I do recall it being a fairly complex process).

I am testing everything right now using a VNC connection from my desktop computer to the rover's Raspberry Pi where I'm running PyGPSClient. The rover is currently mounted outside on a tripod. I'm showing the IMU Monitor, hoping to see data returned.

You're on the right track - this is exactly what I did.

In general terms, in order to communicate with a device like the Feyman IM19 via the ASCII TTY protocol, you need to:

1. ensure you're communicating via the appropriate UART port at the correct baud rate, especially when using one of the Sparkfun PHAT boards, which have a variety of UART configuration options.
2. ensure the GNSS device (F9P) is outputting the requisite high-precision NMEA sentences to the IM19's input UART port - the IM19 needs these to complete the tilt compensation calibration routine.
3. enable 'TTY Protocol' in the PyGPSClient settings panel (this will disable all other input protocols).
4. send a TTY command (e.g. a Feyman AT+ command) via the TTY Commands panel with 'echo' enabled; you should see both the outgoing command (TTY<<...) and the incoming response on the console (you may have to refresh the console first).
5. switch back to 'NMEA protocol' mode and monitor the output of the IMU device via PyGPSClient's IMU widget. In the case of the Feyman IM19, you're looking for a specific set of status codes arriving in a specific sequence via GPFMI messages (this is the visual equivalent of the 'beeps' you refer to on the RTK Torch - the Sparkfun tutorials outline what the various status codes mean at each stage of the calibration process) e.g.

HTH

[steve-talent]

Thanks!

I will refer future questions regarding the specific hardware to the SparkFun community.

best regards,

Steve

[semuadmin]

FYI I do have the original correspondence with Sparkfun re. the calibration process, but I need to check with them if it can be shared in the public domain. If it's OK, I'll post the link here.

[PaulZC]

Just adding a link to @steve-talent 's question on the SparkFun Forum:

https://community.sparkfun.com/t/help-needed-for-tilt-compensation-setup-using-gnss-flex-phat-zed-x20p-im19/67319

Best wishes,
Paul