Feature Request: add lever-arm configuration for F9R

[Eric-FR]

With the last firmware update of the F9R (FW1.00HPS1.40), Realase note (7 February 2025) tells:

2.4 Lever arm support
In systems where the level of accuracy is comparable to the offsets between the various
reference points like GNSS antenna phase center, IMU reference frame, middle of the vehicle
rear axle, these offsets need to be specified generally referred to as lever arms. In previous
releases of the product, the lever arms were confidential messages reserved for advanced
users. These messages are now publicly available to user and supported by u-center.

I would be very interested in being able to set such parameters, as it is difficult to put the F9R juste above the centre of rear axle.

Integration manual (21-Feb-2025):

3.2.4.3.3 User-defined lever arm
The lever arm keys CFG-SFCORE-IMU2CRP, CFG-SFODO-IMU2VRP and CFG-SFIMU-IMU2ANT must be interpreted in the following way:
• LA_X: Corresponds to the x-axis component of the lever arm.
• LA_Y: Corresponds to the y-axis component of the lever arm.
• LA_Z: Corresponds to the z-axis component of the lever arm.

Interface description (18-Feb-2025, Protocol version 33.40):
One can find corresponding configurations in

6.9.20 CFG-SFCORE: Sensor fusion (SF) core configuration
6.9.21 CFG-SFIMU: Sensor fusion (SF) inertial measurement unit (IMU)
configuration
6.9.22 CFG-SFODO: Sensor fusion (SF) odometer configuration

[PaulZC]

Hi Eric (@Eric-FR ),

Thank you for the "heads-up"!

What would you like us to do? Adding the new configuration Key IDs is ~easy. But are you also asking for helper methods to set the lever arm components?

You can set the Key IDs manually if needed. This code example compiles but is untested:

#include <Wire.h> //Needed for I2C to GNSS

#include <SparkFun_u-blox_GNSS_v3.h> //http://librarymanager/All#SparkFun_u-blox_GNSS_v3
SFE_UBLOX_GNSS myGNSS;

void setup()
{
  delay(1000);
  
  Serial.begin(115200);
  Serial.println("SparkFun u-blox Example");

  Wire.begin();

  //myGNSS.enableDebugging(); // Uncomment this line to enable debug messages on Serial

  while (myGNSS.begin() == false) //Connect to the u-blox module using Wire port
  {
    Serial.println(F("u-blox GNSS not detected at default I2C address. Please check wiring."));
  }

  bool result = true;
  result &= myGNSS.newCfgValset(VAL_LAYER_RAM); // Create a new VALSET construct
  result &= myGNSS.addCfgValset(0x30060020 | UBX_CFG_I2, 0);    // Set CFG-SFIMU-IMU2ANT_LA_X in cm (I2, int16_t)
  result &= myGNSS.addCfgValset(0x30060021 | UBX_CFG_I2, -100); // Set CFG-SFIMU-IMU2ANT_LA_Y in cm (I2, int16_t)
  result &= myGNSS.addCfgValset(0x30060022 | UBX_CFG_I2, 40);   // Set CFG-SFIMU-IMU2ANT_LA_Z in cm (I2, int16_t)
  result &= myGNSS.sendCfgValset(); // Apply the configuration
  if (!result)
    Serial.println(F("VALSET failed!"));

}

void loop()
{
}

Best wishes,
Paul

[Eric-FR]

Adding configuration Key IDs would be a good starting point. I'm not sure that, at this point, it is worth implementing more integrated function.

[Eric-FR]

Indeed, one step forward would be to add an option in the RTK Express Plus allowing user to set manually such parameters.

[PaulZC]

The keys have been added in v3.1.9

Commit: 9d9e2ea

[PaulZC]

@Eric-FR :

This is resolved in https://github.com/sparkfun/SparkFun_u-blox_GNSS_v3/releases/tag/v3.1.9

Please open a separate issue in the RTK Firmware Repo to request support in the RTK Firmware. Thanks!