ArduPilot/ardupilot

EAHRS is performing duplicate temperature compenstation

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#25,792 opened on Dec 18, 2023

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BUGExternalAHRSgood first issue

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Description

Bug report

Issue details

Certain devices exposed through EAHRS, like the MicroStrain7, supply data that is already temperature compenstated.

https://s3.amazonaws.com/files.microstrain.com/GQ7+User+Manual/external_content/dcp/Data/sensor_data/data/mip_field_sensor_scaled_mag.htm https://s3.amazonaws.com/files.microstrain.com/GQ7+User+Manual/external_content/dcp/Data/sensor_data/data/mip_field_sensor_scaled_accel.htm

When the External AHRS driver posts data to sensor libraries, they perform temperature compenstation on it again, as long as HAL_INS_TEMPERATURE_CAL_ENABLE is defined, which is based on board size.

Please describe the problem

This causes double temperature compensation, leading to incorrect values.

Proposed Solution Add bool is_temperature_compensated; to AP_ExternalARHS::ins_data_message_t, and then add the necessary hooks in AP_InertialSensor::handle_external(const AP_ExternalAHRS::ins_data_message_t &pkt) to stop doing temperature compensation if the supplied value is already temp-compensated.

See ryanf55:eahrs-precompensated-sensors for a prototype fix (WIP)

Version master 1e644d56a51806b63dcd68d5e6566ec0f10248fc

Platform [ x] All [ ] AntennaTracker [ ] Copter [ ] Plane [ ] Rover [ ] Submarine

Contributor guide

Research direction
Inspect the double temperature compensation path in AP ExternalAHRS and AP InertialSensor. Implement the bool is temperature compensated flag and prevent re compensation if already compensated.
Tech stack
cpp
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75