Lower level magnetic calibration interface. More...

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Classes
struct	MagBuffer

struct	MagCalibration
	Magnetic Calibration Structure. More...

Macros
#define	F_USING_MAG 0x0002

Magnetic Calibration Constants
#define	MAGBUFFSIZEX 14
	x dimension in magnetometer buffer (14x28 equals 392 elements)

#define	MAGBUFFSIZEY (2 * MAGBUFFSIZEX)
	y dimension in magnetometer buffer (14x28 equals 392 elements)

#define	MINMEASUREMENTS4CAL 110
	minimum number of measurements for 4 element calibration

#define	MINMEASUREMENTS7CAL 220
	minimum number of measurements for 7 element calibration

#define	MINMEASUREMENTS10CAL 330
	minimum number of measurements for 10 element calibration

#define	MAXMEASUREMENTS 360
	maximum number of measurements used for calibration

#define	CAL_INTERVAL_SECS 300
	300s or 5min interval for regular calibration checks

#define	MINBFITUT 10.0F
	minimum acceptable geomagnetic field B (uT) for valid calibration

#define	MAXBFITUT 90.0F
	maximum acceptable geomagnetic field B (uT) for valid calibration

#define	FITERRORAGINGSECS 86400.0F
	24 hours: time (s) for fit error to increase (age) by e=2.718

#define	MESHDELTACOUNTS 50
	magnetic buffer mesh spacing in counts (here 5uT)

#define	DEFAULTB 50.0F
	default geomagnetic field (uT)

Functions
Function prototypes for functions in magnetic.c
These functions comprise the core of the magnetic calibration features of the library. Parameter descriptions are not included here, as details are provided in sensor_fusion.h.
void	fInitializeMagCalibration (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer)

void	iUpdateMagBuffer (struct MagBuffer pthisMagBuffer, struct MagSensor pthisMag, int32_t loopcounter)

void	fInvertMagCal (struct MagSensor pthisMag, struct MagCalibration pthisMagCal)

void	fRunMagCalibration (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag, int32_t loopcounter)
	Run the magnetic calibration. Calibration is done in time-slices, to avoid excessive CPU load during each fusion cycle. Three versions of calibration exist, differing in complexity and referred to as 4, 7, and 10 element solvers.

void	fUpdateMagCalibration4 (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag)

void	fUpdateMagCalibration7 (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag)

void	fUpdateMagCalibration10 (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag)

void	fUpdateMagCalibration4Slice (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag)

void	fUpdateMagCalibration7Slice (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag)

void	fUpdateMagCalibration10Slice (struct MagCalibration pthisMagCal, struct MagBuffer pthisMagBuffer, struct MagSensor *pthisMag)

Detailed Description

Lower level magnetic calibration interface.

Many developers can utilize the NXP Sensor Fusion Library without ever making any adjustment to the lower level magnetic calibration functions defined in this file.

Definition in file magnetic.h.

Macro Definition Documentation

◆ CAL_INTERVAL_SECS

#define CAL_INTERVAL_SECS 300

300s or 5min interval for regular calibration checks

Definition at line 38 of file magnetic.h.

◆ DEFAULTB

#define DEFAULTB 50.0F

default geomagnetic field (uT)

Definition at line 43 of file magnetic.h.

◆ F_USING_MAG

#define F_USING_MAG 0x0002

Definition at line 26 of file magnetic.h.

◆ FITERRORAGINGSECS

#define FITERRORAGINGSECS 86400.0F

24 hours: time (s) for fit error to increase (age) by e=2.718

Definition at line 41 of file magnetic.h.

◆ MAGBUFFSIZEX

#define MAGBUFFSIZEX 14

x dimension in magnetometer buffer (14x28 equals 392 elements)

Definition at line 32 of file magnetic.h.

◆ MAGBUFFSIZEY

#define MAGBUFFSIZEY (2 * MAGBUFFSIZEX)

y dimension in magnetometer buffer (14x28 equals 392 elements)

Definition at line 33 of file magnetic.h.

◆ MAXBFITUT

#define MAXBFITUT 90.0F

maximum acceptable geomagnetic field B (uT) for valid calibration

Definition at line 40 of file magnetic.h.

◆ MAXMEASUREMENTS

#define MAXMEASUREMENTS 360

maximum number of measurements used for calibration

Definition at line 37 of file magnetic.h.

◆ MESHDELTACOUNTS

#define MESHDELTACOUNTS 50

magnetic buffer mesh spacing in counts (here 5uT)

Definition at line 42 of file magnetic.h.

◆ MINBFITUT

#define MINBFITUT 10.0F

minimum acceptable geomagnetic field B (uT) for valid calibration

Definition at line 39 of file magnetic.h.

◆ MINMEASUREMENTS10CAL

#define MINMEASUREMENTS10CAL 330

minimum number of measurements for 10 element calibration

Definition at line 36 of file magnetic.h.

◆ MINMEASUREMENTS4CAL

#define MINMEASUREMENTS4CAL 110

minimum number of measurements for 4 element calibration

Definition at line 34 of file magnetic.h.

◆ MINMEASUREMENTS7CAL

#define MINMEASUREMENTS7CAL 220

minimum number of measurements for 7 element calibration

Definition at line 35 of file magnetic.h.

Function Documentation

◆ fInitializeMagCalibration()

void fInitializeMagCalibration	(	struct MagCalibration *	pthisMagCal,
		struct MagBuffer *	pthisMagBuffer
	)

Definition at line 27 of file magnetic.c.

◆ fInvertMagCal()

void fInvertMagCal	(	struct MagSensor *	pthisMag,
		struct MagCalibration *	pthisMagCal
	)

Definition at line 286 of file magnetic.c.

◆ fRunMagCalibration()

void fRunMagCalibration	(	struct MagCalibration *	pthisMagCal,
		struct MagBuffer *	pthisMagBuffer,
		struct MagSensor *	pthisMag,
		int32_t	loopcounter
	)

Run the magnetic calibration. Calibration is done in time-slices, to avoid excessive CPU load during each fusion cycle. Three versions of calibration exist, differing in complexity and referred to as 4, 7, and 10 element solvers.

If a calibration is in progress, indicated by the flag iCalInProgress, then it continues to completion using the same solver. If a calibration is not in progress and has not been done previously, then one is started using the most complex solver suited to the number of measurements available in the buffer. If a calibration is not in progress but has been done previously, then at CAL_INTERVAL_SECS one is started using the most complex solver suited to the number of measurements available in the buffer.

When a solver completes, it indicates this via iNewCalibrationAvailable.

A new calibration is accepted if: mag field strength is within reasonable limits; AND the fit error ftrFitErrorpc is less than 15%; AND the fit error is better than existing cal OR (be from higher-order solver AND fit error less than 3.5%). If (the mag field strength is outside reasonable limits OR the fit error ftrFitErrorpc is greater than 15%) AND the 10-order solver was used, then it is assumed some readings were corrupted so the buffer is cleared and the cal process restarts from the top.

The fit error of the existing calibration is 'aged' slowly, increasing by 1% every 24 hours. This causes a new calibration to be favoured over the old one after sufficient time elapses. I am unsure whether this is desirable in a nautical application where it is conceivable for the vessel to be on a consistent heading for long periods.

Parameters

pthisMagCal	struct containing details of the current calibration.
pthisMagBuffer	buffer of readings to be used for new calibration.
pthisMag	current magnetic reading.
loopcounter	counts iterations of fusion algorithm. Used in timeslicing.

Definition at line 352 of file magnetic.c.

◆ fUpdateMagCalibration10Slice()

void fUpdateMagCalibration10Slice	(	struct MagCalibration *	pthisMagCal,
		struct MagBuffer *	pthisMagBuffer,
		struct MagSensor *	pthisMag
	)

Definition at line 1000 of file magnetic.c.

◆ fUpdateMagCalibration4Slice()

void fUpdateMagCalibration4Slice	(	struct MagCalibration *	pthisMagCal,
		struct MagBuffer *	pthisMagBuffer,
		struct MagSensor *	pthisMag
	)

Definition at line 482 of file magnetic.c.

◆ fUpdateMagCalibration7Slice()

void fUpdateMagCalibration7Slice	(	struct MagCalibration *	pthisMagCal,
		struct MagBuffer *	pthisMagBuffer,
		struct MagSensor *	pthisMag
	)

Definition at line 713 of file magnetic.c.

◆ iUpdateMagBuffer()

void iUpdateMagBuffer	(	struct MagBuffer *	pthisMagBuffer,
		struct MagSensor *	pthisMag,
		int32_t	loopcounter
	)

Definition at line 92 of file magnetic.c.

Classes

Macros

Functions