Mechanical and Electrical Specifications

20

Freescale

Sensor Fusion Library for Kinetis MCUs, Rev. 0.7, 9/2015

Freescale Semiconductor, Inc.

Table 11. Memory Requirements for “All Algorithms” Builds

Freedom Platform

Text

Data

BSS

Flash

RAM

CodeWarrior

FRDM-KL25Z

96028

72

14776

96100

14848

FRDM-KL26Z

96020

72

14780

96092

14852

FRDM-KL46Z

95956

72

14780

96028

14852

FRDM-K20D50M

88116

72

14972

88188

15044

FRDM-K64F

79724

84

16484

79808

16568

KDS

FRDM-KL25Z

77812

172

14816

77984

14988

FRDM-KL26Z

77828

172

14816

78000

14988

FRDM-KL46Z

77772

172

14816

77944

14988

FRDM-K20D50M

67356

172

15008

67528

15180

FRDM-K64F

65024

184

16652

65208

16836

FRDM-K22F

62268

184

16492

62452

16676

Table 12. CodeWarrior Memory Requirements for FRDM-KL25Z and Single Algorithm

Freedom Platform

Text

Data

BSS

Flash

RAM

Accel (Tilt)

34280

64

12580

34344

12644

2D Mag

53904

64

12580

53968

12644

Gyro Only

33944

64

12528

34008

12592

Accel/Mag

55172

64

12588

55236

12652

Accel/Gyro

54716

72

12892

54788

12964

9-axis

75552

64

13664

75616

13728

4.7 Magnetic Calibration Metrics

4.7.1

Background

Hard-iron effects are due to magnetic materials in the vicinity of the sensor. These materials result in an

apparent offset to sensor readings when the source of interference is fixed spatially, relative to the

sensor.

For a given point in space, plotting magnetometer measurements at various sensor rotations results in

the sphere shown on the right hand side of Figure 12. This makes sense, as the magnitude of the 3D

magnetic field should not change just because the sensor is rotated.

Soft-iron effects result from the interaction of ferrous materials near the sensor interacting with the

ambient magnetic field. If the source of soft iron interference is again fixed spatially with respect to the

sensor and does not demonstrate magnetic hysteresis, then the sphere of plotted measurements is

distorted into an ellipsoid. This is shown (along with a hard-iron offset) on the left side of Figure 12.

Reference 2: Orientation Representations provides background on the topic of hard- and soft-iron

magnetic compensation. For the case where the sensor and sources of interference are spatially fixed

with respect to one another, the distortions are linear, and can be reversed mathematically. This is the

function of the Freescale magnetic calibration library.