ADIS16448SLASHPCBZ datasheet(20/24 Pages) AD

20 / 24 page

ADIS16448

Data Sheet

Rev. B | Page 20 of 24

Accelerometer Bias Correction Factors

When the bias estimate is complete, multiply the estimate by

−1 to change its polarity, convert it to the digital format for the

offset correction registers (see Table 40, Table 41 or Table 42)

and write the correction factors to the correction registers. For

example, lower the x-axis bias by 12 LSB (10 mg) by setting

XACCL_OFF = 0xFFF4 (DIN = 0xA1FF, 0xA0F4).

Point of Percussion Alignment

Set MSC_CTRL[6] = 1 (DIN = 0xB446) to enable this feature

and maintain the factory default settings for DIO1. This feature

performs a point of percussion translation to the point identified

in Figure 22. See Table 30 for more information on MSC_CTRL.

ORIGIN ALIGNMENT

REFERENCE POINT

SEE MSC_CTRL[6].

Figure 22. Point of Percussion Physical Reference

MAGNETOMETER CALIBRATION

The ADIS16448 provides registers that contribute to both hard

iron and soft iron correction factors, as shown in Figure 23.

ADC

xMAGN_OUT

MAGNETIC

SENSOR

FACTORY

CALIBRATION

AND FILTERING

1 + xMAGN_SIC

xMAGN_HIC

Figure 23. Hard Iron and Soft Iron Factor Correction

Hard Iron Correction

The XMAGN_HIC (see Table 43), YMAGN_HIC (see

Table 44), and ZMAGN_HIC (see Table 45) registers provide

the user programmable bias adjustment function for the X-, Y-,

and Z-axis magnetometers, respectively. Hard iron effects

result in an offset of the magnetometer response.

Table 43. XMAGN_HIC (Base Address = 0x26), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

X-axis hard iron correction factor,

twos complement, 7 LSB/mgauss, 0x0000 = 0

Table 44. YMAGN_HIC (Base Address = 0x28), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

Y-axis hard iron correction factor,

twos complement, 7 LSB/mgauss, 0x0000 = 0

Table 45. ZMAGN_HIC (Base Address = 0x2A), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

Z-axis hard iron correction factor,

twos complement, 7 LSB/mgauss, 0x0000 = 0 mgauss

Hard Iron Factors

When the hard iron error estimation is complete, take the

following steps:

1. Multiply the estimate by −1 to change its polarity.

2. Convert it into digital format for the hard iron correction

registers (see Table 43).

3. Write the correction factors to the registers. For example,

lower the x-axis bias by 10 LSB (~1.429 mgauss) by setting

XMAGN_HIC = 0xFFF6 (DIN = 0xA7FF, 0xA6F6)

Soft Iron Effects

The XMAGN_SIC (see Table 46), YMAGN_SIC (see Table 47),

and ZMAGN_SIC (see Table 48) registers provide an adjust-

ment variable for the magnetometer sensitivity adjustment

in each magnetometer response to simplify the process of

performing a system level soft iron correction.

Table 46. XMAGN_SIC (Base Address = 0x2C), Read/Write

Bits

Description (Default = 0x8000)

[15:0]

X-axis soft iron correction factor,

twos complement format, 1 LSB = 100%/32,767

0x7FFF = 100% increase (2×)

0x8000 = 100% decrease (0×)

Table 47. YMAGN_SIC (Base Address = 0x2E), Read/Write

Bits

Description (Default = 0x8000)

[15:0]

Y-axis soft iron correction factor,

twos complement format, 1 LSB = 100%/32,767

0x7FFF = 100% increase (2×)

0x8000 = 100% decrease (0×)

Table 48. ZMAGN_SIC (Base Address = 0x30), Read/Write

Bits

Description (Default = 0x8000)

[15:0]

Z-axis soft iron correction factor,

twos complement format, 1 LSB = 100%/32,767

0x7FFF = 100% increase (2×)

0x8000 = 100% decrease (0×)

FLASH UPDATES

When using the user calibration registers to optimize system

level accuracy, set GLOB_CMD[3] = 1 (DIN = 0xBE04) to save

these settings in nonvolatile flash memory. Be sure to consider

the endurance rating of the flash memory when determining how

often to update the user correction factors in the flash memory.

RESTORING FACTORY CALIBRATION

Set GLOB_CMD[1] = 1 (DIN = 0xBE02) to execute the factory

calibration restore function, which resets the gyroscope and accel-

erometer offset registers to 0x0000 and all sensor data to 0. Then, it

automatically updates the flash memory and restarts sampling and

processing data. See Table 25 for information on GLOB_CMD.

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