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ADIS16407

Rev. A | Page 21 of 24

Hard Iron Factors

When the hard iron error estimation is complete, take the

following steps:

Multiply the estimate by −1 to change its polarity.

Convert it into digital format for the hard iron correction

registers (Table 55).

Write the correction factors to the correction registers. For

example, lower the x-axis bias by 10 LSB (5 mgauss) by

setting XMAGN_HIC = 0x1FF6 (DIN = 0xAB1F, 0xAAF6).

Soft Iron Effects

The XMAGN_SIC (Table 58), YMAGN_SIC (Table 59), and

ZMAGN_SIC (Table 60) registers provide an adjustment

variable for the magnetometer sensitivity adjustment in each

magnetometer response to simplify the process of performing a

system level soft iron correction.

Table 58. XMAGN_SIC (Base Address = 0x30), Read/Write

Bits

Description (Default = 0x0000)

[15:12]

Not used

[11:0]

X-axis soft iron correction factor, binary format,

2 = 0xFFF, 1 = 0x800, 0 = 0x000, ~0.0488%/LSB

Table 59. YMAGN_SIC (Base Address = 0x32), Read/Write

Bits

Description (Default = 0x0000)

[15:12]

Not used

[11:0]

Y-axis soft iron correction factor, binary format,

2 = 0xFFF, 1 = 0x800, 0 = 0x000, ~0.0488%/LSB

Table 60. ZMAGN_SIC (Base Address = 0x34), Read/Write

Bits

Description (Default = 0x0000)

[15:12]

Not used

[11:0]

Z-axis soft iron correction factor, binary format,

2 = 0xFFF, 1 = 0x800, 0 = 0x000, ~0.0488%/LSB

Soft Iron Factors

When the soft iron error estimation is complete, convert the

sensitivity into the digital format for the soft iron correction

registers (Table 58) and write the correction factors to the

correction registers. A simple method for converting the

correction factor is to divide it by 2 and multiply it by 4095. For

example, increasing the default soft iron factor to approximately

1.15 uses a binary code for 2355, or 0x933. Increase the soft iron

correction factor for the y-axis to approximately 1.15 by setting

YMAGN_SIC = 0x0933 (DIN = 0xB309, 0xB233).

FLASH UPDATES

When using the user calibration registers to optimize system

level accuracy, keep in mind that the register values are volatile

until their contents are saved in the nonvolatile flash memory.

After writing all of the correction factors into the user correction

registers, set GLOB_CMD[3] = 1 (DIN = 0xC204) 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 = 0xC202) to execute the factory

calibration restore function. This is a single command function,

which resets the gyroscope and accelerometer offset registers to

0x0000 and all sensor data to 0. Then, it automatically updates the

flash memory within 75 ms and restarts sampling and processing

data. See Table 32 for more information on GLOB_CMD.

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