ADIS16480SLASHPCBZ datasheet(29/40 Pages) AD

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Data Sheet

ADIS16480

Rev. 0 | Page 29 of 40

DECLINATION

The DECLN_ANGL register provides a user-programmable

input that can shift the reference frame from magnetic north

to geodetic north (or any arbitrary azimuth heading).

Table 93. DECLN_ANGL (Page 3, Base Address = 0x54)

Bits

Description (Default = 0x0000)

[15:0]

Declination angle, twos complement

Scale factor = π/215 radians/LSB

ADAPTIVE OPERATION

The EKF_CNFG register, in Table 94, offers a number of control

bits for customizing EKF operation.

Table 94. EKF_CNFG (Page 3, Base Address = 0x50)

Bits

Description (Default = 0x0200)

[15:13]

Not used

Automatic reset recovery from divergence

1 = enable, 0 = disable

[11:10]

Not used

Fade enable

1 = enable, 0 = disable

Adaptive EKF enable

1 = enable, 0 = disable

[7:5]

Not used

Orientation format control

1 = rotation matrix, 0 = quaternion and Euler

Body frame enable

1 = enable, 0 = disable

Not for external use, always set to 0

Magnetometer disable

1 = enable, 0 = disable

Gravity removal (from accelerometers)

1 = enable, 0 = disable

Adaptive EKF Enable Bit

EKF_CNFG[8] (see Table 94) provides an on/off control bit

for the adaptive part of the EKF function. The adaptive part

of the EKF computes the measurement covariance terms (R),

which enables real-time adjustments for vibration and magnetic

field disturbances. See Table 80 through Table 83 for read access

to the measurement covariance terms.

Automatic EKF Divergence Reset Control Bit

The EKF algorithm monitors the normalized innovation

squared parameter to detect divergence. The normalized

innovation is the innovation (predicted measurements minus

actual measurements) divided by the statistically computed

expected error, which is based on the error covariance and the

measurement covariance. With a moderate level of divergence,

the divergence indicator bit (SYS_E_FLAG[13] (see Table 59) is

set to a high state. At higher levels of divergence, EKF_CNFG[12]

(see Table 94) provides an on/off control bit for automatically

resetting the Kalman filter, to help speed recovery from

divergence.

Gyroscope Fade Control Bit

EKF_CNFG[9] (see Table 94) provides an on/off control bit for

the gyroscope fade function, which is an internal adjustment

of the gyroscope’s process covariance terms. This reduces the

impact of gyroscope scale errors during transient events, where

the gyroscope rates are quickly changing. The fade function

effectively reduces the weighting of the gyroscope measure-

ments, with respect to the accelerometers and magnetometers,

during these transient events. The adjustment terminates when

the rates return to zero.

Body Frame Enable Bit

EKF_CNFG[3] (see Table 94) provides an on/off control bit for

the body frame enable function. The reference transformation

matrix establishes the difference between the local navigation

frame and the body frame. Set EKF_CNFG[3] = 1 (DIN =

0x8003, DIN = 0xD110) to establish the body frame as the

reference frame.

Orientation Format Control Bit

EKF_CNFG[4] (see Table 94) provides a selection bit for angle

data format. Set EKF_CNFG[4] = 1 (DIN = 0x8003, DIN =

0xD010) to use the rotation matrix format.

Magnetometer Disable Control Bit

EKF_CNFG[1] (see Table 94) provides an on/off control bit

for the magnetometer disable function, which disables the

magnetometer influence over angle calculations in the EKF.

Gravity Removal Control Bit

EKF_CNFG[0] (see Table 94) provides an on/off control bit

for the gravity removal function, which removes the gravity

component from the accelerometer outputs.

Linear Acceleration/Magnetic Disturbance Detection

The ADIS16480 checks the magnitudes of the accelerometers

and magnetometers and compares their values against those of

the corresponding reference vectors. If the difference exceeds

the percentage programmed in the disturbance thresholds, the

algorithm automatically ignores the affected sensor group for

the duration of the external disturbance.

Table 95. ACC_DISTB_THR (Page 3, Base Address = 0x56)

Bits

Description (Default = 0x0020)

[15:8]

Not used

[7:0]

Threshold, binary, scale factor = 0.39%/LSB (50%/128)

Table 96. MAG_DISTB_THR (Page 3, Base Address = 0x58)

Bits

Description (Default = 0x0030)

[15:8]

Not used

[7:0]

Threshold, binary, scale factor = 0.39%/LSB (50%/128)

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