ADIS16480SLASHPCBZ datasheet(19/40 Pages) AD

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Data Sheet

ADIS16480

Rev. 0 | Page 19 of 40

MAGNETOMETERS

The registers that use the x_MAGN_OUT format are the primary

registers for the magnetometer measurements. When processing

data from these registers, use a 16-bit, twos complement data

format. Table 38, Table 39, and Table 40 provide each register’s

numerical format, and Table 41 provides x_MAGN_OUT digital

coding examples.

Table 38. X_MAGN_OUT (Page 0, Base Address = 0x28)

Bits

Description

[15:0]

X-axis magnetometer data; twos complement,

±3.2767 gauss range, 0 gauss = 0x0000,

1 LSB = 0.1 mgauss

Table 39. Y_MAGN_OUT (Page 0, Base Address = 0x2A)

Bits

Description

[15:0]

Y-axis magnetometer data; twos complement,

±3.2767 gauss range, 0 gauss = 0x0000,

1 LSB = 0.1 mgauss

Table 40. Z_MAGN_OUT (Page 0, Base Address = 0x2C)

Bits

Description

[15:0]

Z-axis magnetometer data; twos complement,

±3.2767 gauss range, 0 gauss = 0x0000,

1 LSB = 0.1 mgauss

Table 41. x_MAGN_OUT Data Format Examples

Magnetic Field

Decimal

Hex

Binary

+3.2767 gauss

+32,767

0x7FFF

0111 1111 1111 1111

+0.2 mgauss

0x0002

0000 0000 0000 0010

+0.1 mgauss

0x0001

0000 0000 0000 0001

0 gauss

0x0000

0000 0000 0000 0000

−0.1 mgauss

−1

0xFFFF

1111 1111 1111 1111

−0.2 mgauss

−2

0xFFFE

1111 1111 1111 1110

−3.2768 gauss

−32,768

0x8000

1000 0000 0000 0000

ROLL, PITCH, YAW ANGLES

The EKF_CNFG (Table 94) register contains two bits, which

define the output format of the angle estimates. The first one

is EKF_CNFG[4], which selects the output format. When

EKF_CNFG[4] = 0; the output data is in the format of a

quaternion vector (See Table 42 through Table 45) and Euler

angles (See Table 47 through Table 49). When EKF_CNFG[4] =

1, the output data is in the form of a rotation matrix (see

Table 42 through Table 50).

Quaternion

This four-element hypercomplex number defines the attitude of

the body frame, relative to that of the navigation frame. The

Qx_Cxx_OUT registers (See Table 42 through Table 45) contain

the value for each element (q0, q1, q2, q4). The element, q0, is

the scalar part of the quaternion and represents the magnitude

of the rotation. The vector portion of the quaternion is defined

by (q1, q2, q3)T, which identifies the axis about which the

rotation takes place, in adjusting the body frame to that of the

navigation frame. When the orientation is in its reference

position, q0 is equal to one and q1, 2, and q3 are equal to zero.

These registers update at the same data rate as the gyroscopes

and accelerometers.

Euler Angles

The Euler angle names are yaw (ψ), pitch (θ), and roll (φ).

See Figure 19 for the axial association of these angles. These

three elements represent the most intuitive way of describing

orientation angles. The process of translating body frame

data to the navigation frame can be broken down into three

successive translations. These translations follow as the yaw

rotation about the z-axis, followed by the pitch rotation about

the y-axis, and finally the roll rotation about the x-axis. Reverse

this sequence to resolve a reverse rotation. Difficulties in this

process arise due to the singularities that occur whenever the

pitch approaches ±90° thus making the roll indistinguishable

from the yaw. For applications that may approach these limits,

the quaternion or rotation matrix output may be more appro-

priate. When the ADIS16480 is in its reference position, all

three Euler angles are equal to zero. The update rate for these

variables is the same as the gyroscopes and accelerometers.

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