Moog Crossbow GNAV540 - Manual (Page 90)

7430‐0808‐01 Rev. B
Page 90
GNAV540 User Manual
Y Hard Iron Bias 0x000A I2 2/2^16 Gauss
Soft Iron Scale Ratio 0x000B U2 2/2^16 ‐
Soft Iron Angle 0x000E I2 2*pi/2^16 Radians
Note that the calibration values for an external magnetometer are contained in distinct fields:
Table 61 External Magnetometer Calibration Values
Field Name Field ID Format Scaling Units
X Hard Iron Bias 0x001C I2 2/2^16 Gauss
Y Hard Iron Bias 0x001D I2 2/2^16 Gauss
Soft Iron Scale Ratio 0x001E U2 2/2^16 ‐
Soft Iron Angle 0x001F I2 2*pi/2^16 Radians
or an external magnetometer, there are also configuration fields that allow a user to specify roll and pitch offsets
0x0017, 0x0018), and magnetometer orientation (0x0020).
F
(
The hard iron bias values are scaled from (‐1, 1) Gauss. These values are subtracted from the tangent plane
magnetometer vector before heading is calculated. The soft iron scale ratio is scaled from (0, 2) and is multiplied by
the tangent plane x magnetometer value before heading is calculated.
Heading Track Offset
This field is used to set the offset between vehicle heading and vehicle track to be used by the navigation mode filter
when no magnetometer heading measurements are available.
Field Name Field ID Format Scaling Units
Heading Track Offset 0x000C I2
2*pi/2^16
(360°/2^16) Radians (heading‐track)
(°)
Commands to Program Configuration
Write Fields Command
Table 62 WF Command
Write Fields 746 (‘WF’ = 0x5 )
Preamble Packet Type Length Payload Termination
0x5555 0x5746 1+numFields*4
This command allows the user to write default power‐up configuration fields to the EEPROM. Writing the default
configuration will not take effect until the unit is power cycled. NumFields is the number of words to be written.
The field0, field1, etc. are the field IDs that will be written with the field0Data, field1Data, etc., respectively. The unit
will not write to calibration or algorithm fields.