Moog Crossbow NAV440 Series - Manual (Page 87)

NAV
7430‐0131‐01 Rev. F
Page 87 440 User Manual
Hard and Soft Iron Values
These fields allow access to hard iron bias and soft iron scale ratio values for magnetometer alignment. The
calibration values for the internal magnetometer:
Table 63 Internal Magnetometer Calibration Values
Field Name Field ID Format Scaling Units
X Hard Iron Bias 0x0009 I2 2/2^16 Gauss
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
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.
Table 64 Heading Track Offset
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 65 Write Fields
Write Fields 746 (‘WF’ = 0x5 )
Preamble Packet Type Length Payload Termination
0x5555 0x5746 1+numFields*4 <WF payload> <CRC (U2)>
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.
• If at least one field is successfully written, the unit will respond with a write field response containing
the field IDs of the successfully written fields.
• If any field is unable to be written, the unit will respond with an error response.
Both write fields and an error response may be received as a result of a write fields command. Attempts to
write a field with an invalid value is one way to generate an error response. To view a table of field IDs and
valid field values, refer to Configuration Fields on page 83.