DMU380SA Series
User’s Manual
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Doc# 7430-0026 Rev.01
Page 37
Table 13.
AHRS380SA Default BIT Status Definitions
BITstatus Field
Bits
Meaning
Category
masterFail
0
0 = normal, 1 = fatal error has occurred
BIT
HardwareError
1
0 = normal, 1= internal hardware error
BIT
comError
2
0 = normal, 1 = communication error
BIT
softwareError
3
0 = normal, 1 = internal software error or
magAlignOutofBounds
BIT
Reserved
4:7
N/A
masterStatus
8
0 = nominal, 1 = one or more status alerts
Status
hardwareStatus
9
Disabled
Status
comStatus
10
0 = nominal, 1 = No External GPS Comm
Status
softwareStatus
11
0 = nominal, 1 = Algorithm Initialization, or High Gain
Status
sensorStatus
12
0 = nominal, 1 = Sensor Over Range
Status
Reserved
13:15
N/A
The AHRS380SA also allows a user to configure the Status byte within the BIT message.
To configure the word, select the BIT Configuration tab from the Unit Configuration
menu. The dialog box allows selection of which status types to enable (hardware,
software, sensor, and comm). Like the VG380SA and IMU380SA, MEMSIC
recommends for the vast majority of users, that the default Status byte for the
AHRS380SA is sufficient. For users, who wish to have additional visibility to when the
AHRS380SA EFK algorithm estimates that the AHRS380SA is turning about its Z or
Yaw axis, the softwareStatus bit can be configured to go high during a turn. In other
words, the turnSwitch will turn on the softwareStatus bit. In the AHRS380SA, the
turnSwitch is by default set at 0.5 deg/sec about the Z-axis.
INS380SA Theory of Operation
4.5
The INS380SA supports all of the features and operating modes of the
IMU/VG/AHRS380SA, and it includes an additional internal WAAS capable GPS
receiver and associated software running on the ARM processor, for the computation of
navigation information as well as orientation information. The product name, INS380SA,
stands for Inertial Navigation System 380, and it is indicative of the navigation reference
functionality that the INS380SA provides by outputting GPS information (Latitude,
Longitude, and Altitude), inertially-aided 3-axis velocity information, as well as heading,
roll, and pitch measurements, in addition to digital IMU data. An AHRS380SA
configured and properly connected to an external GPS also behaves as a INS380SA.
At a fixed 100Hz rate, the INS380SA continuously maintains the digital IMU data; the
dynamic roll, pitch, and heading data; as well as the navigation data. As shown in the
software block diagram in Figure 10, after the Sensor Calibration block, the IMU data is
passed into an Integration to Orientation block. The Integration to Orientation block
integrates body frame sensed angular rate to orientation at a fixed 100 times per second
within all of the DMU380SA Series products (except IMU380SA). For improved
accuracy and to avoid singularities when dealing with the cosine rotation matrix, a
quaternion formulation is used in the algorithm to provide attitude propagation.
