DMU380SA Series USER MANUAL
DMU380SA Series
USER MANUAL
Document Part Number: 7430-0026-01
MEMSIC, Inc., 1759 McCarthy Blvd, Milpitas, CA 95035
Tel: 408-964-9700, Fax: 408-854-7702
email: [email protected], website: www.memsic.com
WARNING
This product has been developed by MEMSIC exclusively for commercial applications. It
has not been tested for, and MEMSIC makes no representation or warranty as to
conformance with, any military specifications or that the product is appropriate for any
military application or end-use. Additionally, any use of this product for nuclear,
chemical, biological weapons, or weapons research, or for any use in missiles, rockets,
and/or UAV's of 300km or greater range, or any other activity prohibited by the Export
Administration Regulations, is expressly prohibited without the written consent of
MEMSIC and without obtaining appropriate US export license(s) when required by US
law. Diversion contrary to U.S. law is prohibited.
©2014 MEMSIC, Inc. All rights reserved. Information in this document is subject to
change without notice.
MEMSIC, SoftSensor, INS380SA, AHRS380SA, VG380SA, and IMU380SA are
registered trademarks of MEMSIC, Inc. Other product and trade names are trademarks or
registered trademarks of their respective holders.
DMU380SA Series User’s Manual
Table of Contents
1
2
3
Introduction ..................................................................................................................1
1.1
Manual Overview .................................................................................................1
1.2
Overview of the DMU380SA Series Inertial Systems..........................................2
1.3
Summary of Major Changes from the 440 Series and the 350 Series ..................3
1.3.1
Mechanical Size and Footprint ......................................................................3
1.3.2
Connector Pin Out & Operating Voltage, Current ........................................3
1.3.3
Software Compatibility..................................................................................3
1.3.4
Operating Performance and Accuracy ...........................................................3
Connections..................................................................................................................4
2.1
Connections ..........................................................................................................4
2.2
I/O Cable ...............................................................................................................4
2.3
Power Input and Power Input Ground ..................................................................4
2.4
Serial Data Interface .............................................................................................5
2.5
Serial GPS Interface (INS380SA) ........................................................................5
2.6
External GPS Aiding (VG380SA and AHRS380SA)...........................................5
2.7
1 PPS Output Interface (INS380SA) ....................................................................6
2.8
Sync Pulse Input Interface (IMU, VG, and AHRS380SA)...................................6
2.9
GPS Antenna Connection (INS380SA) ................................................................7
2.10
No Connection ..................................................................................................7
2.11
Quick Digital interface connection ...................................................................7
Installation and Operation of NAV-VIEW ..................................................................9
3.1
NAV-VIEW Computer Requirements ..................................................................9
3.1.1
Install NAV-VIEW ........................................................................................9
3.2
Connections ..........................................................................................................9
3.3
Setting up NAV-VIEW .......................................................................................10
3.4
Data Recording ...................................................................................................10
3.5
Data Playback .....................................................................................................11
3.6
Raw Data Console ..............................................................................................11
3.7
Horizon and Compass View ...............................................................................12
3.8
Packet Statistics View .........................................................................................12
3.9
Unit Configuration ..............................................................................................13
3.10
Advanced Configuration .................................................................................14
3.11
Bit Configuration ............................................................................................15
3.12
Mag Alignment Procedure ..............................................................................16
3.12.1
Hard Iron/Soft Iron Overview .....................................................................16
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3.12.2
3.13
4
Read Unit Configuration .................................................................................19
Theory of Operation ...................................................................................................21
4.1
DMU380SA Series Default Coordinate System .................................................24
4.1.1
4.2
4.2.2
IMU380SA Built-In Test .............................................................................27
VG380SA Theory of Operation ..........................................................................27
4.3.1
VG380SA Advanced Settings .....................................................................29
4.3.2
VG380SA Built-In Test ..............................................................................30
AHRS380SA Theory of Operation .....................................................................31
4.4.1
AHRS380SA Magnetometer Calibration and Alignment ...........................32
4.4.2
AHRS380SA Advanced Settings ................................................................33
4.4.3
AHRS380SA Built-In Test ..........................................................................36
4.5
7
IMU380SA Theory of Operation ........................................................................25
IMU380SA Advanced Settings ...................................................................26
4.4
6
Advanced Settings .......................................................................................25
4.2.1
4.3
5
Mag Alignment Procedure Using NAV-VIEW ...........................................17
INS380SA Theory of Operation .........................................................................37
4.5.1
INS380SA Magnetometer Calibration and Alignment ................................39
4.5.2
INS380SA Advanced Settings.....................................................................39
4.5.3
INS380SA Built-In Test ..............................................................................40
Application Guide ......................................................................................................42
5.1
Introduction.........................................................................................................42
5.2
Fixed Wing Aircraft ............................................................................................42
5.3
Rotorcraft ............................................................................................................43
5.4
Land Vehicle .......................................................................................................43
5.5
Water Vehicle .....................................................................................................44
Programming Guide ...................................................................................................46
6.1
General Settings ..................................................................................................46
6.2
Number Formats .................................................................................................46
6.3
Packet Format .....................................................................................................47
6.3.1
Packet Header ..............................................................................................47
6.3.2
Packet Type .................................................................................................47
6.3.3
Payload Length ............................................................................................48
6.3.4
Payload ........................................................................................................48
6.3.5
16-bit CRC-CCITT ......................................................................................48
6.3.6
Messaging Overview ...................................................................................48
Communicating with the DMU380SA Series ............................................................51
7.1
Link Test. ............................................................................................................51
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7.1.1
Ping Command ............................................................................................51
7.1.2
Ping Response..............................................................................................51
7.1.3
Echo Command ...........................................................................................51
7.1.4
Echo Response.............................................................................................51
7.2
7.2.1
Get Packet Request ......................................................................................51
7.2.2
Algorithm Reset Command .........................................................................52
7.2.3
Algorithm Reset Response ..........................................................................52
7.2.4
Calibrate Command .....................................................................................52
7.2.5
Calibrate Acknowledgement Response .......................................................53
7.2.6
Calibration Completed Parameters Response ..............................................53
7.2.9
Error Response ............................................................................................54
7.3
Output Packets (Polled) ......................................................................................54
7.3.1
Identification Data Packet ...........................................................................54
7.3.2
Version Data Packet ....................................................................................54
7.3.3
Test 0 (Detailed BIT and Status) Packet......................................................55
7.4
8
Interactive Commands ........................................................................................51
Output Packets (Polled or Continuous)...............................................................55
7.4.1
Scaled Sensor Data Packet 0 .......................................................................55
7.4.2
Scaled Sensor Data Packet 1 (Default IMU Data).......................................56
7.4.3
Angle Data Packet 1 (Default AHRS Data) ................................................57
7.4.4
Angle Data Packet 2 (Default VG Data) .....................................................58
7.4.5
Nav Data Packet 0 .......................................................................................59
7.4.6
Nav Data Packet 1 (Default INS Data) ........................................................60
Advanced Commands ................................................................................................62
8.1
Configuration Fields ...........................................................................................62
8.2
Continuous Packet Type Field ............................................................................62
8.3
Digital Filter Settings ..........................................................................................63
8.4
Orientation Field .................................................................................................63
8.5
User Behavior Switches ......................................................................................64
8.6
Hard and Soft Iron Values ..................................................................................65
8.7
Heading Track Offset..........................................................................................65
8.8
Commands to Program Configuration ................................................................66
8.8.1
Write Fields Command ................................................................................66
8.8.2
Set Fields Command ....................................................................................67
8.9
8.10
Read Fields Command ........................................................................................68
Read Fields Response .....................................................................................68
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8.11
Get Fields Command.......................................................................................68
8.12
Get Fields Response ........................................................................................69
9
Advanced BIT ............................................................................................................70
9.1
Built In Test (BIT) and Status Fields ..................................................................70
9.2
Master BIT and Status (BITstatus) Field ............................................................72
9.3
hardwareBIT Field ..............................................................................................73
9.4
hardwarePowerBIT Field ....................................................................................73
9.5
hardwareEnvironmentalBIT Field ......................................................................73
9.6
comBIT Field ......................................................................................................73
9.7
comSerialABIT Field ..........................................................................................74
9.8
comSerialBBIT Field ..........................................................................................74
9.9
softwareBIT Field ...............................................................................................74
9.10
softwareAlgorithmBIT Field ...........................................................................75
9.11
softwareDataBIT Field ....................................................................................75
9.12
hardwareStatus Field .......................................................................................75
9.13
comStatus Field ...............................................................................................75
9.14
softwareStatus Field ........................................................................................76
9.15
sensorStatus Field............................................................................................76
9.16
Configuring the Master Status.........................................................................76
9.16.1
hardwareStatusEnable Field ........................................................................76
9.16.2
comStatusEnable Field ................................................................................77
9.16.3
softwareStatusEnable Field .........................................................................77
9.16.4
sensorStatusEnable Field .............................................................................77
10
Appendix A. Mechanical Specifications ................................................................78
11
Appendix B. NMEA Message Format ...................................................................80
11.1
12
GGA - GPS fix data ........................................................................................80
Appendix C. Sample Packet-Parser Code ..............................................................82
12.1
Overview .........................................................................................................82
12.2
Code listing .....................................................................................................83
13
Appendix D. Sample Packet Decoding ..................................................................89
14
Warranty and Support Information ........................................................................92
14.1
Customer Service ............................................................................................92
14.2
Contact Directory ............................................................................................92
14.3
Return Procedure .............................................................................................92
14.3.1
Authorization ...............................................................................................92
14.3.2
Identification and Protection .......................................................................92
14.3.3
Sealing the Container...................................................................................93
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14.3.4
Marking .......................................................................................................93
14.3.5
Return Shipping Address .............................................................................94
14.4
Warranty..........................................................................................................94
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About this Manual
The following annotations have been used to provide additional information.
 NOTE
Note provides additional information about the topic.
 EXAMPLE
Examples are given throughout the manual to help the reader understand the terminology.
 IMPORTANT
This symbol defines items that have significant meaning to the user
WARNING
The user should pay particular attention to this symbol. It means there is a chance that
physical harm could happen to either the person or the equipment.
The following paragraph heading formatting is used in this manual:
1 Heading 1
1.1 Heading 2
1.1.1 Heading 3
Normal
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1
1.1
Introduction
Manual Overview
This manual provides a comprehensive introduction to MEMSIC’s DMU380SA Series
Inertial System products. For users wishing to get started quickly, please refer to the three
page quick start guide included with each shipment. Table 1 table highlights the content
in each section and suggests how to use this manual.
Table 1. Manual Content
Manual Section
Who Should Read ?
Section 1:
All customers should read sections 1.1 and 1.2.
Manual Overview
Section 2:
Connections
Section 3:
Installation and Operation of NAVVIEW
Customers who are connecting the DMU380SA Series products into a system
with their own power supply and cable.
Customers who are installing the DMU380SA Series products into a system and
need details on using NAV-VIEW.
Section 4:
All customers should read Section 4.
Theory of Operation
As the DMU380SA Series products are inter-related, use the chart at the
beginning of Section 4 to ensure that you get an overview of all of the functions
and features of your DMU380SA Series system. For example, if you have
purchased a INS380SA, you should read not only the section on the INS380SA,
but also familiarize yourself with the theory of operation for the IMU380SA,
VG380SA, and AHRS380SA. The INS380SA builds on the capabilities of the
IMU380SA, VG380SA and AHRS380SA.
Section 5:
Customers who want product configuration tips for operating the DMU380SA
Series Inertial Systems in a wide range of applications – fixed wing, rotary wing,
unmanned vehicles, land vehicles, marine vessels, and more, should review the
part of Section 5 that is relevant to your application. Note: INS and AHRS
DMU380SA Series units are preconfigured for airborne applications with
“normal” dynamics. VG380SA Series units are preconfigured for land
applications with “automotive testing” dynamics. All DMU380SA Series products
allow for complete flexibility in configuration by the user.
Application Guide
Section 6-9:
Programming, Communicating,
Advanced Commands and BIT
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Customers who wish to communicate with the DMU380SA Series system for
sensor and navigation data, should review Section 6 and 7. Section 8 is for
users who wish to configure the DMU380SA Series operating parameters (e.g.,
baud rate or power-up output rate) without NAV-VIEW.
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1.2
Overview of the DMU380SA Series Inertial Systems
This manual provides a comprehensive introduction to the use of MEMSIC’s
DMU380SA Series Inertial System products listed in Table 2. This manual is intended to
be used as a detailed technical reference and operating guide for the DMU380SA Series.
MEMSIC’s DMU380SA Series products combine the latest in high-performance
commercial MEMS (Micro-electromechanical Systems) sensors and digital signal
processing techniques to provide a small, cost-effective alternative to existing IMU
systems and mechanical gyros.
Table 2. DMU380SA Series Feature Description
Product
IMU380SA
VG380SA (-200,-400)
AHRS380SA (-200, -400)
INS380SA (-200, -400)
Features
6- DOF Digital IMU
6-DOF IMU, plus Roll and Pitch
9-DOF IMU (3-Axis Internal Magnetometer) plus Roll, Pitch, and Heading Standard Range, High
Range
9-DOF IMU (3-Axis Internal Magnetometer) and Internal WAAS Capable GPS Receiver plus
Position, Velocity, Roll, Pitch, and Heading Standard Range, High Range
The DMU380SA Series is MEMSIC’s fourth generation of MEMS-based Inertial
Systems, building on over a decade of field experience, and encompassing thousands of
deployed units and millions of operational hours in a wide range of land, marine,
airborne, and instrumentation applications.
At the core of the DMU380SA Series is a rugged 6-DOF (Degrees of Freedom) MEMS
inertial sensor cluster that is common across all members of the DMU380SA Series. The
6-DOF MEMS inertial sensor cluster includes three axes of MEMS angular rate sensing
and three axes of MEMS linear acceleration sensing. These sensors are based on rugged,
field proven silicon bulk micromachining technology. Each sensor within the cluster is
individually factory calibrated for temperature and non-linearity effects during
MEMSIC’s manufacturing and test process using automated thermal chambers and rate
tables.
Coupled to the 6-DOF MEMS inertial sensor cluster is a high performance
microprocessor that utilizes the inertial sensor measurements to accurately compute
navigation information including attitude, heading, and linear velocity thru dynamic
maneuvers (actual measurements are a function of the DMU380SA Series product as
shown in Table 2). In addition, the ARM processor makes use of internal and external
magnetic sensor and/or GPS data to aid the performance of the inertial algorithms and
help correct long term drift and estimate errors from the inertial sensors and
computations. The navigation algorithm utilizes a multi-state configurable Extended
Kalman Filter (EKF) to correct for drift errors and estimate sensor bias values.
Another unique feature of the DMU380SA Series is the extensive field configurability of
the units. This field configurability allows the DMU380SA Series of Inertial Systems to
satisfy a wide range of applications and performance requirements with a single mass
produced hardware platform. The basic configurability includes parameters such as baud
rate, packet type, and update rate, and the advanced configurability includes the defining
of custom axes and how the sensor feedback is utilized in the Kalman filter during the
navigation process.
The DMU380SA Series is packaged in a fully sealed lightweight housing which provides
EMI, vibration, and moisture resistance to levels consistent with most land, marine, and
airborne environments. The DMU380SA Series utilizes an RS-232 serial link for data
communication, and each data transmission includes a BIT (Built-In-Test) message
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providing system health status. The DMU380SA Series is supported by MEMSIC’s
NAV-VIEW, a powerful PC-based operating tool that provides complete field
configuration, diagnostics, charting of sensor performance, and data logging with
playback.
1.3
1.3.1
Summary of Major Changes from the 440 Series and the 350 Series
Mechanical Size and Footprint
The mechanical footprint of MEMSIC’s new DMU380SA Series Inertial Systems is
significantly smaller compared to the prior generation Inertial Systems including
MEMSIC’s 440 Series (IMU440, VG440, AHRS440 and INS440), and 350 series
products. The mounting plate foot print is the smaller and the connector is miniature. For
detailed mechanical and installation drawings, see appendix A of the manual.
1.3.2
Connector Pin Out & Operating Voltage, Current
The micro-DB9 female socket connector on MEMSIC’s DMU380SA Series Inertial
Systems is new to MEMSIC’s product lines, and provides a significant size reduction and
performance improvement. The DMU380SA Series has a secondary optional-use
communications port for internal or external GPS.
1.3.3
Software Compatibility
MEMSIC’s DMU380SA Series Inertial Systems are software compatible with the
MEMSIC 440 series products and 350 series products. The DMU380SA Series products
utilize the same extensible communication protocol as the 440 series and 350 series
products. The protocol is documented in section 7 of this manual.
1.3.4
Operating Performance and Accuracy
The DMU380SA Series has been characterized in a wide range of land and airborne
applications. In the qualification testing, the dynamic accuracy of the DMU380SA Series
has shown improved performance when compared to the equivalent model of 440 and
350 series products, reducing attitude estimation errors in half during certain critical
dynamic maneuvers without the use of GPS aiding. With GPS aiding in the INS380SA,
attitude estimation is improved over the 440 series products. Recommended product
configuration settings are discussed in Section 5, and theory of operation is discussed in
Section 4.
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2
2.1
Connections
Connections
The DMU380SA Series has a micro-DB9 female connector as shown in Figure 1. The
signals are as shown in Table 3.
Figure 1.
9 Pin Micro-DB Connector Female Pinout
Table 3. Connector Pin Assignments
Pin
2.2
Signal
1
Power Input
2
Power Return
3
+RX RS-232 / RS-422
4
-RX RS-422
5
+TX RS-232 / RS-422
6
-TX RS-422
7
Mode Select (RS-232 Short / RS-422 Open)
8
GPS 1PPS Output (INS380SA) / Sync Pulse Input (IMU, VG and AHRS380SA)
9
Signal Return
I/O Cable
The user must provide a shielded cable with the shield connected to the I/O connector
shell in order to provide improved EMI protection. The cable sent with the unit is
intended to provide the user with the ability to test the unit right out of the box, and will
not provide adequate shielding for all environments.
WARNING
The cable sent with the unit is intended to provide the user with the ability to test the unit
right out of the box, and will not provide adequate shielding for all environments.
2.3
Power Input and Power Input Ground
Power is applied to the DMU380SA Series on pins 1 and 2. Pin 2 is ground; Pin 1 should
have 9 to 32 VDC unregulated at 350 mW. If you are using the cable supplied with the
DMU380SA Series, the power supply wires are broken out of the cable at the DB-9
connector. The red wire is connected to the positive power input; the black wire is
connected to the power supply ground.
WARNING
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Do not reverse the power leads or damage may occur.
2.4
Serial Data Interface
The main serial interface is standard RS-232, 9600, 19200, 38400, or 57600 baud, 8 data
bits, 1 start bit, 1 stop bit, no parity, and no flow control and will output at a user
configurable output rate. Pins 3 and 5 are designated as the main RS-232 interface pins.
The secondary serial interface is also standard RS-232, 9600, 19200, 38400, or 57600
baud, 8 data bits, 1 start bit, 1 stop bit, no parity, and no flow control, and is used by
INS380SA models to output internal GPS data. Pins 4 and 6 are designated as the
secondary RS-232 interface pins used by the INU380SA models. The user may opt to set
the output to RS-422 using pin 7. When Pin7 is shorted to ground, the standard RS-232
ports will be available. When Pin 7 is left open, then only the main serial interface will
be available and it will be standard RS-422 , 9600, 19200, 38400, or 57600 baud, 8 data
bits, 1 start bit, 1 stop bit, no parity, and no flow control and will output at a user
configurable output rate. Pins 3 and 4 are used for the RS-422 +Rx and –Rx, and pins 5
and 6 are used for the RS-422 +Tx and –Tx. These settings allow interaction via a
standard PC serial port. The serial data settings can be configured on a DMU380SA
Series unit with NAV-VIEW. In order to set the serial data interface, select Unit
Configuration, under the Menu Tab.
2.5
Serial GPS Interface (INS380SA)
The internal GPS receiver in INS380SA products outputs data in NMEA-0183 format as
defined by the National Marine Electronics Association (NMEA), Standard For
Interfacing Marine Electronic Devices, Version 2.20, January 1, 1997.
The packets are sent at 9600 Baud, 8 data bits, 1 start bit, 1 stop bit, no parity bit, and no
flow control and are output over the secondary serial interface (RS-232 on pins 4 and 6).
The GPS receiver outputs the following messages as shown in Table 4. (Refer to
Appendix B for the detailed message format)
Table 4. GPS Output Packet Format
NMEA Record
GGA
RMC
VTG
2.6
Description
Global positioning system fixed data
Recommended minimum specific GNSS data
Course over ground and ground speed data
External GPS Aiding (VG380SA and AHRS380SA)
The VG380SA/AHRS380SA allows the use of an external GPS receiver to be connected
to the secondary serial interface (RS-232 on pins 4 and 6) port. The user is required to
configure the GPS receiver to output the GPS messages that the DMU380SA Series
expects. The table below shows the supported GPS protocols and guidelines for
configuration. Note that the details of the GPS messages can be found in the respective
GPS protocol documents. The user must configure the VG/AHRS380SA to accept
external GPS information using NAV-VIEW as described in Chapter 3. If the
VG/AHRS380SA is parsing valid external GPS data and the GPS receiver has 3D lock,
then the comStatusnoExternalGPS flag will be zero, otherwise it will be one. See
section 9 for a complete description of system status indications.
Since NMEA protocol does not provide vertical velocity, the vertical velocity that the
DMU380SA Series estimates (based upon GPS altitude changes) may not be sufficient
for airborne applications (See Table 5). Therefore, the NMEA protocol is not
recommended for airborne applications.
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Table 5. Configuration of An External GPS Receiver for VG380SA/AHRS380SA
Protocols
Ublox binary
NovAtel OEM4 and
OEMV Binary
NovAtel OEM4
ASCII
NMEA*
Required Messages
NAV-LLH, NAV-VELNED,
NAV-STATUS
BestPosB, BestVelB
Required Message Rate
4 Hz
PosVelNavDopA
4Hz
GPGGA, GPVTG
4Hz
4Hz
Baud rate
9600, 19200, 38400,
57600$
9600, 19200, 38400,
57600$
19200, 38400, 57600$
9600, 19200, 38400,
57600$
*Not recommended for airborne applications.
$
57600 is the preferred baud rate for optimum performance
The GPS serial communication port should be configured to 8 data bits, 1 start bit, 1 stop
bit, no parity bit, and no flow control.
2.7
1 PPS Output Interface (INS380SA)
The 1PPS output signal on pin 8 is provided by the internal GPS receiver (when GPS
timing is known) on INS380SA products. The 1PPS output signal is open-collector and
should be interfaced to a rising-edge trigger with pull up resistor between 1k and 10k
ohms. The INS380SA Series products synchronize sensor data collection to this 1PPS
signal internally when available. Therefore, the 100Hz navigation algorithm will run
exactly 100 times each second with no slip when locked to 1PPS. Packet data is valid on
the rising edge of 1PPS and 10ms boundaries thereafter. There is, however, up to 500µs
of additional latency in sensor data collection. If 1PPS is provided by the internal GPS
receiver in NAV products, then the rising edge of 1PPS will correspond to the UTC
second boundary. When the system is synchronized to 1PPS, the
hardwareStatusunlocked1PPS flag will be zero, otherwise, it will be one.
Figure 2 shows the sequential order of the signal present at 1 PPS OUT pin.
The 1 PPS signal is aligned to the sampling clock of 23.104 MHz. This results in a timing
resolution of 43 ns.
Figure 2.
2.8
1PPS Output Signal
Sync Pulse Input Interface (IMU, VG, and AHRS380SA)
The Sync Signal Input signal allows the user of IMU, VG, and AHRS 380 products to
force synchronization of sensor data collection to an external synchronization signal (1
KHz). The signal must maintain 0.0-0.2 V zero logic and 3.0-5.0 volts high logic.
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2.9
GPS Antenna Connection (INS380SA)
The GPS receiver needs to receive signals from as many satellites as possible. A GPS
receiver doesn’t work properly in narrow streets and underground parking lots or if
objects or human beings cover the antenna. Poor visibility may result in position drift or a
prolonged Time-To-First-Fix (TTFF). A good sky visibility is therefore a prerequisite.
Even the best receiver can’t make up for signal loss due to a poor antenna, in-band
jamming or a poor RF cable.
The DMU380SA Series unit ships with an external active antenna that must be connected
properly to SMA jack located next to the DB-15 connector. Placing the antenna on a 4
inch or larger ground plane is highly recommended.
 IMPORTANT
Place the antenna with optimal sky visibility and use a ground plane. Route the GPS
Antenna RF cable away from sources of radiated energy (i.e. switching power supplies).
2.10 No Connection
During normal operation of the DMU380SA Series, no connection is made to the factory
test pins. These pins have internal pull-up mechanisms and must have no connections for
the DMU380SA Series to operate properly.
2.11 Quick Digital interface connection
On a standard DB-9 COM port connector, make the connections as described in Table 6
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Table 6. DB-9 COM Port Connections
COM Port Connector
Pin #
DMU380SA Series Connector
Signal
Pin #
Signal
2
RxD
5
TxD
3
TxD
3
RxD
5
GND
9
GND
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3
Installation and Operation of NAV-VIEW
NAV-VIEW has been completely redesigned to allow users to control all aspects of the
DMU380SA Series operation including data recording, configuration and data transfer.
For the first time, you will be able to control the orientation of the unit, sampling rate,
packet type, hard iron calibration and filter settings through NAV-VIEW.
3.1
NAV-VIEW Computer Requirements
The following are minimum requirements for the installation of the NAV-VIEW
Software:
•
CPU: Pentium-class (1.5GHz minimum)
•
RAM Memory: 500MB minimum, 1GB+ recommended
•
Hard Drive Free Memory: 20MB
•
Operating System: Windows 2000™, or XP™,
•
Properly installed Microsoft .NET 2.0 or higher
3.1.1
Install NAV-VIEW
To install NAV-VIEW onto your computer:
1. Insert the CD “Inertial Systems Product Support” (Part No. 8160-0063) in the CDROM drive.
2. Locate the “NAV-VIEW” folder. Double click on the “setup.exe” file.
3. Follow the setup wizard instructions. You will install NAV-VIEW and .NET 2.0
framework.
3.2
Connections
The DMU380SA Series Inertial Systems products are shipped with a cable to connect the
DMU380SA Series to a PC Serial port.
1. Connect the 9-pin micro-DB connector end of the digital signal cable to the port on
the DMU380SA Series product.
2. Connect the 9-pin sub-DB end of the cable marked to the serial port of your
computer.
3. The additional black and red wires on the cable connect power to the DMU380SA
Series product. Match red to (+) power and black to (-) ground. The input voltage
can range from 9-32 VDC with a maximum current draw of 350 mA.
4. Allow at least 60 seconds after power up for the DMU380SA Series product to
initialize. The DMU380SA Series needs to be held motionless during this period.
WARNING
Do not reverse the power leads! Reversing the power leads to the DMU380SA Series
can damage the unit; although there is reverse power protection, MEMSIC is not
responsible for resulting damage to the unit should the reverse voltage protection
electronics fail.
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3.3
Setting up NAV-VIEW
With the DMU380SA Series product powered up and connected to your PC serial port,
open the NAV-VIEW software application.
1. NAV-VIEW should automatically detect the DMU380SA Series product and
display the serial number and firmware version if it is connected.
2. If NAV-VIEW does not connect, check that you have the correct COM port
selected. You will find this under the “Setup” menu. Select the appropriate COM
port and allow the unit to automatically match the baud rate by leaving the
“Auto: match baud rate” selection marked.
3. If the status indicator at the bottom is green and states,
, you’re ready
to go. If the status indicator doesn’t say connected and is red, check the
connections between the DMU380SA Series product and the computer, check the
power supply, and verify that the COM port is not occupied by another device.
4. Under the “View” menu you have several choices of data presentation. Graph
display is the default setting and will provide a real time graph of all the
DMU380SA Series data. The remaining choices will be discussed in the
following pages.
3.4
Data Recording
NAV-VIEW allows the user to log data to a text file (.txt) using the simple interface at
the top of the screen. Customers can now tailor the type of data, rate of logging and can
even establish predetermined recording lengths.
To begin logging data follow the steps below (See Figure 3):
1. Locate the
icon at the top of the page or select “Log to File” from the “File”
drop down menu.
2. The following menu will appear.
Figure 3.
Log to File Dialog Screen
3. Select the “Browse” box to enter the file name and location that you wish to save
your data to.
4. Select the type of data you wish to record. “Engineering Data” records the
converted values provided from the system in engineering units, “Hex Data”
provides the raw hex values separated into columns displaying the value, and the
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“Raw Packets” will simply record the raw hex strings as they are sent from the
unit.
5. Users can also select a predetermined “Test Duration” from the menu. Using the
arrows, simply select the duration of your data recording.
6. Logging Rate can also be adjusted using the features on the right side of the
menu.
7. Once you have completed the customization of your data recording, you will be
returned to the main screen where you can start the recording process using the
button at the top of the page or select “Start Logging” from the “File” menu.
Stopping the data recording can be accomplished using the
button and the
recording can also be paused using the button.
3.5
Data Playback
In addition to data recording, NAV-VIEW allows the user to replay saved data that has
been stored in a log file.
1. To playback data, select “Playback Mode” from the “Data Source” drop down
menu at the top.
2. Selecting Playback mode will open a text prompt which will allow users to
specify the location of the file they wish to play back. All three file formats are
supported (Engineering, Hex, and Raw) for playback. In addition, each time
recording is stopped/started a new section is created. These sections can be
individually played back by using the drop down menu and associated VCR
controls.
3. Once the file is selected, users can utilize the VCR style controls at the top of the
page to start, stop, and pause the playback of the data.
4. NAV-VIEW also provides users with the ability to alter the start time for data
playback. Using the
adjust the starting time.
3.6
slide bar at the top of the page users can
Raw Data Console
NAV-VIEW offers some unique debugging tools that may assist programmers in the
development process. One such tool is the Raw Data Console. From the “View” drop
down menu, simply select the “Raw Data Console”. This console provides users with a
simple display of the packets that have been transmitted to the unit (Tx) and the messages
received (Rx). An example is provided in Figure 4.
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Figure 4.
3.7
Raw Data Console
Horizon and Compass View
If the DMU380SA Series product you have connected is capable of providing heading
and angle information (see Table 2), NAV-VIEW can provide a compass and a simulated
artificial horizon view. To activate these views, simply select “Horizon View” and/or
“Compass View” from the “View” drop down menu at the top of the page (See Figure 5).
Figure 5.
3.8
Horizon and Compass View
Packet Statistics View
Packet statistics can be obtained from the “View” menu by selecting the “Packet
Statistics” option (See Figure 6). This view simply provides the user with a short list of
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vital statistics (including Packet Rate, CRC Failures, and overall Elapsed Time) that are
calculated over a one second window. This tool should be used to gather information
regarding the overall health of the user configuration. Incorrectly configured
communication settings can result in a large number of CRC Failures and poor data
transfer.
Figure 6.
3.9
Packet Statistics
Unit Configuration
The Unit Configuration window (See Figure 7) gives the user the ability to view and alter
the system settings. This window is accessed through the “Unit Configuration” menu
item under the configuration menu. Under the “General” tab, users have the ability to
verify the current configuration by selecting the “Get All Values” button. This button
simply provides users with the currently set configuration of the unit and displays the
values in the left column of boxes.
There are three tabs within the “Unit Configuration” menu; General, Advanced and BIT
Configuration. The General tab displays some of the most commonly used settings. The
Advanced and BIT Configuration menus provide users with more detailed setting
information that they can tailor to meet their specific needs.
To alter a setting, simply select the check box on the left of the value that you wish to
modify and then select the value using the drop down menu on the right side. Once you
have selected the appropriate value, these settings can be set temporarily or permanently
(a software reset or power cycle is required for the changes to take affect) by selecting
from the choices at the bottom of the dialog box. Once the settings have been altered a
“Success” box will appear at the bottom of the page.
 IMPORTANT
Caution must be taken to ensure that the settings selected are compatible with the system
that is being configured. In most cases a “FAIL” message will appear if incompatible
selections are made by the user, however it is the users responsibility to ensure proper
configuration of the unit.
 IMPORTANT
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Unit orientation selections must conform to the right hand coordinate system as noted in
Section 4.1 of this user manual. Selecting orientations that do not conform to this criteria
are not allowed.
Figure 7.
Unit Configuration
3.10 Advanced Configuration
Users who wish to access some of the more advanced features of NAV-VIEW and the
DMU380SA Series products can do so by selecting the “Advanced” tab at the top of the
“Unit Configuration” window.
WARNING
Users are strongly encouraged to read and thoroughly understand the consequences of
altering the settings in the “Advanced” tab before making changes to the unit
configuration. These settings are discussed in detail in Chapter 4 below.
Behavior switches are identified at the top of the page with marked boxes. A blue box
will appear if a switch has been enabled similar to Figure 8 below. The values can be set
in the same manner as noted in the previous section. To set a value, users select the
appropriate “Modify” checkbox on the left side of the menu and select or enable the
appropriate value they wish to set. At the bottom of the page, users have the option of
temporarily or permanently setting values. When all selections have been finalized,
simply press the “Set Values” button to change the selected settings.
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Figure 8.
Advanced Settings
3.11 Bit Configuration
The third and final tab of the unit configuration window is “Bit Configuration” (See
Figure 9). This tab allows the users to alter the logic of individual status flags that affect
the masterStatus flag in the master BITstatus field (available in most output packets). By
enabling individual status flags users can determine which flags are logically OR’ed to
generate the masterStatus flag. This gives the user the flexibility to listen to certain
indications that affect their specific application. The masterFail and all error flags are not
configurable. These flags represent serious errors and should never be ignored.
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Figure 9.
BIT Configuration
3.12 Mag Alignment Procedure
 IMPORTANT
The following section only applies to DMU380SA Series products with magnetometers
(AHRS and INS380SA). If your particular model does not utilize magnetometers for
heading or performance you can disregard Section 3.12.
3.12.1 Hard Iron/Soft Iron Overview
The AHRS and INS380SA products use magnetic sensors to compute heading. Ideally,
the magnetic sensors would be measuring only earth's magnetic field to compute the
heading angle. In the real world, however, residual magnetism in your system adds to the
total magnetic field measured. This residual magnetism (called hard iron and soft iron)
will create errors in the heading measurement if it is not accounted for. In addition,
magnetic material can change the direction of the magnetic field as a function of the input
magnetic field. This dependence of the local magnetic field on input direction is called
the soft iron effect.
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The AHRS and INS380SA products can actually measure the constant magnetic field that
is associated with your system and correct for it. The AHRS and INS380SA products can
also make a correction for some soft iron effects. The process of measuring these nonideal effects and correcting for them is called the “Mag Alignment Procedure”.
Performing a “Mag Alignment Procedure” will help correct for magnetic fields that are
fixed with respect to the DMU380SA Series product. It cannot correct for time varying
fields, or fields created by ferrous material that moves with respect to the DMU380SA
Series product.
The AHRS and INS380SA products account for the extra magnetic field by making a
series of measurements, and using these measurements to model the hard iron and soft
iron environment in your system using a two-dimensional algorithm. The AHRS and
INS380SA products will calculate the hard iron magnetic fields and soft iron corrections
and store these as calibration constants in the EEPROM.
The “Mag Alignment Procedure” should always be performed with the AHRS or
INS380SA product installed in the user system. If you perform the calibration process
with the DMU380SA Series product by itself, you will not be correcting for the
magnetism in the user system. If you then install the DMU380SA Series product in the
system (i.e. a vehicle), and the vehicle is magnetic, you will still see errors arising from
the magnetism of the vehicle.
3.12.2 Mag Alignment Procedure Using NAV-VIEW
The Mag Alignment Procedure using NAV-VIEW can be performed using the following
steps below:
1. Select “Mag Alignment” from the “Configuration” drop down menu at the
top.
2. If you can complete your 360 degree turn within 120 seconds, select the
“Auto-Terminate” box.
3. Select the “Start” button to begin the “MagAlign” Procedure and follow the
instructions at the bottom of the screen as shown in Figure 10 below.
Figure 10.
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4. Rotate the AHRS or INS380SA product through 380 degrees of rotation or
until you receive a message to stop.
5. Once you have completed your rotation, you will be given data concerning
the calibration accuracy. The X and Y offset values indicate how far the
magnetic field has been offset due to hard iron affects from components
surrounding the unit. In addition, you will see a soft iron ratio indicating the
effect of soft iron on the AHRS or INS380SA product.
6. Save this data to the AHRS or INS380SA product by selecting the “Apply”
button (See Figure 11).
Figure 11.
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7. Upon completion of the “Mag Alignment Procedure”, the heading accuracy
should be verified with all third party systems active using a known reference
such as a compass rose, GPS track or a calibrated compass. Heading
inaccuracies greater than the values specified on the data sheet or fluctuating
heading performance may be an indication of magnetic field disturbances
near the unit.
 IMPORTANT
An acceptable calibration will provide X and Y Hard Iron Offset Values of < 2.5 and a
Soft Iron Ratio >0.95. If this procedure generates any values larger than stated above, the
system will assert the softwareErrordataErrormagAlignOutOfBounds error flag. See
section 9 for details on error flag handling. Note that the current release of the software
does not have this functionality. Future releases of software will restore this
functionality. The magnetometer ranges is +/- 4 gauss, thus 2.5 gauss is the
recommended maximum hardiron that should be tolerated for the installation and still
provide ample resolution and headroom to properly determine the earth’s magnetic field
(strength < 0.5 gauss). If the hard iron estimates are larger than 2.5 gauss, then a
different installation location should be investigated.
3.13 Read Unit Configuration
NAV-VIEW allows users to view the current settings and calibration data for a given
DMU380SA Series unit by accessing the “Read Configuration” selection from the
“Configuration” drop down menu (See Figure 12). From this dialog, users can print a
copy of the unit’s current configuration and calibration values with the click of a button.
Simply select the “Read” button at the top of the dialog box and upon completion select
the “Print” or “Print Preview” buttons to print a copy to your local network printer. This
information can be helpful when storing hard copies of unit configuration, replicating the
original data sheet and for troubleshooting if you need to contact MEMSIC’s Support
Staff.
Figure 12.
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4
Theory of Operation
This section of the manual covers detailed theory of operation for each member of the
DMU380SA Series starting with the basic IMU380SA and then reviewing each major
variant (VG, AHRS and INS) with their associated additional features, outputs, and
performance. Table 7 shows the basic features of each member of the DMU380SA Series
with cross references to important sections for review.
Table 7. DMU380SA Series Overview
Product
Features
Learning More
IMU380SA
6- DOF Digital IMU
Read 4.1 and 4.2
VG380SA
6-DOF IMU, plus Dynamic Roll/Pitch (optional external
GPS)
Read 4.1, 4.2 and 4.3
AHRS380SA
6-DOF IMU with 3-Axis Internal Magnetometer Dynamic
Roll, Pitch, and Heading (Optional External GPS)
Read 4.1, 4.2, 4.3 and 4.4
INS380SA
6-DOF IMU with 3-Axis Internal Magnetometer, and
Internal WAAS Capable GPS Receiver
Position, Dynamic Velocity, and Dynamic Roll, Pitch,
Heading
Read 4.1, 4.2, 4.3, 4.4 and 4.5
Figure 13 shows the DMU380SA Series hardware block diagram. At the core of the
DMU380SA Series is a rugged 6-DOF (Degrees of Freedom) MEMS inertial sensor
cluster that is common across all members of the DMU380SA Series. The 6-DOF MEMS
inertial sensor cluster includes three axes of MEMS angular rate sensing and three axes of
MEMS linear acceleration sensing. These sensors are based on rugged, field proven
silicon bulk micromachining technology. Each sensor within the cluster is individually
factory calibrated using MEMSIC’s automated manufacturing process. Sensor errors are
compensated for temperature bias, scale factor, non-linearity and misalignment effects
using a proprietary algorithm from data collected during manufacturing. Accelerometer,
rate gyro, and magnetometer sensor bias shifts over temperature (-40 0C to +71 0C) are
compensated and verified using calibrated thermal chambers and rate tables. The 6-DOF
sensor cluster data is fed into a high-speed microprocessor. The processor outputs attitude
and navigation data via the RS-232 port. As shown in the block diagram (Figure 13), the
INS380SA and AHRS380SA include an internal 3-axis magnetometer, and the
INS380SA includes an internal WAAS capable GPS receiver. In addition, the
AHRS380SA and VG380SA can accept input from external GPS sources as noted in
Chapter 2 of this manual.
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Figure 13.
DMU380SA Series Hardware Block Diagram
System Digital Outputs and Inputs
(Pins 3, 4, 5, 6)
X/Y/Z
High-Speed
Gyros
Sampling &
MEMSIC Serial Protocol
RS-232
X / Y / Z Acceleration
+
X/Y/Z
Accelerometers
Temperature
Sensor
Roll / Pitch / Yaw Rate
Sensor
X / Y / Z Magnetic Fields (INS/AHRS only)
Compensation /
Filtering
RS-422
+
Port
Roll / Pitch / Yaw Angle
Position / Velocity (NAV only)
Navigation &
Attitude
Optional use (Pins 4, 6)
Kalman Filter
(when configured as RS-232)
6-DOF Sensor
Cluster
External GPS Input (VG/AHRS)
Sync 1 KHz Pulse
GPS Receiver
X/Y/Z
Magnetometers
External GPS 1 PPS Input
Pin 8
(WAAS)
INS only
GPS Antenna INS only
Figure 14 shows the software block diagram. The 6-DOF inertial sensor cluster data is
fed into a high speed 200Hz signal processing chain. These 6-DOF signals pass through
one or more of the processing blocks and these signals are converted into output
measurement data as shown. Measurement data packets are available at fixed continuous
output rates or on a polled basis. The type of measurement data packets available depends
on the unit type according to the software block diagram and Table 6. Aiding sensor data
is used by an Extended Kalman Filter (EKF) for drift correction in the INS, AHRS and
VG Series products. Built-In-Test and Status data is available in the measurement packet
or via the special Status Packet T0.
As shown in the software block diagram, the DMU380SA Series has a unit setting and
profile block which configures the algorithm to user and application specific needs. This
feature is one of the more powerful features in the DMU380SA Series architecture as it
allows the DMU380SA Series to work in a wide range of commercial applications by
settings different modes of operation for the DMU380SA Series.
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Figure 14.
DMU380SA Series Software Block Diagram
Measurement
Data Available to
User (Fixed Rate
or Polled)
VG/AHRS – Angle
Packets
(A1, A2)
INS/AHRS/VG
IMU - Scaled Packets
(S0, S1)
All Units
INS/AHRS/VG/IMU
INS - Nav Packets
(N0, N1)
INS/AHRS/VG
6-DOF Sensor Cluster
X / Y / Z Body
Rates
X / Y / Z Body
Accelerometers
Unit Settings & Profile*
200Hz
Signal
Proc.
Chain
Sensor
Calibration
Axes Rotation
Integration to
Attitude
Integration to 100 Hz
Velocity, GPS
Position Output
Extended Kalman Filter (EKF)
Drift Correction Module
Communication Settings
Axes Orientation
Low Pass Filtering
Free Integrate
UseGPS
UseMags
TurnSwitch Threshold
DynamicMotion
Restart On Overange
Dynamic Motion
Programmable BIT Alerts
Built In Test
& Status
Data
Available to
User
Kalman Filter and Dynamic State Model
Hard/Soft Iron
Calibration
UseMags
Free Integrate
TurnSwitch
Threshold
UseGPS
Stationary Yaw
Lock
Status
Packet
(T0)
Aiding Sensors
X/Y/Z
Magnetometers
INS/AHRS only
Gravity Reference
Turn Rate
(Internal
Computation)
GPS Data
Internal/External
Simplified functional block diagrams for INS, AHRS and VG series products derived
from Figure 14 are shown in Figure 15 to highlight key features of each product. The
DMU380SA Series products are mainly differentiated by types of aiding sensors used in
the EKF for the drift correction of the 6-DOF inertial sensor cluster.
For the AHRS product, a 3-axis magnetometer is used for correcting the drift on
yaw/heading angle. For the INS product, a 3-axis magnetometer and a GPS receiver are
used for correcting the drift on yaw/heading angle, increasing the accuracy of the attitude
estimation by incorporating these sensor signals into the EKF, and providing a navigation
solution. The common aiding sensor for the drift correction for the attitude (i.e., roll and
pitch only) is a 3-axis accelerometer. This is the default configuration for the VG product.
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Figure 15.
4.1
Functional Block Diagram of INS, AHRS and VG Default Operating Mode.
DMU380SA Series Default Coordinate System
The DMU380SA Series Inertial System default coordinate system is shown in Figure 16.
As with many elements of the DMU380SA Series, the coordinate system is configurable
with either NAV-VIEW or by sending the appropriate serial commands. These
configurable elements are known as Advanced Settings. This section of the manual
describes the default coordinate system settings of the DMU380SA Series when it leaves
the factory.
With the DMU380SA Series product connector facing you, and the mounting plate down,
the axes are defined as follows:
Figure 16.
DMU380SA Series Default Coordinate System
+X
+Y
+Z
X-axis – from face with connector through the 380 unit
Y-axis – along the face with connector from left to right
Z-axis – along the face with the connector from top to bottom
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The axes form an orthogonal SAE right-handed coordinate system. Acceleration is
positive when it is oriented towards the positive side of the coordinate axis. For example,
with a DMU380SA Series product sitting on a level table, it will measure zero g along
the x- and y-axes and -1 g along the z-axis. Normal Force acceleration is directed
upward, and thus will be defined as negative for the DMU380SA Series z-axis.
The angular rate sensors are aligned with these same axes. The rate sensors measure
angular rotation rate around a given axis. The rate measurements are labeled by the
appropriate axis. The direction of a positive rotation is defined by the right-hand rule.
With the thumb of your right hand pointing along the axis in a positive direction, your
fingers curl around in the positive rotation direction. For example, if the DMU380SA
Series product is sitting on a level surface and you rotate it clockwise on that surface, this
will be a positive rotation around the z-axis. The x- and y-axis rate sensors would
measure zero angular rates, and the z-axis sensor would measure a positive angular rate.
The magnetic sensors are aligned with the same axes definitions and sign as the linear
accelerometers. For example, when oriented towards magnetic North, you will read
approximately +0.25 Gauss along X, 0.0 Gauss along Y, and +0.35 Gauss along Z
direction (North America). Magnetic values at other geographic locations can be found at
http://www.ngdc.noaa.gov/seg/WMM/DoDWMM.shtml.
Pitch is defined positive for a positive rotation around the y-axis (pitch up). Roll is
defined as positive for a positive rotation around the x-axis (roll right). Yaw is defined as
positive for a positive rotation around the z-axis (turn right).
The angles are defined as standard Euler angles using a 3-2-1 system. To rotate from the
body frame to an earth-level frame, roll first, then pitch, and then yaw.
The position output from GPS is represented in Latitude, Longitude, and Altitude (LLA)
convention on the WGS84 Ellipsoid. This is the most commonly used spherical
coordinate system. The GPS velocity is defined in North, East and Down reference
frame. The users can convert this into Cartesian coordinate system, called EarthCentered, Earth-Fixed (ECEF). ECEF uses three-dimensional XYZ coordinates (in
meters) to describe the location of a GPS user or satellite. Several online resources are
available to help users with this transformation. For example, refer to the application note
on MEMSIC website, http://www.memsic.com/support/documentation/inertialsystems/category/3-application-notes.html
4.1.1
Advanced Settings
The DMU380SA Series Inertial Systems have a number of advanced settings that can be
changed. The specific settings available vary from unit to unit, and a detailed description
of each unit (IMU, VG, AHRS, and INS) is found in the subsequent sections of this
manual. All units support baud rate, power-up output packet type, output rate, sensor low
pass filtering, and custom axes configuration. The units can be configured using NAVVIEW, as described in Section 3, and also directly with serial commands as described in
Sections 6-9.
4.2
IMU380SA Theory of Operation
The product name, IMU380SA, stands for Inertial Measurement Unit 380, and the name
is indicative of the inertial measurement unit functionality that the IMU380SA provides
by providing inertial rate and acceleration data in 6-DOF (six degrees of freedom). The
IMU380SA signal processing chain consists of the 6-DOF sensor cluster, programmable
low-pass filters, and the ARM signal processor for sensor error compensation. The
IMU380SA, as with other DMU380SA Series variants, has an RS-232 serial
communications link.
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After passing thru a digitally controlled programmable low-pass filter, the rate and
acceleration sensor signals are obtained at 200Hz. The sensor data is filtered by the ARM
using FIR filters. The factory calibration data, stored in EEPROM, is used by the ARM to
remove temperature bias, misalignment, scale factor errors, and non-linearities from the
sensor data. Additionally any advanced user settings such as axes rotation are applied to
the IMU data. The 200Hz IMU data is continuously being maintained inside the
IMU380SA. Digital IMU data is output over the RS-232 serial link at a selectable fixed
rate (100, 50, 25, 20, 10, 5 or 2 Hz) or on as requested basis using the GP, ‘Get Packet’
command. The digital IMU data is available in one of several measurement packet
formats including Scaled Sensor Data (‘S1’ Packet). In the Scaled Sensor Data (‘S1’
Packet) data is output in scaled engineering units. See Section 7 of the manual for full
packet descriptions.
 IMPORTANT
The Delta-Theta, Delta-V packet is only recommended for use in continuous output mode
at 5Hz or greater. Polled requests for this packet will produce values accumulated since
the last poll request, and thus, are subject to overflow (data type wrap around).
4.2.1
IMU380SA Advanced Settings
The IMU380SA advanced settings are described in Table 8 below. All of the advanced
settings are accessible thru NAV-VIEW under the Configuration Menu, Unit
Configuration settings.
Table 8. IMU380SA Advanced Settings
Setting
Default
Comments
Baud Rate
38,400 baud
9600, 19200, 57600 also available
Packet Type
S0
S1 also available
Packet Rate
100Hz
This setting sets the rate at which selected Packet Type, packets are output. If
polled mode is desired, then select Quiet. If Quiet is selected, the IMU380SA
will only send measurement packets in response to GP commands.
Orientation
See Fig 12.
To configure the axis orientation, select the desired measurement for each
axis: NAV-VIEW will show the corresponding image of the IMU380SA, so it
easy to visualize the mode of operation. Refer to Section 8.4 Orientation Field
settings for the twenty four possible orientation settings. The default setting
points the connector AFT.
Filter Settings (5,
10, 20, 50 Hz)
20 Hz
The low pass filters are set to a default of 20 Hz for the accelerometers, and 20
Hz for the angular rate sensors. There is one filter setting for all three angular
rate sensors. There is one filter setting for all three accelerometers.
BIT
See 4.2.2
NOTE on Filter Settings
Why change the filter settings? Generally there is no reason to change the low-pass filter
settings on the IMU380SA or other DMU380SA Series Inertial Systems. However, when
a DMU380SA Series product is installed in an environment with a lot of vibration, it can
be helpful to reduce the vibration-based signal energy and noise prior to further
processing on the signal. Installing the IMU380SA in the target environment and
reviewing the data with NAV-VIEW can be helpful to determine if changing the filter
settings would be helpful. Although the filter settings can be helpful in reducing vibration
based noise in the signal, low filter settings (e.g., 5Hz) also reduce the bandwidth of the
signal, i.e. can wash out the signals containing the dynamics of a target. Treat the filter
settings with caution.
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4.2.2
IMU380SA Built-In Test
The IMU380SA Built-In Test capability allows users of the IMU380SA to monitor
health, diagnostic, and system status information of the unit in real-time. The Built-In
Test information consists of a BIT word (2 bytes) transmitted in every measurement
packet. In addition, there is a diagnostic packet ‘T0’ that can be requested via the Get
Packet ‘GP’ command which contains a complete set of status for each hardware and
software subsystem in the IMU380SA. See Sections 6-8 Programming Guide, for details
on the ‘T0’ packet.
The BIT word, which is contained within each measurement packet, is detailed below.
The LSB (Least Significant Bit) is the Error byte, and the MSB (Most Significant Bit) is
a Status byte with programmable alerts. Internal health and status are monitored and
communicated in both hardware and software. The ultimate indication of a fatal problem
is the masterFail flag.
The masterStatus flag is a configurable indication that can be modified by the user. This
flag is asserted as a result of any asserted alert signals which have been enabled. See
Advanced BIT (Section 9) for details regarding the configuration of the masterStatus
flags. Table 9 shows the BIT definition and default settings for BIT programmable alerts
in the IMU380SA.
Table 9. IMU380SA Default BIT Status Definition
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
BIT
Reserved
4:7
N/A
masterStatus
8
0 = nominal, 1 = Alert, Sensor Over Range
Status
hardwareStatus
9
Disabled
Status
comStatus
10
Disabled
Status
softwareStatus
11
Disabled
Status
sensorStatus
12
0 = nominal, 1 = Sensor Over Range
Status
Reserved
13:15
N/A
The IMU380SA 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). In the case of the IMU380SA which has fewer features and
options than other DMU380SA Series products, the only meaningful parameter is sensor
over-range. It is recommended that users leave the default configuration, which is
sensorStatus enabled and flag on sensor over-range. The over-range only applies to the
rotational rate sensors. Because instantaneous acceleration levels due to vibration can
exceed the accelerometer sensor range in many applications, none of the DMU380SA
Series products trigger over-range on accelerometer readings.
4.3
VG380SA Theory of Operation
The VG380SA supports all of the features and operating modes of the IMU380SA, and it
includes additional internal software, running on the ARM processor, for the computation
of dynamic roll and pitch. The product name, VG380SA, stands for Vertical Gyro 380,
and it is indicative of the vertical gyro functionality that the VG380SA replicates by
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providing dynamic roll and pitch measurements, in addition to the IMU data. The
dynamic roll and pitch measurements are stabilized by the using the accelerometers as a
long-term gravity reference. Unlike the VG400 and earlier MEMSIC VG Series products,
the VG380SA can also output a free integrating yaw angle measurement that is not
stabilized by a magnetometer or compass heading (see AHRS380SA or INS380SA for
stabilized heading). At a fixed 200Hz rate, the VG380SA continuously maintains both the
digital IMU data as well as the dynamic roll and pitch data. As shown in the software
block diagram Figure 14, after the Sensor Calibration block, the IMU data is passed into
an Integration to Orientation block (Please refer to the Figure 11 if external GPS aiding
will be used). The Integration to Orientation block integrates body frame sensed angular
rate to orientation at a fixed 200 times per second within all of the DMU380SA Series
products. 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.
As also shown in the software block diagram, the Integration to Orientation block
receives drift corrections from the Extended Kalman Filter or Drift Correction Module. In
general, rate sensors and accelerometers suffer from bias drift, misalignment errors,
acceleration errors (g-sensitivity), nonlinearity (square terms), and scale factor errors.
The largest error in the orientation propagation is associated with the rate sensor bias
terms. The Extended Kalman Filter (EKF) module provides an on-the-fly calibration for
drift errors, including the rate sensor bias, by providing corrections to the Integration to
Orientation block and a characterization of the gyro bias state. In the VG380SA, the
internally computed gravity reference vector provides a reference measurement for the
EKF when the VG380SA is in quasi-static motion to correct roll and pitch angle drift and
to estimate the X and Y gyro rate bias. Because the gravity vector has no horizontal
component, the EKF has no ability to estimate either the yaw angle error or the Z gyro
rate bias. The VG380SA adaptively tunes the EKF feedback in order to best balance the
bias estimation and attitude correction with distortion free performance during dynamics
when the object is accelerating either linearly (speed changes) or centripetally (false
gravity forces from turns). Because centripetal and other dynamic accelerations are often
associated with yaw rate, the VG380SA maintains a low-passed filtered yaw rate signal
and compares it to the turnSwitch threshold field (user adjustable). When the user
platform to which the VG380SA is attached exceeds the turnSwitch threshold yaw rate,
the VG380SA lowers the feedback gains from the accelerometers to allow the attitude
estimate to coast through the dynamic situation with primary reliance on angular rate
sensors. This situation is indicated by the softwareStatusturnSwitch status flag. Using
the turn switch maintains better attitude accuracy during short-term dynamic situations,
but care must be taken to ensure that the duty cycle of the turn switch generally stays
below 10% during the vehicle mission. A high turn switch duty cycle does not allow the
system to apply enough rate sensor bias correction and could allow the attitude estimate
to become unstable.
The VG380SA algorithm has two major phases of operation. The first phase of operation
is the initialization phase. During the initialization phase, the VG380SA is expected to be
stationary or quasi-static so the EKF weights the accelerometer gravity reference heavily
in order to rapidly estimate the roll and pitch angles, and X, Y rate sensor bias. The
initialization phase lasts approximately 60 seconds, and the initialization phase can be
monitored in the softwareStatus BIT transmitted by default in each measurement packet.
After the initialization phase, the VG380SA operates with lower levels of feedback (also
referred to as EKF gain) from the accelerometers to continuously estimate and correct for
roll and pitch errors, as well as to estimate X and Y rate sensor bias.
If a user wants to reset the algorithm or re-enter the initialization phase, sending the
algorithm reset command, ‘AR’, will force the algorithm into the reset phase.
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The VG380SA outputs digital measurement data over the RS-232 serial link at a
selectable fixed rate (100, 50, 25, 20, 10, 5 or 2 Hz) or on as requested basis using the
GP, ‘Get Packet’ command. In addition to the scaled sensor packets described in the
IMU380SA section, the VG380SA has additional measurement output packets including
the default ‘A2’ Angle Packet which outputs the roll angle, pitch angle, and digital IMU
data. ‘N0’ and ‘N1’ packets are also available for use with an external GPS receiver. See
Section 6 and 7 of the manual for full packet descriptions.
4.3.1
VG380SA Advanced Settings
In addition to the configurable baud rate, packet rate, axis orientation, and sensor lowpass filter settings, the VG380SA provides additional advanced settings which are
selectable for tailoring the VG380SA to a specific application requirements. These
VG380SA advanced settings are shown in Table 10 below:
Table 10. VG380SA Series Advanced Settings
Setting
Default
Comments
Baud Rate
38,400
baud
9600, 19200, 57600 also available
Packet Type
A2
S1, N0, N1 also available
Packet Rate
25Hz
This setting sets the rate at which selected Packet Type, packets are output. If polled
mode is desired, then select Quiet. If Quiet is selected, the VG380SA will only send
measurement packets in response to GP commands.
Orientation
See
Fig. 12
To configure the axis orientation, select the desired measurement for each axes: NAVVIEW will show the corresponding image of the VG380SA, so it easy to visualize the
mode of operation. See Section 8.4 Orientation Field settings for the twenty four possible
orientation settings. The default setting points the connector AFT.
Filter
Settings (5,
10, 20, 50 Hz)
20 Hz
The low pass filters are set to a default of 5Hz for the accelerometers, and 20 Hz for the
angular rate sensors. There is one filter setting for all three angular rate sensors. There
are two settings for the accelerometers, one for the X and Y axes, and a separate setting
for the Z axis. The reason for a separate setting in the Z-axis is that in many installations,
the Z-axis vibration level is much higher than in the X and Y axes, and it can prove helpful
to filter the Z-axis at a lower cutoff than the X and Y axes.
Freely
Integrate
OFF
The Freely Integrate setting allows a user to turn the VG380SA into a ‘free gyro’. In free
gyro mode, the roll, pitch and yaw are computed exclusively from angular rate with no
kalman filter based corrections of roll, pitch, or yaw. When turned on, there is no coupling
of acceleration based signals into the roll and pitch. As a result, the roll, pitch, and yaw
outputs will drift roughly linearly with time due to sensor bias. For best performance, the
Freely Integrate mode should be used after the algorithm has initialized. This allows the
Kalman Filter to estimate the roll and pitch rate sensor bias prior to entering the free gyro
mode. Upon exiting the ‘free gyro’ mode (OFF), one of two behaviors will occur
(1) If the VG380SA has been in freely integrate mode for less than sixty seconds,
the algorithm will resume operation at normal gain settings
(2) If the VG380SA has been in freely integrate mode for greater than sixty
seconds, the algorithm will force a reset and reinitialize with high gains
automatically.
Restart On
Over Range
OFF
This setting forces an algorithm reset when a sensor over range occurs i.e., a rotational
rate on any of the three axes exceeds the maximum range. The default setting is OFF for
the VG380SA. Algorithm reset returns the VG380SA to a high gain state, where the
VG380SA rapidly estimates the gyro bias and uses the accelerometer feedback heavily.
This setting is recommended when the source of over-range is likely to be sustained and
potentially much greater than the rate sensor operating limit. Large and sustained angular
rate over-ranges result in unrecoverable errors in roll and pitch outputs. An unrecoverable
error is one where the EKF can not stabilize the resulting roll and pitch reading. If the
over-ranges are expected to be of short duration (<1 sec) and a modest percentage over
the maximum operating range, it is recommended that the restart on over range setting
be turned off. Handling of an inertial rate sensor over-range is controlled using the
restartOnOverRange switch. If this switch is off, the system will flag the overRange status
flag and continue to operate through it. If this switch is on, the system will flag a
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masterFail error during an over-range condition and continue to operate with this flag until
a quasi-static condition is met to allow for an algorithm restart. The quasi-static condition
required is that the absolute value of each low-passed rate sensor fall below 3 deg/sec to
begin initialization. The system will then attempt a normal algorithm start.
Dynamic
Motion
ON
The default setting is ON for the VG380SA. Turning off the dynamic motion setting results
in a higher gain state that uses the accelerometer feedback heavily. During periods of
time when there is known low dynamic acceleration, this switch can be turned off to allow
the attitude estimate to quickly stabilize.
Turn Switch
threshold
10.0
deg/sec
With respect to centripetal or false gravity forces from turning dynamics (or coordinated
turn), the VG380SA monitors the yaw-rate. If the yaw rate exceeds a given Turnswitch
threshold, the feedback gains from the accelerometer signals for attitude correction are
reduced because they are likely corrupted.
BIT
4.3.2
See 4.3.2
VG380SA Built-In Test
As with the IMU380SA, the VG380SA Built-In Test capability allows users of the
VG380SA to monitor health, diagnostic, and system status information of the unit in realtime. The Built-In Test information consists of a BIT word (2 bytes) transmitted in every
measurement packet. In addition, there is a diagnostic packet ‘T0’ that can be requested
via the Get Packet ‘GP’ command which contains a complete set of status for each
hardware and software subsystem in the VG380SA. See Sections 6 and 7 for details on
the ‘T0’ packet.
The BIT word contained within each measurement packet is detailed below. The LSB
(Least Significant Bit) is the Error byte, and the MSB (Most Significant Bit) is a Status
byte with programmable alerts. Internal health and status are monitored and
communicated in both hardware and software. The ultimate indication of a fatal problem
is the masterFail flag.
The masterStatus flag is a configurable indication that can be modified by the user. This
flag is asserted as a result of any asserted alert signals which have been enabled. See
Advanced BIT (Section 9) for details on configuring the masterStatus flags. Table 11
shows the BIT definition and default settings for BIT programmable alerts in the
VG380SA.
Table 11. VG380SA Default BIT Status Definition
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
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
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The VG380SA 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 IMU380SA, MEMSIC recommends for the vast majority of
users, that the default Status byte for the VG380SA is sufficient. For users, who wish to
have additional visibility to when the VG380SA EFK algorithm estimates that the
VG380SA 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 VG380SA, the turnSwitch is by default set at 10.0 deg/sec about the z-axis.
4.4
AHRS380SA Theory of Operation
The AHRS380SA supports all of the features and operating modes of the IMU380SA and
VG380SA, and it includes an additional internal 3-axis magnetometer and associated
software running on the ARM processor, for the computation of dynamic heading, as
well as dynamic roll and pitch. The product name, AHRS380SA, stands for Attitude
Heading Reference System 380, and it is indicative of the attitude and heading reference
functionality that the AHRS380SA replicates by providing dynamic heading, roll, and
pitch measurements, in addition to the VG and IMU data. The dynamic heading
measurement is stabilized using the 3-axis magnetometer as a magnetic north reference.
As in the VG380SA, the dynamic roll and pitch measurements are stabilized using the
accelerometers as a long-term gravity reference. Unlike the AHRS400 and earlier
MEMSIC AHRS Series products, the AHRS380SA can be configured to turn on and off
the magnetic reference for user defined periods of time (see Section 8 Advanced
Commands). In addition, the AHRS380SA can accept external GPS data (refer to the
INS380SA section for details) for improved performance.
At a fixed 200Hz rate, the AHRS380SA continuously maintains the digital IMU data as
well as the dynamic roll, pitch, and heading. As showing in Figure 10, after the Sensor
Calibration Block, the IMU data is passed to the Integration to Orientation block. The
Integration to Orientation block integrates body frame sensed angular rate to orientation
at a fixed 200 times per second within all of the DMU380SA Series products. 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.
As also shown in the software block diagram, the Integration to Orientation block
receives drift corrections from the Extended Kalman Filter or Drift Correction Module. In
general, rate sensors and accelerometers suffer from bias drift, misalignment errors,
acceleration errors (g-sensitivity), nonlinearity (square terms), and scale factor errors.
The largest error in the orientation propagation is associated with the rate sensor bias
terms. The Extended Kalman Filter (EKF) module provides an on-the-fly calibration for
drift errors, including the rate sensor bias, by providing corrections to the Integration to
Orientation block and a characterization of the gyro bias state. In the AHRS380SA, the
internally computed gravity reference vector and the distortion corrected magnetic field
vector provide an attitude and a heading reference measurement for the EKF when the
AHRS380SA is in quasi-static motion to correct roll, pitch, and heading angle drift and to
estimate the X, Y and Z gyro rate bias. The AHRS380SA adaptively tunes the EKF
feedback gains in order to best balance the bias estimation and attitude correction with
distortion free performance during dynamics when the object is accelerating either
linearly (speed changes) or centripetally (false gravity forces from turns). Because
centripetal and other dynamic accelerations are often associated with yaw rate, the
AHRS380SA maintains a low-passed filtered yaw rate signal and compares it to the
turnSwitch threshold field (user adjustable). When the user platform (with the
AHRS380SA attached) exceeds the turnSwitch threshold yaw rate, the AHRS380SA
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lowers the feedback gains from the accelerometers to allow the attitude estimate to coast
through the dynamic situation with primary reliance on angular rate sensors. This
situation is indicated by the softwareStatusturnSwitch status flag. Using the turn switch
maintains better attitude accuracy during short-term dynamic situations, but care must be
taken to ensure that the duty cycle of the turn switch generally stays below 10% during
the vehicle mission. A high turn switch duty cycle does not allow the system to apply
enough rate sensor bias correction and could allow the attitude estimate to become
unstable.
As described in 4.3 VG380SA theory of operation, the AHRS380SA algorithm also has
two major phases of operation. The first phase of operation is the high-gain initialization
phase. During the initialization phase, the AHRS380SA is expected to be stationary or
quasi-static so the EKF weights the accelerometer gravity reference and Earth’s magnetic
field reference heavily in order to rapidly estimate the X, Y, and Z rate sensor bias, and
the initial attitude and heading of the AHRS380SA. The initialization phase lasts
approximately 60 seconds, and the initialization phase can be monitored in the
softwareStatus BIT transmitted by default in each measurement packet. After the
initialization phase, the AHRS380SA operates with lower levels of feedback (also
referred to as EKF gain) from the accelerometers and magnetometers to continuously
estimate and correct for roll, pitch, and heading (yaw) errors, as well as to estimate X, Y,
and Z rate sensor bias.
The AHRS380SA digital data is output over the RS-232 serial link at a selectable fixed
rate (100, 50, 25, 20, 10, 5 or 2 Hz) or on as requested basis using the GP, ‘Get Packet’
command. The AHRS400 supports the same scaled sensor and angle mode packet format
of the VG380SA. The AHRS380SA defaults to the ‘A1’ Angle Packet which outputs the
roll angle, pitch angle, yaw angle, and digital IMU data. In the AHRS380SA, the ‘A1’
packets contain accurate magnetometer readings. See Sections 6 and 7 of the manual for
full packet descriptions.
 IMPORTANT
For proper operation, the AHRS380SA relies on magnetic field readings from its internal
3-axis magnetometer. The AHRS380SA must be installed correctly and calibrated for
hard-iron and soft iron effects to avoid any system performance degradation. See section
4.4.1 for information and tips regarding installation and calibration.
4.4.1
AHRS380SA Magnetometer Calibration and Alignment
The AHRS380SA uses magnetic sensors to compute heading. Ideally, the magnetic
sensors would measure only the earth's magnetic field to compute the heading angle. In
the real world, however, residual magnetism in your system will add to the magnetic field
measured by the AHRS380SA. This extra magnetic field will create errors in the heading
measurement if they are not accounted for. These extra magnetic fields are called hard
iron magnetic fields. In addition, magnetic material can change the direction of the
magnetic field as a function of the input magnetic field. This dependence of the local
magnetic field on input direction is called the soft iron effect. The AHRS380SA can
actually measure any constant magnetic field that is associated with your system and
correct for it. The AHRS380SA can also make a correction for some soft iron effects.
The process of measuring these non-ideal effects and correcting for them is called hard
iron and soft iron calibration. This calibration will help correct for magnetic fields that
are fixed with respect to the AHRS380SA. It cannot help for time varying fields, or fields
created by parts that move with respect to the AHRS380SA. Because time varying fields
cannot be compensated, selection of a proper installation location is important.
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During the calibration procedure, the AHRS380SA makes a series of measurements
while the user system is being turned through a complete 360 degree circle. A 360 degree
rotation gives the AHRS380SA visibility to hard and soft iron distortion in the horizontal
plane. Using NAV-VIEW, a user can see the hard and soft iron effects by selecting the
Misalignment option on the Configuration Menu, and viewing the magnetic circle during
the calibration.
The AHRS380SA uses these measurements to model the hard iron and soft iron
environment in your system, and store these as calibration constants in the EEPROM.
The status of the AHRS380SA magnetometer calibration is indicated by the
softwareErrordataErrormagAlignOutOfBounds error flag available in the ‘T0’
packet. The current release of this software does not currently implement this feature
however. In future releases, this functionality will be restored. The user can access the
hardIron and softIronScaleRatio calibration data as configuration fields in NAV-VIEW,
or by using the communication protocol. Also, the softwareError bit of the masterFail
byte within the BIT word is transmitted in every measurement packet. When the
AHRS380SA has not been properly calibrated, this softwareError bit will be set to fail
(high). The current release of this software does not currently implement this feature
however. In future releases, this functionality will be restored.
In order for the AHRS380SA calibration to work properly, the AHRS380SA must be
installed in your system prior to calibration. If you perform the calibration process with
the AHRS380SA by itself, you will only correct for the magnetism in the AHRS380SA
itself. If you then install the AHRS380SA in a vehicle (for instance), and the vehicle is
magnetic, you will still see errors arising from the magnetism of the vehicle. The
AHRS380SA must be calibrated after installation and prior to use of the system
The AHRS380SA also provides a command interface for initiating the hard iron / soft
iron calibration without the using NAV-VIEW. The user can send a ‘WC’ command to
initiate the calibration, and then rotate the user system through 360 degrees. The ‘WC’
command has two options – auto-termination and manual termination. With, autotermination, the AHRS380SA tracks the yaw movement and after 380 degrees of rotation
returns the calibration complete response, ‘CD’. The auto-termination sequence can
falsely terminate if the 360 degree rotation is not completed within 2 minutes of the ‘WC’
command initiation. Manual termination requires the user to send a second ‘WC’
command with the termination code in the payload. Manual termination is a good option
when the user system moves very slowly (e.g., large marine vessel) and completing the
360 degree rotation may require more than two minutes.
The calibration complete, ‘CD’, command response message contains the X and Y hard
iron bias, as well as the soft iron ratio and soft iron phase angle. This information can be
interpreted to give an indication of the quality of the calibration. See Section 3.12 for
more information on the hard iron bias and soft iron ratio. Section 7 has programming
details for the ‘WC’ and ‘CD’ commands.
WARNING
The AHRS380SA and INS380SA units must be mounted at least 24” away from large
ferrous objects and fluctuating magnetic fields. Failure to locate the unit in a clean
magnetic environment will affect the attitude solution.
4.4.2
AHRS380SA Advanced Settings
In addition to the configurable baud rate, packet rate, axis orientation, and sensor lowpass filter settings, the AHRS380SA provides additional advanced settings which are
selectable for tailoring the AHRS380SA to a specific application requirements. The
AHRS380SA advanced settings are shown in Table 12:
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Table 12. AHRS380SA Series Advanced Settings
Setting
Default
Comments
Baud Rate
38,400
baud
9600, 19200, 57600 also available
Packet
Type
A1
S0, S1, A2, N0, N1 also available
Packet
Rate
25 Hz
This setting sets the rate at which selected Packet Type, packets are output. If polled
mode is desired, then select Quiet. If Quiet is selected, the VG380SA will only send
measurement packets in response to GP commands.
Orientation
See
To configure the axis orientation, select the desired measurement for each axes: NAVVIEW will show the corresponding image of the AHRS380SA, so it easy to visualize the
mode of operation. See section 8.4 Orientation Field settings for the twenty four possible
orientation settings. The default setting points the connector AFT.
Fig. 12
Filter
Settings
20 Hz
accels
20 Hz
rates
Freely
Integrate
OFF
The low pass filters are set to a default of 20Hz for the accelerometers, and 20Hz for the
angular rate sensors. There is one filter setting for all three angular rate sensors. There
is one filter setting for all three accelerometer sensors. The reason for filtering the
accelerometers is that in many installations, the vibration level can be high, and it can
prove helpful to filter accelerometers.
The Freely Integrate setting allows a user to turn the AHRS380SA into a ‘free gyro’. In
free gyro mode, the roll, pitch and yaw are computed exclusively from angular rate with
no kalman filter based corrections of roll, pitch, or yaw. When turned on, there is no
coupling of acceleration based signals into the roll and pitch or magnetometer based
signals to the yaw. As a result, the roll, pitch, and yaw outputs will drift roughly linearly
with time due to sensor bias. For best performance, the Freely Integrate mode should be
used after the algorithm has initialized. This allows the Kalman Filter to estimate the roll
and pitch rate sensor bias prior to entering the free gyro mode. Upon exiting the ‘free
gyro’ mode (OFF), one of two behaviors will occur
(1) If the AHRS380SA has been in freely integrate mode for less than sixty
seconds, the algorithm will resume operation at normal gain settings
(2) If the AHRS380SA has been in freely integrate mode for greater than sixty
seconds, the algorithm will force a reset and reinitialize with high gains
automatically.
Use Mags
ON
Restart On
Over
Range
OFF
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The Use Mags setting allows users to turn on and off the magnetometer feedback
for yaw/heading stabilization. The default setting is ON for the AHRS380SA. When
Use Mags is turned ON, the AHRS380SA uses the magnetic field sensor readings
to stabilize the drift in yaw, and it slaves the yaw to the compass reading provided
from the magnetic field sensor readings. When Use Mags is turned OFF, the
heading (yaw) angle measurement of the AHRS380SA will drift and freely integrate.
In effect, this setting converts an AHRS380SA into the functionality of the
VG380SA. However, unlike a VG380SA this can be done on a selectable basis and
changed in real time during a mission. The reason for this setting is to give the user
an ability to turn off the magnetometer stabilization when severe magnetic distortion
may be occurring. This setting is desirable when the user system temporarily
moves in close proximity to a large ferrous object. When the Use Mags switch is
turned from OFF to ON, the AHRS380SA will reinitialize the yaw/heading angle
with the compass reading provided from the magnetic field sensor readings.
This setting forces an algorithm reset when a sensor over range occurs i.e., a rotational
rate on any of the three axes exceeds the maximum range. The default setting is OFF for
the AHRS380SA. Algorithm reset returns the AHRS380SA to a high gain state, where
the AHRS380SA rapidly estimates the gyro bias and uses the accelerometer feedback
heavily. This setting is recommended when the source of over-range is likely to be
sustained and potentially much greater than the rate sensor operating limit. Large and
sustained angular rate over-ranges result in unrecoverable errors in roll and pitch
outputs. An unrecoverable error is one where the EKF can not stabilize the resulting roll
and pitch reading. If the over-ranges are expected to be of short duration (<1 sec) and a
modest percentage over the maximum operating range, it is recommended that the
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restart on over range setting be turned off. Handling of an inertial rate sensor over-range
is controlled using the restartOnOverRange switch. If this switch is off, the system will
flag the overRange status flag and continue to operate through it. If this switch is on, the
system will flag a masterFail error during an over-range condition and continue to
operate with this flag until a quasi-static condition is met to allow for an algorithm restart.
The quasi-static condition required is that the absolute value of each low-passed rate
sensor fall below 3 deg/sec to begin initialization. The system will then attempt a normal
algorithm start.
Dynamic
Motion
ON
The default setting is ON for the AHRS380SA. Turning off the dynamic motion setting
results in a higher gain state that uses the accelerometer feedback heavily. During
periods of time when there is known low dynamic acceleration, this switch can be turned
off to allow the attitude estimate to quickly stabilize.
Turn
Switch
threshold
0.5
deg/sec
With respect to centripetal or false gravity forces from turning dynamics (or coordinated
turn), the AHRS380SA monitors the yaw-rate. If the yaw rate exceeds a given Turnswitch
threshold, the feedback gains from the accelerometer signals for attitude correction are
reduced because they are likely corrupted.
BIT
4.4.3
See 4.4.3
AHRS380SA Built-In Test
As with the IMU380SA and VG380SA, the Built-In Test capability allows users of the
AHRS380SA to monitor health, diagnostic, and system status information of the unit in
real-time. The Built-In Test information consists of a BIT word (2 bytes) transmitted in
every measurement packet. In addition, there is a diagnostic packet ‘T0’ that can be
requested via the Get Packet ‘GP’ command which contains a complete set of status for
each hardware and software subsystem in the AHRS380SA. See Sections 6 and 7 of the
Programming Guide, for details on the ‘T0’ packet.
The BIT word contained within each measurement packet is detailed below. The LSB
(Least Significant Bit)) is the Error byte, and the MSB (Most Significant Bit) is a Status
byte with programmable alerts. Internal health and status are monitored and
communicated in both hardware and software. The ultimate indication of a fatal problem
is the masterFail flag. The softwareError bit also provides useful information regarding
the status and quality of the AHRS380SA magnetic alignment. If the AHRS380SA has
not been properly magnetically calibrated, the AHRS380SA shall indicate a
softwareError.
The masterStatus flag is a configurable indication that can be modified by the user. This
flag is asserted as a result of any asserted alert signals which has been enabled. See
Section 9 Advanced BIT for details on configuring the masterStatus flags. Table 13
shows the BIT definition and default settings for BIT programmable alerts in the
AHRS380SA.
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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.
4.5
INS380SA Theory of Operation
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.
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Following the integration to orientation block, the body frame accelerometer signals are
rotated into the NED level frame and are integrated to velocity. At this point, the data is
blended with GPS position data, and output as a complete navigation solution.
As shown in Figure 10, the Integration to Orientation and the Integration to Velocity
signal processing blocks receive drift corrections from the Extended Kalman Filter (EKF)
drift correction module. The drift correction module uses data from the aiding sensors,
when they are available, to correct the errors in the velocity, attitude, and heading
outputs. Additionally, when aiding sensors are available corrections to the rate gyro and
accelerometers are performed.
The INS380SA blends GPS derived heading and accelerometer measurements into the
EKF update depending on the health and status of the associated sensors. If the GPS link
is lost or poor, the Kalman Filter solution stops tracking accelerometer bias, but the
algorithm continues to apply gyro bias correction and provides stabilized angle outputs.
The EKF tracking states are reduced to angles and gyro bias only. The accelerometers
will continue to integrate velocity, however, accelerometer noise, bias, and attitude error
will cause the velocity estimates to start drifting within a few seconds. The attitude
tracking performance will degrade, the heading will freely drift, and the filter will revert
to the VG only EKF formulation. The UTC packet synchronization will drift due to
internal clock drift.
The status of GPS signal acquisition can be monitored from the hardwareStatus BIT as
discussed in Section 4.5.3 INS380SA Built in Test. From a cold start, it typically takes 40
seconds for GPS to lock. The actual lock time depends on the antenna’s view of the sky
and the number of satellites in view.
The ARM performs time-triggered trajectory propagation at 100Hz and will synchronize
the sensor sampling with the GPS UTC (Universal Coordinated Time) second boundary
when available.
As with the AHRS380SA and VG380SA, the algorithm has two major phases of
operation. Immediately after power-up, the INS380SA uses the accelerometers and
magnetometers to compute the initial roll, pitch and yaw angles. The roll and pitch
attitude will be initialized using the accelerometer’s reference of gravity, and yaw will be
initialized using the leveled magnetometers X and Y axis reference of the earth’s
magnetic field. During the first 60 seconds of startup, the INS380SA should remain
approximately motionless in order to properly initialize the rate sensor bias. The
initialization phase lasts approximately 60 seconds, and the initialization phase can be
monitored in the softwareStatus BIT transmitted by default in each measurement packet.
After the initialization phase, the INS380SA operates with lower levels of feedback (also
referred to as EKF gain) from the GPS, accelerometers, and magnetometers.
Digital data is output over the RS-232 serial link at a selectable fixed rate (100, 50, 25,
20, 10, 5 or 2 Hz) or on as requested basis using the GP, ‘Get Packet’ command. In
addition to the angle mode packets of the AHRS380SA and scaled sensor packets of the
IMU380SA, the INS380SA has additional output measurement packets including the
default ‘N1’ Navigation Packet which outputs the Latitude, Longitude, Altitude, X,Y,Z
velocities, accelerations, and roll angle, pitch angle, yaw angle, and digital IMU data. See
Section 6 and 7 of the manual for full packet descriptions.
 IMPORTANT
For proper operation, the INS380SA relies on magnetic field readings from its internal 3axis magnetometer. The INS380SA must be installed correctly and calibrated for hardiron and soft iron effects to avoid any system performance degradation. See section 4.4.1
for information and tips regarding installation and calibration and why magnetic
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calibration is necessary. Please review this section of the manual before proceeding to use
the INS380SA.
 IMPORTANT
For optimal performance the INS380SA utilizes GPS readings from its internal GPS
receiver. The GPS receiver requires proper antennae installation for operation. See
section 4.4.1 for information and tips regarding installation and calibration.
4.5.1
INS380SA Magnetometer Calibration and Alignment
The INS380SA requires the three axis magnetic field sensor to be calibrated while
installed in its operating environment. See section 4.4.1 for information and tips
regarding installation and calibration and why magnetic calibration is necessary. Please
review this section of the manual before proceeding to use the INS380SA.
4.5.2
INS380SA Advanced Settings
In addition to the configurable baud rate, packet rate, axis orientation, and sensor lowpass filter settings, the INS380SA provides additional advanced settings which are
selectable for tailoring the INS380SA to a specific application requirements. The
INS380SA advanced settings are shown in Table 14 below:
Table 14. INS380SA Series Advanced Settings
Setting
Default
Comments
Baud Rate
38,400
baud
9600, 19200, 57600 also available
Packet Type
N1
S0, S1, A1, A2, N0 also available
Packet Rate
25 Hz
This setting sets the rate at which selected Packet Type, packets are output. If polled
mode is desired, then select Quiet. If Quiet is selected, the INS380SA will only send
measurement packets in response to GP commands.
Orientation
See
To configure the axis orientation, select the desired measurement for each axes; NAVVIEW will show the corresponding image of the INS380SA, so it easy to visualize the
mode of operation. See section 8.4 Orientation Field settings for the twenty four possible
orientation settings. The default setting points the connector AFT.
Fig. 12
Filter Settings
20 Hz
accels
20 Hz
rates
Freely Integrate
OFF
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The low pass filters are set to a default of 20Hz for the accelerometers, and 20Hz for the
angular rate sensors. There is one filter setting for all three angular rate sensors. There is
one filter setting for all three accelerometer sensors. The reason for filtering the
accelerometers is that in many installations, the vibration level can be high, and it can
prove helpful to filter accelerometers.
The Freely Integrate setting allows a user to turn the INS380SA into a ‘free gyro’. In free
gyro mode, the roll, pitch and yaw are computed exclusively from angular rate with no
kalman filter based corrections of roll, pitch, and yaw. When turned on, there is no
coupling of acceleration based signals into the roll and pitch or magnetometer based
signal to the yaw. As a result, the roll, pitch, and yaw outputs will drift roughly linearly with
time due to sensor bias. For best performance, the Freely Integrate mode should be
used after the algorithm has initialized. This allows the Kalman Filter to estimate the roll
and pitch rate sensor bias prior to entering the free gyro mode. Upon exiting the ‘free
gyro’ mode (OFF), one of two behaviors will occur
(1)
If the INS380SA has been in freely integrate mode for less than sixty seconds,
the algorithm will resume operation at normal gain settings
(2)
If the INS380SA has been in freely integrate mode for greater than sixty
seconds, the algorithm will force a reset and reinitialize with high gains
automatically.
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Use GPS
ON
The Use GPS setting allows users to turn on and off the GPS feedback. The default
setting is ON for the INS380SA. When Use GPS is turned OFF, the INS380SA’s behavior
will revert to that of an AHRS380SA. See the AHRS380SA Theory of Operation for
detailed description.
Stationary Yaw
Lock
OFF
This setting defaults to OFF on the INS380SA, and it is recommended to be OFF for the
INS380SA. The stationary yaw lock setting is only recommended for consideration when
the INS380SA is operating with GPS (Use GPS = ON) and WITHOUT magnetometer
feedback (Use Mags = OFF). Stationary yaw lock may be appropriate if the user platform
is a wheeled land vehicle.
Use Mags
ON
The Use Mags setting allows users to turn on and off the magnetometer feedback for
yaw/heading stabilization. The default setting is ON for the INS380SA. When Use Mags
is turned ON, the INS380SA uses the magnetic field sensor readings to stabilize the drift
in yaw, and it slaves the yaw to the compass reading provided from the magnetic field
sensor readings. When UseMags is turned OFF, the heading (yaw) angle measurement
of the INS380SA will be slaved to the GPS heading if GPS is available, otherwise the
heading will drift feely. The reason for this setting is to give the user an ability to turn off
the magnetometer stabilization when severe magnetic distortion may be occurring. This
setting is desirable when the user vehicle temporarily moves in close proximity to a large
ferrous object. When the Use Mags switch is turned from OFF to ON, the INS380SA will
reinitialize the yaw/heading angle with the compass reading provided from the magnetic
field sensor readings.
Restart On Over
Range
OFF
This setting forces an algorithm reset when a sensor over range occurs i.e., a rotational
rate on any of the three axes exceeds the maximum range. The default setting is OFF for
the INS380SA. Algorithm reset returns the INS380SA to a high gain state, where the
INS380SA rapidly estimates the gyro bias and uses the accelerometer feedback heavily.
This setting is recommended when the source of over-range is likely to be sustained and
potentially much greater than the rate sensor operating limit. Large and sustained
angular rate over-ranges result in unrecoverable errors in roll and pitch outputs. An
unrecoverable error is one where the EKF can not stabilize the resulting roll and pitch
reading. If the over-ranges are expected to be of short duration (<1 sec) and a modest
percentage over the maximum operating range, it is recommended that the restart on
over range setting be turned off. Handling of an inertial rate sensor over-range is
controlled using the restartOnOverRange switch. If this switch is off, the system will flag
the overRange status flag and continue to operate through it. If this switch is on, the
system will flag a masterFail error during an over-range condition and continue to operate
with this flag until a quasi-static condition is met to allow for an algorithm restart. The
quasi-static condition required is that the absolute value of each low-passed rate sensor
fall below 3 deg/sec to begin initialization. The system will then attempt a normal
algorithm start.
Dynamic
Motion
ON
The default setting is ON for the INS380SA. Turning off the dynamic motion setting
results in a higher gain state that uses the accelerometer feedback heavily. During
periods of time when there is known low dynamic acceleration, this switch can be turned
off to allow the attitude estimate to quickly stabilize.
Turn Switch
threshold
0.5
deg/sec
With respect to centripetal or false gravity forces from turning dynamics (or coordinated
turn), the INS380SA monitors the yaw-rate. If the yaw rate exceeds a given Turnswitch
threshold, the feedback gains from the accelerometer signals for attitude correction are
reduced because they are likely corrupted.
BIT
4.5.3
See 4.5.3
INS380SA Built-In Test
As with the IMU, VG and AHRS380SA, the Built-In Test capability allows users of the
INS380SA to monitor health, diagnostic, and system status information of the unit in
real-time. The Built-In Test information consists of a BIT word (2 bytes) transmitted in
every measurement packet. In addition, there is a diagnostic packet ‘T0’ that can be
requested via the Get Packet ‘GP’ command which contains a complete set of status for
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each hardware and software subsystem in the INS380SA. See Section 6 and 7
Programming Guide, for details on the ‘T0’ packet.
The BIT word contained within each measurement packet is detailed below. The LSB
(Least Significant Bit) is the Error byte, and the MSB (Most Significant Bit) is a Status
byte with programmable alerts. Internal health and status are monitored and
communicated in both hardware and software. The ultimate indication of a fatal problem
is the masterFail flag. The softwareError bit also provides useful information regarding
the status and quality of the INS380SA magnetic alignment. If the INS380SA has not
been properly magnetically calibrated, the INS380SA shall indicate a softwareError.
The masterStatus flag is a configurable indication that can be modified by the user. This
flag is asserted as a result of any asserted alert signals which have been enabled. See
Advanced Settings for details for configuring the masterStatus flags. Table 15 shows the
BIT definition and default settings for BIT programmable alerts in the INS380SA.
Table 15. INS380SA 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 alert
Status
hardwareStatus
9
0 = nominal, 1 = Internal GPS unlocked or 1PPS
invalid
Status
comStatus
10
Disabled
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 INS380SA 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 IMU, VG and AHRS380SA, MEMSIC
recommends for the vast majority of users, that the default Status byte for the INS380SA
is sufficient. For users, who wish to have additional visibility or alerts relative to the GPS
sensor status or algorithm status, they can configure additional triggers for both the
softwareStatus and hardwareStatus (See Sections 9 of the user’s manual for all the BIT
fields).
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5
5.1
Application Guide
Introduction
This section provides recommended advanced settings for tailoring the DMU380SA
Series of inertial systems to different types of application and platform requirements.
5.2
Fixed Wing Aircraft
A fixed-wing aircraft is a heavier-than-air craft where movement of the wings in relation
to the aircraft is not used to generate lift. The term is used to distinguish from rotary-wing
aircraft, where the movement of the wing surfaces relative to the aircraft generates lift.
The fixed wing aircraft can range in size from the smallest experimental plane to the
largest commercial jet. The dynamic characteristics of the fixed wing aircraft depends
upon types of aircraft (i.g., glider, propeller aircraft, and jet aircraft) and mission phases
(i.e., launch, landing, and maneuver). In order to meet application requirements, users
must dial in proper advanced settings so that the DMU380SA Series can provide the best
possible solution under given dynamic conditions. For example, Table 16 provides the
recommended advanced settings for four different dynamic conditions.
Table 16. Recommended Advanced Settings for Fixed Wing Aircraft
Recommended
Product
AHRS380SA or INS380SA
Dynamic Condition
Recommended
Settings
Pre-launch or known
straight and level unaccelerated flight
Launch
Normal
Dynamics
(Default)
High Dynamics
UseMags
ON
ON
ON
ON
UseGPS
ON
ON (< 4g)
ON
ON (< 4g)
FreelyIntegrate
OFF
OFF§
OFF
OFF (< 2g)
Stationary Yaw Lock
OFF
OFF
OFF
OFF
Restart Over Range
ON
OFF
OFF
OFF
Dynamic Motion
OFF
ON
ON
ON
0.5 deg/s
0.5 deg/s
0.5 deg/s
0.5 deg/s
XY Filter Accel
5 Hz
5 Hz
5 Hz*
15 Hz
Z Filter Accel
5 Hz
5 Hz
5 Hz*
15 Hz
Filter Rate Sensor
20 Hz
20 Hz
20 Hz*
20 Hz
Turn Switch Threshold
*A cutoff frequency of filters may be varied depending on the fastest dynamic mode of the
aircraft. For example, the conventional aircraft has five dynamic modes, short-period, phugoid,
spiral, dutch-roll, and roll, and the fastest one is the roll mode. The natural frequency of this
mode is around 6~8 radian/sec or (about 2 Hz) in most cases. Therefore, the recommended
filter setting would not reject desired frequency components (or dynamic modes) that one
wants to capture. However, the larger the bandwidth (or cutoff frequency) is, the noisier the
corresponding signal is, which may result in the performance degradation. If the aircraft is
operated under severe vibrations, also, the recommended filter setting may need to be further
reduced in order to reject the frequency components caused by the vibration.
§FreelyIntegrate should only be set to “ON” for severe launch conditions. Normal takeoff
dynamics that a standard aircraft would experience will see the best performance with this
setting in the “OFF” position.
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5.3
Rotorcraft
Rotorcraft is a category of heavier-than-air flying machines that use lift generated by
rotors. They may also include the use of static lifting surfaces, but the primary
distinguishing feature being lift provided by rotating lift structures. Rotorcraft includes
helicopters, autogyros, gyrodynes and tiltrotors.
The rotor blade dynamics itself is much faster than that of the fixed wing aircraft and
contains high frequency components. At the same time, however, it may cause severe
vibrations on the airframe. Also, the overall dynamics (translational and rotational
motion) of the rotor craft is much slower than the fixed wing aircraft due to a mechanical
mechanism of rotors generating the aerodynamic forces and moments. Table 17 provides
the recommended advanced settings for two different dynamic conditions.
Table 17. Recommended Advanced Settings for Rotorcraft
Recommended Product
AHRS380SA or INS380SA
Dynamic Condition
Recommended Settings
Normal Dynamics
High Dynamics
(with uncoordinated tail motion)
UseMags
ON
UseGPS
ON
ON (< 4g)
FreelyIntegrate
OFF
OFF (< 2g)
Stationary Yaw Lock
OFF
OFF
Restart Over Range
OFF
ON
Dynamic Motion
ON
ON
1.0 deg/s §
30.0 deg/s §
XY Filter Accel
5 Hz*
5 Hz
Z Filter Accel
5 Hz*
5 Hz
Filter Rate Sensor
20 Hz*
20 Hz
Turn Switch Threshold
ON
§The helicopter can change its heading angle rapidly unlike the aircraft
which requires banking. A turn switch threshold that is too low may cause
turn switch activation with high duty cycle causing random walk in roll and
pitch angles due to low feedback gains.
*A cutoff frequency must be far away from major frequency components
caused by the rotor vibration.
5.4
Land Vehicle
Some examples of land vehicles are: Automobiles, trucks, heavy equipment, trains,
snowmobiles, and other tracked vehicles. Table 18 provides the recommended advanced
settings for two different types of application.
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Table 18.
Recommended Advanced Settings for Land Vehicle
Recommended Product
VG380SA or INS380SA
Dynamic Condition
Recommended Settings
Heavy Equipment
Application
Automotive Testing (IMU and VG default)
UseMags
ON§
UseGPS
ON
FreelyIntegrate
OFF
OFF
Stationary Yaw Lock
OFF
OFF
Restart Over Range
ON
OFF
Dynamic Motion
ON
ON
5.0 deg/s
10.0 deg/s
XY Filter Accel
5 Hz
5 Hz
Z Filter Accel
5 Hz
5 Hz
Filter Rate Sensor
20 Hz
20 Hz
Turn Switch Threshold
ON§
ON (< 4g)
§When not in distorted magnetic environment.
5.5
Water Vehicle
Water vehicle is a craft or vessel designed to float on or submerge and provide transport
over and under water. Table 19 provides the recommended advanced settings for two
different types of application.
Table 19.
Recommended Advanced Settings for Water Vehicle
Recommended Product
Recommended Settings
INS380SA
Application
Surfaced
Submerged
UseMags
ON§
ON§
UseGPS
ON
OFF
FreeIntegrate
OFF
OFF
Stationary Yaw Lock
OFF
OFF
Restart Over Range
OFF
OFF
Dynamic Motion
ON
ON
10 deg/s
5 deg/s
XY Filter Accel
5 Hz
2 Hz
Z Filter Accel
5 Hz
2 Hz
Filter Rate Sensor
15 Hz
10 Hz
Turn Switch Threshold
§When not in distorted magnetic environment.
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 EXAMPLE
Figure 17 shows a typical flight profile of the fixed wing aircraft and the corresponding
advanced settings that one can configure adaptively depending on a flight phase:

Prelaunch is the phase of flight in which an aircraft goes through a series of
checkups (hardware and software) on the ground before takeoff. The aircraft is a
static condition,

Takeoff is the phase of flight in which an aircraft goes through a transition from
moving along the ground (taxiing) to flying in the air, usually along a runway.
The aircraft is under horizontal acceleration and may suffer from vibrations
coming from an engine and ground contact forces transmitted from its landing
gear.

Climb is the phase of a flight, after take off, consisting of getting the aircraft to
the desired flight level altitude. More generally, the term 'climb' means increasing
the altitude. The aircraft is under vertical acceleration until it reaches the steadystate climb rate.

Straight and level flight is the phase of flight in which an aircraft reaches its
nominal flight altitude and maintains its speed and altitude. The aircraft is under
equilibrium (See Figure 17).

Maneuver is the phase of flight in which an aircraft accelerates, decelerates, and
turns. The aircraft is under non-gravitational acceleration and/or deceleration
(See Figure 17).

Descent is the phase of flight in which an aircraft decreases altitude for an
approach to landing. The aircraft is under vertical deceleration until it captures a
glide slope (See Figure 17).

Landing is the last part of a flight, where the aircraft returns to the ground (See
Figure 17).
Figure 17.
Typical flight profiles of fixed wing aircraft and the corresponding advanced settings.
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6
Programming Guide
The DMU380SA Series contains a number of different products which have different
measurement capabilities. Depending on the model you purchased, various commands
and output modes are supported. However, all models support a common packet structure
that includes both command or input data packets (data sent to the DMU380SA Series)
and measurement output or response packet formats (data sent from the DMU380SA
Series). This section of the manual explains these packet formats as well as the supported
commands. NAV-VIEW also features a number of tools that can help a user understand
the packet types available and the information contained within the packets. This section
of the manual assumes that the user is familiar with ANSI C programming language and
data type conventions.
For an example of the code required to parse input data packets, please see refer to
Appendix C.
For qualified commercial OEM users, a source code license of NAV-VIEW can be made
available under certain conditions. Please contact your MEMSIC representative for more
information.
6.1
General Settings
The serial port settings are RS232 with 1 start bit, 8 data bits, no parity bit, 1 stop bit, and
no flow control. Standard baud rates supported are: 9600, 19200, 38400, and 57600.
Common definitions include:

A word is defined to be 2 bytes or 16 bits.

All communications to and from the unit are packets that start with a single word
alternating bit preamble 0x5555. This is the ASCII string “UU”.

All multiple byte values are transmitted Big Endian (Most Significant Byte First).

All communication packets end with a single word CRC (2 bytes). CRC’s are
calculated on all packet bytes excluding the preamble and CRC itself. Input
packets with incorrect CRC’s will be ignored.

Each complete communication packet must be transmitted to the DMU380SA
Series inertial system within a 4 second period.
6.2
Number Formats
Number Format Conventions include:

0x as a prefix to hexadecimal values

single quotes (‘’) to delimit ASCII characters

no prefix or delimiters to specify decimal values.
Table 20 defines number formats:
Table 20. Number Formats
Descriptor
U1
U2
U4
Description
Unsigned Char
Unsigned Short
Unsigned Int
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Size (bytes)
1
2
4
Comment
Range
0 to 255
0 to 65535
0 to 2^32-1
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I2
I2*
Signed Short
Signed Short
2
2
2’s Complement
Shifted 2’s Complement
I4
F4
Signed Int
Floating Point
4
4
SN
String
N
2’s Complement
IEEE754 Single
Precision
ASCII
6.3
-2^15 to 2^15-1
Shifted to specified
range
-2^31 to 2^31-1
-1*2^127 to 2^127
Packet Format
All of the Input and Output packets, except the Ping command, conform to the following
structure:
0x5555
<2-byte packet type
(U2)>
<payload byte-length
(U1)>
<variable length
payload>
<2-byte CRC (U2)>
The Ping Command does not require a CRC, so a DMU380SA Series unit can be pinged
from a terminal emulator. To Ping a DMU380SA Series unit, type the ASCII string
‘UUPK’. If properly connected, the DMU380SA Series unit will respond with ‘PK’. All
other communications with the DMU380SA Series unit require the 2-byte CRC. {Note:
A DMU380SA Series unit will also respond to a ping command using the full packet
formation with payload 0 and correctly calculated CRC. Example: 0x5555504B009ef4 }.
6.3.1
Packet Header
The packet header is always the bit pattern 0x5555.
6.3.2
Packet Type
The packet type is always two bytes long in unsigned short integer format. Most input
and output packet types can be interpreted as a pair of ASCII characters. As a semantic
aid consider the following single character acronyms:
P = packet
F = fields
Refers to Fields which are settings or data contained in the unit
E = EEPROM
Refers to factory data stored in EEPROM
R = read
Reads default non-volatile fields
G = get
Gets current volatile fields or settings
W = write
Writes default non-volatile fields. These fields are stored in non-volatile memory
and determine the unit’s behavior on power up. Modifying default fields take
effect on the next power up and thereafter.
S = set
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Sets current volatile fields or settings. Modifying current fields will take effect
immediately by modifying internal RAM and are lost on a power cycle.
6.3.3
Payload Length
The payload length is always a one byte unsigned character with a range of 0-255. The
payload length byte is the length(in bytes) of the <variable length payload> portion of
the packet ONLY, and does not include the CRC.
6.3.4
Payload
The payload is of variable length based on the packet type.
6.3.5
16-bit CRC-CCITT
Packets end with a 16-bit CRC-CCITT calculated on the entire packet excluding the
0x5555 header and the CRC field itself. A discussion of the 16-bit CRC-CCITT and
sample code for implementing the computation of the CRC is included at the end of this
document. This 16-bit CRC standard is maintained by the International
Telecommunication Union (ITU). The highlights are:
Width = 16 bits
Polynomial 0x1021
Initial value = 0xFFFF
No XOR performed on the final value.
See Appendix C for sample code that implements the 16-bit CRC algorithm.
6.3.6
Messaging Overview
Table 21 summarizes the messages available by DMU380SA Series model. Packet types
are assigned mostly using the ASCII mnemonics defined above and are indicated in the
summary table below and in the detailed sections for each command. The payload bytelength is often related to other data elements in the packet as defined in the table below.
The referenced variables are defined in the detailed sections following. Output messages
are sent from the DMU380SA Series inertial system to the user system as a result of a
poll request or a continuous packet output setting. Input messages are sent from the user
system to the DMU380SA Series inertial system and will result in an associated Reply
Message or NAK message. Note that reply messages typically have the same <2-byte
packet type (U2)> as the input message that evoked it but with a different payload.
Table 21. Message Table
ASCII
Mnemonic
<2-byte
packet
type (U2)>
<payload
byte-length
(U1)>
Description
Type
Products
Available
PK
0x504B
0
0x4348
N
Input/Reply
Message
Input/Reply
Message
ALL
CH
Ping Command
and Response
Echo Command
and Response
Interactive
Commands
GP
0x4750
2
Get Packet
Request
Input
Message
ALL
Link Test
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AR
0x4152
0
Algorithm Reset
NAK
0x1515
2
Error Response
WC
0x5743
2
CD
0x4344
10
Calibrate
Command and
Response
Calibration
Completed
Output
Messages:
Status & Other,
(Polled Only)
ID
0x4944
5+N
Identification Data
VR
0x5652
5
Version Data
T0
0x5430
28
Test 0 (Detailed
BIT and Status)
Output
Messages:
Measurement
Data
(Continuous or
Polled)
S0
0x5330
30
S1
0x5331
24
A1
0x4131
32
Scaled Sensor 0
Data
Scaled Sensor 1
Data
Angle 1 Data
A2
0x4132
30
Angle 2 Data
N0
0x4E30
32
Nav 0 Data
N1
0x4E31
42
Nav 1 Data
Advanced
Commands
WF
0x5746
WF
0x5746
SF
0x5346
SF
0x5346
numFields*4+
1
numFields*2+
1
numFields*4+
1
numFields*2+
1
Write Fields
Request
Write Fields
Response
Set Fields
Request
Set Fields
Response
RF
0x5246
RF
0x5246
GF
0x4746
numFields*2+
1
numFields*4+
1
numFields*2+
1
Read Fields
Request
Read Fields
Response
Get Fields
Request
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Input/Reply
Message
Reply
Message
Input/Reply
Message
VG,AHRS, INS
Reply
Message
AHRS, INS
Output
Message
Output
Message
Output
Message
ALL
Output
Message
Output
Message
Output
Message
Output
Message
Output
Message
Output
Message
AHRS, INS
Input
Message
Reply
Message
Input
Message
Reply
Message
Input
Message
Reply
Message
Input
Message
ALL
ALL
AHRS, INS
ALL
ALL
ALL
AHRS, INS
VG, AHRS,
INS
VG, AHRS,
INS
VG,,AHRS,
INS
ALL
ALL
ALL
ALL
ALL
ALL
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GF
0x4746
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numFields*4+
1
Get Fields
Response
Reply
Message
ALL
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7 Communicating with the DMU380SA Series
7.1
Link Test.
7.1.1 Ping Command
Ping (‘PK’ = 0x504B)
Preamble
0x5555
Packet Type
0x504B
Length
-
Termination
-
The ping command has no payload. Sending the ping command will cause the unit to
send a ping response. To facilitate human input from a terminal, the length and CRC
fields are not required. (Example: 0x5555504B009ef4 or 0x5555504B))
7.1.2 Ping Response
Ping (‘PK’ = 0x504B)
Preamble
0x5555
Packet Type
0x504B
Length
0x00
Termination
<CRC (U2)>
The unit will send this packet in response to a ping command.
7.1.3 Echo Command
Echo (‘CH’ = 0x4348)
Preamble
0x5555
Packet Type
0x4348
Length
N
Payload
<echo payload>
Termination
<CRC (U2)>
The echo command allows testing and verification of the communication link. The unit
will respond with an echo response containing the echo data. The echo data is N bytes
long.
7.1.4 Echo Response
Echo Payload Contents
Byte Offset
0
1
…
N-2
N-1
7.2
Name
echoData0
echoData1
…
echoData...
echoData…
Format
U1
U1
U1
U1
U1
Scaling
-
Units
-
Description
first byte of echo data
Second byte of echo data
Echo data
Second to last byte of echo data
Last byte of echo data
Interactive Commands
Interactive commands are used to interactively request data from the DMU380SA Series,
and to calibrate or reset the DMU380SA Series.
7.2.1 Get Packet Request
Get Packet (‘GP’ = 0x4750)
Preamble
0x5555
Packet Type
0x4750
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Length
0x02
Payload
<GP payload>
Termination
<CRC (U2)>
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This command allows the user to poll for both measurement packets and special purpose
output packets including ‘T0’, ‘VR’, and ‘ID’.
GP Payload Contents
Byte Offset
0
Name
requestedPacketType
Format
U2
Scaling
-
Units
-
Description
The requested packet
type
Refer to the sections below for Packet Definitions sent in response to the ‘GP’ command
7.2.2 Algorithm Reset Command
Algorithm Reset (‘AR’ = 0x4152)
Preamble
0x5555
Packet Type
0x4152
Length
0x00
Payload
-
Termination
<CRC (U2)>
This command resets the state estimation algorithm without reloading fields from
EEPROM. All current field values will remain in affect. The unit will respond with an
algorithm reset response.
7.2.3 Algorithm Reset Response
Algorithm Reset (‘AR’ = 0x4152)
Preamble
0x5555
Packet Type
0x4152
Length
0x00
Termination
<CRC (U2)>
The unit will send this packet in response to an algorithm reset command.
7.2.4 Calibrate Command
Calibrate (‘WC’ = 0x5743)
Preamble
0x5555
Packet Type
0x5743
Length
0x02
Payload
<WC payload>
Termination
<CRC (U2)>
This command allows the user to perform various calibration tasks with the DMU380SA
Series. See the calibration command table below for details. The unit will respond
immediately with a calibrate response containing the calibrationRequest received or an
error response if the command cannot be performed.
WC Payload Contents
Byte Offset
0
Name
calibrationRequest
Format
U2
Scaling
-
Units
-
Description
The requested calibration
task
Currently, magnetic alignment is the only function supported by the calibrate command.
There are two magnetic alignment procedures supported; (1) magnetic alignment with
automatic yaw tracking termination, and magnetic alignment without automatic
termination.
calibrationRequest
Description
0x0009
Begin magnetic alignment without automatic termination. Rotate vehicle
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through >360 degrees yaw and then send 0x000B calibration request to
terminate.
Terminate magnetic alignment. The unit will send a CC response containing
the hard-iron and soft-iron values. To accept the parameters, store them
using the write magnetic calibration command.
Begin magnetic calibration with automatic termination. Rotate the unit
through 380 degrees in yaw. The unit will send a CC response containing
the hard-iron and soft-iron values upon completion of the turn. To accept the
parameters, store them using the write magnetic calibration command.
Write magnetic calibration. The unit will write the parameters to EEPROM
and then send a calibration response.
0x000B
0x000C
0x000E
7.2.5 Calibrate Acknowledgement Response
Calibrate (‘WC’ = 0x5743)
Preamble
0x5555
Packet Type
0x5743
Length
0x02
Payload
<WC payload>
Termination
<CRC (U2)>
The unit will send this packet in response to a calibrate request if the procedure can be
performed or initiated.
WC Payload Contents
Byte Offset
0
Name
calibrationRequest
Format
U2
Scaling
-
Units
-
Description
The requested calibration
task
7.2.6 Calibration Completed Parameters Response
Calibrate Completed (‘CD’ = 0x4344)
Preamble
0x5555
Packet Type
0x4344
Length
0x0A
Payload
<CD payload>
Termination
<CRC (U2)>
The unit will send this packet after a calibration has been completed. Currently, there is
only one message of this type sent after a magnetic calibration has been completed (with
or without automatic termination) and the parameters have been calculated. Thus, the
calibrationRequest field will be 0x000B or 0x000C.
CD Payload Contents
Byte Offset
0
Name
calibrationRequest
Format
U2
Scaling
-
Units
-
2
4
6
xHardIron
yHardIron
softIronScaleRatio
I2
I2
U2
20/2^16
20/2^16
2/2^16
G
G
-
8
softIronAngle
I2
2*pi/2^16
(360/2^16)
Rad
Deg
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Description
The requested calibration
task
The x hard iron bias
The y hard iron bias
The scaling ratio between
the x and y axis
The soft iron phase angle
between x and y axis
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7.2.9 Error Response
Error Response (ASCII NAK, NAK = 0x1515)
Preamble
0x5555
Packet Type
0x1515
Length
0x02
Payload
<NAK payload>
Termination
<CRC (U2)>
The unit will send this packet in place of a normal response to a faiiledInputPacketType
request if it could not be completed successfully.
NAK Payload Contents
Byte Offset
0
7.3
Name
failedInputPacketType
Format
U2
Scaling
-
Units
-
Description
the failed request
Output Packets (Polled)
The following packet formats are special informational packets which can be requested
using the ‘GP’ command.
7.3.1 Identification Data Packet
Identification Data (‘ID’ = 0x4944)
Preamble
0x5555
Packet Type
0x4944
Length
5+N
Payload
<ID payload>
Termination
<CRC (U2)>
This packet contains the unit serialNumber and modelString. The model string is
terminated with 0x00. The model string contains the programmed versionString (8-bit
Ascii values) followed by the firmware part number string delimited by a whitespace.
ID Payload Contents
Byte Offset
0
4
4+N
Name
serialNumber
modelString
0x00
Format
U4
SN
U1
Scaling
-
Units
-
Description
Unit serial number
Unit Version String
Zero Delimiter
7.3.2 Version Data Packet
Version Data (‘VR’ = 0x5652)
Preamble
0x5555
Packet Type
0x5652
Length
5
Payload
<VR payload>
Termination
<CRC (U2)>
This packet contains firmware version information. majorVersion changes may introduce
serious incompatibilities. minorVersion changes may add or modify functionality, but
maintain backward compatibility with previous minor versions. patch level changes
reflect bug fixes and internal modifications with little effect on the user. The build stage
is one of the following: 0=release candidate, 1=development, 2=alpha, 3=beta. The
buildNumber is incremented with each engineering firmware build. The buildNumber and
stage for released firmware are both zero. The final beta candidate is v.w.x.3.y, which is
then changed to v.w.x.0.1 to create the first release candidate. The last release candidate
is v.w.x.0.z, which is then changed to v.w.x.0.0 for release.
VR Payload Contents
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Byte Offset
0
1
2
3
Name
majorVersion
minorVersion
patch
stage
Format
U1
U1
U1
-
Scaling
-
Units
-
4
buildNumber
U1
-
-
Description
Major firmware version
Minor firmware version
Patch level
Development Stage (0=release
candidate, 1=development,
2=alpha, 3=beta)
Build number
7.3.3 Test 0 (Detailed BIT and Status) Packet
Test (‘T0’ = 0x5430)
Preamble
03.3x5555
Packet Type
0x5430
Length
0x1C
Payload
<T0 payload>
Termination
<CRC (U2)>
This packet contains detailed BIT and status information. The full BIT Status details are
described in Section 9 of this manual.
T0 Payload Contents
Byte Offset
0
2
4
6
Name
BITstatus
hardwareBIT
hardwarePowerBIT
hardwareEnvironmentalBIT
Format
U2
U2
U2
U2
Scaling
-
Units
-
8
10
comBIT
comSerialABIT
U2
U2
-
-
12
comSerialBBIT
U2
-
-
14
16
18
20
22
24
26
softwareBIT
softwareAlgorithmBIT
softwareDataBIT
hardwareStatus
comStatus
softwareStatus
sensorStatus
U2
U2
U2
U2
U2
U2
U2
-
-
7.4
Description
Master BIT and Status Field
Hardware BIT Field
Hardware Power BIT Field
Hardware Environmental BIT
Field
communication BIT Field
Communication Serial A BIT
Field
Communication Serial B BIT
Field
Software BIT Field
Software Algorithm BIT Field
Software Data BIT Field
Hardware Status Field
Communication Status Field
Software Status Field
Sensor Status Field
Output Packets (Polled or Continuous)
7.4.1 Scaled Sensor Data Packet 0
Scaled Sensor Data (‘S0’ = 0x5330)
Preamble
0x5555
Packet Type
0x5330
Length
0x1E
Payload
<S0 payload>
Termination
<CRC (U2)>
This packet contains scaled sensor data. The scaled sensor data is fixed point, 2 bytes per
sensor, MSB first, for 13 sensors in the following order: accels(x,y,z); gyros(x,y,z);
mags(x,y,z); temps(x,y,z,board). Data involving angular measurements include the factor
pi in the scaling and can be interpreted in either radians or degrees.
Angular rates: scaled to range of 3.5* [-pi,+pi) or [-630 deg/sec to +630 deg/sec)
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Accelerometers: scaled to a range of [-10,+10) g
Magnetometers: scaled to a range of [-1,+1) Gauss
Temperature: scaled to a range of [-100, +100)°C
S0 Payload Contents
Byte Offset
0
2
4
6
Name
xAccel
yAccel
zAccel
xRate
Format
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
I2
U2
Scaling
20/2^16
20/2^16
20/2^16
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
20/2^16
20/2^16
20/2^16
200/2^16
200/2^16
200/2^16
200/2^16
truncated
Units
g
g
g
rad/s
[°/sec]
rad/s
[°/sec]
rad/s
[°/sec]
Gauss
Gauss
Gauss
deg. C
deg. C
deg. C
deg. C
ms
8
yRate
I2
10
zRate
I2
12
14
16
18
20
22
24
26
xMag
yMag
zMag
xRateTemp
yRateTemp
zRateTemp
boardTemp
GPSITOW
28
BITstatus
U2
-
-
Description
X accelerometer
Y accelerometer
Z accelerometer
X angular rate
Y angular rate
Z angular rate
X magnetometer
Y magnetometer
Z magnetometer
X rate temperature
Y rate temperature
Z rate temperature
CPU board temperature
GPS ITOW (lower 2 bytes)
Not implemented
Master BIT and Status
7.4.2 Scaled Sensor Data Packet 1 (Default IMU Data)
Scaled Sensor Data (‘S1’ = 0x5331)
Preamble
0x5555
Packet Type
0x5331
Length
0x18
Payload
<S1 payload>
Termination
<CRC (U2)>
This packet contains scaled sensor data. Data involving angular measurements include
the factor pi in the scaling and can be interpreted in either radians or degrees.
Angular rates: scaled to range of 3.5* [-pi,+pi) or [-630 deg/sec to +630 deg/sec)
Accelerometers: scaled to a range of [-10,+10)g
Temperature: scaled to a range of [-100, +100)°C
S1 Payload Contents
Byte Offset
0
2
4
6
Name
xAccel
yAccel
zAccel
xRate
Format
I2
I2
I2
I2
8
yRate
I2
10
zRate
I2
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Scaling
20/2^16
20/2^16
20/2^16
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
Units
g
g
g
rad/s
[°/sec]
rad/s
[°/sec]
rad/s
Description
X accelerometer
Y accelerometer
Z accelerometer
X angular rate
Y angular rate
Z angular rate
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12
14
16
18
xRateTemp
yRateTemp
zRateTemp
boardTemp
I2
I2
I2
I2
[1260°/2^16]
200/2^16
200/2^16
200/2^16
200/2^16
[°/sec]
deg. C
deg. C
deg. C
deg. C
20
22
Counter
BITstatus
U2
U2
-
packets
-
X rate temperature
Y rate temperature
Z rate temperature
CPU board
temperature
Output packet counter
Master BIT and Status
7.4.3 Angle Data Packet 1 (Default AHRS Data)
Angle Data (‘A1’ = 0x4131)
Preamble
0x5555
Packet Type
0x4131
Length
0x20
Payload
<A1 payload>
Termination
<CRC (U2)>
This packet contains angle data and selected sensor data scaled in most cases to a signed
2^16 2’s complement number. Data involving angular measurements include the factor pi
in the scaling and can be interpreted in either radians or degrees.
Angles: scaled to a range of [-pi,+pi) or [-180 deg to +180 deg).
Angular rates: scaled to range of 3.5* [-pi,+pi) or [-630 deg/sec to +630 deg/sec)
Accelerometers: scaled to a range of [-10,+10) g
Magnetometers: scaled to a range of [-10,+10) Gauss
Temperature: scaled to a range of [-100, +100) °C
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A1 Payload Contents
Byte Offset
0
Name
rollAngle
Format
I2
I2
I2
I2
I2
I2
I2
I2
U4
Scaling
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
20/2^16
20/2^16
20/2^16
20/2^16
20/2^16
20/2^16
200/2^16
1
Units
Radians
[°]
Radians
[°]
Radians
[°]
rad/s
[°/sec]
rad/s
[°/sec]
rad/s
[°/sec]
g
g
g
Gauss
Gauss
Gauss
Deg C
ms
2
pitchAngle
I2
4
yawAngleMag
I2
6
xRateCorrected
I2
8
yRateCorrected
I2
10
zRateCorrected
I2
12
14
16
18
20
22
24
26
xAccel
yAccel
zAccel
xMag
yMag
zMag
xRateTemp
timeITOW
30
BITstatus
U2
-
-
Description
Roll angle
Pitch angle
Yaw angle (magnetic
north)
X angular rate Corrected
Y angular rate Corrected
Z angular rate Corrected
X accelerometer
Y accelerometer
Z accelerometer
X magnetometer
Y magnetometer
Z magnetometer
X rate temperature
DMU ITOW (sync to GPS)
Not Implemented
Master BIT and Status
7.4.4 Angle Data Packet 2 (Default VG Data)
Angle Data (‘A2’ = 0x4132)
Preamble
0x5555
Packet Type
0x4132
Length
0x1E
Payload
<A2 payload>
Termination
<CRC (U2)>
This packet contains angle data and selected sensor data scaled in most cases to a signed
2^16 2’s complement number. Data involving angular measurements include the factor pi
in the scaling and can be interpreted in either radians or degrees.
Angles: scaled to a range of [-pi,+pi) or [-180 deg to +180 deg).
Angular rates: scaled to range of 3.5* [-pi,+pi) or [-630 deg/sec to +630 deg/sec)
Accelerometers: scaled to a range of [-10,+10) g
Temperature: scaled to a range of [-100, +100) °C
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A2 Payload Contents
Byte Offset
0
Name
rollAngle
Format
I2
I2
I2
I2
I2
I2
I2
U4
Scaling
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
20/2^16
20/2^16
20/2^16
200/2^16
200/2^16
200/2^16
1
Units
Radians
[°]
Radians
[°]
Radians
[°]
rad/s
[°/sec]
rad/s
[°/sec]
rad/s
[°/sec]
g
g
g
deg. C
deg. C
deg. C
ms
2
pitchAngle
I2
4
yawAngleTrue
I2
6
xRateCorrected
I2
8
yRateCorrected
I2
10
zRateCorrected
I2
12
14
16
18
20
22
24
xAccel
yAccel
zAccel
xRateTemp
yRateTemp
zRateTemp
timeITOW
28
BITstatus
U2
-
-
Description
Roll angle
Pitch angle
Yaw angle (free)
X angular rate corrected
Y angular rate corrected
Z angular rate corrected
X accelerometer
Y accelerometer
Z accelerometer
X rate temperature
Y rate temperature
Z rate temperature
DMU ITOW (sync to GPS)
Not Implemented
Master BIT and Status
7.4.5 Nav Data Packet 0
Nav Data (‘N0’ = 0x4E30)
Preamble
0x5555
Packet Type
0x4E30
Length
0x20
Payload
<N0 payload>
Termination
<CRC (U2)>
This packet contains navigation data and selected sensor data scaled in most cases to a
signed 2^16 2’s complement number. Data involving angular measurements include the
factor pi in the scaling and can be interpreted in either radians or degrees.
Angles: scaled to a range of [-pi,+pi) or [-180 deg to +180 deg).
Angular rates: scaled to range of 3.5* [-pi,+pi) or [-630 deg/sec to +630 deg/sec)
Accelerometers: scaled to a range of [-10,+10) g
Temperature: scaled to a range of [-100, +100) °C
Velocities are scaled to a range of [-256,256) m/s
Altitude is scaled to a range of [-100,16284) m using a shifted 2’s complement
representation.
Longitude and latitude are scaled to a range of [-pi,pi) or [-180 deg to +180 deg).
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N0 Payload Contents
Byte Offset
0
Name
rollAngle
Format
I2
I2*
U2
Scaling
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
512/2^16
512/2^16
512/2^16
2*pi/2^32
[360°/2^32]
2*pi/2^32
[360°/2^32]
2^14/2^16
truncated
Units
Radians
[°]
Radians
[°]
Radians
[°]
rad/s
[°/sec]
rad/s
[°/sec]
rad/s
[°/sec]
m/s
m/s
m/s
Radians
[°]
Radians
[°]
m
ms
2
pitchAngle
I2
4
yawAngleTrue
I2
6
xRateCorrected
I2
8
yRateCorrected
I2
10
zRateCorrected
I2
12
14
16
18
nVel
eVel
dVel
longitudeGPS
I2
I2
I2
I4
22
latitudeGPS
I4
26
28
altitudeGPS
GPSITOW
30
BITstatus
U2
-
-
Description
Roll angle
Pitch angle
Yaw angle (true north)
X angular rate corrected
Y angular rate corrected
Z angular rate corrected
North velocity
East velocity
Down velocity
GPS Longitude
GPS Latitude
GPS altitude [-100,16284)
GPS ITOW (lower 2 bytes)
Not Implemented
Master BIT and Status
7.4.6 Nav Data Packet 1 (Default INS Data)
Nav Data (‘N1’ = 0x4E31)
Preamble
0x5555
Packet Type
0x4E31
Length
0x2A
Payload
<N1 payload>
Termination
<CRC (U2)>
This packet contains navigation data and selected sensor data scaled in most cases to a
signed 2^16 2’s complement number. Data involving angular measurements include the
factor pi in the scaling and can be interpreted in either radians or degrees.
Angles: scaled to a range of [-pi,+pi) or [-180 deg to +180 deg).
Angular rates: scaled to range of 3.5* [-pi,+pi) or [-630 deg/sec to +630 deg/sec)
Accelerometers: scaled to a range of [-10,+10) g
Temperature: scaled to a range of [-100, +100) °C
Velocities are scaled to a range of [-256,256) m/s
Altitude is scaled to a range of [-100,16284) m using a shifted 2’s complement
representation.
Longitude and latitude are scaled to a range of [-pi,pi) or [-180 deg to +180 deg).
N1 Payload Contents
Byte Offset
0
Name
rollAngle
Doc# 7430-0026 Rev. 01
Format
I2
Scaling
2*pi/2^16
Units
Radians
Description
Roll angle
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I2*
I2
U4
[360°/2^16]
2*pi/2^16
[360°/2^16]
2*pi/2^16
[360°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
7*pi/2^16
[1260°/2^16]
20/2^16
20/2^16
20/2^16
512/2^16
512/2^16
512/2^16
2*pi/2^32
[360°/2^32]
2*pi/2^32
[360°/2^32]
2^14/2^16
200/2^16
1
[°]
Radians
[°]
Radians
[°]
rad/s
[°/sec]
rad/s
[°/sec]
rad/s
[°/sec]
g
g
g
m/s
m/s
m/s
Radians
[°]
Radians
[°]
m
deg C
ms
U2
-
-
2
pitchAngle
I2
4
yawAngleTrue
I2
6
xRateCorrected
I2
8
yRateCorrected
I2
10
zRateCorrected
I2
12
14
16
18
20
22
24
xAccel
yAccel
zAccel
nVel
eVel
dVel
longitudeGPS
I2
I2
I2
I2
I2
I2
I4
28
latitudeGPS
I4
32
34
36
altitudeGPS
xRateTemp
timeITOW
40
BITstatus
Doc# 7430-0026 Rev.01
Pitch angle
Yaw angle (true north)
X angular rate corrected
Y angular rate corrected
Z angular rate corrected
X accelerometer
Y accelerometer
Z accelerometer
North velocity
East velocity
Down velocity
GPS Longitude
GPS Latitude
GPS altitude [-100,16284)
X rate sensor temperature
DMU ITOW (sync to GPS)
Not Implemented
Master BIT and Status
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8 Advanced Commands
The advanced commands allow users to programmatically change the DMU380SA Series
settings. This section of the manual documents all of the settings and options contained
under the Unit Configuration tab within NAV-VIEW. Using these advanced commands,
a user’s system can change or modify the settings without the need for NAV-VIEW.
8.1
Configuration Fields
Configuration fields determine various behaviors of the unit that can be modified by the
user. These include settings like baud rate, packet output rate and type, algorithm type,
etc. These fields are stored in EEPROM and loaded on power up. These fields can be
read from the EEPROM using the ‘RF’ command. These fields can be written to the
EEPROM affecting the default power up behavior using the ‘WF’ command. The current
value of these fields (which may be different from the value stored in the EEPROM) can
also be accessed using the ‘GF’ command. All of these fields can also be modified
immediately for the duration of the current power cycle using the ‘SF’ command. The
unit will always power up in the configuration stored in the EEPROM. Configuration
fields can only be set or written with valid data from Table 22 below.
Table 22. Configuration Fields
configuration fields
field ID
Valid Values
description
Packet rate divider
Unit BAUD rate
0x0001
0x0002
Continuous packet type
Unused
0x0003
0x0004
0,1,2,5,10, 20, 25, 50
0,1,2,3
Any output packet
type
quiet, 100Hz, 50Hz, 25Hz, 20Hz, 10Hz, 5Hz, 2Hz
9600, 19200, 38400, 57600
Not all output packets available for all products.
See detailed product descriptions.
Gyro Filter Setting
0x0005
Accelerometer Filter Setting
0x0006
7142-65535 [5Hz]
3571-7141 [10Hz]
1530-3570 [20Hz]
0-1529 [50 Hz]
7142-65535 [5Hz]
3571-7141 [10Hz]
1530-3570 [20Hz]
0-1529 [50 Hz]
Orientation
0x0007
See below
User Behavior Switches
X Hard Iron Bias
Y Hard Iron Bias
Soft Iron Scale Ratio
Heading Track Offset
0x0008
0x0009
0x000A
0x000B
Any
Any
Any
Any
0x000C
Any
Sets low pass cutoff for rate sensors. Cutoff
Frequency choices are 5, 10, 20, and 50Hz
Sets low pass cutoff for accelerometers. Cutoff
Frequency choices are 5, 10, 20, and 50Hz
Determine forward, rightward, and downward
facing sides
Free Integrate (60 seconds), Use Mags, Use GPS,
Stationary Yaw Lock, …
I2 scaled from [-1,1)
I2 scaled from [-1,1)
U2 scaled from [0,2)
Heading-Track Offset to use in NAV filter track
update mode.
Note: BAUD rate SF has immediate effect. Some output data may be lost. Response will
be received at new BAUD rate.
8.2
Continuous Packet Type Field
This is the packet type that is being continually output. The supported packet depends on
the model number. Please refer to Section 6.4 for a complete list of the available packet
types.
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8.3
Digital Filter Settings
These two fields set the digital low pass filter cutoff frequencies (See Table 23). Each
sensor listed is defined in the default factory orientation. Users must consider any
additional rotation to their intended orientation.
Table 23. Digital Filter Settings
Filter Setting
FilterGyro
FilterAccel
8.4
Sensor
Ux,Uy,Uz Rate
Ux,Uy,Uz Accel
Orientation Field
This field defines the rotation from the factory to user axis sets. This rotation is relative to
the default factory orientation (connector aft, baseplate down). The default factory axis
setting for the DMU380SA orientation field is (-Ux, -Uy, +Uz) as shown in Figure 18
below. With this default orientation, +X is defined as opposite where the connector is
pointing, +Z is down through the base, and +Y is created by making the final orthogonal
axis right-hand-rule. The user axis set is (X, Y, Z) as defined by this default orientation
field loaded at the factory, but this can be changed as per Table 24.
Figure 18.
DMU380 Orientation Field (0x0009)
+X (-Ux)
Roll
Pitch
Yaw
+Z (+Uz)
+Y (-Uy)
Table 24. DMU380 Orientation Definitions
Description
X Axis Sign
X Axis
Y Axis Sign
Y Axis
Z Axis Sign
Z Axis
Reserved
Bits
0
1:2
3
4:5
6
7:8
9:15
Meaning
0 = positive, 1 = negative
0 = Ux, 1 = Uy, 2 = Uz, 3 = N/A
0 = positive, 1 = negative
0 = Uy, 1 = Uz, 2 = Ux, 3 = N/A
0 = positive, 1 = negative
0 = Uz, 1 = Ux, 2 = Uy, 3 = N/A
N/A
There are 24 possible orientation configurations (See Table 25). Setting/Writing the field
to anything else generates a NAK and has no effect.
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Table 25. DMU380 Orientation Fields
Orientation Field Value
X Axis
Y Axis
Z Axis
0x0000
0x0009
0x0023
0x002A
0x0041
0x0048
0x0062
0x006B
0x0085
0x008C
0x0092
0x009B
0x00C4
0x00CD
0x00D3
0x00DA
0x0111
0x0118
0x0124
0x012D
0x0150
0x0159
0x0165
0x016C
+Ux
-Ux
-Uy
+Uy
-Ux
+Ux
+Uy
-Uy
-Uz
+Uz
+Uy
-Uy
+Uz
-Uz
-Uy
+Uy
-Ux
+Ux
+Uz
-Uz
+Ux
-Ux
-Uz
+Uz
+Uy
-Uy
+Ux
-Ux
+Uy
-Uy
+Ux
-Ux
+Uy
-Uy
+Uz
-Uz
+Uy
-Uy
+Uz
-Uz
+Uz
-Uz
+Ux
-Ux
+Uz
-Uz
+Ux
-Ux
+Uz
+Uz
+Uz
+Uz
-Uz
-Uz
-Uz
-Uz
+Ux
+Ux
+Ux
+Ux
-Ux
-Ux
-Ux
-Ux
+Uy
+Uy
+Uy
+Uy
-Uy
-Uy
-Uy
-Uy
8.5
User Behavior Switches
This field allows on the fly user interaction with behavioral aspects of the algorithm (See
Figure 26).
Table 26. DMU380 Behavior Switches
Description
Bits
Meaning
Free Integrate
0
Use Mags
1
Use GPS
2
Stationary Yaw Lock
3
Restart on Over-range
4
Dynamic Motion
5
Reserved
6:15
0 = use feedback to stabilize the algorithm, 1 = 6DOF inertial
integration without stabilized feedback for 60 seconds
0 = Do not use mags to stabilize heading (heading will run open
loop or be stabilized by GPS track), 1 = Use mags to stabilize
heading
0 = Do not use GPS to stabilize the system, 1 = Use GPS when
available
0 = Do not lock yaw when GPS speed is near zero (<0.75 m/s), 1
= Lock yaw when GPS speed is near zero
0 = Do not restart the system after a sensor over-range, 1 =
restart the system after a sensor over-range
0=vehicle is static, force high gain corrections, 1= vehicle is
dynamic, use nominal corrections
N/A
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8.6
Hard and Soft Iron Values
These fields allow access to hard iron bias and soft iron scale ratio values for
magnetometer alignment (See Table 27):
Table 27. DMU380 Magnetic Alignment Parameters
Field Name
Field ID
Format
Scaling
Units
X Hard Iron Bias
Y Hard Iron Bias
Soft Iron Scale Ratio
0x0009
0x000A
0x000B
I2
I2
U2
20/2^16
20/2^16
2/2^16
Gauss
Gauss
-
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.
8.7
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
(See Table 28).
Table 28. DMU380 Heading Track Offset
Field Name
Field ID
Format
Scaling
Units
0x000C
I2
2*pi/2^16
[360°/2^16]
Radians (heading-track)
[°]
Heading Track Offset
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8.8
Commands to Program Configuration
8.8.1 Write Fields Command
Write Fields (‘WF’ = 0x5746)
Preamble
0x5555
Packet Type
0x5746
Length
1+numFields*4
Payload
<WF payload>
Terminatio
n
<CRC
(U2)>
This command allows the user to write default power-up configuration fields to the
EEPROM. Writing the default configuration will not take affect 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 fields 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. Note that both a 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. A table of field IDs and valid field values is available in
Section 8.1.
WF Payload Contents
Byte Offset
0
1
3
5
7
…
numFields*4 -3
numFields*4 -1
Name
numFields
field0
field0Data
field1
field1Data
…
field…
field…Data
Format
U1
U2
U2
U2
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields to write
The first field ID to write
The first field ID’s data to write
The second field ID to write
The second field ID’s data
…
The last field ID to write
The last field ID’s data to write
Write Fields Response
Write Fields (‘WF’ = 0x5746)
Preamble
0x5555
Packet Type
0x5746
Length
1+numFields*2
Payload
<WF payload>
Termination
<CRC (U2)>
The unit will send this packet in response to a write fields command if the command has
completed without errors.
WF Payload Contents
Byte Offset
0
1
3
Name
numFields
field0
field1
Doc# 7430-0026 Rev. 01
Format
U1
U2
U2
Scaling
-
Units
-
Description
The number of fields written
The first field ID written
The second field ID written
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________________________________________________________________________
…
numFields*2 – 1
…
Field…
U2
U2
-
-
More field IDs written
The last field ID written
8.8.2 Set Fields Command
Set Fields (‘SF’ = 0x5346)
Preamble
0x5555
Packet Type
0x5346
Length
1+numFields*4
Payload
<SF payload>
Termination
<CRC (U2)>
This command allows the user to set the unit’s current configuration (SF) fields
immediately which will then be lost on power down. NumFields is the number of words
to be set. The field0, field1, etc. are the field IDs that will be written with the field0Data,
field1Data, etc., respectively. This command can be used to set configuration fields. The
unit will not set calibration or algorithm fields. If at least one field is successfully set, the
unit will respond with a set fields response containing the field IDs of the successfully set
fields. If any field is unable to be set, the unit will respond with an error response. Note
that both a set fields and an error response may be received as a result of one set fields
command. Attempts to set a field with an invalid value is one way to generate an error
response. A table of field IDs and valid field values is available in Section 8.1.
SF Payload Contents
Byte Offset
0
1
3
5
7
…
numFields*4 -3
numFields*4 -1
Name
numFields
field0
field0Data
field1
field1Data
…
field…
field…Data
Format
U1
U2
U2
U2
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields to set
The first field ID to set
The first field ID’s data to set
The second field ID to set
The second field ID’s data to set
…
The last field ID to set
The last field ID’s data to set
Set Fields Response
Set Fields (‘SF’ = 0x5346)
Preamble
0x5555
Packet Type
0x5346
Length
1+numFields*2
Payload
<SF payload>
Termination
<CRC (U2)>
The unit will send this packet in response to a set fields command if the command has
completed without errors.
SF Payload Contents
Byte Offset
0
1
3
…
numFields*2 - 1
Name
numFields
field0
field1
…
Field…
Doc# 7430-0026 Rev.01
Format
U1
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields set
The first field ID set
The second field ID set
More field IDs set
The last field ID set
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8.9 Read Fields Command
Read Fields (‘RF’ = 0x5246)
Preamble
0x5555
Packet Type
0x5246
Length
1+numFields*2
Payload
<RF payload>
Termination
<CRC (U2)>
This command allows the user to read the default power-up configuration fields from the
EEPROM. NumFields is the number of fields to read. The field0, field1, etc. are the field
IDs to read. RF may be used to read configuration and calibration fields from the
EEPROM. If at least one field is successfully read, the unit will respond with a read fields
response containing the field IDs and data from the successfully read fields. If any field is
unable to be read, the unit will respond with an error response. Note that both a read
fields and an error response may be received as a result of a read fields command.
RF Payload Contents
Byte Offset
0
1
3
…
numFields*2 - 1
Name
numFields
field0
field1
…
Field…
Format
U1
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields to read
The first field ID to read
The second field ID to read
More field IDs to read
The last field ID to read
8.10 Read Fields Response
Read Fields (‘RF’ = 0x5246)
Preamble
0x5555
Packet Type
0x5246
Length
1+numFields*4
Payload
<RF payload>
Termination
<CRC (U2)>
The unit will send this packet in response to a read fields request if the command has
completed without errors.
RF Payload Contents
Byte Offset
0
1
3
5
7
…
numFields*4 -3
numFields*4 -1
Name
numFields
field0
field0Data
field1
field1Data
…
field…
field…Data
Format
U1
U2
U2
U2
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields read
The first field ID read
The first field ID’s data read
The second field ID read
The second field ID’s data read
…
The last field ID read
The last field ID’s data read
8.11 Get Fields Command
Get Fields (‘GF’ = 0x4746)
Preamble
0x5555
Packet Type
0x4746
Doc# 7430-0026 Rev. 01
Length
1+numFields*2
Payload
<GF Data>
Termination
<CRC (U2)>
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________________________________________________________________________
This command allows the user to get the unit’s current configuration fields. NumFields is
the number of fields to get. The field0, field1, etc. are the field IDs to get. GF may be
used to get configuration, calibration, and algorithm fields from RAM. Multiple
algorithm fields will not necessarily be from the same algorithm iteration. If at least one
field is successfully collected, the unit will respond with a get fields response with data
containing the field IDs of the successfully received fields. If any field is unable to be
received, the unit will respond with an error response. Note that both a get fields and an
error response may be received as the result of a get fields command.
GF Payload Contents
Byte Offset
0
1
3
…
numFields*2 – 1
Name
numFields
field0
field1
…
Field…
Format
U1
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields to get
The first field ID to get
The second field ID to get
More field IDs to get
The last field ID to get
8.12 Get Fields Response
Get Fields (‘GF’ = 0x4746)
Preamble
0x5555
Packet Type
0x4746
Length
1+numFields*4
Payload
<GF Data>
Termination
<CRC (U2)>
The unit will send this packet in response to a get fields request if the command has
completed without errors.
GF Payload Contents
Byte Offset
0
1
3
5
7
…
numFields*4 -3
numFields*4 -1
Name
numFields
field0
field0Data
field1
field1Data
…
field…
field…Data
Doc# 7430-0026 Rev.01
Format
U1
U2
U2
U2
U2
U2
U2
U2
Scaling
-
Units
-
Description
The number of fields retrieved
The first field ID retrieved
The first field ID’s data retrieved
The second field ID retrieved
The second field ID’s data
…
The last field ID retrieved
The last field ID’s data retrieved
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9 Advanced BIT
9.1
Built In Test (BIT) and Status Fields
Internal health and status are monitored and communicated in both hardware and
software. The ultimate indication of a fatal problem is a hardware BIT signal on the user
connector which is mirrored in the software BIT field as the masterFail flag. This flag is
thrown as a result of a number of instantly fatal conditions (known as a “hard” failure) or
a persistent serious problem (known as a “soft” failure). Soft errors are those which must
be triggered multiple times within a specified time window to be considered fatal. Soft
errors are managed using a digital high-pass error counter with a trigger threshold.
The masterStatus flag is a configurable indication as determined by the user. This flag is
asserted as a result of any asserted alert signals which the user has enabled.
The hierarchy of BIT and Status fields and signals is depicted here:
 BITstatus Field
 masterFail

hardwareError

hardwareBIT Field
 powerError
 hardwarePowerBIT Field

inpPower

inpCurrent

inpVoltage

fiveVolt

threeVolt

twoVolt

twoFiveRef

sixVolt

grdRef
 environmentalError
 hardwareEnvironmentalBIT Field


pcbTemp
comError

comBIT Field
 serialAError
 comSerialABIT Field
Doc# 7430-0026 Rev. 01

transmitBufferOverflow

receiveBufferOverflow

framingError

breakDetect
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
parityError
 serialBError
 comSerialBBIT Field


transmitBufferOverflow

receiveBufferOverflow

framingError

breakDetect

parityError
softwareError

softwareBIT Field
 algorithmError
 softwareAlgorithmBIT Field

initialization

overRange

missedIntegrationStep
 dataError
 softwareDataBIT Field

calibrationCRCError

magAlignOutOfBounds
 masterStatus

hardwareStatus

hardwareStatus Field
 unlocked1PPS (enabled by default on INS)
 unlockedInternalGPS (enabled by default on INS)
 noDGPS
 unlockedEEPROM

comStatus

comStatus Field
 noExternalGPS (enabled by default on VG and AHRS)

softwareStatus

softwareStatus Field
 algorithmInitialization (enabled by default)
 highGain (enabled by default)
 attitudeOnlyAlgorithm
 turnSwitch

sensorStatus
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
sensorStatus Field
 overRange (enabled by default)
9.2
Master BIT and Status (BITstatus) Field
The BITstatus field is the global indication of health and status of the DMU380SA Series
product (See Table 29). The LSB contains BIT information and the MSB contains status
information.
There are four intermediate signals that are used to determine when masterFail and the
hardware BIT signal are asserted. These signals are controlled by various systems checks
in software that are classified into three categories: hardware, communication, and
software. Instantaneous soft failures in each of these four categories will trigger these
intermediate signals, but will not trigger the masterFail until the persistency conditions
are met.
There are four intermediate signals that are used to determine when the masterStatus flag
is asserted: hardwareStatus, sensorStatus, comStatus, and softwareStatus. masterStatus is
the logical OR of these intermediate signals. Each of these intermediate signals has a
separate field with individual indication flags. Each of these indication flags can be
enabled or disabled by the user. Any enabled indication flag will trigger the associated
intermediate signal and masterStatus flag.
Table 29. DMU380 BIT Status Field
BITstatus Field
masterFail
HardwareError
comError
softwareError
Reserved
masterStatus
Bits
0
1
2
3
4:7
8
hardwareStatus
comStatus
softwareStatus
sensorStatus
Reserved
9
10
11
12
13:15
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Meaning
0 = normal, 1 = fatal error has occurred
0 = normal, 1= internal hardware error
0 = normal, 1 = communication error
0 = normal, 1 = internal software error
N/A
0 = nominal, 1 = hardware, sensor, com, or
software alert
0 = nominal, 1 = programmable alert
0 = nominal, 1 = programmable alert
0 = nominal, 1 = programmable alert
0 = nominal, 1 = programmable alert
N/A
Category
BIT
BIT
BIT
BIT
Status
Status
Status
Status
Status
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9.3
hardwareBIT Field
The hardwareBIT field contains flags that indicate various types of internal hardware
errors (See Table 30). Each of these types has an associated message with low level error
signals. The hardwareError flag in the BITstatus field is the bit-wise OR of this
hardwareBIT field.
Table 30. DMU380 Hardware BIT Field
hardwareBIT Field
powerError
environmentalError
reserved
9.4
Bits
0
1
2:15
Meaning
0 = normal, 1 = error
0 = normal, 1 = error
N/A
Category
Soft
Soft
hardwarePowerBIT Field
The hardwarePowerBIT field contains flags that indicate low level power system errors
(See Table 31). The powerError flag in the hardwareBIT field is the bit-wise OR of this
hardwarePowerBIT field.
Table 31. DMU380 Hardware Power BIT Field
hardwarePowerBIT Field
inpPower
inpCurrent
inpVoltage
fiveVolt
threeVolt
twoVolt
twoFiveRef
sixVolt
grdRef
Reserved
9.5
Bits
0
1
2
3
4
5
6
7
8
9:15
Meaning
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
0 = normal, 1 = out of bounds
N/A
Category
Soft
Soft
Soft
Soft
Soft
Soft
Soft
Soft
Soft
hardwareEnvironmentalBIT Field
The hardwareEnvironmentalBIT field contains flags that indicate low level hardware
environmental errors (See Table 32). The environmentalError flag in the hardwareBIT
field is the bit-wise OR of this hardwareEnvironmentalBIT field.
Table 32. DMU380 Hardware Environment BIT Field
hardwareEnvironmentalBIT Field
pcbTemp
Reserved
9.6
Bits
0
9:15
Meaning
0 = normal, 1 = out of bounds
N/A
Category
Soft
comBIT Field
The comBIT field contains flags that indicate communication errors with external devices
(See Table 33). Each external device has an associated message with low level error
signals. The comError flag in the BITstatus field is the bit-wise OR of this comBIT field.
Table 33. DMU380 COM BIT Field
comBIT Field
serialAError
serialBError
Reserved
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Bits
0
1
2:15
Meaning
0 = normal, 1 = error
0 = normal, 1 = error
N/A
Category
Soft
Soft
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9.7
comSerialABIT Field
The comSerialABIT field (See Table 34) contains flags that indicate low level errors with
external serial port A (the user serial port). The serialAError flag in the comBIT field is
the bit-wise OR of this comSerialABIT field.
Table 34. DMU380 Serial Port A BIT Field
comSerialABIT Field
transmitBufferOverflow
receiveBufferOverflow
framingError
breakDetect
parityError
Reserved
9.8
Bits
0
1
2
3
4
5:15
Meaning
0 = normal, 1 = overflow
0 = normal, 1 = overflow
0 = normal, 1 = error
0 = normal, 1 = error
0 = normal, 1 = error
N/A
Category
Soft
Soft
Soft
Soft
Soft
comSerialBBIT Field
The comSerialBBIT field (See Table 35) contains flags that indicate low level errors with
external serial port B (the aiding serial port). The serialBError flag in the comBIT field is
the bit-wise OR of this comSerialBBIT field.
Table 35. DMU380 Serial Port B BIT Field
comSerialBBIT Field
transmitBufferOverflow
receiveBufferOverflow
framingError
breakDetect
parityError
Reserved
9.9
Bits
0
1
2
3
4
5:15
Meaning
0 = normal, 1 = overflow
0 = normal, 1 = overflow
0 = normal, 1 = error
0 = normal, 1 = error
0 = normal, 1 = error
N/A
Category
Soft
Soft
Soft
Soft
Soft
softwareBIT Field
The softwareBIT field contains flags that indicate various types of software errors (See
Table 36). Each type has an associated message with low level error signals. The
softwareError flag in the BITstatus field is the bit-wise OR of this softwareBIT field.
Table 36. DMU380 Softrware BIT Field
softwareBIT Field
algorithmError
dataError
Reserved
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Bits
0
1
2:15
Meaning
0 = normal, 1 = error
0 = normal, 1 = error
N/A
Category
Soft
Soft
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9.10 softwareAlgorithmBIT Field
The softwareAlgorithmBIT field contains flags that indicate low level software algorithm
errors (See Table 37). The algorithmError flag in the softwareBIT field is the bit-wise OR
of this softwareAlgorithmBIT field.
Table 37. DMU380 Software Algorithm BIT Field
SoftwareAlgorithmBIT Field
initialization
overRange
missedNavigationStep
Bits
0
1
2
Reserved
3:15
Meaning
0 = normal, 1 = error during algorithm initialization
0 = normal, 1 = fatal sensor over-range
0 = normal, 1 = fatal hard deadline missed for
navigation
N/A
Category
Hard
Hard
Hard
9.11 softwareDataBIT Field
The softwareDataBIT field contains flags that indicate low level software data errors (See
Table 38). The dataError flag in the softwareBIT field is the bit-wise OR of this
softwareDataBIT field.
Table 38. DMU380 Software Data BIT Field
SoftwareDataBIT Field
calibrationCRCError
Bits
0
magAlignOutOfBounds
N/A
Reserved
2:15
Meaning
0 = normal, 1 = incorrect CRC on
calibration EEPROM data or data has been
compromised by a WE command.
Parameter not implemented in this
software version
N/A
Category
Hard
N/A
9.12 hardwareStatus Field
The hardwareStatus field contains flags that indicate various internal hardware conditions
and alerts that are not errors or problems (See Table 39). The hardwareStatus flag in the
BITstatus field is the bit-wise OR of the logical AND of the hardwareStatus field and the
hardwareStatusEnable field. The hardwareStatusEnable field is a bit mask that allows the
user to select items of interest that will logically flow up to the masterStatus flag.
Table 39. DMU380 Hardware Status BIT Field
hardwareStatus Field
unlocked1PPS
unlockedInternalGPS
noDGPS
unlockedEEPROM
Reserved
Bits
0
1
2
3
4:15
Meaning
0 = not asserted, 1 = asserted
0 = not asserted, 1 = asserted
0 = DGPS lock, 1 = no DGPS
0=locked, WE disabled, 1=unlocked, WE enabled
N/A
9.13 comStatus Field
The comStatus field contains flags that indicate various external communication
conditions and alerts that are not errors or problems (See Table 40). The comStatus flag
in the BITstatus field is the bit-wise OR of the logical AND of the comStatus field and
the comStatusEnable field. The comStatusEnable field is a bit mask that allows the user
to select items of interest that will logically flow up to the masterStatus flag.
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Table 40. DMU380 COM Status BIT Field
comStatus Field
noExternalGPS
Bits
0
Reserved
1:15
Meaning
0 = external GPS data is being received, 1 = no external
GPS data is available
N/A
9.14 softwareStatus Field
The softwareStatus field contains flags that indicate various software conditions and
alerts that are not errors or problems (See Table 41). The softwareStatus flag in the
BITstatus field is the bit-wise OR of the logical AND of the softwareStatus field and the
softwareStatusEnable field. The softwareStatusEnable field is a bit mask that allows the
user to select items of interest that will logically flow up to the masterStatus flag.
Table 41. DMU380 Software Status Field
softwareStatus Field
algorithmInit
highGain
attitudeOnlyAlgorithm
turnSwitch
Reserved
Bits
0
1
2
3
4:15
Meaning
0 = normal, 1 = the algorithm is in initialization mode
0 = low gain mode, 1 high gain mode
0 = navigation state tracking, 1 = attitude only state tracking
0 = off, 1 = yaw rate greater than turnSwitch threshold
N/A
9.15 sensorStatus Field
The sensorStatus field contains flags that indicate various internal sensor conditions and
alerts that are not errors or problems (See Table 42). The sensorStatus flag in the
BITstatus field is the bit-wise OR of the logical AND of the sensorStatus field and the
sensorStatusEnable field. The sensorStatusEnable field is a bit mask that allows the user
to select items of interest that will logically flow up to the masterStatus flag.
Table 42. DMU380 Sensor Status Field
sensorStatus Field
overRange
Reserved
Bits
0
1:15
Meaning
0 = not asserted, 1 = asserted
N/A
9.16 Configuring the Master Status
The masterStatus byte and its associated programmable alerts are configured using the
Read Field and Write Field command as described in Section 8, Advanced Commands.
Table 43 shows the definition of the bit mask for configuring the status signals.
Table 43. DMU380 Master Status Byte Configuration Fields
configuration fields
hardwareStatusEnable
comStatusEnable
softwareStatusEnable
sensorStatusEnable
9.16.1
field ID
0x0010
Valid Values
Any
0x0011
0x0012
0x0013
Any
Any
Any
Description
Bit mask of enabled hardware status signals
Bit mask of enabled communication status
signals
Bit mask of enabled software status signals
Bit mask of enabled sensor status signals
hardwareStatusEnable Field
This field is a bit mask of the hardwareStatus field (see BIT and status definitions). This
field allows the user to determine which low level hardwareStatus field signals will flag
the hardwareStatus and masterStatus flags in the BITstatus field. Any asserted bits in this
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field imply that the corresponding hardwareStatus field signal, if asserted, will cause the
hardwareStatus and masterStatus flags to be asserted in the BITstatus field.
9.16.2
comStatusEnable Field
This field is a bit mask of the comStatus field (see BIT and status definitions). This field
allows the user to determine which low level comStatus field signals will flag the
comStatus and masterStatus flags in the BITstatus field. Any asserted bits in this field
imply that the corresponding comStatus field signal, if asserted, will cause the comStatus
and masterStatus flags to be asserted in the BITstatus field.
9.16.3
softwareStatusEnable Field
This field is a bit mask of the softwareStatus field (see BIT and status definitions). This
field allows the user to determine which low level softwareStatus field signals will flag
the softwareStatus and masterStatus flags in the BITstatus field. Any asserted bits in this
field imply that the corresponding softwareStatus field signal, if asserted, will cause the
softwareStatus and masterStatus flags to be asserted in the BITstatus field.
9.16.4
sensorStatusEnable Field
This field is a bit mask of the sensorStatus field (see BIT and status definitions). This
field allows the user to determine which low level sensorStatus field signals will flag the
sensorStatus and masterStatus flags in the BITstatus field. Any asserted bits in this field
imply that the corresponding sensorStatus field signal, if asserted, will cause the
sensorStatus and masterStatus flags to be asserted in the BITstatus field.
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10 Appendix A. Mechanical Specifications
Figure 19.
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DMU380SA Series Outline Drawing (IMU, VG, AHRS)
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Figure 20.
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DMU380SA Series Outline Drawing (INS)
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11 Appendix B. NMEA Message Format
The GPS receiver outputs data in NMEA-0183 format at 9600 Baud, 8 bits, no parity bit,
and 1 stop bit. The GGA and RMC message packet formats are explained in this section.
11.1 GGA - GPS fix data
Time and position, together with GPS fixing related data (number of satellites in use, and
the resulting HDOP, age of differential data if in use, etc.).
$GPGGA,hhmmss.ss,Latitude,N,Longitude,E,FS,NoSV,HDOP,msl,m,
Altref,m,DiffAge,DiffStation*cs<CR><LF>
ASCII String
Name
Format
Description
Example
$GPGGA
string
$GPGGA
Message ID:
GGA protocol header
hhmmss.ss
hhmmss.sss
092725.00
UTC Time: Current time
Latitude
dddmm.mmmm
4717.11399
Latitude: Degrees + minutes
N
character
N
N/S Indicator:
N=north or S=south
Longitude
dddmm.mmmm
00833.91590
Longitude:
Degrees + minutes
E
character
E
E/W indicator:
E=east or W=west
FS
1 digit
1
Position Fix Indicator
(See Table below)
NoSV
numeric
8
Satellites Used:
Range 0 to 12
HDOP
numeric
1.01
HDOP: Horizontal Dilution of Precision
msl
numeric
499.6
MSL Altitude (m)
m
character
M
Units: Meters (fixed field)
Altref
blank
48.0
Geoid Separation (m)
m
blank
M
Units: Meters (fixed field)
DiffAge
numeric
DiffStation
numeric
0
Diff. Reference Station ID
cs
hexadecimal
*5B
Checksum
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Age of Differential Corrections (sec):
Blank (Null) fields when DGPS is not
used
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<CR> <LF>
End of message
Fix Status Description
0
No fix / Invalid
1
Standard GPS (2D/3D)
2
Differential GPS
6
Estimated (DR) Fix
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12 Appendix C. Sample Packet-Parser Code
12.1 Overview
This appendix includes sample code written in ANSI C for parsing packets from data sent
by the DMU380SA Series Inertial Systems. This code can be used by a user application
reading data directly from the DMU380SA Series product, or perhaps from a log file.
The sample code contains the actual parser, but also several support functions for CRC
calculation and circular queue access.:

process_xbow_packet – for parsing out packets from a queue. Returns these
fields in structure XBOW_PACKET (see below). Checks for CRC errors

calcCRC – for calculating CRC on packets.

Initialize - initialize the queue

AddQueue - add item in front of queue

DeleteQueue - return an item from the queue

peekWord - for retrieving 2-bytes from the queue, without popping

peekByte – for retrieving a byte from the queue without popping

Pop - discard item(s) from queue

Size – returns number of items in queue

Empty – return 1 if queue is empty, 0 if not

Full - return 1 if full, 0 if not full
The parser will parse the queue looking for packets. Once a packet is found and the CRC
checks out, the packet’s fields are placed in the XBOW_PACKET structure. The parser
will then return to the caller. When no packets are found the parser will simply return to
the caller with return value 0.
The XBOW_PACKET stucture is defined as follows:
typedef struct xbow_packet
{
unsigned short packet_type;
char
length;
unsigned short crc;
char
data[256];
} XBOW_PACKET;
Typically, the parser would be called within a loop in a separate process, or in some time
triggered environment, reading the queue looking for packets. A separate process might
add data to this queue when it arrives. It is up to the user to ensure circular-queue
integrity by using some sort of mutual exclusion mechanism withing the queue access
funtions.
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12.2 Code listing
#include <stdio.h>
/* buffer size */
#define MAXQUEUE 500
/*
* circular queue
*/
typedef struct queue_tag
{
int count;
int front;
int rear;
char entry[MAXQUEUE];
} QUEUE_TYPE;
/*
* MEMSIC packet
*/
typedef struct xbow_packet
{
unsigned short packet_type;
char
length;
unsigned short crc;
char
data[256];
} XBOW_PACKET;
QUEUE_TYPE circ_buf;
/*******************************************************************************
* FUNCTION: process_xbow_packet looks for packets in a queue
* ARGUMENTS: queue_ptr: is pointer to queue to process
*
result: will contain the parsed info when return value is 1
* RETURNS:
0 when failed.
*
1 when successful
*******************************************************************************/
int process_xbow_packet(QUEUE_TYPE *queue_ptr, XBOW_PACKET *result)
{
unsigned short myCRC = 0, packetCRC = 0, packet_type = 0, numToPop=0,
counter=0;
char packet[100], tempchar, dataLength;
if(Empty(queue_ptr))
{
return 0;
/* empty buffer */
}
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/* find header */
for(numToPop=0; numToPop+1<Size(queue_ptr) ;numToPop+=1)
{
if(0x5555==peekWord(queue_ptr, numToPop)) break;
}
Pop(queue_ptr, numToPop);
if(Size(queue_ptr) <= 0)
{
/* header was not found */
return 0;
}
/* make sure we can read through minimum length packet */
if(Size(queue_ptr)<7)
{
return 0;
}
/* get data length (5th byte of packet) */
dataLength = peekByte(queue_ptr, 4);
/* make sure we can read through entire packet */
if(Size(queue_ptr) < 7+dataLength)
{
return 0;
}
/* check CRC */
myCRC = calcCRC(queue_ptr, 2,dataLength+3);
packetCRC = peekWord(queue_ptr, dataLength+5);
if(myCRC != packetCRC)
{
/* bad CRC on packet – remove the bad packet from the queue and return */
Pop(queue_ptr, dataLength+7);
return 0;
}
/* fill out result of parsing in structure */
result->packet_type = peekWord(queue_ptr, 2);
result->length
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result->crc
= packetCRC;
for(counter=0; counter < result->length; counter++)
{
result->data[counter] = peekByte(queue_ptr, 5+counter);
}
Pop(queue_ptr, dataLength+7);
return 1;
}
/*******************************************************************************
* FUNCTION: calcCRC calculates a 2-byte CRC on serial data using
*
CRC-CCITT 16-bit standard maintained by the ITU
*
(International Telecommunications Union).
* ARGUMENTS: queue_ptr is pointer to queue holding area to be CRCed
*
calculation
startIndex is offset into buffer where to begin CRC
*
num is offset into buffer where to stop CRC calculation
* RETURNS:
2-byte CRC
*******************************************************************************/
unsigned short calcCRC(QUEUE_TYPE *queue_ptr, unsigned int startIndex, unsigned
int num) {
unsigned int i=0, j=0;
unsigned short crc=0x1D0F; //non-augmented inital value equivalent to
augmented initial value 0xFFFF
for (i=0; i<num; i+=1) {
crc ^= peekByte(queue_ptr, startIndex+i) << 8;
for(j=0;j<8;j+=1) {
if(crc & 0x8000) crc = (crc << 1) ^ 0x1021;
else crc = crc << 1;
}
}
return crc;
}
/*******************************************************************************
* FUNCTION: Initialize - initialize the queue
* ARGUMENTS: queue_ptr is pointer to the queue
*******************************************************************************/
void Initialize(QUEUE_TYPE *queue_ptr)
{
queue_ptr->count = 0;
queue_ptr->front = 0;
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queue_ptr->rear = -1;
}
/*******************************************************************************
* FUNCTION: AddQueue - add item in front of queue
* ARGUMENTS: item holds item to be added to queue
*
queue_ptr is pointer to the queue
* RETURNS:
returns 0 if queue is full. 1 if successful
*******************************************************************************/
int AddQueue(char item, QUEUE_TYPE *queue_ptr)
{
int retval = 0;
if(queue_ptr->count >= MAXQUEUE)
{
retval = 0; /* queue is full */
}
else
{
queue_ptr->count++;
queue_ptr->rear = (queue_ptr->rear + 1) % MAXQUEUE;
queue_ptr->entry[queue_ptr->rear] = item;
retval = 1;
}
return retval;
}
/*******************************************************************************
* FUNCTION: DeleteQeue - return an item from the queue
* ARGUMENTS: item will hold item popped from queue
*
queue_ptr is pointer to the queue
* RETURNS:
returns 0 if queue is empty. 1 if successful
*******************************************************************************/
int DeleteQueue(char *item, QUEUE_TYPE *queue_ptr)
{
int retval = 0;
if(queue_ptr->count <= 0)
{
retval = 0; /* queue is empty */
}
else
{
queue_ptr -> count--;
*item = queue_ptr->entry[queue_ptr->front];
queue_ptr->front = (queue_ptr->front+1) % MAXQUEUE;
retval=1;
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}
return retval;
}
/*******************************************************************************
* FUNCTION: peekByte returns 1 byte from buffer without popping
* ARGUMENTS: queue_ptr is pointer to the queue to return byte from
*
index is offset into buffer to which byte to return
* RETURNS:
1 byte
* REMARKS:
does not do boundary checking. please do this first
*******************************************************************************/
char peekByte(QUEUE_TYPE *queue_ptr, unsigned int index) {
char byte;
int firstIndex;
firstIndex = (queue_ptr->front + index) % MAXQUEUE;
byte = queue_ptr->entry[firstIndex];
return byte;
}
/*******************************************************************************
* FUNCTION: peekWord returns 2-byte word from buffer without popping
* ARGUMENTS: queue_ptr is pointer to the queue to return word from
*
index is offset into buffer to which word to return
* RETURNS:
2-byte word
* REMARKS:
does not do boundary checking. please do this first
*******************************************************************************/
unsigned short peekWord(QUEUE_TYPE *queue_ptr, unsigned int index) {
unsigned short word, firstIndex, secondIndex;
firstIndex = (queue_ptr->front + index) % MAXQUEUE;
secondIndex = (queue_ptr->front + index + 1) % MAXQUEUE;
word = (queue_ptr->entry[firstIndex] << 8) & 0xFF00;
word |= (0x00FF & queue_ptr->entry[secondIndex]);
return word;
}
/*******************************************************************************
* FUNCTION: Pop - discard item(s) from queue
* ARGUMENTS: queue_ptr is pointer to the queue
*
* RETURNS:
numToPop is number of items to discard
return the number of items discarded
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*******************************************************************************/
int Pop(QUEUE_TYPE *queue_ptr, int numToPop)
{
int i=0;
char tempchar;
for(i=0; i<numToPop; i++)
{
if(!DeleteQueue(&tempchar, queue_ptr))
{
break;
}
}
return i;
}
/*******************************************************************************
* FUNCTION: Size
* ARGUMENTS: queue_ptr is pointer to the queue
* RETURNS:
return the number of items in the queue
*******************************************************************************/
int Size(QUEUE_TYPE *queue_ptr)
{
return queue_ptr->count;
}
/*******************************************************************************
* FUNCTION: Empty
* ARGUMENTS: queue_ptr is pointer to the queue
* RETURNS:
return 1 if empty, 0 if not
*******************************************************************************/
int Empty(QUEUE_TYPE *queue_ptr)
{
return queue_ptr->count <= 0;
}
/*******************************************************************************
* FUNCTION: Full
* ARGUMENTS: queue_ptr is pointer to the queue
* RETURNS:
return 1 if full, 0 if not full
*******************************************************************************/
int Full(QUEUE_TYPE *queue_ptr)
{
return queue_ptr->count >= MAXQUEUE;
}
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13 Appendix D. Sample Packet Decoding
Figure 21.
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Example payload from Angle Data Packet 2 (A2)
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Figure 22.
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Example payload from Scaled Data Packet 1 (S1)
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Figure 23.
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Example payload from Nav Data Packet 1 (N1)
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14 Warranty and Support Information
14.1 Customer Service
As a MEMSIC customer you have access to product support services, which include:

Single-point return service

Web-based support service

Same day troubleshooting assistance

Worldwide MEMSIC representation

Onsite and factory training available

Preventative maintenance and repair programs

Installation assistance available
14.2 Contact Directory
United States: Phone: 1-408-964-9700 (8 AM to 5 PM PST)
Fax:
1-408-854-7702 (24 hours)
Email: [email protected]
Non-U.S.:
Refer to website
www.memsic.com
14.3 Return Procedure
14.3.1 Authorization
Before returning any equipment, please contact MEMSIC to obtain a Returned Material
Authorization number (RMA).
Be ready to provide the following information when requesting a RMA:

Name

Address

Telephone, Fax, Email

Equipment Model Number

Equipment Serial Number

Installation Date

Failure Date

Fault Description

Will it connect to NAV-VIEW?
14.3.2 Identification and Protection
If the equipment is to be shipped to MEMSIC for service or repair, please attach a tag TO
THE EQUIPMENT, as well as the shipping container(s), identifying the owner. Also
indicate the service or repair required, the problems encountered and other information
considered valuable to the service facility such as the list of information provided to
request the RMA number.
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Place the equipment in the original shipping container(s), making sure there is adequate
packing around all sides of the equipment. If the original shipping containers were
discarded, use heavy boxes with adequate padding and protection.
14.3.3 Sealing the Container
Seal the shipping container(s) with heavy tape or metal bands strong enough to handle the
weight of the equipment and the container.
14.3.4 Marking
Please write the words, “FRAGILE, DELICATE INSTRUMENT” in several places on
the outside of the shipping container(s). In all correspondence, please refer to the
equipment by the model number, the serial number, and the RMA number.
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14.3.5 Return Shipping Address
Use the following address for all returned products:
MEMSIC, Inc.
1759 McCarthy Blvd.
Milpitas, CA 95035
Attn: RMA Number (XXXXXX)
14.4 Warranty
The MEMSIC product warranty is one year from date of shipment.
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1759 McCarthy Blvd.
Milpitas, CA 95035
Phone: 408.964.9700
Fax: 408.854.7702
Website: www.memsic.com
Email: [email protected]
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