GNAV540 User Manual Installation Configuration Reference www.moog‐crossbow.com 1 Moog, Inc., 1421 McCarthy Blvd.
©2011 Moog, Inc. All rights reserved. Information in this document is subject to change without notice. Crossbow and GNAV540 are registered trademarks of Moog, Inc. Other product and trade names are trademarks or registered trademarks of their respective holders. Page 2 GNAV540 User Manual 7430‐0808‐01 Rev.
Table of Contents Preface................................................................................................................................................................................ 13 Intended Audience.................................................................................................................................................................................................13 Contents......................................................................................
Chapter 4. Magnetometer Calibration and Alignment Guidelines ......................................................... 39 Compensation for Magnetic Fields .................................................................................................................................................................39 Magnetometer Alignment Using NAV‐VIEW 2.2 ......................................................................................................................................
Chapter 8. Data Packet Structure ....................................................................................................................... 61 General Settings ......................................................................................................................................................................................................61 Number Formats..........................................................................................................................
Nav Data Packet 3 (default packet) ...............................................................................................................................................................80 Nav Data Packet 4...................................................................................................................................................................................................82 Chapter 10. Programming Guidelines................................................................
hardwareStatusEnable Field .....................................................................................................................................................................106 comStatusEnable Field.................................................................................................................................................................................107 softwareStatusEnable Field .......................................................................................
Tables Table 1 Chapter Summaries ..................................................................................................................................................................................13 Table 2 Reference Documents..............................................................................................................................................................................15 Table 3 Text Conventions .....................................................................
Table 34 Version Data PKT ....................................................................................................................................................................................71 Table 35 VR Payload .................................................................................................................................................................................................72 Table 36 T2 Payload....................................................................
Table 71 RF Response ..............................................................................................................................................................................................93 Table 72 RF Payload .................................................................................................................................................................................................93 Table 73 GF Command...............................................................
Figure 3 GNAV540 Functions................................................................................................................................................................................24 Figure 4 GNAV540 Default Coordinate System ............................................................................................................................................24 Figure 5 1PPS Output Signal..............................................................................................
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Preface This document provides information about GNAV540, including operational functions and configuration options. Intended Audience This document is intended for those who install, configure, extract data and use inertial systems. It is assumed the reader is familiar with the technology of navigation. For advanced use of the GNAV540, knowledge of C programming is required. NOTE: Uploading firmware (DMU upgrade) to the unit is outside the scope of this document.
Chapter / Appendix Summary Built In Test (BIT) Appendix A. Application Examples Configuration examples of the unit installed in various vehicles Appendix B. Sample Packet— Parser Code Example of parser code Appendix C. Sample Packet Decoding Examples of packet decoding Appendix D. Mechanical Specifications Mechanical specifications, and drawings and measurements of the enclosed model units Appendix E.
Chapter / Appendix Summary Policies process and contact information Appendix F. Revision History List and description of document release: updates, changes Related Documents NOTE: Moog, Inc. is ISO9001:2008 certified.
Glossary Table 4 Glossary Term Definition 6DOF Six Degree of Freedom ACL Accelerometer AHRS Attitude Heading Reference BIT Built In Test DSP Digital Signal Processor ECEF Earth‐Centered Earth‐Fixed ESS Environmental Stress Screening EKF Extended Kalman Filter FIR Finite Impulse Response GB‐GRAM Ground‐Based GPS Receiver Application Module GPS Global Positioning System Hard failure Fatal condition, non‐operational Hard iron Magnetism is retained (permanent) IMU Inertial Measurem
Chapter 1. Overview This chapter provides a high level summary of the GNAV540: • Features, page 17 • Software Compatibility, page 18 • GNAV540 Unit, page 18 Features • Pitch and roll accuracy of <0.4°, heading error < 0.
Measurement Accuracy Attitude Range: Roll, Pitch ±180°, ±90° Accuracy <0.4° Angular Rate Range: Roll, Pitch, Yaw ±200° Bias Stability in run <10°/hr Bias Stability over temp <0.02°/sec Acceleration Input Range ±4 g Bias Stability in run <1 mg Bias Stability over temp <4 mg Signal Interface The J1 port of the GNAV540 provides the connections listed in Table 6 below. Details of the signal interface, including I/O pin out, is provided in Chapter 3. Hardware Interface on page 35.
temperature and non‐linearity effects during Crossbow’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 Digital Signal Processor (DSP) 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 GNAV540 as shown in Table 2).
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Chapter 2. GNfAV540 Functions This chapter provides an overview of the hardware and software systems of the GNAV540 unit, and the functions provided. • GNAV540 System, page 21 • Configuring GNAV540 Functions, page 21 • Software Structure, page 22 • GNAV540 Default Coordinate System, page 24 • IMU Function, page 25 • Vertical Gyroscope (VG) Function, page 26 • AHRS Function, page 29 • NAV Function, page 31 GNAV540 System GNAV540 is a compact MEMS based GPS/inertial navigation system.
Figure 1 GNAV540 System Software Structure Figure 2 below shows the software block diagram. The 6‐DOF inertial sensor cluster data is fed into a high speed 100Hz 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.
Figure 2 GNAV540 Software Block Diagram Measurement Data Available to User (Fixed Rate or Polled) IMU - Scaled Packets (S0,S1,S2) All Units NAV/AHRS/VG/IMU VG/AHRS– Angle Packets (A0,A1,A2) NAV/AHRS/VG NAV - Nav Packets (N0,N1,N2, N3) NAV/AHRS/VG 6-DOF Sensor Cluster X / Y / Z Body Rates X / Y / Z Body Accelerometers 100Hz Signal Proc.
Figure 3 GNAV540 Functions NAV Function AHRS Function Attitude and velocity propagation 100 Hz accels, rates, MAGS, attitude, , velocity, GPS position ∑ Attitude propagation 100 Hz accels, rates, mags, attitude, ∑ Correction algorithm Correction algorithm Roll/pitch heading velocity Roll/pitch heading velocity Accelerometer tilt Magnetometer heading GPS velocity VG Function with External GPS Attitude and velocity propagation 100 Hz ∑ ? Accelerometer tilt , Magnetometer heading VG Functi
measure zero g along the x and y‐axes and ‐1 g along the z‐axis. Normal Force acceleration is directed upward, which would be defined as negative for the GNAV540 z‐axis. The angular rate sensors are aligned with the 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.
NOTE: 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; they are subject to overflow (data type wrap around). IMU Advanced Settings The IMU advanced settings are described in Table 7 below. All of the advanced settings are accessible thru NAV‐ VIEW 2.2 under the Configuration Menu→Unit Configuration settings. For information about using NAV‐VIEW 2.
VG Function 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 unit maintains a low‐pass filtered yaw rate signal and compares it to the turnSwitch threshold field (user adjustable).
Setting Default Value Comments Freely Integrate OFF The Freely Integrate setting allows configuring the unit into a free gyroscope. In free gyroscope 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.
AHRS Function The Attitude Heading Reference System (AHRS) Function utilizes a 3‐axis magnetometer (internal or external) in addition to the accelerometers and gyroscopes, as well as the associated software running on the DSP processor. This enables the computation of dynamic heading, as well as dynamic roll and pitch. AHRS Function provides dynamic heading, roll, and pitch measurements in addition to the VG Function and IMU Function data.
Setting Default Value Comments Orientation See Figure 4 on page 24. To configure the axis orientation, select the desired measurement for each axis: NAV‐VIEW 2.2 then shows the corresponding image of the unit, making it easy to visualize the mode of operation. Refer to Orientation Field on page 86 for the twenty four possible orientation settings. The default setting points the connector AFT. Freely Integrate OFF The Freely Integrate setting allows a user to turn the unit into a free gyroscope.
Setting Default Value Comments 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. Algorithm reset returns the unit to a high gain state, where the unit rapidly estimates the gyroscope bias and uses the accelerometer feedback heavily.
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 gyroscopes and accelerometers are performed. The NAV Function blends GPS derived heading and accelerometer measurements into the EKF update depending on the health and status of the associated sensors.
Setting Default Value Comments Orientation See Figure 4 on page 24. To configure the axis orientation, select the desired measurement for each axis: NAV‐VIEW 2.2 will show the corresponding image of the unit, so it easy to visualize the mode of operation. Refer to Orientation Field on page 86 for the twenty four possible orientation settings. The default setting points the connector AFT. Freely Integrate OFF The Freely Integrate setting allows a user to turn the unit into a free gyroscope.
Setting Default Value Comments Restart On Over Range ON 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.. Algorithm reset returns the unit to a high gain state, where the unit rapidly estimates the gyroscope bias and uses the accelerometer feedback heavily.
Chapter 3. Hardware Interface This chapter provides information about the power and signal interface connectors. J1—I/O Connector NOTE: Signals labeled as NC have internal pull‐up mechanisms. To ensure proper operation of the unit, ensure there are no connections to these pins. Table 11 I/O Connector Pin No. Signal Pin No.
I/O Port Interface The following ports are accessible through the J1 connector. Refer to J1—I/O Connector on page 35 for the pin out listing. NOTE: The GNAV540 can be purchased with a developer’s kit: a cable is provided with a 37 pin connector on one end, and five connectors on the other end to connect to external devices. This cable is designed only for laboratory use. See Figure 31 on page 126.
1 PPS Output Interface The 1PPS output signal is provided by the internal GPS receiver (when GPS timing is known) on the GNAV540. 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 GNAV540 synchronizes 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.
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Chapter 4. Magnetometer Calibration and Alignment Guidelines This chapter provides general guidelines for calibrating and aligning a magnetometer with the GNAV540 unit. • Compensation for Magnetic Fields, page 39 • Magnetometer Alignment Using NAV‐VIEW 2.2, page 39 • Magnetometer Alignment Using Code, page 40 • Installation Guidelines, page 40 This section provides guidelines to calibrate and align the magnetometer.
in the horizontal plane. Using NAV‐VIEW 2.2, the hard and soft iron effects can be viewed by selecting the Misalignment option on the Configuration Menu, and viewing the magnetic circle during the calibration. For calibration instructions, refer to Aligning the Magnetometer on page 57. Magnetometer Alignment Using Code The unit provides a command interface for initiating the hard iron/soft iron calibration without using NAV‐VIEW 2.2.
Serial Data Interface The GNA540 receives information through a serial interface that is dedicated for an external magnetometer. Refer to Table 11 on page 35 for the signal pin out of the J1 connector. GNAV540 User Manual 7430‐0808‐01 Rev.
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Chapter 5. Installation Guidelines This chapter provides information to set up the GNAV540 unit and NAV‐VIEW 2.2 software for laboratory test. NOTE: Directions to install a unit in a vehicle for field use is outside the scope of this document. • Overview, page 43 • Installation Requirements, page 43 • 1. Install Software—NAV‐VIEW 2.2, page 44 • 2. Prepare the Communication Port, page 44 • 3. Connect the GPS Antenna, page 44 • 4.
1. Install Software—NAV‐VIEW 2.2 Instructions a. Insert the CD GNAV540 Inertial System in the CD‐ROM drive. b. On the CD, go to the NAV‐VIEW 2.2 folder and double click the setup.exe file. c. Follow the wizard instructions to install NAV‐VIEW 2.2 and if necessary, the .NET 4.0 framework. 2. Prepare the Communication Port The GNAV540 unit can communicate to the computer via Ethernet or directly to the computer via serial port: determine which communication port to use.
4. Turn on the GNAV540 Instructions a. Ensure the voltage level of the power supply is set between +8 VDC and +32 VDC, and then turn off the power supply. b. Secure the cable to the GNAV540 unit. a. Connect the unit cable to the DC voltage power supply: • Connect the red plug to the positive terminal (+). • Connect the black plug to the ground terminal (‐) ground. CAUTION: If the input power leads are reversed, the unit may be damaged.
Trouble‐Shooting Tips • • If the unit is connected but not working, check the following: o The power supply is connected and the output voltage and current levels are correct. o If using the serial port, verify the correct serial connector of the cable is being used. If the adaptor is being used verify the switch setting of the adaptor. o If using the Ethernet port, verify the IP address of the unit is correct.
Chapter 6. Viewing and Logging Data with NAV‐VIEW 2.2 NOTE: It is assumed that GNAV540 and NAV‐VIEW 2.2 have been set up, connected and turned on. For instructions, refer to Chapter 5. Installation Guidelines on page 43. Figure 8 on page 48 shows the main page of NAV‐VIEW. The functions are accessed from the menu bar at the top of the page. The graphs are displayed in the main body of the page.
Figure 8 Main Screen Communication Port The GNAV540 can be accessed via serial or Ethernet port, which is selected in the Setup menu. To select a port, click Setup and then select the desired port from the drop menu. A dialog window then opens, enabling configuration. Page 48 GNAV540 User Manual 7430‐0808‐01 Rev.
Serial Port Figure 9 Configure Serial Port The Configure Serial Port dialog shows the current Port and Baud rate, which can both be configured. To do so: 1. Select the desired COM Port. 2. Either manually select the desired Baud Rate or select Auto. 3. To apply the configuration, click Apply. 4. To ensure the configuration is saved in NAV‐VIEW, click Save and Close. Ethernet Port Figure 10 Configure Ethernet Port The Ethernet settings are configured in the EthernetForm dialog. To do so: 1.
1. icon at the top of the page, or Locate the click File and then select Log to File from the drop down menu. The dialog window opens. 2. Click the Browse button and select the location for saving data. 3. In the Log Type section, select the type of data to record: Figure 11 Log to File Menu Engineering Data records the converted values provided from the system in engineering units (default selection). Hex Data provides the raw hex values separated into columns displaying the value.
2. Once the file is selected, users can utilize the VCR style controls at the top of the page to start, stop, or pause the playback of the data. NAV‐VIEW 2.2 also provides users with the ability to alter the start time for data playback. The slide bar at the top of the page can be used to adjust the starting time. Raw Data Console NAV‐VIEW 2.2 offers some unique debugging tools that may assist programmers in the development process. One such tool is the Raw Data Console.
Horizon and Compass Views NAV‐VIEW 2.2 provides a compass and a simulated artificial horizon view. • To activate these views, click View at the menu bar, and then select Horizon View and/or Compass View from drop down menu. Figure 13 Horizon and Compass Views Packet Statistics View To view packet statistics, click View at the menu bar and then select the Packet Statistics.
Chapter 7. Configuring GNAV540 with NAV‐VIEW 2.2 It is assumed the GNAV540 unit and NAV‐VIEW 2.2 have been set up. For instructions, refer to Chapter 5. Installation Guidelines. This section provides instructions to configure the unit via NAV‐VIEW 2.2, a GUI application. For information about configuring the unit via programming code, refer to Chapter 10. Programming Guidelines.
Method 2: 1. Figure 16 View Current Configuration At the main screen, select Unit Configuration from the menu bar, then select Configuration from the drop menu. The dialog window opens (Figure 16). 2. Click Get All Values at the bottom of the screen. The current configuration values will be displayed. Configuring the Unit The Unit Configuration window enables viewing and configuring the system configurations.
Viewing Current Configuration Figure 17 Unit Configuration To view the current configuration, click the Get All Values button. The current settings will be displayed in the text fields. Changing Configurations To change a configuration setting: 1. Checkmark the desired item(s) in the left Colum 2. Using the drop menus in the right column, select the new values. 3. Select either Temporary or Permanent. Temporary: The configuration will not be stored in non‐volatile memory (EEPROM).
Advanced The Advanced tab provides access to more complex configurations, such as user behavior settings. Viewing Current Configuration Figure 19 Advanced Settings To view the current configuration, click the Get All Values button. The current settings will be displayed in the text fields. A box filled with blue color indicates the behavior switch is enabled. Refer to Figure 19. Changing Configurations 1. To enable a switch: a. Checkmark the desired item under Value to Set. 2.
Viewing Current Configuration Figure 20 BIT Configuration To view the current configuration, click the Get All Values button. The current settings will be displayed in the text fields. Under Current Value, a box filled with blue color indicates the status field is enabled. Refer to Figure 20. Changing Configurations To view the current settings, click the Get All Values button. To modify Status Field(s): 1. Checkmark the desired item(s) under Modify. 2.
greater than the values specified on the data sheet or fluctuating heading performance may indicate magnetic field disturbances near the unit. NOTE: An acceptable calibration will provide X and Y Hard Iron Offset Values of <0.1 and a Soft Iron Ratio >0.95. If this procedure generates calibration parameters significantly outside of this range, the system will assert the softwareErrorÆdataErrorÆmagAlignOutOfBounds error flag. Refer to Chapter 11. Built In Test (BIT)) for details about error flag handling.
After completing the rotation, data will be displayed with the calibration values. The X and Y offset values indicate how far the magnetic field has been shifted due to hard iron affects from components surrounding the unit. Figure 22 Magnetometer Alignment Values The soft iron ratio will also be displayed, which is the effect of soft iron on the GNAV540 unit. 6. The save the calibration values, click the Apply button.
Rotational Alignment 1. Ensure the unit is configured to use the external magnetometer. Refer to Advanced on page 56. 2. Ensure the leveling alignment of the magnetometer has been configured (Leveling Alignment, page 59). 3. Click Configuration and then select Magnetometer Alignment from the drop menu. 4. If the 360 degree turn can be completed within 120 seconds, check AutoTerminate. 5. Under Rotational Alignment, select the Start button to begin the alignment.
Chapter 8. Data Packet Structure NOTE: This section of the manual assumes the reader is familiar with ANSI C programming language and data type conventions. The unit supports a common packet structure that includes both command or input data packets, and measurement output or response packet formats. This section of the manual explains these packet formats as well as the supported commands. NAV‐VIEW 2.
Descriptor Description Size (bytes) Comment Range F4 Floating Point 4 IEEE754 Single Precision ‐1*2^127 to 2^127 SN String N ASCII Packet Format All of the Input and Output packets, except the Ping command, conform to the following structure: 0x5555 <2‐byte packet type (U2)> <2‐byte CRC (U2)> The Ping Command does not require a CRC, so a GNAV540 unit can be pinged from a terminal emulator.
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 portion of the packet ONLY, and does not include the CRC. Payload The payload is of variable length based on the packet type. 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.
ASCII Mnemonic <2‐byte packet type (U2)> WC 0x5743 CC 0x4343 Description Type Available Functions 2 Calibrate Command and Response Input/Reply Message AHRS, NAV 8 Calibration Completed Reply Message AHRS, NAV Output Messages: Status and Other, (Polled Only) ID 0x4944 5+N Identification Data Output Message ALL VR 0x5652 5 Version Data Output Message ALL T2 0x5432 30 Test 0 (Detailed BIT and Status) Output Message ALL Output Messages: Measurement
ASCII Mnemonic <2‐byte packet type (U2)> RF 0x5246 RF Description Type Available Functions numFields*2+1 Read Fields Request Input Message ALL 0x5246 numFields*4+1 Read Fields Response Reply Message ALL GF 0x4746 numFields*2+1 Get Fields Request Input Message ALL GF 0x4746 numFields*4+1 Get Fields Response Reply Message ALL GNAV540 User Manual 7430‐0808‐01 Rev.
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Chapter 9. Communicating with the GNAV540 Unit Communication commands are used to verify a unit is present and alive. Ping Command Table 15 Ping Command Ping (‘PK’ = 0x504B) Preamble Packet Type Length Termination 0x5555 ‐ 0x504B ‐ 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.
Interactive Commands Interactive commands are used to interactively request data from the GNAV540 unit, and to calibrate or reset the unit. Get Packet Request Table 18 GP Request Get Packet (‘GP’ = 0x4750) Preamble Packet Type Length Payload Termination 0x5555 0x02 0x4750 This command allows the user to poll for both measurement packets and special purpose output packets including T0, VR, and ID.
This command performs a core CPU reset, functionally equivalent to a power cycle. All default power‐up field settings will apply. The unit will respond with software reset response before the system goes down. Software Reset Response Table 23 Software Reset Response Software Reset (‘SR’ = 0x5352) Preamble Packet Type Length Termination 0x5555 0x00 0x5352 The unit will send this packet in response to a software reset command.
calibrationRequest Description calibration command. Write magnetic calibration. The unit will write the parameters to EEPROM and then send a calibration response. 0x000E Calibrate Acknowledgement Response Table 27 Calibrate WC ACK Response Calibrate (‘WC’ = 0x5743) Preamble Packet Type Length Payload Termination 0x5555 0x02 0x5743 The unit will send this packet in response to a calibrate request if the procedure can be performed or initiated.
Error Response Table 31 Error Response Error Response (ASCII NAK, NAK = 0x1515) Preamble Packet Type Length Payload Termination 0x5555 0x02 0x1515 The unit will send this packet in place of a normal response to a failedInputPacketType request if it could not be completed successfully.
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.
T2 Payload Contents Byte Offset Name Format Scaling Units Description BIT Field 14 comSerialCBIT U2 — — Communication Serial C BIT Field 16 softwareBIT U2 — — Software BIT Field 16 softwareAlgorithmBIT U2 — — Software Algorithm BIT Field 20 softwareDataBIT U2 — — Software Data BIT Field 22 hardwareStatus U2 — — Hardware Status Field 24 comStatus U2 — — Communication Status Field 26 softwareStatus U2 — — Software Status Field 28 sensorStatus U2 — — Sensor
S0 Payload Contents Byte Offset Name Format Scaling Units Description 8 yRate I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Y angular rate 10 zRate I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Z angular rate 12 xMag I2 2/2^16 Gauss X magnetometer 14 yMag I2 2/2^16 Gauss Y magnetometer 16 zMag I2 2/2^16 Gauss Z magnetometer 18 xRateTemp I2 200/2^16 deg. C X rate temperature 20 yRateTemp I2 200/2^16 deg. C Y rate temperature 22 zRateTemp I2 200/2^16 deg.
S1 Payload Contents Byte Offset Name Format Scaling Units Description 10 zRate I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Z angular rate 12 xRateTemp I2 200/2^16 deg. C X rate temperature 14 yRateTemp I2 200/2^16 deg. C Y rate temperature 16 zRateTemp I2 200/2^16 deg. C Z rate temperature 18 boardTemp I2 200/2^16 deg.
Angle Data Packet 0 Table 43 A0 Data Packet Angle Data (‘A0’ = 0x4130) Preamble Packet Type Length Payload Termination 0x5555 0x1E 0x4130 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.
A0 Payload Contents Byte Offset Name Format Scaling Units Description 26 GPSITOW U2 truncated ms GPS ITOW (lower 2 bytes) 28 BITstatus U2 — — Master BIT and Status Angle Data Packet 1 (Default AHRS Data) Table 45 A1 Data Packet Angle Data (‘A1’ = 0x4131) Preamble Packet Type Length Payload Termination 0x5555 0x20 0x4131 This packet contains angle data and selected sensor data scaled in most cases to a signed 2^16 2’s complement number.
A1 Payload Contents Byte Offset Name Format Scaling Units Description 18 xMag I2 2/2^16 Gauss X magnetometer 20 yMag I2 2/2^16 Gauss Y magnetometer 22 zMag I2 2/2^16 Gauss Z magnetometer 24 xRateTemp I2 200/2^16 Deg C X rate temperature 26 timeITOW U4 1 ms DMU ITOW (sync to GPS) 30 BITstatus U2 — — Master BIT and Status Nav Data Packet 0 Table 47 N0 Data Packet Nav Data (‘N0’ = 0x4E30) Preamble Packet Type Length Payload Termination 0x5555 0x20
N0 Payload Contents Byte Offset Name Format Scaling Units (1260°/2^16) (°/sec) Description 8 yRateCorrected I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Y angular rate corrected 10 zRateCorrected I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Z angular rate corrected 12 nVel I2 512/2^16 m/s North velocity 14 eVel I2 512/2^16 m/s East velocity 16 dVel I2 512/2^16 m/s Down velocity 18 longitudeGPS I4 2*pi/2^32 (360°/2^32) Radians (°) GPS Longitude 22 latitudeGPS I4 2*pi/2^32
Table 50 N1 Payload N1 Payload Contents Byte Offset Name Format Scaling Units Description 0 rollAngle I2 2*pi/2^16 (360°/2^16) Radians (°) Roll angle 2 pitchAngle I2 2*pi/2^16 (360°/2^16) Radians (°) Pitch angle 4 yawAngleTrue I2 2*pi/2^16 (360°/2^16) Radians (°) Yaw angle (true north) 6 xRateCorrected I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) X angular rate corrected 8 yRateCorrected I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Y angular rate corrected 10 zRateCorrected I2
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.
N3 Payload Contents Byte Offset Name Form at Scaling Units Description 20 eVel I2 512/2^16 m/s GPS East velocity 22 dVel I2 512/2^16 m/s GPS Down velocity 24 longitudeGPS I4 2*pi/2^32 (360°/2^32) Radians (°) GPS Longitude 28 latitudeGPS I4 2*pi/2^32 (360°/2^32) Radians (°) GPS Latitude 32 altitudeGPS I2* 2^14/2^16 m GPS altitude (‐100,16284) 34 GPS heading I2 2*pi/2^16 (360°/2^16) Radians (°) heading angle from GPS measurement 36 xRateTemp I2 200/2^16 deg C X r
Table 54 N4 Payload N4 Payload Contents Byte Offset Name Format Scaling Units Description 0 rollAngle I2 2*pi/2^16 (360°/2^16) Radians (°) Roll angle 2 pitchAngle I2 2*pi/2^16 (360°/2^16) Radians (°) Pitch angle 4 yawAngleTrue I2 2*pi/2^16 (360°/2^16) Radians (°) Yaw angle (true north) 6 xRateCorrected I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) X angular rate corrected 8 yRateCorrected I2 7*pi/2^16 (1260°/2^16) rad/s (°/sec) Y angular rate corrected 10 zRateCorrected I2
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Chapter 10. Programming Guidelines The advanced commands allow users to programmatically change the GNAV540 settings. This section of the manual documents all of the settings and options contained under the Unit Configuration tab within NAV‐VIEW 2.2. Using these advanced commands, the settings of a GNAV540 unit can be modified without NAV‐VIEW 2.2. Configuration Fields Configuration fields determine various behaviors of the unit that can be modified by the user.
index Configuration fields Field ID Valid Values Description 17 comStatusEnable 0x0011 Any Bit mask of enabled communication status signals 18 softwareStatusEnable 0x0012 Any Bit mask of enabled software status signals 19 sensorStatusEnable 0x0013 Any Bit mask of enabled sensor status signals 20 Serial Port B BAUD rate 0x0014 ‐1,0,1,2,3 Auto baud, 9600, 19200, 38400, 57600 21 Serial Port B Protocol 0x0015 ‐1,0,1,2,3 GPS support protocol, ICD‐153 22 reserved N/A N/A N/A 23
pointing in the –Ux direction and the baseplate pointing in the +Uz direction. The user axis set is (X, Y, Z) as defined by this field.
Orientation Field Value X Axis Y Axis Z Axis 0x009B ‐Uy ‐Uz +Ux 0x00C4 +Uz +Uy ‐Ux 0x00CD ‐Uz ‐Uy ‐Ux 0x00D3 ‐Uy +Uz ‐Ux 0x00DA +Uy ‐Uz ‐Ux 0x0111 ‐Ux +Uz +Uy 0x0118 +Ux ‐Uz +Uy 0x0124 +Uz +Ux +Uy 0x012D ‐Uz ‐Ux +Uy 0x0150 +Ux +Uz ‐Uy 0x0159 ‐Ux ‐Uz ‐Uy 0x0165 ‐Uz +Ux ‐Uy 0x016C +Uz ‐Ux ‐Uy An example of orientation field value 0x12D is shown in the figure below.
Algorithm Aspect Bits Values Use Mags 1 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 Use GPS 2 0: Do not use GPS to stabilize the system, 1: Use GPS when available Stationary Yaw Lock 3 0: Do not lock yaw when GPS speed is near zero (<0.
Y Hard Iron Bias 0x000A I2 2/2^16 Gauss Soft Iron Scale Ratio 0x000B U2 2/2^16 ‐ Soft Iron Angle 0x000E I2 2*pi/2^16 Radians Note that the calibration values for an external magnetometer are contained in distinct fields: Table 61 External Magnetometer Calibration Values Field Name Field ID Format Scaling Units X Hard Iron Bias 0x001C I2 2/2^16 Gauss Y Hard Iron Bias 0x001D I2 2/2^16 Gauss Soft Iron Scale Ratio 0x001E U2 2/2^16 ‐ Soft Iron Angle 0x001F I2 2*pi/2^16 Rad
• If at least one field is successfully written, the unit will respond with a write field response containing the field IDs of the successfully written fields. • If any field is unable to be written, the unit will respond with an error response. Both write fields and an error response may be received as a result of a write fields command. Attempts to write a field with an invalid value is one way to generate an error response.
Set Fields Command Table 66 SF Commands Set Fields (‘SF’ = 0x5346) Preamble Packet Type Length Payload Termination 0x5555 1+numFields*4 0x5346 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.
WF Payload Contents Byte Offset Name Format Scaling Units Description 1 field0 U2 — — The first field ID written 3 field1 U2 — — The second field ID written … … U2 — — More field IDs written numFields*2 – 1 Field… U2 — — The last field ID written Table RF Command Read Fields Command Read Fields (‘RF’ = 0x5246) Preamble Packet Type Length Payload Termination 0x5555 1+numFields*2 0x5246 This command allows the user to read the default power‐up con
Byte Offset Name Format Scaling Units Description 0 numFields U1 — — The number of fields read 1 field0 U2 — — The first field ID read 3 field0Data U2 — — The first field ID’s data read 5 field1 U2 — — The second field ID read 7 field1Data U2 — — The second field ID’s data read … … U2 — — … numFields*4 ‐3 field… U2 — — The last field ID read numFields*4 ‐1 field…Data U2 — — The last field ID’s data read Get Fields Command Table 73 GF Command Get Fields
Get Fields (‘GF’ = 0x4746) Preamble Packet Type Length Payload Termination 0x5555 1+numFields*4 0x4746 The unit will send this packet in response to a get fields request if the command has completed without errors.
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Chapter 11. Built In Test (BIT) The Built‐In Test capability allows users to monitor health, diagnostic, and system status information of the unit in real‐time. Built‐In Test information is transmitted in each measurement packet. NOTE: A diagnostic test packet (T2) can be requested via GP. To contains a complete set of status for each hardware and software subsystem. For more information, refer to Test 2 (Detailed BIT and Status) Packet on page 72 and Get Packet Request on page 68.
BITstatus Field Bits Value Reserved 5:7 N/A Configurable N Status Byte Fields masterStatus 8 0: nominal 1: one or more status alerts occurred: hardware; com; software; sensor 0: nominal 1: programmable alert (refer to Programmable Status below) hardwareStatus 9 comStatus 10 0: nominal 1: programmable alert (refer to Programmable Status Fields below) Y softwareStatus 11 0: nominal 1: programmable alert (refer to Programmable Status Fields below) Y sensorStatus 12 0: nominal 1: programma
Status Byte Field hardwareStatus (bit 9) Default Values • AHRS: disabled • IMU: disabled • VG: disabled • NAV: 0 = nominal, 1 = Internal GPS unlocked or 1PPS invalid For additional visibility or alerts relative to the GPS sensor status or algorithm status, configure additional triggers for both softwareStatus and hardwareStatus. For information about configuring this status field, refer to BIT Configuration on page 56, hardwareStatus Field on page 105 and Configuring masterStatus on page 106.
Status Byte Field Default Values sensorStatus (bit 12) • AHRS: 0 = nominal 1 = Sensor Over Range • IMU: 0 = nominal 1 = Sensor Over Range Sensor Over Range only applies to the rotational rate sensors; over‐range is not triggered for accelerometer readings. In many applications, vibration causes instantaneous acceleration levels to exceed the accelerometer sensor range.
hardwarePowerBIT Field Bit Values Category threeVolt 4 0 = normal, 1 = out of bounds Soft twoVolt 5 0 = normal, 1 = out of bounds Soft twoFiveRef 6 0 = normal, 1 = out of bounds Soft sixVolt 7 0 = normal, 1 = out of bounds Soft grdRef 8 0 = normal, 1 = out of bounds Soft fourVolt 9 0 = normal, 1 = out of bounds Soft Reserved 10:15 N/A N/A hardwareEnvironmentalBIT Field The hardwareEnvironmentalBIT field contains flags that indicate low level hardware environmental errors.
comSerialABIT Field The comSerialABIT field 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 the comSerialABIT field.
softwareBIT Field The softwareBIT field contains flags that indicate various types of software errors. Each type has an associated message with low level error signals. The softwareError flag in the BITstatus field is the bit‐wise OR of the softwareBIT field.
hardwareStatus Field The hardwareStatus field contains flags that indicate various internal hardware conditions and alerts that are not errors or problems. 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 enables selecting items of interest that will logically flow up to the masterStatus flag.
softwareStatus Field Bits Values turnSwitch 3 0 = off, 1 = yaw rate greater than turnSwitch threshold Reserved 4 N/A noMagnetometerheading Reference (T0 N/A) 5 0 = aided with Magnetometer heading reference noGPSTrackReference (T0 N/A) 6 1 = no Magnetometer heading reference 0 = aided with GPS track reference 1 = no GPS track reference Reserved 7:15 N/A sensorStatus Field The sensorStatus field contains flags that indicate various internal sensor conditions and alerts that are not errors or
comStatusEnable Field This field is a bit mask of the comStatus field (refer to BIT Status Fields on page 98). 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.
Figure 28 BIT Error and Status Hierarchy Page 108 GNAV540 User Manual 7430‐0808‐01 Rev.
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Appendix A. Application Examples This section provides recommended advanced settings for tailoring the GNAV540 unit of inertial systems to different types of application and platform requirements. 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.
Table 95 Recommended Advanced Settings for Rotorcraft Dynamic Condition Recommended Settings Normal Dynamics High Dynamics (with uncoordinated tail motion) UseMags ON ON UseGPS ON ON (< 4g) FreelyIntegrate OFF OFF (< 2g) Stationary Yaw Lock OFF OFF Restart Over Range OFF ON Dynamic Motion ON ON Turn Switch Threshold 1.0 deg/s § 30.0 deg/s § §The helicopter can change its heading angle rapidly unlike the aircraft which requires banking.
Surfaced Submerged UseMags ON 2 ON3 UseGPS ON OFF FreeIntegrate OFF OFF Stationary Yaw Lock OFF OFF Restart Over Range OFF OFF Dynamic Motion ON ON Turn Switch Threshold 10 deg/s 5 deg/s Example Table 98 below shows a typical flight profile of the fixed wing aircraft and the corresponding advanced settings that can be configured per flight phase.
Figure 29 Flight Profiles: Fixed Wing Aircraft Corresponding Settings GNAV540 User Manual 7430‐0808‐01 Rev.
Appendix B. Sample Packet—Parser Code Overview This section includes an example of code written in ANSI C for parsing packets from data sent by the GNAV540 Inertial Systems. This example is for reading data directly from the GNAV540 unit or from a log file. Sample Code The sample code contains the actual parser as well as several support functions for CRC calculation and circular queue access. Table 99 Code Functions Function Description process_xbow_packet Parse out packets from a queue.
user to ensure circular‐queue integrity by using some sort of mutual exclusion mechanism within the queue access functions. Code Listing#include
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
* ARGUMENTS: queue_ptr is pointer to queue holding area to be CRCed * startIndex is offset into buffer where to begin CRC calculation * 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 fo
/******************************************************************************* * 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.
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 * numToPop is number of items to discard * RETURNS: return the number of items discarded ***************************************************************************
Appendix C. Sample Packet Decoding Example payload from Scaled Sensor 1 data packet (S1) 5555 5331 preamble type 18 0000fffef332 fff30001fff8 23b9242624ca2aff length 9681 counter 0300 248a CRC (invalid) Accelerometers Angular Rates Temperature BIT status Field Hex Data Value (g) Hex Data Value (deg/s) Hex Data Value (deg. C) Field Value masterFail 0 0000 0 FFF3 -0.25 23B9 28.241 hardwareError 0 comError 0 2426 28.
Example payload from Angle Data Packet 2 (A2) 5555 4132 1e preamble type 0006ffe4ed91 fff9fffdffed fff7fff9f331 2c642ce12d85 00010b1c 0300 length 0006ffe4ed91 6945 CRC (invalid) fff9fffdffed fff7fff9f331 2c642ce12d85 00010b1c 0300 timeITOW Angles Hex Data Value (s) 00010b1c 68380 Accelerometers Hex Data Value (deg) Hex Data Value (g) 0006 (roll) 0.033 FFF7 (x) -0.0027 FFE4 (pitch) -0.154 FFF9 (y) -0.0021 ED91 (yaw) -25.922 F331 (z) -1.
Example payload from Nav Data Packet 1 (N1) 5555 4e31 2a 001bffdf3a5bfffe0000ffe . . . fff8fff70000002d1900288a3e0300 a3ad preamble type length 001bffdf3a5b CRC (invalid) fffe0000ffea fff8fff7f337 0015fda9fd4f 00000000000000000000 2d19 00288a3e 0300 Accelerometers Angles Hex Data 001b FFFD 3A5B Hex Data Value (g) FFF8 -0.0024 FFF7 -0.0027 F337 -0.9988 Temperature Value (deg) 0.148 -0.181 82.062 Hex Data Value (m/s) 0015 0.164 FDA9 -4.680 FD4F -5.
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Appendix D. Mechanical Specifications J1 Connector Interface J1 is a 37 pin circular connector. Recommended plug and backshell to interface to J2: • D38999/26FD35SN: Circular milspec connectors, straight plug, 37 pin, size 15; AERO ELECTRIC Specifications Environment Operating Temperature ‐40° to +71°C Enclosure IP66 compliant Electrical Input Voltage 9 to 32 VDC Power Consumption < 4 W Digital Interface 10/100 Ethernet or RS‐422 Physical Size 5.3”w x 4.8”l x 2.7”h Weight 2.7 lbs (1.
Mechanical Drawings Figure 30 GNAV540 Casing GNAV540 User Manual 7430‐0808‐01 Rev.
Interface Cable—Accessory NOTE: This cable is provided when the GNAV540 is purchased with the developer’s kit. Figure 31 Interface Cable—Accessory NOTE: The ON/OFF switch on the MAGNETOMETER port is normally switched OFF. It is only switched ON for upgrading firmware. Page 126 GNAV540 User Manual 7430‐0808‐01 Rev.
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Appendix E. Crossbow Service Policies Customer Service Moog customers have access to product support services: • Single‐point return service • Web‐based support service • Same day troubleshooting assistance • Worldwide Crossbow representation • Onsite and factory training available • Preventative maintenance and repair programs • Installation assistance available Warranty The Crossbow product warranty is one year from the date of shipment.
• Attach a tag to the equipment, as well as the shipping container(s): on the tab, include the RAM and the owner. • Include a description of the service or repair required, a description of the problems with the unit, and the conditions that the problems occurred, such what function was being used. • Place the equipment in the original shipping container(s), making sure there is adequate packing around all sides of the equipment.
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Appendix F. Revision History Table 100 Document Revision History Revision Date Contributor(s) Comments A 26 May 2011 S. McGuigan R. Ayeras First release B 25 Sept 2011 J. Zhang S. McGuigan R. Ayeras A. Malerich Add information about USER_PORT_SEL_CONN (p. 35, 46) Update logo and business name Technical corrections, per ECO 2023 GNAV540 User Manual 7430‐0808‐01 Rev.
Moog, Inc. Navigation, Guidance and Sensors 1421 McCarthy Blvd. Milpitas, CA 95035 Phone: 408.965.3300 Fax: 408.324.4840 Email: info@moog‐crossbow.com Website: www.moog‐crossbow.com Page 132 GNAV540 User Manual 7430‐0808‐01 Rev.
