x-IMU User Manual 2.1 - x
x-IMU User Manual 2.1
x-io Technologies
May 31, 2011
1
Version
Date
Notes
2.1
17/05/2011
2.0
17/05/2011
1.0
10/05/2011
- Minor corrections spelling/wording/layout/appearance througout.
- IMU/AHRS algorithm section has been updated.
- TODO: link to API docuemtnation etc.
- Minor corrections spelling/wording/layout/appearance througout.
- Documented changes introduced by firmware 5.0, API 8.0 and GUI 7.0. See
individual release notes for details.
Compatible versions: firmware 5.x, GUI 7.x, API 8.x.
- Initial release.
Compatible versions: firmware 4.x, GUI 6.x, API 7.x.
Table 1: Document version history
1
Disclaimer
The x-IMU and associated software are provided in an ‘as in’ condition. No warranties, whether express,
implied or statutory, including but not limited to implied warranties of merchantability and fitness for a
particular purpose apply. x-io Technologies shall not in any circumstances, be liable for special, incidental
or consequential damages, for any reason whatsoever.
2
Contents
1 x-IMU overview
1.1 x-IMU Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 x-IMU Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
4
5
2 Getting started
6
3 Hardware overview
3.1 Power switch . . . . . . . . .
3.2 Push button . . . . . . . . . .
3.3 LEDs . . . . . . . . . . . . .
3.3.1 Status LED (Green) .
3.3.2 SD card LED (Amber)
3.3.3 Bluetooth LED (Blue)
3.3.4 Charging LED (Red) .
3.4 USB socket . . . . . . . . . .
3.5 Micro-SD card socket . . . . .
3.6 Bluetooth radio . . . . . . . .
3.7 Battery connector . . . . . .
4 Software overview
4.1 x-IMU GUI . . .
4.1.1 Tab page:
4.1.2 Tab page:
4.1.3 Tab page:
4.1.4 Tab page:
4.1.5 Tab page:
4.1.6 Tab page:
4.1.7 Tab page:
4.1.8 Tab page:
4.1.9 Tab page:
4.1.10 Tab page:
4.2 x-IMU API . . .
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7
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8
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Serial port . . . . . .
Registers . . . . . . .
Date/time . . . . . . .
Commands . . . . . .
View sensor data . . .
Auxillary port . . . .
Data logger . . . . . .
SD card . . . . . . . .
Hard-iron calibration
Upload firmware . . .
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9
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5 USB
17
5.1 Installing USB drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.2 USB bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6 Bluetooth
6.1 Pairing the x-IMU with a Bluetooth host
6.2 Bluetooth LED . . . . . . . . . . . . . . .
6.3 Bluetooth bandwidth . . . . . . . . . . . .
6.4 Optimising Bluetooth performance . . . .
7 SD
7.1
7.2
7.3
7.4
card
Creating and closing files . .
SD card LED . . . . . . . . .
SD card bandwidth . . . . . .
Magnetic distortions from the
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SD
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card
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18
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21
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socket
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21
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8 Real-time clock and calendar
22
8.1 Maintaining clock power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
9 Sensors
23
3
9.1
9.2
9.3
9.4
9.5
Battery voltmeter .
Thermometer . . .
Gyroscope . . . . .
Accelerometer . . .
Magnetometer . . .
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10 Sensor calibration
23
23
24
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25
25
11 IMU/AHRS algorithms
11.1 Principle of operation . . . . . . . . . . .
11.2 Algorithm parameters . . . . . . . . . . .
11.2.1 Algorithm mode . . . . . . . . . .
11.2.2 Algorithm gains . . . . . . . . . .
11.2.3 Algorithm magnetic feild rejection
11.2.4 Algorithm tare quaternion . . . . .
11.3 Algorithm operations . . . . . . . . . . . .
11.3.1 Algorithm initialise . . . . . . . . .
11.3.2 Algorithm tare . . . . . . . . . . .
11.3.3 Algorithm clear tare . . . . . . . .
11.3.4 Algorithm initialise then tare . . .
11.4 Optimising algorithm performance . . . .
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25
26
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26
12 Power management
12.1 External supply . . . . . . . . . . . . . .
12.2 Battery and charging . . . . . . . . . . .
12.3 Low battery voltage detection . . . . . .
12.4 Sleep mode . . . . . . . . . . . . . . . .
12.5 Sleep timer . . . . . . . . . . . . . . . .
12.6 Motion triggered wake up . . . . . . . .
12.7 Tips for minimising power consumption
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26
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28
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13 Auxiliary port
28
14 Communication protocol
28
15 Commands
15.1 Individual commands . . . . . . . . . . . . . . . . .
15.1.1 Null command . . . . . . . . . . . . . . . .
15.1.2 Reset . . . . . . . . . . . . . . . . . . . . .
15.1.3 Sleep . . . . . . . . . . . . . . . . . . . . . .
15.1.4 Reset sleep timer . . . . . . . . . . . . . . .
15.1.5 Sample gyroscope bias at temperature 1 . .
15.1.6 Sample gyroscope bias at temperature 2 . .
15.1.7 Calculate gyroscope bias parameters . . . .
15.1.8 Look up accelerometer bias and sensitivity
15.1.9 Measure magnetometer bias and sensitivity
15.1.10 Algorithm initialise . . . . . . . . . . . . . .
15.1.11 Algorithm tare . . . . . . . . . . . . . . . .
15.1.12 Algorithm clear tare . . . . . . . . . . . . .
15.1.13 Algorithm initialise then tare . . . . . . . .
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28
29
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31
16 Error messages
31
16.1 Individual error messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
16.1.1 NoError . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
16.1.2 Low battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4
16.1.3 USB receive buffer overrun . . . . . . . .
16.1.4 USB transmit buffer overrun . . . . . . .
16.1.5 Bluetooth receive buffer overrun . . . . .
16.1.6 Bluetooth transmit buffer overrun . . . .
16.1.7 SD card write buffer overrun . . . . . . .
16.1.8 Too few bytes in packet . . . . . . . . . .
16.1.9 Too many bytes in packet . . . . . . . . .
16.1.10 Invalid checksum . . . . . . . . . . . . . .
16.1.11 Unknown packet header . . . . . . . . . .
16.1.12 Invalid number of bytes for packet header
16.1.13 Invalid register address . . . . . . . . . . .
16.1.14 Register read-only . . . . . . . . . . . . .
16.1.15 Invalid register value . . . . . . . . . . . .
16.1.16 Invalid command . . . . . . . . . . . . . .
16.1.17 Gyroscope not stationary . . . . . . . . .
16.1.18 Magnetometer saturation . . . . . . . . .
16.1.19 Incorrect auxiliary port mode . . . . . . .
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31
31
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32
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33
17 Registers
17.1 Reading and writing registers . . . . . . . . . . . . .
17.2 Individual register details . . . . . . . . . . . . . . .
17.2.1 Firmware version major number . . . . . . .
17.2.2 Firmware version minor number . . . . . . .
17.2.3 Device ID . . . . . . . . . . . . . . . . . . . .
17.2.4 Button mode . . . . . . . . . . . . . . . . . .
17.2.5 Battery voltmeter sensitivity . . . . . . . . .
17.2.6 Battery voltmeter bias . . . . . . . . . . . . .
17.2.7 Thermometer sensitivity . . . . . . . . . . . .
17.2.8 Thermometer bias . . . . . . . . . . . . . . .
17.2.9 Gyroscope x-axis sensitivity . . . . . . . . . .
17.2.10 Gyroscope y-axis sensitivity . . . . . . . . . .
17.2.11 Gyroscope z-axis sensitivity . . . . . . . . . .
17.2.12 Gyroscope x-axis bias . . . . . . . . . . . . .
17.2.13 Gyroscope y-axis bias . . . . . . . . . . . . .
17.2.14 Gyroscope z-axis bias . . . . . . . . . . . . .
17.2.15 Gyroscope x-axis bias temperature sensitivity
17.2.16 Gyroscope y-axis bias temperature sensitivity
17.2.17 Gyroscope z-axis bias temperature sensitivity
17.2.18 Gyroscope sample 1 - Temperature . . . . . .
17.2.19 Gyroscope sample 1 - x-axis bias . . . . . . .
17.2.20 Gyroscope sample 1 - y-axis bias . . . . . . .
17.2.21 Gyroscope sample 1 - z-axis bias . . . . . . .
17.2.22 Gyroscope sample 2 - Temperature . . . . . .
17.2.23 Gyroscope sample 2 - x-axis bias . . . . . . .
17.2.24 Gyroscope sample 2 - y-axis bias . . . . . . .
17.2.25 Gyroscope sample 2 - z-axis bias . . . . . . .
17.2.26 Accelerometer full-scale . . . . . . . . . . . .
17.2.27 Accelerometer x-axis sensitivity . . . . . . . .
17.2.28 Accelerometer y-axis sensitivity . . . . . . . .
17.2.29 Accelerometer z-axis sensitivity . . . . . . . .
17.2.30 Accelerometer x-axis bias . . . . . . . . . . .
17.2.31 Accelerometer y-axis bias . . . . . . . . . . .
17.2.32 Accelerometer z-axis bias . . . . . . . . . . .
17.2.33 Magnetometer full-scale . . . . . . . . . . . .
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33
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17.2.34 Magnetometer x-axis sensitivity . . . . . . . . . . . .
17.2.35 Magnetometer y-axis sensitivity . . . . . . . . . . . .
17.2.36 Magnetometer z-axis sensitivity . . . . . . . . . . . .
17.2.37 Magnetometer x-axis bias . . . . . . . . . . . . . . .
17.2.38 Magnetometer y-axis bias . . . . . . . . . . . . . . .
17.2.39 Magnetometer z-axis bias . . . . . . . . . . . . . . .
17.2.40 Magnetometer x-axis hard-iron bias . . . . . . . . .
17.2.41 Magnetometer y-axis hard-iron bias . . . . . . . . .
17.2.42 Magnetometer z-axis hard-iron bias . . . . . . . . .
17.2.43 Algorithm mode . . . . . . . . . . . . . . . . . . . .
17.2.44 Algorithm proportional gain . . . . . . . . . . . . . .
17.2.45 Algorithm integral gain . . . . . . . . . . . . . . . .
17.2.46 Algorithm initial proportional gain . . . . . . . . . .
17.2.47 Algorithm initilasation period . . . . . . . . . . . . .
17.2.48 Algorithm minimum valid magnetic field magnitude
17.2.49 Algorithm maximum valid magnetic field magnitude
17.2.50 Tare quaternion (element 0) . . . . . . . . . . . . . .
17.2.51 Tare quaternion (element 1) . . . . . . . . . . . . . .
17.2.52 Tare quaternion (element 2) . . . . . . . . . . . . . .
17.2.53 Tare quaternion (element 3) . . . . . . . . . . . . . .
17.2.54 Sensor data mode . . . . . . . . . . . . . . . . . . .
17.2.55 Date/time data output rate . . . . . . . . . . . . . .
17.2.56 Battery and thermometer data output rate . . . . .
17.2.57 Inertial and magnetic data output rate . . . . . . . .
17.2.58 Quaternion data output rate . . . . . . . . . . . . .
17.2.59 SD card new file name . . . . . . . . . . . . . . . . .
17.2.60 Battery shotdown voltage . . . . . . . . . . . . . . .
17.2.61 Sleep timer . . . . . . . . . . . . . . . . . . . . . . .
17.2.62 Motion trigger wake up . . . . . . . . . . . . . . . .
17.2.63 Bluetooth power . . . . . . . . . . . . . . . . . . . .
17.2.64 Auxiliary port mode . . . . . . . . . . . . . . . . . .
17.2.65 Digital I/O direction . . . . . . . . . . . . . . . . . .
17.2.66 Digital I/O data output rate . . . . . . . . . . . . .
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1
x-IMU overview
The x-IMU was designed to be the most versatile IMU/AHRS product available. Its host of on-board
sensors, algorithms and configurable 8-channel auxiliary port make the x-IMU both a powerful sensor and
controller. Communication is enabled via USB or Bluetooth for wireless applications. The on-board SD
card, battery charger (via USB), real-time clock/calendar and motion trigger wake up also make the x-IMU
an ideal stand-alone data logger.
The open source x-IMU GUI allow users configure all internal x-IMU settings, view sensor data in realtime and export data to software such as MATLAB and Microsoft Excel. Custom user software may be
developed using the x-IMU API.
1.1
x-IMU Features
On-board sensors
• Triple axis 16-bit gyroscope (2000 ◦ /s range)
• Triple axis 12-bit accelerometer (configurable range up to 8 g)
• Triple axis 12-bit magnetometer (configurable range up to 8.1 G)
• 16-bit thermometer
• Battery level
• Calibrated and temperature compensated (gyroscope only)
• Configurable sample rates up to 256 Hz
On-board algorithms
• IMU algorithm for real-time measurement of pitch and roll relative to the Earth surface, immune to
magnetic inferences
• AHRS algorithm for real-time measurement of full orientation relative to the Earth coordinate frame
• Sensor calibration algorithms for user maintenance
Connectivity
• USB
• Bluetooth (class 1, 100m range, SPP)
• Micro-SD card (supports SDHC and FAT16/32 for capacities up to 2 TBs)
Power options
• USB
• LiPo battery (on-board charging via USB)
• External source (3.6 V to 7.7 V)
• Low power consumption (35 mA to 100 mA dependant on settings and usage, 130 A sleep mode)
Low profile
• Dimensions: 33 × 42 × 10 mm
• Weight: 12g
7
Other features
• Motion triggered wake-up and sleep
• Real-time clock and calendar
• Configurable command button
• Configurable 8 channel auxiliary port
Auxiliary port modes
• Digital I/O (outputs controlled via USB or Bluetooth)
1.2
x-IMU Software
The x-IMU GUI (Graphical User Interface) provides interface to all features and functionality of the x-IMU
via the x-IMU API. The x-IMU GUI is open source and is intended to serve as a comprehensive template
for those using the x-IMU API to develop their own applications. Additional software examples using the
x-IMU API for different applications can be found on the x-IMU Examples webpage.
Features
• View, edit and backup all internal x-IMU settings
• Real-time 2D and 3D data graphics
• Control panels for auxiliary port
• Data logger and file converter for exporting data; e.g. to MATLAB, Microsoft Excel, etc.
• Magnetic calibration tools
• Firmware bootloader to access new features in future x-IMU firmware versions
8
2
Getting started
1. Install the USB drivers (5.1) and/or pair the x-IMU as a Bluetooth device (6.1).
2. Download and install the latest version of the x-IMU GUI.
3. Connect to the x-IMU via the Serial port tab page (4.1.1) of the x-IMU GUI.
The x-IMU and accompanying software were designed to be versatile and intuitive. New users are
advised to explore the x-IMU through the x-IMU GUI and consult this user manual when required. If
you are struggling to use the system and feel that this user manual is not providing you with appropriate
documentation, please contact us so that we update the document appropriatly.
9
3
Hardware overview
Figure 1: x-IMU top
Figure 2: x-IMU bottom
3.1
Power switch
The power switch is used to switch the battery and USB power on or off. The battery and USB power is
completely disconnected when the switch is in the off position. The x-IMU may be powered by an external
supply (12.1) via the auxiliary port (13). For this the power switch must be in the off position.
3.2
Push button
The push button may be configured to execute x-IMU commands (15). The mode of the push button is
defined in the Button mode register (17.2.4). The default mode is sleep/wake.
10
3.3
3.3.1
LEDs
Status LED (Green)
The green LED indicates the status of the x-IMU. The green LED will remain lit while the device is sampling
and sending data packets and will otherwise be extinguished; for example, during the execution of commands
(15). In sleep mode (12.4) the green LED will blink once every 3 seconds. The green LED will flash rapidly
while the on-board bootloader is active.
3.3.2
SD card LED (Amber)
The amber LED indicates SD card (7) activity. Details on the SD LED behaviour are provided in the SD
card LED section (7.2).
3.3.3
Bluetooth LED (Blue)
The blue LED indicates the state of the Bluetooth (6) connection and power status. Details of the Bluetooth
LED behaviour are summarised in Table 2.
3.3.4
Charging LED (Red)
The red LED indicates the charging state of the battery (12.2). The red LED will remain lit while the
battery is charging and will be extinguished once the battery is charged.
3.4
USB socket
The USB mini-B socket is used to connect the x-IMU to a computer via a standard USB A to mini B (5
pin) type cable. The USB connect can also be used to power the x-IMU. See the USB section (5) for more
information.
3.5
Micro-SD card socket
The micro SD card socket is used to log all data generated by the x-IMU to an SD card. The x-IMU
supports standard SD and HCSD cards formatted as either FAT16 or FAT32. A new file is created and
logging starts each time the x-IMU is switch on, wakes up or is reset. The file is automatically closed when
the x-IMU enters sleep mode (12.4) or is reset. The file must be closed before the SD card is removed or
the x-IMU switched of otherwise the current file will corrupt and data lost. See the SD card section (7) for
more information.
3.6
Bluetooth radio
The on-board Bluetooth radio is used to connect the x-IMU to a computer via Bluetooth. The on-board
Bluetooth radio is a class I device with a maximum range of 100 m. The radio uses the Serial Port Profile
(SPP) to enable connection to any Bluetooth host without the need to install specific drivers. Power to
the Bluetooth radio can be disabled (17.2.63) to converse power. See the Bluetooth section (3.6) for more
information.
3.7
Battery connector
The on-board battery connector allows the x-IMU to be powered by any single-cell Lithium Polymer battery.
The battery is automatically charged while the x-IMU is connected via USB. See the battery and charging
section (12.2) for more information.
11
4
4.1
4.1.1
Software overview
x-IMU GUI
Tab page: Serial port
The serial port tab page is used to manage the USB or Bluetooth connection between the software and the
x-IMU. The USB and Bluetooth connections will each appear as a separate serial port; see the USB section
(5) and Bluetooth section (6) for more information and how to find the serial port name assigned to each
connection.
To connect to the x-IMU, the user first select the correct serial port name the x-IMU appears as in the
Port name drop down list. If the name does not appear in the list, the user can either press the Refresh List
button to update the drop down list or type in the port name directly. The Open Port button may then be
pressed to connect to the device.
Figure 3: x-IMU GUI serial port tab page
4.1.2
Tab page: Registers
The registers tab page allows the user to view, edit and back up all internal settings on the x-IMU; see the
registers section (17) for more infomation on x-IMU registers. All registers are organised into sections within
a tree view where the end node of each branch is an individual register name and text box or drop down list
containing the register value. Register values that have been read directly from the x-IMU or loaded from
file will appear as blue text. Any registers values then edited will appear as red text. A right click on any
register will show the action menu.
To read all register on the x-IMU, the user should right click anywhere in the registers tab page and
select Read all registers. The software will then read each register and update the values in the tree view.
Individual registers or groups of registers may be read by first selecting a register or group within the tree
view and then selecting Read this register only or Read all registers in this group only. Register values in
the tree view may be written to teh x-IMU using the Write all regisers, Write this register only and Write
all registers in this group only options in the action menu.
12
Figure 4: x-IMU GUI registers tab page with (right click) action menu
4.1.3
Tab page: Date/time
The date/time tab page allows the user to view and set the date and time of the x-IMU’s real-time clock
and calendar. The Received date/time text box displays the date and time each time it is received from the
x-IMU. The Read Date/Time button may be used to read the current date and time of the x-IMU; this is
of use if date/time data rate has been disabled. Pressing the Set Date/Time button will set the x-IMU date
and time equal to computer date and time.
Figure 5: x-IMU GUI date/time tab page
13
4.1.4
Tab page: Commands
The commands tab page is used to send commands to the x-IMU. See the commands section (15) for more
information on individual commands. Once the x-IMU has processed a command it will echo the command
back and it will appear in a message box. To suppress these message boxes, un-check the Display received
command messages in message box check box.
Figure 6: x-IMU GUI date/time tab page
4.1.5
Tab page: View sensor data
The view sensor data tab page contains buttons to show or hide separate real-time data graphic windows
for incoming x-IMU sensor data.
14
Figure 7: x-IMU GUI view sensor data tab page
The data from individual sensors is displayed in real-time data graphs as seen in Figure 7. The controls
bar at the bottom of each graph allow the view and scaling to be adjusted.
Figure 8: x-IMU GUI gyroscope data window
Orientation data received may be displayed in a graph as ZYX Euler angles and displayed as the
orientation of a 3D cuboid as seen in figure 9. The cuboid is displayed in a screen coordinate frame where
the x-axis is aligned to the width of the screen (left to right), the z-axis aligned to the height (bottom to top)
and the y-axis projects into the screen. To align the motion of the physical x-IMU and 3D cuboid displayed
on the screen, the user should first align the axes of the physical x-IMU to the screen coordinate frame and
then use the Tare command (??).
15
Figure 9: x-IMU GUI 3D cuboid window
4.1.6
Tab page: Auxillary port
The auxiliary port tab page contains buttons to show or hide individual control windows for the different
modes of the auxiliary port.
Figure 10: x-IMU GUI auxiliary port tab page
Digital I/O control panel The digital I/O control panel displays the state and mode of each channel of
the auxiliary port when in digital I/O mode as shown in figure 11. Each channel is represented by a check
box. If the channel mode is output then the check box is enabled and may be checked or un-checked to set
the channel high or low respectively. If the channel is an input the check box is disabled and will be checked
or un-checked if the channel is high or low respectively.
16
Figure 11: x-IMU GUI digital I/O control panel
4.1.7
Tab page: Data logger
The data logger tab allows the user to log incoming real-time data to file. These files may be imported to
user software such as Microsoft Excel and MATLAB. The user may select the location and first part of the
file name in the File path text box. This file name will be extended with an appropriate description and
extension when the individual data files are created. For example, if a file name of myFile is specified, Euler
angle and date/time data will be saved to myFile_EulerAngles.csv and myFile_DateTime.txt.
Figure 12: x-IMU GUI data logger tab page
The Start/Stop Logging button is used to start and stop the data logger. When logging is stopped, a
report window will be presented detailing the number of each type of packet logged and the specific data
files created; as shown in figure 13.
17
Figure 13: x-IMU GUI data logger report
4.1.8
Tab page: SD card
The SD card tab page allows the user to convert binary files (.bin) saved to the SD card in to readable data
files. These files may be imported to user software such as Microsoft Excel and MATLAB. The location and
file name must be specified in the File path text box. The file conversion will start when the Convert button
is clicked. This process occurs in the background and may take a while if a large binary file is specified.
Figure 14: x-IMU GUI SD card tab page
Once the conversion is complete, a report window will be presented detailing the number of each type
of packet read and the specific data files created; as shown in figure 15.
18
Figure 15: x-IMU GUI binary file conversion report
4.1.9
Tab page: Hard-iron calibration
The hard-iron calibration tab page provides all the functionality required for the user to calibrate for hardiron interferences affecting the x-IMU. It is necessary to re-calibrate hard-iron parameters whenever the
x-IMU’s magnetic characterises are changed; for example, when the x-IMU if fitted to a battery or mounting
that includes ferromagnetic elements. The 3 group boxes, Step 1 - Clear Hard-Iron Bias Registers, Step 2
- Collect Hard-Iron Calibration Dataset and Step 3 - Run Hard-Iron Calibration Algorithm represent the 3
steps that must be performed in order. See the hard-iron calibration section (??) for more information.
Figure 16: x-IMU GUI hard-iron calibration tab page
4.1.10
Tab page: Upload firmware
The bootloader tab page allows the x-IMU firmware to be updated. The bootloader may only be used
while the x-IMU is connected via USB and the serial port closed. See the bootloader section (??) for more
information.
19
4.2
x-IMU API
The x-IMU API (Application Programming Interface) is a code library that contains all the classes, data
structures and methods required to interface to all features and functionality of the x-IMU. The x-IMU API
is an open source project written in C# and targets Microsoft .NET 3.5. Documentation for use of the API
is represented by the XML comments throughout the source code which is accessed automatically by Visual
Studio’s IntelliSense. The open source x-IMU GUI serves as a comprehensive template for use of all features
of the x-IMU API. See the x-IMU Examples web page for further open-source examples and applications.
5
USB
The x-IMU streams all communication data simultaneously and identically via USB, Bluetooth (6) and to
a file on the SD card (7). The USB and Bluetooth connections are also be used to send commands (15),
read/write registers and settings (17) and control the auxiliary port outputs (13) from the host computer.
As both USB and Bluetooth connections appear as serial ports, use of either communication channel is
identical.
The x-IMU can be connected to a computer via a standard USB A to mini B (5 pin) type cable. The
on-board FTDI USB chip is widely used USB interface with drivers available for Windows, Mac OS X and
Linux. Once the drivers have been installed (5.1) and the x-IMU connected to the computer, the x-IMU
will appear as a serial port and be assigned an available port name; for example COM2. The computer may
then communicate with the x-IMU by opening this serial port. This is achieved via the Serial Port tab page
(4.1.1) of the x-IMU GUI.
The USB connection is a reliable communication channel that cannot be comprised by user settings;
the x-IMU will not enter sleep mode (12.4) due to the sleep timer (12.5) or low battery voltage detection
(12.3) while the USB is connected. The USB connection can be used to power the x-IMU and is used by the
on-board charging circuit to charge the battery if connected (12.2). The on-board USB interface is powered
directly by the USB connection so that the x-IMU will remain detectable and the serial port may be held
open by the computer even while the x-IMU is switched off or in sleep mode (12.4).
5.1
Installing USB drivers
The Windows USB drivers can be downloaded from the x-IMU webpage. Drivers for other operating systems
are available of the FTDI website. To install the Windows drivers, simply run the .exe file. This will
automatically detect specific Windows operating system being used and install the correct drivers. Once the
drivers have been installed and the x-IMU connected to the computer, the x-IMU will appear as a serial port
and be assigned an available port name; for example COM2. The port name assigned to the x-IMU USB
connection can be confirmed at any time by viewing the computer’s Ports in Windows device manager; as
shown in Figure 20.
20
Figure 17: Confirming the port name assigned to the x-IMU USB connection
Windows serial mouse bug Windows may misinterpret the constant stream of data from the x-IMU as
the behaviour of a serial mouse when the x-IMU USB is connected. This will lead to the mouse cursor being
‘hi-jacked’ by apparent random behaviour. If this happens the x-IMU should be unplugged and reconnected
while switched off or in sleep mode (15.1.3) for the first few seconds of connection. The ‘hi-jacked’ activity
may leave the mouse buttons disabled which can be undone by entering and then leaving the Ctrl + Alt +
Del screen.
5.2
USB bandwidth
It is possible for the user to define data output rate settings (e.g. 17.2.56, 17.2.57, 17.2.58) so that the data
being generated by the x-IMU exceeds the bandwidth of a communication channel. If the USB bandwidth is
exceed, the USB transmit buffer will overrun and some data will be lost. When this happens a USB transmit
buffer overrun error (16.1.4) will be generated. As this error message is sent immediately after the buffer
has overrun, the error message will be successfully transmitted. This error can be avoided by reducing the
data output rate settings (e.g. 17.2.56, 17.2.57, 17.2.58).
All data sent to the x-IMU via USB is buffered in the USB receive buffer before being processed. The
time required to process the received data is dependent on the data. If data is sent to the x-IMU via USB
at a rate at a rate greater than it can be processed then the receive buffer will overflow and some data will
be lost. When this happens a USB receive buffer overrun error (16.1.3) will be generated.
6
Bluetooth
The x-IMU streams all communication data simultaneously and identically via USB (5), Bluetooth and to
a file on the SD card (7). The USB and Bluetooth connections are also be used to send commands (15),
read/write registers and settings (17) and control the auxiliary port outputs (13) from the host computer.
As both USB and Bluetooth connections appear as serial ports, use of either communication channel is
identical.
The on-board Bluetooth radio is a class I device with a maximum range of 100 m. The radio uses the
Serial Port Profile (SPP) to enable connection to any Bluetooth host without the need to install specific
21
drivers. Once paired (6.1) with a host computer, the x-IMU will appear as a serial port and be assigned an
available port name; for example COM3. The computer connects to the x-IMU via Bluetooth by opening
this serial port. This is achieved via the Serial Port tab page (4.1.1) of the x-IMU GUI. The Bluetooth
connection will be lost when the x-IMU is switch off, enters sleep mode or is out of range. The connection
status of the x-IMU is indicated by the Bluetooth LED (6.2). The Bluetooth radio can be completely disabled
by the user via the Bluetooth power register (17.2.63) to conserve power.
6.1
Pairing the x-IMU with a Bluetooth host
As with any Bluetooth device, the x-IMU must first be paired with the host computer before a Bluetooth
connection can be made. This pairing process is the same for all Bluetooth devices and will be familiar those
who have used other Bluetooth devices such as printers or mobile phones.
To pair the x-IMU with a host computer, the host computer’s Bluetooth must be enabled and the x-IMU
must be switched on and the Bluetooth radio powered (17.2.63). The user may then use the host computer
to search for and the x-IMU to be paired with the computer. The x-IMU will appear with the name x-IMU0000 where the last 4 digits are the x-IMU’s Device ID (17.2.3). For example, Figure 18 shows how this is
done in Windows 7 having right clicked the Bluetooth icon the task bar.
Figure 18: Searching for the x-IMU as a new Bluetooth device in Windows 7
Once the x-IMU has been found by the host computer, it can be added. This will require the user to
enter the x-IMU’s Bluetooth pass code: ‘1234’. The x-IMU Bluetooth pairing will be assigned an available
serial port name by the host computer; for example COM3. For example, Figure 19 shows this being done
in Windows 7.
22
Figure 19: Adding the x-IMU as a new Bluetooth device in Windows 7
The port name assigned to the x-IMU Bluetooth pairing can be confirmed at any time by viewing the
services of the x-IMU. For example, Figure 20 shows how this is done in Windows 7 having right clicked the
x-IMU Bluetooth device icon.
Figure 20: Confirming the port name assigned to the x-IMU Bluetooth pairing
6.2
Bluetooth LED
The blue Bluetooth LED indicates the Bluetooth radio state. The LED behaviour and associated Bluetooth
radio states are detailed in table 2.
23
LED behaviour
Off
Flashing (1 Hz)
On
Bluetooth state
Switched off. Power to the radio is completely disconnected
Fully powered and discoverable
Fully powered and connected
Table 2: Bluetooth LED states
6.3
Bluetooth bandwidth
It is possible for the user to define data output rate settings (e.g. 17.2.56, 17.2.57, 17.2.58) so that the
data being generated by the x-IMU exceeds the bandwidth of a communication channel. If the Bluetooth
bandwidth is exceed, the Bluetooth transmit buffer will overrun and some data will be lost. When this
happens a Bluetooth transmit buffer overrun error (16.1.6) will be generated. As this error message is sent
immediately after the buffer has overrun, the error message will be successfully transmitted. This error can
be avoided by reducing the data output rate settings (e.g. 17.2.56, 17.2.57, 17.2.58).
All data sent to the x-IMU via Bluetooth is buffered in the Bluetooth receive buffer before being processed. The time required to process the received data is dependent on the data. If data is sent to the
x-IMU via Bluetooth at a rate at a rate greater than it can be processed then the receive buffer will overflow
and some data will be lost. When this happens a Bluetooth receive buffer overrun error (16.1.5) will be
generated.
6.4
Optimising Bluetooth performance
The practical range and quality of the Bluetooth connection are dependent on a number of factors. A poor
Bluetooth connection will be unable to handle higher data output rates and so result in missing data and
Bluetooth transmit buffer overrun errors (16.1.6). The use of lower data output rate settings (e.g. 17.2.56,
17.2.57, 17.2.58) can help achieve a more reliable Bluetooth communication channel.
The x-IMU uses a class I Bluetooth radio which represents a maximum range of 100 m. However, the
practical performance is also limited by computer’s Bluetooth class; for example a class II Bluetooth dongle
(representing a range of 10 m) will limit the x-IMU’s operating range to 10 m. Performance also varies
between Bluetooth dongle brands; a dongle from a reputable brand may be expected to perform better than
a low-cost, ‘budget’ product. Bluetooth is a radio system and so the location of the antennae (usually built
into the dongle) should be given consideration. For example, a miniature Bluetooth dongle plugged in to
the back a desktop PC can be expected to achieve worse performance than if the dongle was fixed to a front
USB port with line-of-sight to the x-IMU.
7
SD card
The x-IMU streams all communication data simultaneously and identically via USB (5), Bluetooth (6) and
to a file on the SD card. The SD card may therefore be used in conjunction with the USB and/or Bluetooth
or as the sole communication channel allowing the x-IMU to function as a standalone data logger. Data is
logged to the SD card on separate files binary files that are automatically created each time the x-IMU is
switched on, reset or wakes up. Logging is only then stopped once the x-IMU is reset or enters sleep mode.
The binary files (.bin) created may be read form the SD card on to any PC and then converted
to individual Comma Separated Variable (.csv) files using via the x-IMU GUI SD Card tab page (4.1.8).
Alternatively the x-IMU Binary File Converter may be used for command-line-based or automated conversion
of multiple files. Converted CSV and text files can be directly imported into programmes such as MATLAB
and Microsoft Excel. The MATLAB x-IMU Library includes all the tools required to import, structure and
plot x-IMU data.
The x-IMU supports conventional SD cards and HCSD cards. Cards may be formatted as FAT16
(usually cards equal or less than 2 GB) and FAT32 (for card greater than 2 GB). For reliable performance
it is recommended that the SD card is formatted prior to each use.
24
7.1
Creating and closing files
The x-IMU automatically creates a new file on the SD card each time the x-IMU is switched on, reset or
wakes up. If an SD card is not accessible at this point, the x-IMU will not create a file and the SD card will
not be used. The new file name is created as the 5 digit number stored in the SD card new file name register
(17.2.59); for example, 00000.bin. The number stored in this register is automatically incremented each
time a new file is created. This ensures that each file created by the x-IMU is given a unique file name until
the maximum file name of 65535.bin is reached, the file name will then automatically reset to 00000.bin
and start again. The user can reset this value to any number by writing to the register (17.2.59). If the
x-IMU attempts to create a file name that already exists on the SD card, the x-IMU automatically increment
the file name and try again. If all file names have been used, the x-IMU will not create a file and the SD
card will not be used.
File must be closed before the SD card is removed or the x-IMU switched off otherwise the file will be
corrupted and all data written to the file will have been lost. The file is automatically closed when the
x-IMU is reset or enters sleep mode (12.4). Users wishing to frequently remove the SD card may wish to
have the push button (3.2) configured in sleep/wake mode.
7.2
SD card LED
The amber SD card LED indicates SD card activity. The LED remains lit each time a burst of data is
written to the SD card. If the user low defines data output rates then the LED will blink infrequenctly, high
data output rates will mean the LED will flash rapidly. The SD card LED therefore provides an indication
of SD card bandwidth performance (7.3).
7.3
SD card bandwidth
It is possible for the user to define data output rate settings (e.g. 17.2.56, 17.2.57, 17.2.58) so that the data
being generated by the x-IMU exceeds the bandwidth of a communication channel. The SD card bandwidth
is greater than the USB and Bluetooth bandwidth and so the SD card may still provide reliable data logging
when the USB or Bluetooth channel bandwidth is exceeded. If the SD card bandwidth is exceed, the SD
card buffer will overrun and some data will be lost. When this happens an SD card write buffer overrun
error (16.1.7) will be generated. As this error packet is sent immediately after the buffer has overrun, the
error message will be successfully logged to the SD card. This error can be avoided by reducing the data
output rate settings (e.g. 17.2.56, 17.2.57, 17.2.58). The SD card LED (7.2) may be used to provides an
indication of SD card bandwidth performance while access to error messages is not available.
The effective bandwidth of SD card varies between different SD card manufacturers and may decrease
significantly if the SD card becomes fragmented. It is therefore recommended that the SD card is formatted
prior to each use.
7.4
Magnetic distortions from the SD card socket
The SD card socket contains a ferromagnetic mechanism that may distort magnetometer measurements in
different ways dependant of the presence of an SD card. These distortions are removed through hard-iron
calibration and each x-IMU is calibrated and supplied with a dummy SD card that may be used to ensure
constant SD card socket magnetic characteristics.
8
Real-time clock and calendar
The on-board real-time clock and calendar provides accurate measurement of the date and time and is preprogrammed to account for leap-years between the year 2000 and 2099. The real-time clock and calendar
data can be viewed and synchronised with the computer clock using the x-IMU GUI via the Date/Time tab
page (4.1.3).
The real-time clock and calendar data a is provided by the x-IMU in the write date/time data packets.
The output rate of these packets of either disabled or 1 Hz is specified in the date/time data rate register
25
(17.2.55). A single date/time data packet is always sent on device reset regardless of user settings so that
the date and time are hardcoded as the first packet written to the SD card (7). The real-time clock and
calendar is set by sending a write date/time data packet to the x-IMU, once the new date and time have
been set the x-IMU will respond with a write date/time data containing the real-time clock and calendar
data. The date and time may read at any time by sending a read date/time data packet to the x-IMU.
8.1
Maintaining clock power
The real-time clock and calendar require power to operate. If power is lost or the x-IMU switch off then the
date and time will reset to 01/01/2000 00:00:00. Applications that require date and time to be maintained
should ensure that the x-IMU is never switched off and instead take advantage of sleep mode (12.4).
9
Sensors
The x-IMU’s on-board sensors include a triple axis gyroscope, triple axis accelerometer, triple axis magnetometer, thermometer and a battery voltmeter. The user may access individual sensor data as either Raw
un-calibrated ADC results or as Calibrated units by specifying the mode in the Sensor data mode register
(17.2.54). The data from individual sensors is provided in either the Raw inertial/magnetic data and Raw
battery and thermometer data packets or the Calibrated inertial/magnetic data and Calibrated battery and
thermometer data packets. The data output rate of these packets may be specified up to 256 Hz in the Battery and thermometer data output rate (17.2.56) and Inertial/magnetic data output rate (17.2.57) registers.
Alternatively the individual output rates may be disabled to prevent data from being sent.
9.1
Battery voltmeter
The battery voltmeter allows the battery voltage to be monitored by the user application. The battery
voltmeter must be correctly calibrated if the low battery voltage detection functionality is to be used. The
battery voltmeter has 12-bit resolution and a range of 0 V to 6.6 V. When the power switch is in the off
position (so that the x-IMU may be powered from an external source via the auxiliary port) the battery
voltmeter will instead measure the voltage of the external source.
Raw ADC data: In raw data mode the battery voltmeter data is the ADC integer value between 0 and
4096 corresponding to a voltage between 0 V and 6.6 V. This data is provided in the Raw battery and
thermometer data packets.
Calibrated data: In calibrated data mode the battery voltmeter data is the calibrated measurement
in Volts. This data is provided in the Calibrate battery and thermometer data packets. The calibrated
measurement v is calculated from the raw ADC measurements ṽ according to a sensitivity sv and bias bv
as described by equation (1). Parameters bv and sv are defined in the battery voltmeter sensitivity (17.2.5)
and bias (17.2.6) registers.
v=
9.2
1
(ṽ − bv )
sv
(1)
Thermometer
The thermometer is built in to the gyroscope and provides a measurement of the temperature of the device.
The thermometer must be correctly calibrated for calibrated gyroscope measurements to compensate for
gyroscope bias temperature sensitivity. The thermometer has 16-bit resolution and has a range of -30◦ C to
+85◦ C. See the IMU-30001 datasheet for further information on the thermometer’s characteristics.
1 x-IMUs
of generations prior to version 1.3 use the ITG-3200 gyroscope.
26
Raw ADC data: In raw data mode the thermometer data is the ADC integer value between −32, 768 and
+32, 767 linearly proportional to temperature. This data is provided in the Raw battery and thermometer
data packets.
Calibrated data: In calibrated data mode the thermometer data is the calibrated temperature in ◦ C.
This data is provided in the Calibrate battery and thermometer data packets. The calibrated measurement τ
is calculated from the raw ADC measurement τ̃ according to a defined sensitivity sτ and bias bτ as described
by equation (2). Parameters bτ and sτ are defined in the battery voltmeter sensitivity (17.2.7) and bias
(17.2.8) registers.
τ=
9.3
1
(τ̃ − bτ )
sτ
(2)
Gyroscope
The triple axis gyroscope provides a measurement of the angular velocities around the x, y and z axes of
the x-IMU. The gyroscope must be correctly calibrated in order for the IMU and AHRS algorithms to be
able to function correctly; the algorithms use measurements of angular velocities to filter out errors in the
estimated orientation caused by linear accelerations and temporal magnetic distortions. The gyroscope has
16-bit resolution and a range of ±2000◦ /s. See the IMU-30002 datasheet for further information on the
gyroscope’s characteristics.
Raw ADC data: In raw data mode the gyroscope data is the ADC integer values between −32, 768 and
+32, 767 linearly proportional to angular velocities. This data is provided in the Raw inertial/magnetic data
packets.
Calibrated data: In calibrated data mode the gyroscope data are calibrated angular velocities in ◦ /s. This
data is provided in the Calibrated inertial/magnetic data packets. The calibrated measurements gx , gy and
gz are calculated from the raw ADC measurements g̃x , g̃y and g̃z according to the defined sensitivities sgx ,
sgy and sgz , temperature of the device τ , biases at 25◦ C bgx , bgy and bgz and bias temperature sensitivities
fx , fy and fz . The calibrated measurmndts are described by equation (3). Parameters sgx , sgy , sgz , bgx , bgy ,
bgz , fx , fy and fz are defined in the separate gyroscope calibration parameter registers (17.2.9 to 17.2.17).
  
−1     
−1 

gx
sgx
0
0
g̃x
fx 0 0
τ − 25
bgx


gy  =  0 sgy
0  g̃y  − bgy  −  0 fy 0  τ − 25
(3)
gz
0
0 sgz
bg z
0 0 fz
τ − 25
g̃z
9.4
Accelerometer
The triple axis accelerometer and provides a measurement of the accelerations along the x, y and z axes
of the x-IMU. The accelerometer must be correctly calibrated in order for the IMU and AHRS algorithms
to be able to function correctly; the algorithms use the accelerometer to measure the direction of gravity
and provide an absolute reference for the pitch and roll components of the estimated orientation. The
acceleroemter has 12-bit resolution and selectable ranges from ±2 g to ±8 g. The measurement range of the
accelerometer is defined in Accelerometer full scale register (17.2.26). See the LSM303DLH datasheet for
further information on the accelerometer’s characteristics.
Raw ADC data: In raw data mode the accelerometer data is the ADC integer values between −4096
and +4095 linearly proportional to accelerations. This data is provided in the Raw inertial/magnetic data
packets.
2 x-IMUs
of generations prior to version 1.3 use the ITG-3200 gyroscope.
27
Calibrated data: In calibrated data mode the accelerometer data are calibrated accelerations in g. This
data is provided in the Calibrated inertial/magnetic data packets. The calibrated measurements ax , ay and
az is calculated from the raw ADC measurements ãx , ãy and ãz according to the defined sensitivities sax ,
say and saz and biases bax , bay and baz as described by equation (4). Parameters sax , say , saz , bax , bay
and baz are defined in the separate accelerometer calibration parameter registers (17.2.27 to 17.2.32). The
sensitivities and biases will be different for each full-scale measurement range (17.2.26).
  
ax
sax
ay  =  0
az
0
9.5
0
say
0
−1    
0
ãx
bax
0  ãy  − bay 
saz
ãz
baz
(4)
Magnetometer
The triple axis magnetometer and provides a measurement of the magnetic flux along the x, y and z axes.
The magnetometer must be correctly calibrated in order for the AHRS algorithm to be able to function
correctly; the algorithm uses the magnetometer to measure the Earth’s magnetic field and provide an absolute
reference for the heading component of the estimated orientation. The magnetometer has 12-bit resolution
and selectable ranges from ±1.3 G to ±8.1 G. The measurement range of the magnetometer is defined in
Magnetometer full scale register (17.2.33). See the LSM303DLH datasheet for further information on the
magnetometer’s characteristics.
Raw ADC data: In raw data mode the magnetometer data is the ADC integer values between −4096
and +4095 linearly proportional to magnetic flux. This data is provided in the Raw inertial/magnetic data
packets. A value fo -4096 will be provided when the measurement saturates in either direction.
Calibrated data: In calibrated data mode the magnetometer data are calibrated accelerations in G. This
data is provided in the Calibrated inertial/magnetic data packets. The calibrated measurements mx , my and
mz are calculated from the raw ADC measurements m̃x , m̃y and m̃z according to the defined sensitivities
smx , smy and smz , biases bmx , bmy and bmz and hard-iron biases hx , hy and hz as described by equation
(5). Parameters smx , smy , smz , bmx , bmy , bmz , hx , hy and hz are defined in the separate magnetometer
calibration parameter registers (17.2.34 to 17.2.42). The sensitivities and biases will be different for each
full-scale measurement range (17.2.33).
  
mx
smx
my  =  0
mz
0
10
0
smy
0
  
−1   
hx
bmx
m̃x
0
0  m̃y  − bmy  − hy 
m̃z
smz
bmz
hz
(5)
Sensor calibration
This section is currently unavailable but can be updated on request.
11
IMU/AHRS algorithms
- On-board algorithms provde oreitnation relative to Earth - Uses gyro, accel, mag - Oreintation data
provided as quaternion in quaternion packet. Data output rate set by register - API includes class methods
for conversion to rotation matrix and Euler angles. - Oreintation viewed in GUI with 3D cuboid and Euler
angles.
- Algorithm update rate = 256 Hz regardless of data output rate - Algorithm performance is dependant
on calibration. - Performance can be tuned by adjusting algorithm paramters. See section 11.4 for more
information.
28
11.1
Principle of operation
- use gyroscope data to estimate oreintaiton.... however gyroscope measeutnts alone cannot work because of
drift. - this drift is compensated for through meaurments of the Earth’s gravitational and magentic feilds,
provided by the accelermeter and magnetoemter respectivly. - accelerometer measures accelerations and the
direction of gravity.... it is used to counter drift relative to the Earth’s surface; i.e. the estimated pitch and
roll. As the acceleoemter also measures accelerations as well as gravitry, - magnetometer measures direction
fo Earth’s magentic feild... used to counter drift relative to the magnetic poles of the Earth; i.e. in the
estimated heading. - the proportional gain governs how much influence
IMU mode: - The IMU algorithm uses only the gyroscope and acceleormeter and so will not compensate
for drift in heading. This is suitable for many applciations where only pitch and roll are required and/or it is
possible to ‘reset’ heading periodically. - The advantage of excluding the magnetoemter from the algorithm
is: magnetic calbration unessary, local magnetic distortion have no effect; e.g. if x-IMU used within a
magnetically noisey enviroment
AHRS mode: - The IMU algorithm uses only the gyroscope and acceleormeter and magnetoemer. Free
form drift in all axes. As magnetoem
11.2
Algorithm parameters
11.2.1
Algorithm mode
11.2.2
Algorithm gains
11.2.3
Algorithm magnetic feild rejection
11.2.4
Algorithm tare quaternion
11.3
11.3.1
Algorithm operations
Algorithm initialise
- init on reset
11.3.2
Algorithm tare
11.3.3
Algorithm clear tare
11.3.4
Algorithm initialise then tare
11.4
12
Optimising algorithm performance
Power management
The x-IMU may be powered via USB (5), an external supply (12.1) or a single cell lithium polyer (LiPo)
battery cell (12.2).
12.1
External supply
The x-IMU may be powered by a 3.5 to 7.7 V external supply via the auxiliary port (13). The supply should
be connected to the GND and EXT pins. This power supply is only enabled while the power switch (3.1)
is in the off position. In this situation, the battery volt meter (9.1) will measure the voltage of the external
supply.
29
12.2
Battery and charging
The x-IMU has a standard connector for a 3.7 V single cell Lithium Polymer (LiPo) battery cell. These
batteries are widely available in range of capacities, for example 1000 mAh and 2000 mAh. The battery life
is dependent on user settings and usage. See the tips on minimising power consumption section (12.7).
The x-IMU has an on-board battery charger specially designed for LiPo battery cells. The battery is
charged automatically while the x-IMU is connected to a USB port. The red charging LED (3.3.4) will
remain lit while the battery is charging. Charging stops automatically once complete. The x-IMU may be
used as normal while the battery is charging. It is not necessary for the connected computer to have the
USB drivers installed for charging; however, the charging process will be faster if the drivers are installed.
12.3
Low battery voltage detection
The calibrated battery voltmeter (9.1) is used to trigger sleep mode (12.4) once the battery voltage falls
below a specific level defined in the battery shutdown voltage register (17.2.60). This allows the x-IMU to
execute critical tasks prior to power failure; for example closing the file on the SD card and notifying the
user or host software of the situation (16.1.2). By entering sleep mode prior to power failure, the x-IMU also
ensures that the date and time of the real-time clock and calendar (8) are not lost. The low battery voltage
detection is disabled while USB is connected.
12.4
Sleep mode
In sleep mode, the x-IMU remains powered but all on-board components are shutdown. This allows the
device to be effectively ‘turned off’ without disabling power to essential components; for example, the real
time clock and calendar (8). The green status LED (3.3.1) will blink once every 3 seconds to indicate that the
device is in sleep mode. Sleep mode is enabled through the sources listed below. The x-IMU will reset upon
wake up so that the same behaviour may be expected when the devices is powered on, reset or awakened.
The wake up sources are listed below.
Sleep mode enable sources:
• Push button (3.2) in sleep/wake mode
• Sleep command via USB or Bluetooth
• Low battery voltage detection (12.3)
• Sleep timer (12.5)
Wake up sources
• Push button (3.2) in sleep/wake mode
• Motion trigger wake up (12.6)
12.5
Sleep timer
The sleep timer will trigger sleep mode after the period of time defined in the sleep timer register (17.2.61)
has elapsed. The sleep timer countdown starts when the x-IMU starts up and may be reset by the sources
listed below. These sources enable the detection of motion, the user or the host software to prevent the
x-IMU from entering sleep mode. The sleep timer is disabled by specifying a sleep timer register (17.2.61)
value of 0 seconds. The sleep timer is disabled while USB is connected.
Sleep timer reset sources
• Reset sleep timer command (15.1.4)
• Motion trigger wake up (12.6)
30
12.6
Motion triggered wake up
The motion trigger wake up is enabled via the motion trigger wake up register (17.2.62) and may be either
disabled or set to a low or high sensitivity. Motion is detected using accelerometer. If motion is detected
while the x-IMU is in sleep mode then the x-IMU will wake up. While the x-IMU is not in sleep mode
the motion trigger wake up is used to reset the sleep timer (17.2.61) and thus postpone sleep while motion
persists. For example, if the sleep timer is set to 20 seconds and there is sufficient motion once every 10
seconds the motion trigger wake up will prevent the sleep timer from expiring.
12.7
Tips for minimising power consumption
Battery powered applications require that power consumption is minimised in order to extend the battery
life. The x-IMU is designed to optimised power consumption according to user settings. The user may
therefore expect a considerable reduction in power consumption and extended battery life simply by using
register settings appropriate to their application.
Tips
• Set data rates of unused data to Disabled.
• Use the minimum data rates required by application.
• Set IMU/AHRS algorithm (11) mode to Disabled if not required.
• Disable Bluetooth (6) if not required.
• Use the sleep timer (12.5) and motion trigger wake up (12.6) to automatically enter sleep mode during
periods of inactivity.
13
Auxiliary port
This section is currently unavailable but can be updated on request.
14
Communication protocol
This section is currently unavailable. Users wishing to develop their own x-IMU communication interface
are advised to study the open source x-IMU API (4.2). The API is source code is written in C# and well
commented; porting the API (or aspects of) to another language should be a straight forward exercise.
15
Commands
Commands are executed by either sending a command packet to the x-IMU or by pressing the push button
which may be configured to execute a specific command. Commands are sent using the x-IMU GUI via the
Commands tab page (4.1.4). Once a command has been executed the x-IMU will echo the command packet
back to the host computer as confirmation. As all communication from the x-IMU to the host computer is
logged to the SD card (7), all command confirmations will be logged on the SD card. If a command packet
is sent containing an invalid command code the x-IMU will respond with an invalid command error message
(16.1.16).
Sending a command packet to the x-IMU will cause the x-IMU to momentarily pause sensor sampling
and processing while the received data is processed. This may cause discrepancies in the otherwise fixed
data output rates.
31
15.1
15.1.1
Individual commands
Null command
Command code:
Description:
15.1.2
Reset
Command code:
Description:
15.1.3
0x0003
The reset sleep timer command will reset the sleep timer (12.5) countdown and so postpone sleep. An example usage of this command is to create behaviour where the x-IMU
will automatically enter sleep mode when communication with the host software ends or
connection is lost.
Sample gyroscope bias at temperature 1
Command code:
Description:
15.1.6
0x0002
A sleep command will put the device into sleep mode (12.4). The x-IMU will close any
open files on the SD card before entering sleep mode. The x-IMU may be taken out of
sleep mode by using the push button configured in sleep/wake mode or using the motion
triggered wake up functionality (12.6).
Reset sleep timer
Command code:
Description:
15.1.5
0x0001
A reset command causes a software reset of the x-IMU. The x-IMU will close any open
files on the SD card before reset, in this way the reset command may be of use to users
wishing to break up a logging session into multiple files. The reset command is used
put the x-IMU into bootloader (??) mode in order to upload new firmware. A reset
command is sent by the x-IMU to the host computer as confirmation of reset, power on
and wake up.
Sleep
Command code:
Description:
15.1.4
0x0000
A null command is a valid command code but will result in no action. As all commands
sent to the x-IMU are echoed back to the sender, a null command may be used by the
host software to confirm communication with the x-IMU.
0x0004
The sample gyroscope bias at temperature 1 command is used to calibrate the gyroscope
bias parameters. This command should be sent while the x-IMU is stationary and at
the lowest temperature the device is required to operate at. The x-IMU will measure
the mean temperature and gyroscope output over approximately 16 seconds, store the
results to registers (17.2.18 to 17.2.21) and then trigger a calculate gyroscope bias parameters command (15.1.7). The execution of this command will be aborted if a gyroscope
not stationary error (16.1.17) occurs. See the gyroscope calibration section for more
information (??).
Sample gyroscope bias at temperature 2
Command code:
Description:
0x0005
The sample gyroscope bias at temperature 2 command is used to calibrate the gyroscope
bias parameters. This command should be sent while the x-IMU is stationary and at
the highest temperature the device is required to operate at. The x-IMU will measure
the mean temperature and gyroscope output over approximately 16 seconds, store the
results to registers (17.2.22 to 17.2.25) and then trigger a calculate gyroscope bias parameters command (15.1.7).The execution of this command will be aborted if a gyroscope
not stationary error (16.1.17) occurs. See the gyroscope calibration section for more
information (??).
32
15.1.7
Calculate gyroscope bias parameters
Command code:
Description:
15.1.8
Look up accelerometer bias and sensitivity
Command code:
Description:
15.1.9
0x0009
The algorithm initialise command will re-start the algorithm from initial conditions. This
command can be used to ’force’ the algorithm to converge to steady state conditions if
previous distortions to magnetic or other extreme sensor measurements have left the IMU
or AHRS algorithm output at an erroneous orientation. See the IMU/AHRS algorithms
section (11) for more information.
Algorithm tare
Command code:
Description:
15.1.12
0x0008
The measure magnetometer bias and sensitivity command is used to run an on-board
magnetometer calibration algorithm. The x-IMU use the magnetometer’s internal field
generator to measure the mean magnetometer bias and sensitivity over approximately
16 seconds independent of external magnetic interference. The magnetometer sensitivity (17.2.34 to 17.2.36) and bias (17.2.37 to 17.2.39) registers and then automatically
updated. This command should be used each time the accelerometer full-scale range
(17.2.33) is changed. The execution of this command will be aborted if a magnetometer saturation error (16.1.18) occurs. See the magnetometer calibration section (??) for
more information.
Algorithm initialise
Command code:
Description:
15.1.11
0x0007
The look up accelerometer bias and sensitivity command is used to set the accelerometer
sensitivity (17.2.27 to 17.2.29) and bias registers (17.2.30 to 17.2.32) to the calibrated
parameters defined by the accelerometer manufacturer. This command should be used
each time the accelerometer full-scale range (17.2.26) is changed. See the accelerometer
calibration section (??) for more information.
Measure magnetometer bias and sensitivity
Command code:
Description:
15.1.10
0x0006
The calculate gyroscope bias parameters command is used to execute the on-board gyroscope bias calibration calculation. The algorithm uses the register values (17.2.18 to
17.2.25) previously sampled by the sample gyroscope bias at temperature 1 (15.1.5) and
sample gyroscope bias at temperature 2 (15.1.6) commands to calculate the gyroscope
bias parameters and update the registers (17.2.12 to 17.2.17). See the gyroscope calibration section for more information (??).
0x000A
The algorithm tare command is used to set the algorithm datum orientation and store the
reference quaternion to the tare quaternion registers (17.2.50 to 17.2.53). These registers
may be then be cleared using the clear tare command (15.1.12). See the IMU/AHRS
algorithms section for more information (11).
Algorithm clear tare
Command code:
Description:
0x000B
The algorithm clear tare command is used to clear the tare quaternion registers (17.2.50
to 17.2.53) and return the datum orientation to alignment with the Earth coordinate
frame.
33
15.1.13
Algorithm initialise then tare
Command code:
Description:
16
0x000C
The algorithm initialise then tare command will execute an algorithm initialise command (15.1.10) and then execute an algorithm clear tare command (15.1.11) once the
initialisation is complete.
Error messages
Error messages are sent by the x-IMU to warn the user or host software of any internal errors that have
occurred. The x-IMU GUI will display these errors in message boxes for user acknowledgment. As all
communication from the x-IMU to the host computer is logged to the SD card (7), all error messages will
be logged on the SD card.
16.1
16.1.1
Individual error messages
NoError
Error code:
Description:
16.1.2
Low battery
Error code:
Description:
16.1.3
0x0002
A USB receive buffer over error will be sent if the USB receive buffer overruns and data to
be received was lost. This occurs when data is transmitted to the x-IMU at a rate greater
than the rate it can be processed. Consider reducing the rate at which data is sent to the
x-IMU if this error occurs repeatedly.
USB transmit buffer overrun
Error code:
Description:
16.1.5
0x0001
A low battery error is sent when the low battery voltage detection (12.3) detects that the
battery voltage has fallen below the specific level defined in the battery shutdown voltage
register (17.2.60). This message is sent immediately before the x-IMU enters sleep mode
(12.4). See the low battery voltage detection section (12.3) for more information.
USB receive buffer overrun
Error code:
Description:
16.1.4
0x0000
No error.
0x0003
A transmit buffer overrun error will be sent if the USB transmit buffer overruns and data
due to be transmitted was lost. This will occur when the communication channel bandwidth
is unable to cope with the amount of data being transmitted. Consider using lower data
output rates if this error occurs repeatedly. This error may be ignored in applications where
USB data is not essential and the SD card is the intended data output. In such applications,
the user need only be concerned with SD card write buffer overrun errors (16.1.7). The xIMU will attempt to transmit data via USB while the USB is detected as connected, if the
USB is connect but the associated serial port not open then the USB transmit buffer will
continue to overrun until the port is opened or the USB disconnected.
Bluetooth receive buffer overrun
Error code:
Description:
0x0004
A Bluetooth receive buffer over error will be sent if the Bluetooth receive buffer overruns
and data to be received was lost. This occurs when data is transmitted to the x-IMU at a
rate greater than the rate it can be processed. Consider reducing the rate at which data is
sent to the x-IMU if this error occurs repeatedly.
34
16.1.6
Bluetooth transmit buffer overrun
Error code:
Description:
16.1.7
SD card write buffer overrun
Error code:
Description:
16.1.8
0x0009
An invalid checksum error will be sent if the received packet contains a valid number of
bytes but contains an invalid checksum. This error is only relevant users developing their
own communication software and not using the x-IMU API or x-IMU GUI.
Unknown packet header
Error code:
Description:
16.1.12
0x0008
A too many bytes in packet error will be sent if the received packet does not contains too
many bytes to be valid. This error is only relevant users developing their own communication
software and not using the x-IMU API or x-IMU GUI.
Invalid checksum
Error code:
Description:
16.1.11
0x0007
A too few bytes in packet error will be sent if the received packet does not contain enough
bytes to be valid. This error is only relevant users developing their own communication
software and not using the x-IMU API or x-IMU GUI.
Too many bytes in packet
Error code:
Description:
16.1.10
0x0006
An SD card buffer over error will be sent if the SD card buffer is overrun and data to be
written to the SD was lost. Consider using lower data output rates if this error occurs
repeatedly. An occurrence of this error may go unnoticed while the USB and Bluetooth are
not used. The red SD card LED (3.3.4) indicates SD card activity, if this LED behaviour
approaches that of being solidly on then it is likely that the this error is occurring.
Too few bytes in packet
Error code:
Description:
16.1.9
0x0005
A transmit buffer overrun error will be sent if the Bluetooth transmit buffer overruns and
data due to be transmitted was lost. This will occur when the communication channel
bandwidth is unable to cope with the amount of data being transmitted. Consider using
lower data output rates if this error occurs repeatedly. Transmit buffer overrun errors may
be expected in the Bluetooth communication channel quality deteriorates; for example, if
out of range. This error may be ignored in applications where the Bluetooth data is not
essential and the SD card is the intended data output. In such applications, the user need
only be concerned with SD card write buffer overrun errors (16.1.7).
0x000A
An Unknown packet header error will be sent if the received packet contains a valid number
of bytes and checksum but the header is not recognised. This error is only relevant users
developing their own communication software and not using the x-IMU API or x-IMU GUI.
Invalid number of bytes for packet header
Error code:
Description:
0x000B
An invalid number of bytes for packet header error will be sent if the received packet contains
a valid number of bytes, checksum and packet header but the number of bytes does not match
that expected for the specific packet header. This error is only relevant users developing
their own communication software and not using the x-IMU API or x-IMU GUI.
35
16.1.13
Invalid register address
Error code:
Description:
16.1.14
Register read-only
Error code:
Description:
16.1.15
0x0011
A magnetometer saturation error will be sent if the measurements taken during the execution
of the measure magnetometer bias and sensitivity command (15.1.9) were detected as having
saturated and the execution of the command was aborted. See the magnetometer calibration
section (??) for more information.
Incorrect auxiliary port mode
Error code:
Description:
17
0x0010
A gyroscope not stationary error will be sent if the gyroscope was detected as not being
stationary during the execution of a sample gyroscope bias command (15.1.5 or 15.1.6) and
the execution of the process was aborted. See the gyroscope calibration section (??) for
more information.
Magnetometer saturation
Error code:
Description:
16.1.19
0x000F
An invalid command error will be sent if the command code within the command packet
is not valid. This error is only relevant users developing their own communication software
and not using the x-IMU API or x-IMU GUI.
Gyroscope not stationary
Error code:
Description:
16.1.18
0x000E
An invalid register value error will be sent if the write register packet contains an invalid
register value for the specific address. This error is only relevant users developing their own
communication software and not using the x-IMU API or x-IMU GUI.
Invalid command
Error code:
Description:
16.1.17
0x000D
A register read-only error will be sent if the write register packet represents an attempt to
write a read-only register. This error is only relevant users developing their own communication software and not using the x-IMU API or x-IMU GUI.
Invalid register value
Error code:
Description:
16.1.16
0x000C
An invalid register address error will be sent if the read or write register packet contains an
invalid register address. This error is only relevant users developing their own communication software and not using the x-IMU API or x-IMU GUI.
0x0012
An incorrect auxiliary port mode error will be sent if an auxiliary port action is requested
while the auxiliary port is not in the correct mode (17.2.64) for that action. For example,
an incorrect auxiliary port mode error will be sent if a digital IO data packet is received
while the auxiliary port mode is Disabled. See the auxiliary port section (13) for more
information.
Registers
All x-IMU settings are saved in a bank of registers stored to non-volatile flash memory. Each register has
a 16-bit address and 16-bit value. These values may be viewed, edited, read, written and backed up to file
36
using the x-IMU GUI via the registers tab page.
17.1
Reading and writing registers
Any register may be read by sending a read register packet containing register address to be read. The
x-IMU will respond with a register write packet containing the register address and value. The x-IMU will
automatically send all register values so that settings are hardcoded as the first packets written to the SD
card (7). Registers may be written by sending a register write packet containing the register address to be
written to and the new register value. The x-IMU will respond with a register write packet containing the
register address and new value.
If a read register or register write packet is sent containing an invalid register address the x-IMU will
respond with an invalid register address error message (16.1.13). If a register write packet is sent containing
an read-only register address the x-IMU will respond with a register read-only error message (16.1.14). If a
register write packet is sent containing register value that is invalid for the specified address the x-IMU will
respond with an invalid register value error message (16.1.15).
Sending a read register or register write packet to the x-IMU will cause the x-IMU to momentarily pause
sensor sampling and processing while the packet is processed. This may cause discrepancies in the otherwise
fixed data output rates.
17.2
17.2.1
Individual register details
Firmware version major number
Address:
Value:
Description:
17.2.2
Firmware version minor number
Address:
Value:
Description:
17.2.3
0x0001
0 to 65535. Read-only.
The minor number of the current firmware version loaded on the x-IMU.
Device ID
Address:
Value:
Description:
17.2.4
0x0000
0 to 65535. Read-only.
The major number of the current firmware version loaded on the x-IMU.
0x0002
0x0000 to 0xFFFF. Read-only.
The unique 4 hexadecimal digit ID of the x-IMU taken as the last 2 bytes of the Bluetooth
MAC address.
Button mode
Address:
Value:
Description:
0x0003
0x0000 = Disabled
0x0001 = Reset command (15.1.2)
0x0002 = Sleep/Wake command (15.1.3)
0x0003 = Algorithm initialise command (15.1.10)
0x0004 = Algorithm tare command (15.1.11)
0x0005 = Algorithm initialise then tare command (15.1.13)
The command to be executed when the push button (3.2) is pressed. See the commands
section for more information on individual commands.
37
17.2.5
Battery voltmeter sensitivity
Address:
Value:
Description:
17.2.6
Battery voltmeter bias
Address:
Value:
Description:
17.2.7
0x0009
Q6.10 signed fixed point value between −32 and +32.
Calibrated sensitivity of the gyroscope y-axis in ◦ /s/lsb. See parameter sgy in the gyroscope
section (9.3). The typical value is provided as 16.4 ◦ /s/lsb. in the IMU-30003 datasheet.
Gyroscope z-axis sensitivity
Address:
Value:
Description:
17.2.12
0x0008
Q6.10 signed fixed point value between −32 and +32.
Calibrated sensitivity of the gyroscope x-axis in ◦ /s/lsb. See parameter sgx in the gyroscope
section (9.3). The typical value is provided as 16.4 ◦ /s/lsb. in the IMU-30003 datasheet.
Gyroscope y-axis sensitivity
Address:
Value:
Description:
17.2.11
0x0007
Q16.0 signed fixed point value between −32768 and +32677.
Calibrated bias of the thermometer in lsb. See parameter bτ (9.2) in the thermometer
section (9.2). The typical value is provided as −23, 000 lsb in the IMU-30003 datasheet.
Gyroscope x-axis sensitivity
Address:
Value:
Description:
17.2.10
0x0006
Q10.6 signed fixed point value between −512 and +512.
Calibrated sensitivity of the thermometer in ◦ C/lsb. See parameter sτ in the thermometer
section (9.2). The typical value is provided as 280 ◦ C/lsb in the IMU-30003 datasheet.
Thermometer bias
Address:
Value:
Description:
17.2.9
0x0005
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the battery ADC in lsb. See parameter bv in the battery voltmeter section
(9.1). The typical value is 0 lsb.
Thermometer sensitivity
Address:
Value:
Description:
17.2.8
0x0004
Q11.5 signed fixed point value between −1024 and +1024.
Calibrated sensitivity of the battery ADC in V/lsb. See parameter sv in the battery voltmeter section (9.1). The typical value is 621 V/lsb.
0x000A
Q6.10 signed fixed point value between −32 and +32.
Calibrated sensitivity of the gyroscope z-axis in ◦ /s/lsb. See parameter sgz in the gyroscope
section (9.3). The typical value is provided as 16.4 ◦ /s/lsb. in the IMU-30003 datasheet.
Gyroscope x-axis bias
Address:
Value:
Description:
0x000B
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the gyroscope x-axis at 25 ◦ C in lsb. See parameter bgx in the gyroscope
section (9.3). The typical value is provided as 0 lsb in the IMU-30003 datasheet. The xIMU has build in algorithms to accuracy evaluate this parameter automatically using the
Calculate gyroscope bias parameters command (15.1.7), see the gyroscope calibration section
for more information (??).
38
17.2.13
Gyroscope y-axis bias
Address:
Value:
Description:
17.2.14
Gyroscope z-axis bias
Address:
Value:
Description:
17.2.15
0x000F
Q6.10 signed fixed point value between −32 and +32.
Calibrated bias temperature sensitivity of the gyroscope y-axis in lsb/◦ C. See parameter fy
in the gyroscope section (9.3). The x-IMU has build in algorithms to accuracy evaluate this
parameter automatically using the Calculate gyroscope bias parameters command (15.1.7),
see the gyroscope calibration section for more information (??).
Gyroscope z-axis bias temperature sensitivity
Address:
Value:
Description:
17.2.18
0x000E
Q6.10 signed fixed point value between −32 and +32.
Calibrated bias temperature sensitivity of the gyroscope x-axis in lsb/◦ C. See parameter fx
in the gyroscope section (9.3). The x-IMU has build in algorithms to accuracy evaluate this
parameter automatically using the Calculate gyroscope bias parameters command (15.1.7),
see the gyroscope calibration section for more information (??).
Gyroscope y-axis bias temperature sensitivity
Address:
Value:
Description:
17.2.17
0x000D
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the gyroscope z-axis at 25 ◦ C in lsb. See parameter bgz in the gyroscope
section (9.3). The typical value is provided as 0 lsb in the IMU-30004 datasheet. The xIMU has build in algorithms to accuracy evaluate this parameter automatically using the
Calculate gyroscope bias parameters command (15.1.7), see the gyroscope calibration section
for more information (??).
Gyroscope x-axis bias temperature sensitivity
Address:
Value:
Description:
17.2.16
0x000C
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the gyroscope y-axis at 25 ◦ C in lsb. See parameter bgy in the gyroscope
section (9.3). The typical value is provided as 0 lsb in the IMU-30004 datasheet. The xIMU has build in algorithms to accuracy evaluate this parameter automatically using the
Calculate gyroscope bias parameters command (15.1.7), see the gyroscope calibration section
for more information (??).
0x0010
Q6.10 signed fixed point value between −32 and +32.
Calibrated bias temperature sensitivity of the gyroscope z-axis in lsb/◦ C. See parameter fz
in the gyroscope section (9.3). The x-IMU has build in algorithms to accuracy evaluate this
parameter automatically using the Calculate gyroscope bias parameters command (15.1.7),
see the gyroscope calibration section for more information (??).
Gyroscope sample 1 - Temperature
Address:
Value:
Description:
0x0011
Q8.8 signed fixed point value between −128 and +128.
Temperature at gyroscope bias sample 1 in ◦ C. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 1
is recorded using the Sample gyroscope bias at temperature 1 command (15.1.5). See the
gyroscope calibration section for more information (??).
39
17.2.19
Gyroscope sample 1 - x-axis bias
Address:
Value:
Description:
17.2.20
Gyroscope sample 1 - y-axis bias
Address:
Value:
Description:
17.2.21
0x0014
Q8.8 signed fixed point value between −128 and +128.
z-axis bias at gyroscope bias sample 1 in lsb. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 1
is recorded using the Sample gyroscope bias at temperature 1 command (15.1.5). See the
gyroscope calibration section for more information (??).
Gyroscope sample 2 - Temperature
Address:
Value:
Description:
17.2.23
0x0013
Q8.8 signed fixed point value between −128 and +128.
y-axis bias at gyroscope bias sample 1 in lsb. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 1
is recorded using the Sample gyroscope bias at temperature 1 command (15.1.5). See the
gyroscope calibration section for more information (??).
Gyroscope sample 1 - z-axis bias
Address:
Value:
Description:
17.2.22
0x0012
Q8.8 signed fixed point value between −128 and +128.
x-axis bias at gyroscope bias sample 1 in lsb. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 1
is recorded using the Sample gyroscope bias at temperature 1 command (15.1.5). See the
gyroscope calibration section for more information (??).
0x0015
Q8.8 signed fixed point value between −128 and +128.
Temperature at gyroscope bias sample 2 in ◦ C. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 2
is recorded using the Sample gyroscope bias at temperature 2 command (15.1.6). See the
gyroscope calibration section for more information (??).
Gyroscope sample 2 - x-axis bias
Address:
Value:
Description:
0x0016
Q8.8 signed fixed point value between −128 and +128.
x-axis bias at gyroscope bias sample 2 in lsb. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 2
is recorded using the Sample gyroscope bias at temperature 2 command (15.1.6). See the
gyroscope calibration section for more information (??).
40
17.2.24
Gyroscope sample 2 - y-axis bias
Address:
Value:
Description:
17.2.25
Gyroscope sample 2 - z-axis bias
Address:
Value:
Description:
17.2.26
Description:
0x001A
Q11.4 signed fixed point value between −2048 and +2048.
Calibrated sensitivity of the accelerometer x-axis in g/lsb. See parameter sax in the accelerometer section (9.4). The typical values are provided for each full-scale range (17.2.26)
in the LSM303DLH datasheet. These values can be set automatically using the Look up
accelerometer bias and sensitivity command (15.1.8).
Accelerometer y-axis sensitivity
Address:
Value:
Description:
17.2.29
0x0019
0x0000 = ±2 g
0x0001 = ±4 g
0x0002 = ±8 g
Sets the full-scale range of the accelerometer. Each full-scale range will have different
associated sensitivity (17.2.27 to 17.2.29) and bias (17.2.30 to 17.2.32) values. The Look
up accelerometer bias and sensitivity command (15.1.8) may be used to recall the correct
calibrated sensitivity and bias values for the selected full-scale range.
Accelerometer x-axis sensitivity
Address:
Value:
Description:
17.2.28
0x0018
Q8.8 signed fixed point value between −128 and +128.
z-axis bias at gyroscope bias sample 2 in lsb. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 2
is recorded using the Sample gyroscope bias at temperature 2 command (15.1.6). See the
gyroscope calibration section for more information (??).
Accelerometer full-scale
Address:
Value:
17.2.27
0x0017
Q8.8 signed fixed point value between −128 and +128.
y-axis bias at gyroscope bias sample 2 in lsb. Gyroscope bias samples 1 and 2 are required
for the automatic calculation of the gyroscope bias parameters (17.2.12 to 17.2.17) using
the Calculate gyroscope bias parameters command (15.1.7). The gyroscope bias sample 2
is recorded using the Sample gyroscope bias at temperature 2 command (15.1.6). See the
gyroscope calibration section for more information (??).
0x001B
Q11.4 signed fixed point value between −2048 and +2048.
Calibrated sensitivity of the accelerometer y-axis in g/lsb. See parameter say in the accelerometer section (9.4). The typical values are provided for each full-scale range (17.2.26)
in the LSM303DLH datasheet. These values can be set automatically using the Look up
accelerometer bias and sensitivity command (15.1.8).
Accelerometer z-axis sensitivity
Address:
Value:
Description:
0x001C
Q11.4 signed fixed point value between −2048 and +2048.
Calibrated sensitivity of the accelerometer z-axis in g/lsb. See parameter saz in the accelerometer section (9.4). The typical values are provided for each full-scale range (17.2.26)
in the LSM303DLH datasheet. These values can be set automatically using the Look up
accelerometer bias and sensitivity command (15.1.8).
41
17.2.30
Accelerometer x-axis bias
Address:
Value:
Description:
17.2.31
Accelerometer y-axis bias
Address:
Value:
Description:
17.2.32
0x001F
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the accelerometer z-axis in lsb. See parameter baz in the accelerometer
section (9.4). A typical value of 0 lsb is provided in the LSM303DLH datasheet. This value
can be set automatically using the Look up accelerometer bias and sensitivity command
(15.1.8).
Magnetometer full-scale
Address:
Value:
Description:
17.2.34
0x001E
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the accelerometer y-axis in lsb. See parameter bay in the accelerometer
section (9.4). A typical value of 0 lsb is provided in the LSM303DLH datasheet. This value
can be set automatically using the Look up accelerometer bias and sensitivity command
(15.1.8).
Accelerometer z-axis bias
Address:
Value:
Description:
17.2.33
0x001D
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the accelerometer x-axis in lsb. See parameter bax in the accelerometer
section (9.4). A typical value of 0 lsb is provided in the LSM303DLH datasheet. This value
can be set automatically using the Look up accelerometer bias and sensitivity command
(15.1.8).
0x0020
0x0000 = ±1.3 G
0x0001 = ±1.9 G
0x0002 = ±2.5 G
0x0003 = ±4.0 G
0x0004 = ±4.7 G
0x0005 = ±5.6 G
0x0006 = ±8.1 G
Sets the full-scale range of the magnetometer. Each full-scale range will have different
associated sensitivity (17.2.34 to 17.2.36) and bias (17.2.37 to 17.2.39) values. The Measure
magnetometer bias and sensitivity command (15.1.9) may be used to measure the correct
calibrated sensitivity and bias values for the selected full-scale range using an on-board
algorithm.
Magnetometer x-axis sensitivity
Address:
Value:
Description:
0x0021
Q11.4 signed fixed point value between −2048 and +2048.
Calibrated sensitivity of the magnetometer x-axis in G/lsb. See parameter smx in the magnetometer section (9.5). The typical values are provided for each full-scale range (17.2.33)
in the LSM303DLH datasheet. Accurate values can be set automatically using the Measure
magnetometer bias and sensitivity command (15.1.9).
42
17.2.35
Magnetometer y-axis sensitivity
Address:
Value:
Description:
17.2.36
Magnetometer z-axis sensitivity
Address:
Value:
Description:
17.2.37
0x0025
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the magnetometer y-axis in lsb. See parameter bmy in the magnetometer section (9.5). The typical values are provided for each full-scale range (17.2.33) in
the LSM303DLH datasheet. Accurate values can be set automatically using the Measure
magnetometer bias and sensitivity command (15.1.9).
Magnetometer z-axis bias
Address:
Value:
Description:
17.2.40
0x0024
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the magnetometer x-axis in lsb. See parameter bmx in the magnetometer section (9.5). The typical values are provided for each full-scale range (17.2.33) in
the LSM303DLH datasheet. Accurate values can be set automatically using the Measure
magnetometer bias and sensitivity command (15.1.9).
Magnetometer y-axis bias
Address:
Value:
Description:
17.2.39
0x0023
Q11.4 signed fixed point value between −2048 and +2048.
Calibrated sensitivity of the magnetometer z-axis in G/lsb. See parameter smz in the magnetometer section (9.5). The typical values are provided for each full-scale range (17.2.33)
in the LSM303DLH datasheet. Accurate values can be set automatically using the Measure
magnetometer bias and sensitivity command (15.1.9).
Magnetometer x-axis bias
Address:
Value:
Description:
17.2.38
0x0022
Q11.4 signed fixed point value between −2048 and +2048.
Calibrated sensitivity of the magnetometer y-axis in G/lsb. See parameter smy in the magnetometer section (9.5). The typical values are provided for each full-scale range (17.2.33)
in the LSM303DLH datasheet. Accurate values can be set automatically using the Measure
magnetometer bias and sensitivity command (15.1.9).
0x0026
Q8.8 signed fixed point value between −128 and +128.
Calibrated bias of the magnetometer z-axis in lsb. See parameter bmz in the magnetometer section (9.5). The typical values are provided for each full-scale range (17.2.33) in
the LSM303DLH datasheet. Accurate values can be set automatically using the Measure
magnetometer bias and sensitivity command (15.1.9).
Magnetometer x-axis hard-iron bias
Address:
Value:
Description:
0x0027
Q5.11 signed fixed point value between −16 and +16.
Calibrated hard-iron bias affecting the magnetometer x-axis in G. See parameter hx in the
magnetometer section (9.5). The hard-iron bias parameters will change when the x-IMU’s
local magnetic environment is altered; for example, when the x-IMU is fixed to the battery.
Use of the magnetometer and AHRS algorithm requires that the hard-iron bias parameters
are accurately calibrated. See the hard-iron calibrations section for more information (??).
43
17.2.41
Magnetometer y-axis hard-iron bias
Address:
Value:
Description:
17.2.42
Magnetometer z-axis hard-iron bias
Address:
Value:
Description:
17.2.43
Description:
0x002B
Q8.8 signed fixed point value between 0 and +128.
Algorithm proportional feedback gain. The proportional gain governs the rate at which
the algorithm output converges to an orientation assumed by the accelerometer and magnetometer; a low value will ’trust’ the gyroscope data more and the accelerometer and
magnetometer less, a high value will ’trust’ the gyroscope less and the accelerometer and
magnetometer more. See the IMU/AHRS algorithms section for more information (11).
Algorithm integral gain
Address:
Value:
Description:
17.2.46
0x002A
0x0000 = Disabled
0x0000 = IMU
0x0001 = AHRS
Sets the algorithm mode, see the IMU/AHRS algorithms section for more information (11).
The algorithm mode can be set to Disabled to reduce power consumption when the algorithms are not required.
Algorithm proportional gain
Address:
Value:
Description:
17.2.45
0x0029
Q5.11 signed fixed point value between −16 and +16.
Calibrated hard-iron bias affecting the magnetometer z-axis in G. See parameter hx in the
magnetometer section (9.5). The hard-iron bias parameters will change when the x-IMU’s
local magnetic environment is altered; for example, when the x-IMU is fixed to the battery.
Use of the magnetometer and AHRS algorithm requires that the hard-iron bias parameters
are accurately calibrated. See the hard-iron calibrations section for more information (??).
Algorithm mode
Address:
Value:
17.2.44
0x0028
Q5.11 signed fixed point value between −16 and +16.
Calibrated hard-iron bias affecting the magnetometer y-axis in G. See parameter hx in the
magnetometer section (9.5). The hard-iron bias parameters will change when the x-IMU’s
local magnetic environment is altered; for example, when the x-IMU is fixed to the battery.
Use of the magnetometer and AHRS algorithm requires that the hard-iron bias parameters
are accurately calibrated. See the hard-iron calibrations section for more information (??).
0x002C
Q2.14 signed fixed point value between 0 and +2.
Algorithm integral feedback gain. The integral gain governs the rate at which the algorithm compensates for gyroscope bias drift. It is recommended that users ensure accurate
gyroscope bias temperature sensitivity calibration and use an integral feedback gain of 0 to
avoid instabilities. See the IMU/AHRS algorithms section for more information (11).
Algorithm initial proportional gain
Address:
Value:
Description:
0x002D
Q10.6 signed fixed point value between 0 and 512.
Algorithm initial proportional feedback gain used each time the algorithm resets. The effective proportional gain will ramp down from the initial proportional gain to the proportional
gain 17.2.44 over a specified period of time 17.2.47. See the IMU/AHRS algorithms section
for more information (11).
44
17.2.47
Algorithm initilasation period
Address:
Value:
Description:
17.2.48
Algorithm minimum valid magnetic field magnitude
Address:
Value:
Description:
17.2.49
0x002F
Q1.15 signed fixed point value between −1 and +1.
Quaternion stored to compute the algorithm output after a tare operation ?? has been
preformed. The tare quaternion can be set using the tare command (??) and cleared using
the clear tare command (??). See the IMU/AHRS algorithms section for more information
(11).
Tare quaternion (element 1)
Address:
Value:
Description:
17.2.52
0x0042
Q5.11 signed fixed point value between −16 and +16.
The maximum valid magnetic field magnitude (in G) that may be used by the algorithm in
the estimation of heading. Magnetic fields of an invalid magnitude will be ignored by the
AHRS algorithm so that heading is determined from gyroscope measurements alone. See
the IMU/AHRS algorithms section for more information (11).
Tare quaternion (element 0)
Address:
Value:
Description:
17.2.51
0x0041
Q5.11 signed fixed point value between −16 and +16.
The minimum valid magnetic field magnitude (in G) that may be used by the algorithm in
the estimation of heading. Magnetic fields of an invalid magnitude will be ignored by the
AHRS algorithm so that heading is determined from gyroscope measurements alone. See
the IMU/AHRS algorithms section for more information (11).
Algorithm maximum valid magnetic field magnitude
Address:
Value:
Description:
17.2.50
0x002E
Q8.8 signed fixed point value between 0 and +128.
Algorithm ramp down period (in seconds) used each time the algorithm resets. The effective
proportional gain will ramp down from the initial proportional gain (17.2.44) to the proportional gain 17.2.44 over a specified period of time 17.2.47. See the IMU/AHRS algorithms
section for more information (11).
0x0030
Q1.15 signed fixed point value between −1 and +1.
Quaternion stored to compute the algorithm output after a tare operation ?? has been
preformed. The tare quaternion can be set using the tare command (??) and cleared using
the clear tare command (??). See the IMU/AHRS algorithms section for more information
(11).
Tare quaternion (element 2)
Address:
Value:
Description:
0x0031
Q1.15 signed fixed point value between −1 and +1.
Quaternion stored to compute the algorithm output after a tare operation ?? has been
preformed. The tare quaternion can be set using the tare command (??) and cleared using
the clear tare command (??). See the IMU/AHRS algorithms section for more information
(11).
45
17.2.53
Tare quaternion (element 3)
Address:
Value:
Description:
17.2.54
Sensor data mode
Address:
Value:
Description:
17.2.55
Description:
0x0034
0x0000 = Disabled (sent on reset/wake only)
0x0001 = 1 Hz
Output rate of the date/time data packets. Data rates can be reduced or disabled to conserve
power.
Battery and thermometer data output rate
Address:
Value:
Description:
17.2.57
0x0033
0x0000 = Raw ADC results
0x0001 = Calibrated measurements
Sets the data output mode of the sensors. See the sensors section for more details (9).
Date/time data output rate
Address:
Value:
17.2.56
0x0032
Q1.15 signed fixed point value between −1 and +1.
Quaternion stored to compute the algorithm output after a tare operation ?? has been
preformed. The tare quaternion can be set using the tare command (??) and cleared using
the clear tare command (??). See the IMU/AHRS algorithms section for more information
(11).
0x0035
0x0000 = Disabled
0x0001 = 1 Hz
0x0002 = 2 Hz
0x0003 = 4 Hz
0x0004 = 8 Hz
0x0005 = 16 Hz
0x0006 = 32 Hz
0x0007 = 64 Hz
0x0008 = 128 Hz
0x0009 = 256 Hz
Output rate of the battery and thermometer data packets. Data rates can be reduced or
disabled to conserve power.
Inertial and magnetic data output rate
Address:
Value:
Description:
0x0036
0x0000 = Disabled
0x0001 = 1 Hz
0x0002 = 2 Hz
0x0003 = 4 Hz
0x0004 = 8 Hz
0x0005 = 16 Hz
0x0006 = 32 Hz
0x0007 = 64 Hz
0x0008 = 128 Hz
0x0009 = 256 Hz
Output rate of the inertial and magnetic data packets. Data rates can be reduced or disabled
to conserve power.
46
17.2.58
Quaternion data output rate
Address:
Value:
Description:
17.2.59
SD card new file name
Address:
Value:
Description:
17.2.60
0x003A
0 to 65535
Sleep timer value in seconds. Once this period has elapsed, the x-IMU will enter sleep mode
(12.4). A value of 0 seconds will disable the sleep timer. See the sleep timer (12.5) section
for more information.
Motion trigger wake up
Address:
Value:
Description:
17.2.63
0x0039
Q4.12 signed fixed point value between 3.5 and +8.
Minimum voltage threshold for the device to shutdown. See the low battery voltage detection section for more information (12.3).
Sleep timer
Address:
Value:
Description:
17.2.62
0x0038
00000 to 65535
The file name used to be used when the next file is created on the SD card. See the SD
card section for more information (7).
Battery shotdown voltage
Address:
Value:
Description:
17.2.61
0x0037
0x0000 = Disabled
0x0001 = 1 Hz
0x0002 = 2 Hz
0x0003 = 4 Hz
0x0004 = 8 Hz
0x0005 = 16 Hz
0x0006 = 32 Hz
0x0007 = 64 Hz
0x0008 = 128 Hz
0x0009 = 256 Hz
Output rate of the quaternion data packets. Data rates can be reduced or disabled to
conserve power.
0x003B
0x0000 = Disabled
0x0001 = Low sensitivity
0x0001 = High sensitivity
Enables the sensitivity of the motion trigger wake up. See the motion trigger wake up
section for more information (12.6).
Bluetooth power
Address:
Value:
Description:
0x003C
0x0000 = Disabled
0x0001 = Enabled
Enables or disables Bluetooth. The Bluetooth can be disabled to conserve power.
47
17.2.64
Auxiliary port mode
Address:
Value:
Description:
17.2.65
Digital I/O direction
Address:
Value:
Description:
17.2.66
0x003D
0x0000 = Disabled
0x0001 = Digital I/O
Sets the auxiliary port mode. See the auxiliary port section for more information (13).
0x003F
0x0000 = All channels are inputs
0x0001 = Channels 0, 1, 2, 3, 4, 5 and 6 are inputs, 7 is an output
0x0002 = Channels 0, 1, 2, 3, 4 and 5 are inputs, 6 and 7 are outputs
0x0003 = Channels 0, 1, 2, 3 and 4 are inputs, 5, 6 and 7 are outputs
0x0004 = Channels 0, 1, 2 and 3 are inputs, 4, 5, 6 and 7 are outputs
0x0005 = Channels 0, 1 and 2 are inputs, 3, 4, 5, 6 and 7 are outputs
0x0006 = Channels 0 and 1 are inputs, 2, 3, 4, 5, 6 and 7 are outputs
0x0007 = Channel 0 is an input, 1, 2, 3, 4, 5, 6 and 7 are outputs
0x0008 = All channels are outputs
Sets the direction of the auxiliary port channels when in digital I/O mode. See the digital
I/O mode section for more information (??).
Digital I/O data output rate
Address:
Value:
Description:
0x0040
0x0000 = On change only
0x0001 = 1 Hz
0x0002 = 2 Hz
0x0003 = 4 Hz
0x0004 = 8 Hz
0x0005 = 16 Hz
0x0006 = 32 Hz
0x0007 = 64 Hz
0x0008 = 128 Hz
0x0009 = 256 Hz
Output rate of the digital I/O data packets. See the digital I/O mode section for more
information (??).
48
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