x-IMU User Manual 4.4 - x

x-IMU User Manual 4.4 - x
x-IMU User Manual 4.4
x-io Technologies
August 30, 2012
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.
1
Contents
1 x-IMU overview
1.1 x-IMU Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 x-IMU Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
7
8
2 Getting started
9
3 Hardware overview
3.1 Power switch . . . . . . . . .
3.2 Command 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 module . . . . . .
3.7 Battery connector . . . . . .
3.8 Auxiliary port header . . . .
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:
4.2 x-IMU API . . .
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10
10
10
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11
11
11
11
11
11
11
11
. . . . . . . . . . . . .
Serial port . . . . . .
Registers . . . . . . .
Date/time . . . . . . .
Commands . . . . . .
View sensor data . . .
Auxiliary port . . . .
Data logger . . . . . .
SD card . . . . . . . .
Hard-iron calibration
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11
11
11
12
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14
14
16
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18
19
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5 USB
20
5.1 Installing USB drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.2 USB bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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 . . . . . .
6.5 Connecting to multiple x-IMUs via Bluetooth
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21
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24
7 SD
7.1
7.2
7.3
7.4
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24
25
25
25
25
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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socket
8 Command button
26
9 Real-time clock and calendar
26
2
9.1
Maintaining clock power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 Sensors
10.1 Battery voltmeter .
10.2 Thermometer . . .
10.3 Gyroscope . . . . .
10.4 Accelerometer . . .
10.5 Magnetometer . . .
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26
26
27
27
27
28
28
11 Sensor calibration
29
11.0.1 Magnetometer hard-iron calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
12 IMU and AHRS algorithms
30
13 Power management
13.1 External supply . . . . . . . . . . . . . .
13.2 Battery and charging . . . . . . . . . . .
13.3 Sleep mode . . . . . . . . . . . . . . . .
13.4 Low battery voltage detection . . . . . .
13.5 Sleep timer . . . . . . . . . . . . . . . .
13.6 Motion triggered wake up . . . . . . . .
13.7 Tips for minimising power consumption
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30
30
30
30
31
31
31
31
14 Auxiliary port
14.1 Disabled . . . . . . . . . .
14.2 Digital I/O mode . . . . .
14.3 Analogue input . . . . . .
14.4 PWM output mode . . . .
14.5 ADXL345 bus mode . . .
14.6 UART mode . . . . . . .
14.6.1 UART bandwidth
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32
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33
34
34
35
35
35
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.
15 Communication protocol
36
16 Commands
16.1 Individual commands . . . . . . . . . . . . . . . . .
16.1.1 Null command . . . . . . . . . . . . . . . .
16.1.2 Factory reset . . . . . . . . . . . . . . . . .
16.1.3 Reset . . . . . . . . . . . . . . . . . . . . .
16.1.4 Sleep . . . . . . . . . . . . . . . . . . . . . .
16.1.5 Reset sleep timer . . . . . . . . . . . . . . .
16.1.6 Sample gyroscope axis at 200 dps . . . . . .
16.1.7 Calculate gyroscope sensitivity . . . . . . .
16.1.8 Sample gyroscope bias at temperature 1 . .
16.1.9 Sample gyroscope bias at temperature 2 . .
16.1.10 Calculate gyroscope bias parameters . . . .
16.1.11 Sample accelerometer axis at 1 g . . . . . .
16.1.12 Calculate accelerometer bias and sensitivity
16.1.13 Measure magnetometer bias and sensitivity
16.1.14 Algorithm initialise . . . . . . . . . . . . . .
16.1.15 Algorithm tare . . . . . . . . . . . . . . . .
16.1.16 Algorithm clear tare . . . . . . . . . . . . .
16.1.17 Algorithm initialise then tare . . . . . . . .
17 Errors
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36
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3
17.1 Individual errors . . . . . . . . . . . . . . . . . .
17.1.1 No error . . . . . . . . . . . . . . . . . . .
17.1.2 Factory reset failed . . . . . . . . . . . . .
17.1.3 Low battery . . . . . . . . . . . . . . . . .
17.1.4 USB receive buffer overrun . . . . . . . .
17.1.5 USB transmit buffer overrun . . . . . . .
17.1.6 Bluetooth receive buffer overrun . . . . .
17.1.7 Bluetooth transmit buffer overrun . . . .
17.1.8 SD card write buffer overrun . . . . . . .
17.1.9 Too few bytes in packet . . . . . . . . . .
17.1.10 Too many bytes in packet . . . . . . . . .
17.1.11 Invalid checksum . . . . . . . . . . . . . .
17.1.12 Unknown packet header . . . . . . . . . .
17.1.13 Invalid number of bytes for packet header
17.1.14 Invalid register address . . . . . . . . . . .
17.1.15 Register read-only . . . . . . . . . . . . .
17.1.16 Invalid register value . . . . . . . . . . . .
17.1.17 Invalid command . . . . . . . . . . . . . .
17.1.18 Gyroscope axis not at 200 dps . . . . . .
17.1.19 Gyroscope not stationary . . . . . . . . .
17.1.20 Accelerometer axis not at 1g . . . . . . .
17.1.21 Magnetometer saturation . . . . . . . . .
17.1.22 Incorrect auxiliary port mode . . . . . . .
17.1.23 UART receive buffer overrun . . . . . . .
17.1.24 UART transmit buffer overrun . . . . . .
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18 Registers
18.1 Reading registers . . . . . . . . . . . . . . . . . . . .
18.2 Writing registers . . . . . . . . . . . . . . . . . . . .
18.3 Individual registers . . . . . . . . . . . . . . . . . . .
18.3.1 Firmware version major number . . . . . . .
18.3.2 Firmware version minor number . . . . . . .
18.3.3 Device ID . . . . . . . . . . . . . . . . . . . .
18.3.4 Button mode . . . . . . . . . . . . . . . . . .
18.3.5 Battery voltmeter sensitivity . . . . . . . . .
18.3.6 Battery voltmeter bias . . . . . . . . . . . . .
18.3.7 Thermometer sensitivity . . . . . . . . . . . .
18.3.8 Thermometer bias . . . . . . . . . . . . . . .
18.3.9 Gyroscope full-scale . . . . . . . . . . . . . .
18.3.10 Gyroscope x-axis sensitivity . . . . . . . . . .
18.3.11 Gyroscope y-axis sensitivity . . . . . . . . . .
18.3.12 Gyroscope z-axis sensitivity . . . . . . . . . .
18.3.13 Gyroscope sampled x-axis at +200 dps . . . .
18.3.14 Gyroscope sampled y-axis at +200 dps . . . .
18.3.15 Gyroscope sampled z-axis at +200 dps . . . .
18.3.16 Gyroscope sampled x-axis at -200 dps . . . .
18.3.17 Gyroscope sampled y-axis at -200 dps . . . .
18.3.18 Gyroscope sampled z-axis at -200 dps . . . .
18.3.19 Gyroscope x-axis bias at 25 degrees Celsius .
18.3.20 Gyroscope y-axis bias at 25 degrees Celsius .
18.3.21 Gyroscope z-axis bias at 25 degrees Celsius .
18.3.22 Gyroscope x-axis bias temperature sensitivity
18.3.23 Gyroscope y-axis bias temperature sensitivity
18.3.24 Gyroscope z-axis bias temperature sensitivity
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4
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18.3.25 Gyroscope sample 1 - Temperature . . . . . . . . . .
18.3.26 Gyroscope sample 1 - x-axis bias . . . . . . . . . . .
18.3.27 Gyroscope sample 1 - y-axis bias . . . . . . . . . . .
18.3.28 Gyroscope sample 1 - z-axis bias . . . . . . . . . . .
18.3.29 Gyroscope sample 2 - Temperature . . . . . . . . . .
18.3.30 Gyroscope sample 2 - x-axis bias . . . . . . . . . . .
18.3.31 Gyroscope sample 2 - y-axis bias . . . . . . . . . . .
18.3.32 Gyroscope sample 2 - z-axis bias . . . . . . . . . . .
18.3.33 Accelerometer full-scale . . . . . . . . . . . . . . . .
18.3.34 Accelerometer x-axis sensitivity . . . . . . . . . . . .
18.3.35 Accelerometer y-axis sensitivity . . . . . . . . . . . .
18.3.36 Accelerometer z-axis sensitivity . . . . . . . . . . . .
18.3.37 Accelerometer x-axis bias . . . . . . . . . . . . . . .
18.3.38 Accelerometer y-axis bias . . . . . . . . . . . . . . .
18.3.39 Accelerometer z-axis bias . . . . . . . . . . . . . . .
18.3.40 Accelerometer sampled x-axis at +1 g . . . . . . . .
18.3.41 Accelerometer sampled y-axis at +1 g . . . . . . . .
18.3.42 Accelerometer sampled z-axis at +1 g . . . . . . . .
18.3.43 Accelerometer sampled x-axis at -1 g . . . . . . . . .
18.3.44 Accelerometer sampled y-axis at -1 g . . . . . . . . .
18.3.45 Accelerometer sampled z-axis at -1 g . . . . . . . . .
18.3.46 Magnetometer full-scale . . . . . . . . . . . . . . . .
18.3.47 Magnetometer x-axis sensitivity . . . . . . . . . . . .
18.3.48 Magnetometer y-axis sensitivity . . . . . . . . . . . .
18.3.49 Magnetometer z-axis sensitivity . . . . . . . . . . . .
18.3.50 Magnetometer x-axis bias . . . . . . . . . . . . . . .
18.3.51 Magnetometer y-axis bias . . . . . . . . . . . . . . .
18.3.52 Magnetometer z-axis bias . . . . . . . . . . . . . . .
18.3.53 Magnetometer x-axis hard-iron bias . . . . . . . . .
18.3.54 Magnetometer y-axis hard-iron bias . . . . . . . . .
18.3.55 Magnetometer z-axis hard-iron bias . . . . . . . . .
18.3.56 Algorithm mode . . . . . . . . . . . . . . . . . . . .
18.3.57 Algorithm gain Kp . . . . . . . . . . . . . . . . . . .
18.3.58 Algorithm gain Ki . . . . . . . . . . . . . . . . . . .
18.3.59 Algorithm initial proportional gain . . . . . . . . . .
18.3.60 Algorithm initialisation period . . . . . . . . . . . .
18.3.61 Algorithm minimum valid magnetic field magnitude
18.3.62 Algorithm maximum valid magnetic field magnitude
18.3.63 Tare quaternion (element 0) . . . . . . . . . . . . . .
18.3.64 Tare quaternion (element 1) . . . . . . . . . . . . . .
18.3.65 Tare quaternion (element 2) . . . . . . . . . . . . . .
18.3.66 Tare quaternion (element 3) . . . . . . . . . . . . . .
18.3.67 Sensor data mode . . . . . . . . . . . . . . . . . . .
18.3.68 Date/time data output rate . . . . . . . . . . . . . .
18.3.69 Battery and thermometer data output rate . . . . .
18.3.70 Inertial and magnetic data output rate . . . . . . . .
18.3.71 Quaternion data output rate . . . . . . . . . . . . .
18.3.72 SD card new file name . . . . . . . . . . . . . . . . .
18.3.73 Battery shutdown voltage . . . . . . . . . . . . . . .
18.3.74 Sleep timer . . . . . . . . . . . . . . . . . . . . . . .
18.3.75 Motion trigger wake up . . . . . . . . . . . . . . . .
18.3.76 Bluetooth power . . . . . . . . . . . . . . . . . . . .
18.3.77 Auxiliary port mode . . . . . . . . . . . . . . . . . .
18.3.78 Digital I/O direction . . . . . . . . . . . . . . . . . .
5
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18.3.79 Digital I/O data output rate . .
18.3.80 Analogue input data mode . . .
18.3.81 Analogue input data output rate
18.3.82 Analogue input sensitivity . . . .
18.3.83 Analogue input bias . . . . . . .
18.3.84 PWM frequency . . . . . . . . .
18.3.85 ADXL345 bus data mode . . . .
18.3.86 ADXL345 bus data output rate .
18.3.87 ADXL345 A x-axis sensitivity . .
18.3.88 ADXL345 A y-axis sensitivity . .
18.3.89 ADXL345 A z-axis sensitivity . .
18.3.90 ADXL345 A x-axis bias . . . . .
18.3.91 ADXL345 A y-axis bias . . . . .
18.3.92 ADXL345 A z-axis bias . . . . .
18.3.93 ADXL345 B x-axis sensitivity . .
18.3.94 ADXL345 B y-axis sensitivity . .
18.3.95 ADXL345 B z-axis sensitivity . .
18.3.96 ADXL345 B x-axis bias . . . . .
18.3.97 ADXL345 B y-axis bias . . . . .
18.3.98 ADXL345 B z-axis bias . . . . .
18.3.99 ADXL345 C x-axis sensitivity . .
18.3.100ADXL345 C y-axis sensitivity . .
18.3.101ADXL345 C z-axis sensitivity . .
18.3.102ADXL345 C x-axis bias . . . . .
18.3.103ADXL345 C y-axis bias . . . . .
18.3.104ADXL345 C z-axis bias . . . . .
18.3.105ADXL345 D x-axis sensitivity . .
18.3.106ADXL345 D y-axis sensitivity . .
18.3.107ADXL345 D z-axis sensitivity . .
18.3.108ADXL345 D x-axis bias . . . . .
18.3.109ADXL345 D y-axis bias . . . . .
18.3.110ADXL345 D z-axis bias . . . . .
18.3.111UART baud rate . . . . . . . . .
18.3.112UART hardware flow control . .
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62
1
x-IMU overview
The x-IMU was designed to be the most versatile Inertial Measurement Unit (IMU) and Attitude Heading
Reference System (AHRS) product available. Its host of on-board sensors, algorithms and configurable 8channel 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 - Selectable range up to ±2000◦ /s
• Triple axis 12-bit accelerometer - Selectable range up to ±8 g
• Triple axis 12-bit magnetometer - Selectable range up to ±8.1 G
• 16-bit thermometer
• 12-bit battery voltage level
• Factory calibrated
• Temperature compensated (gyroscope only)
• Selectable data rates up to 512 Hz
On-board algorithms
• IMU and AHRS algorithms provide real-time measurement of orientation relative to the Earth
• Internal states updated at 512 Hz
• Algorithm ‘initialise’ and ’tare’ commands can be sent in real-time
• Complete sensor calibration algorithms for user maintenance
Connectivity
• USB
• Bluetooth - Class 1, 100m range, SPP
• Micro SD card - Supports FAT16/32 and SDHC
• UART (see auxiliary port mode)
Power options
• USB
• LiPo battery - On-board charging via USB
• External source from 3.6 V to 6.3 V
• Low power consumption - 50 mA to 150 mA dependent on settings and usage, 130 A sleep mode
7
Low profile
• Dimensions: 33 × 42 × 10 mm (57 × 38 × 21 mm with plastic housing and battery)
• Weight: 12g (100 g with plastic housing and battery)
Other features
• Motion triggered wake-up and sleep timer
• Real-time clock and calendar
• Configurable command button
• Configurable 8 channel auxiliary port
Auxiliary port modes
• External power in from 3.6 V to 6.3 V
• 3.3 V power out up to 100 mA
• Digital I/O mode - 8 channels, controlled via USB or Bluetooth
• Analogue input mode - 8 channels, 12-bit resolution, 0 to 3.3 V
• PWM output mode - 4 channels, 1 to 65,535 Hz; controlled via USB or Bluetooth
• ADXL345 bus mode - 4 external triple-axis, 16g, 13-bit resolution accelerometers
• UART mode - 3.3 V, 2400 to 921.6k baud, substitutes 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 so is intended to serve as a comprehensive template
for those using the x-IMU API to develop their own applications. Additional open source software examples
using the x-IMU API for various 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 or pair the x-IMU as a Bluetooth device.
2. Download and install the latest version of the x-IMU GUI.
3. Connect to the x-IMU via the serial port tab page of the x-IMU GUI.
9
3
Hardware overview
Figure 1: x-IMU and battery in plastic housing
Figure 2: x-IMU top
3.1
Figure 3: x-IMU bottom
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 via the auxiliary port if the power switch must be in the off position.
3.2
Command button
The command button that allows the execution of commands while the x-IMU is operating as a standalone
device. See the command button section for more information.
3.3
3.3.1
LEDs
Status LED (Green)
The green LED indicates the status of the x-IMU. It will remain lit while the device is sampling and sending
data and will otherwise be extinguished; for example, during the execution of some commands. In sleep
10
mode 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 activity. See the SD card LED section for more information.
3.3.3
Bluetooth LED (Blue)
The blue LED indicates the state of the Bluetooth connection and power status. See the Bluetooth LED
section for more information.
3.3.4
Charging LED (Red)
The red LED indicates the charging state of the battery. The red LED will remain lit while the battery is
charging and will be extinguished once the battery is charged. See the battery and charging section for more
information.
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. See the USB section 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 SDHC cards formatted as either FAT16 or FAT32. 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 for more information.
3.6
Bluetooth module
The on-board Bluetooth module is used to connect the x-IMU to a Bluetooth host. See the Bluetooth section
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 (LiPo)
battery. The battery is automatically charged while the x-IMU is connected to a USB host. See the battery
and charging section for more information.
3.8
Auxiliary port header
The auxiliary port that can be configured to one of many modes. The auxiliary port connector is a 2 × 6,
2.54 mm pitch female header socket. The socket pins include: ground, external power input, 3.3 V output,
hard reset and 8 I/O lines. See the auxiliary port section for more information.
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
11
section and Bluetooth section 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 4: 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 for more information 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 the x-IMU using the Write all registers, Write this register only and Write
all registers in this group only options in the action menu.
12
Figure 5: 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 6: 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 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 7: 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 8: x-IMU GUI view sensor data tab page
The data from individual sensors is displayed in real-time data graphs as seen in Figure 8. The controls
bar at the bottom of each graph allow the view and scaling to be adjusted.
Figure 9: 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 10. 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 algorithm tare command.
15
Figure 10: x-IMU GUI 3D cuboid window
4.1.6
Tab page: Auxiliary port
The auxiliary port tab page contains buttons to show or hide individual control windows for the different
modes of the auxiliary port.
Figure 11: 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 12. 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 12: 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 13: 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 14.
17
Figure 14: 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 15: 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 16.
18
Figure 16: 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 hard-iron
interferences affecting the x-IMU. It is necessary to re-calibrate hard-iron parameters whenever the x-IMU’s
magnetic characteristics 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 magnetometer hard-iron calibration section for more information.
Figure 17: x-IMU GUI hard-iron calibration tab page
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
19
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 and to a
file on the SD card. The USB and Bluetooth connections are also be used to send commands, read/write
registers and control the auxiliary port outputs from the host software application. 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 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 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 due to the sleep timer or low battery voltage detection 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. 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.
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 18.
20
Figure 18: 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 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 rates so that the amount of 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 will
be generated. As this error is sent immediately after the buffer has overrun, the error will be successfully
transmitted. This error can be avoided by reducing the data output rates.
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 will be generated.
6
Bluetooth
The x-IMU streams all communication data simultaneously and identically via USB, Bluetooth and to a
file on the SD card. The USB and Bluetooth connections are also be used to send commands, read/write
registers and control the auxiliary port outputs from the host software application. 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
drivers. Once paired with a Bluetooth host, 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 of the x-IMU GUI. The Bluetooth connection
21
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. The Bluetooth radio can be completely disabled by the user via
the Bluetooth power register to reduce power consumption.
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 power enabled so that the Bluetooth LED is flashing. 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-IMU-ABCD” where the characters “ABCD” are the device ID of the x-IMU. For
example, Figure 19 shows how this is done in Windows 7 having right clicked the Bluetooth icon the task
bar.
Figure 19: 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 20 shows this being done
in Windows 7.
22
Figure 20: 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 21 shows how this is done in Windows 7 having right clicked the
x-IMU Bluetooth device icon.
Figure 21: 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 1.
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 1: Bluetooth LED states
6.3
Bluetooth bandwidth
It is possible for the user to define data output rates so that the amount of 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 will be generated. As this error is sent immediately after the buffer has overrun, the error will
be successfully transmitted. This error can be avoided by reducing the data output rates.
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 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. The use of lower data output rates 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.
6.5
Connecting to multiple x-IMUs via Bluetooth
A single Bluetooth host/master (e.g. Bluetooth dongle) can connect to up to 7 Bluetooth slaves (e.g. xIMUs) simultaneously. Each x-IMU is assigned a separate serial port name and operates independently.
However, the bandwidth will be limited to that of the single Bluetooth host.
7
SD card
The x-IMU streams all communication data simultaneously and identically via USB, Bluetooth 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. 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 x-IMU MATLAB Library includes all the tools required to import, structure and plot
x-IMU data.
24
The x-IMU supports standard SD cards and SDHC cards1 . 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.
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. 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 may also edit this value to any number by writing to the register. 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.
Files 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 be lost. The file is automatically closed when the x-IMU is
reset or enters sleep mode. Users wishing to frequently remove the SD card may wish to have the command
button 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 infrequently, high
data output rates will mean the LED will flash rapidly. In this way the SD card LED provides an indication
of SD card bandwidth performance.
7.3
SD card bandwidth
It is possible for the user to define data output rates so that the amount of 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 will be generated. This
error packet is sent immediately after the buffer has overrun so that the error will always be successfully
logged to the SD card. This error can be avoided by reducing the data output rates. The SD card LED may
be used to provides an indication of SD card bandwidth performance while access to errors is not available.
The effective bandwidth of SD card is varies between different SD card brands 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 on whether an SD card is inserted or not. These distortions are removed from
measurements through hard-iron calibration. Each x-IMU is calibrated and supplied with a dummy SD card
that may be used to ensure constant SD card socket magnetic characteristics.
1 The x-IMU has known compatibility issues with counterfeit SDHC cards. It is recommended that you only use genuine
products from a reputable brand.
25
8
Command button
The x-IMU features a configurable command button that allows the execution of commands while the xIMU is operating as a standalone device. The command button modes are detailed below. Only reset and
sleep/wake up modes remain active while the x-IMU is in sleep mode. The command button is also used to
confirm the factory reset command.
Command button modes
• Disabled
• Reset command
• Sleep/wake up
• Algorithm initialise command
• Algorithm tare command
• Algorithm initialise then tare command
9
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 via the Date/Time tab page.
The real-time clock and calendar data is provided by the x-IMU in the write date/time data packets.
The data output rate of these packets may be set to disabled, 1 Hz, 2 Hz, 4 Hz, 8 Hz, 16 Hz, 32 Hz, 64 Hz,
128 Hz, 256 Hz or 512 Hz in the date/time data rate register. A single date/time data packet is always sent
on device reset regardless of user settings so that the date and time are always available as the first packet
written to the SD card. 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.
9.1
Maintaining clock power
The real-time clock and calendar requires 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.
10
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.
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 set to disabled, 1 Hz, 2 Hz, 4 Hz, 8 Hz, 16 Hz, 32
Hz, 64 Hz, 128 Hz, 256 Hz or 512 Hz in the battery and thermometer data output rate and inertial/magnetic
data output rate registers.
26
10.1
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 and the x-IMU is powered from an external supply via the auxiliary port the battery voltmeter will
measure the voltage of the external supply.
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 and bias
registers.
v=
10.2
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-3000 datasheet for further information on the thermometer’s characteristics.
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 thermometer sensitivity and bias registers.
τ=
10.3
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 ±250◦ /s, ±500◦ /s, ±1000◦ /s or ±2000◦ /s selected in the gyroscope full-scale
register. See the IMU-3000 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.
27
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 , bias temperature sensitivities
fx , fy and fz , and bias drift compensation parameters αx , αy and αz provided by the IMU and AHRS
algorithms. The calibrated measurements are described by equation (3). Parameters sgx , sgy , sgz , bgx , bgy ,
bgz , fx , fy and fz are defined in the separate gyroscope calibration parameters registers. The sensitivities
and biases will be different for each full-scale measurement range.
  
−1     
−1 
  
gx
sgx
0
0
g̃x
bgx
fx 0 0
τ − 25
αx


gy  =  0 sgy
0  g̃y  − bgy  −  0 fy 0  τ − 25 − αy 
(3)
gz
0
0 sgz
g̃z
bgz
0 0 fz
τ − 25
αz
10.4
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
accelerometer 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. 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.
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 parameters registers. The sensitivities and biases
will be different for each full-scale measurement range.
  
ax
sax
ay  =  0
az
0
10.5
0
say
0
−1    
ãx
bax
0
0  ãy  − bay 
baz
saz
ãz
(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. 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 of -4096 will be provided when the measurement saturates in either direction.
28
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 parameters registers. The sensitivities and biases will be different for each full-scale measurement
range.
  
mx
smx
 my  =  0
mz
0
11
0
smy
0
−1   
  
0
m̃x
bmx
hx
0  m̃y  − bmy  − hy 
smz
m̃z
bmz
hz
(5)
Sensor calibration
The sensitivity and bias of the gyroscope, accelerometer and magnetometer are calibrated at the factory
using precision equipment. The user is recommended not to attempt to recalibrate these parameters. Please
contact x-io Technologies for more information.
11.0.1
Magnetometer hard-iron calibration
Magnetic elements fixed to the x-IMU such as metal screws, the battery or electronics components may
introduce hard-iron biases to magnetometer measurements. These biases must be compensated for through
hard-iron calibration. Uncalibrated hard-iron distortions will cause significant errors in the x-IMUs estimated
heading. Each x-IMU is fully calibrated at the factory. However, many applications may alter the hard-iron
characteristics and so require the user perform hard-iron calibration using the x-IMU GUI.
Before performing hard-iron calibration, the x-IMU registers must be set to output calibrated inertial and
magnetic data packets at 256 Hz. Calibration can then be performed by following steps 1, 2 and 3 indicated
on the Hard-Iron Calibration tab in the x-IMU GUI. Step 2 requires the user to collect a calibration dataset
where the x-IMU (and any ferromagnetic elements it is fixed to) are rotated through as many and as different
orientations as possible far away from other magnetic distortions. The x-IMU should held far from all objects
in a room for the duration of the dataset collection.
Figure 22: x-IMU GUI hard-iron calibration tab page
29
The SD card socket will have different magnetic characteristics depending if an SD card is secured in
the socket or not. Each x-IMU is calibrated at the factory with a dummy SD card inserted to reduce the
need for user calibration.
12
IMU and AHRS algorithms
The x-IMU features an sensor fusion algorithm that use the on-board sensors to compute a measurement of
orientation relative to the Earth. The algorithm can operate in either IMU or AHRS mode. IMU mode uses
only the gyroscope and accelerometer. In this mode, the head component of the measurement orientation
will slowly drift over time. However, magnetic distortions or interference will have no effect on the sensor as
the magnetometer is not used. IMU mode is of use in application that require only an accurate measurement
of the pitch and roll components of an orientation or do not need an absolute measurement of heading.
AHRS mode uses all of the on-board sensors so that the measurement of orientation is free from drift.
The sensor fusion algorithm has a number of associated commands. The Initialise command will cause
the algorithm to reinitialise so that the proportional gain (Kp) governing how quickly the algorithm output
converges to the accelerometer and magnetometer measurements, starts at a high value and is ramped down
to the operating value. The Tare command will save the current orientation so that all algorithm becomes
relative to this datum. A Tare operation is saved to non-volatile memory and so will remain in effect even
if the device is reset. A Clear Tare command will cancel this operation and clear the memory.
13
Power management
The x-IMU may be powered via USB, an external power supply or a single cell lithium polymer (LiPo)
battery cell which will be charged automatically while the x-IMU is connected to a USB port.
13.1
External supply
The x-IMU may be powered by a 3.5 to 6.3 V external supply via the auxiliary port. The supply should be
connected to the GND and EXT pins of the auxiliary port. This power supply is only enabled while the
power switch is in the off position. In this situation, the battery voltmeter will measure the voltage of the
external supply.
13.2
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.
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 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.
13.3
Sleep mode
In sleep mode, the x-IMU remains powered but all on-board components are shutdown. This allows the
device to be powered down without removing power from essential components; for example, the real time
clock and calendar. The green status LED 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.
30
Sleep mode enable sources:
• Command button in sleep/wake mode
• Sleep command via USB, Bluetooth or UART
• Low battery voltage detection
• Sleep timer
Wake up sources
• Command button in sleep/wake mode
• Motion trigger wake up
13.4
Low battery voltage detection
The calibrated battery voltmeter is used to trigger sleep mode when the battery voltage falls below a specific
level defined in the battery shutdown voltage register. 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 with a
low battery error. 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 are not lost. The low battery voltage detection is disabled while
USB is connected.
13.5
Sleep timer
The sleep timer will trigger sleep mode after the period of time defined in the sleep timer register 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 value of 0 seconds. The
sleep timer is disabled while USB is connected.
Sleep timer reset sources
• reset sleep timer command
• Motion trigger wake up
13.6
Motion triggered wake up
The motion trigger wake up is enabled via the motion trigger wake up register 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 and thus postpone sleep while motion persists.
For example, if the sleep timer is set to 20 seconds and there is motion is detected at least once every 20
seconds the motion trigger wake up will prevent the sleep timer from expiring and the x-IMU will not enter
sleep mode. However, if no motion is detected for 20 seconds the x-IMU will enter sleep mode. If motion is
then detected while in sleep mode, the x-IMU will wake up.
13.7
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 optimise 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.
31
Tips
• Set data output rates of unused data to disabled.
• Use the minimum data output rates required by application.
• Set algorithm mode to disabled if the IMU and AHRS algorithms are not required.
• Disable Bluetooth power if not Bluetooth is unused.
• Use the sleep timer and motion trigger wake up to automatically enter sleep mode during periods of
inactivity.
14
Auxiliary port
The x-IMU features an auxiliary port that can be configured to one of many modes. The auxiliary port
connector is a 2 × 6, 2.54 mm pitch female header socket. The socket pins include: ground, an external
power input, 3.3 V power output, hard reset and 8 I/O channels. The pins are annotated in Figure 23 and
summarised in table 2.
Figure 23: Auxiliary port pins
32
Pin
GND
EXT
RST
3V3
AX0 to AX7
Description
Common ground
External power input
Hard reset (active low)
3.3 V power output
I/O channels
Min/Max
N/A
3.5 V to 6.3 V
0 V to 3.3 V
100 mA
0 V to 3.3 V, 4 mA source/sink
Table 2: Auxiliary port pins
The mode of the auxiliary port is set by the auxiliary port mode register. If the x-IMU receives a packet
associated with a specific axillary port mode while the axillary port is not in that mode the x-IMU will
respond with an incorrect auxiliary port mode error. For example, this will happen if the x-IMU receives a
digital I/O packet to change a digital output channel while the axillary port mode is disabled.
Auxiliary port modes
• Disabled
• Digital I/O
• Analogue input
• PWM output
• ADXL345 bus
• UART
14.1
Disabled
When disabled, all auxiliary port channels are configured as high-impedance inputs. The auxiliary port in
disabled when the x-IMU is in sleep mode. Table 3 summarises the auxiliary port pin assignments when
disabled.
Pin
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
I/O
Input
Input
Input
Input
Input
Input
Input
Input
Description
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Unused
Table 3: Auxiliary port pin assignments when disabled
14.2
Digital I/O mode
In digital I/O mode each pin of the auxiliary port functions as either a digital input or output. The direction
of each pin is defined within the digital I/O direction register. Digital input data is provided in either the
digital I/O data packets received from the x-IMU. The data output rate of these packets may be set to on
change only, 1 Hz, 2 Hz, 4 Hz, 8 Hz, 16 Hz, 32 Hz, 64 Hz, 128 Hz, 256 Hz or 512 Hz in the digital I/O data
output rate register. Digital outputs are set by sending a digital I/O data packet to the x-IMU.
33
Pin
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
I/O
Input/Output
Input/Output
Input/Output
Input/Output
Input/Output
Input/Output
Input/Output
Input/Output
Description
Digital I/O
Digital I/O
Digital I/O
Digital I/O
Digital I/O
Digital I/O
Digital I/O
Digital I/O
Table 4: Auxiliary port pin assignments in digital I/O mode
14.3
Analogue input
In analogue input mode all 8 pins of the auxiliary port function as analogue inputs. Each analogue input
channel sas a 12-bit resolution and a range of 0 V to 3.3 V. The user may access analogue input data as
either raw un-calibrated ADC results or as calibrated units by specifying the mode in the analogue input data
mode register. Analogue input data is provided in either the raw analogue input data or calibrated analogue
input data packets. The data output rate of these packets may be set to disabled, 1 Hz, 2 Hz, 4 Hz, 8 Hz, 16
Hz, 32 Hz, 64 Hz, 128 Hz, 256 Hz or 512 Hz in the analogue input data output rate register.
Raw ADC data: In raw data mode the analogue input data is the ADC integer value between 0 and 4096
corresponding to a voltage between 0 V and 3.3 V. This data is provided in the raw analogue input data
packets.
Calibrated data: In calibrated data mode the analogue data is the calibrated measurement in Volts.
This data is provided in the calibrate analogue data packets. The calibrated measurement an is calculated
from the raw ADC measurements ṽ according to a sensitivity san and bias ban as described by equation (6).
Parameters san and ban are defined in the analogue input sensitivity and bias registers.
an =
Pin
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
I/O
Input
Input
Input
Input
Input
Input
Input
Input
1
san
(a˜n − ban )
Description
Analogue input
Analogue input
Analogue input
Analogue input
Analogue input
Analogue input
Analogue input
Analogue input
channel
channel
channel
channel
channel
channel
channel
channel
(6)
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
Table 5: Auxiliary port pin assignments for analogue input mode
14.4
PWM output mode
In PWM output mode four pins of the auxiliary port function as digital PWM outputs. Unused pins are
configured as high-impedance inputs. The PWM frequency may be set from 3 Hz to 65,535 Hz in the PWM
frequency register. The duty cycle of each of the four PWM output channels are set by sending a PWM data
packet to the x-IMU. The x-IMU echo back the packet as confirmation after the duty cycles have been set.
34
Pin
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
I/O
Output
Input
Output
Input
Output
Input
Output
Input
Description
PWM output
Unused
PWM output
Unused
PWM output
Unused
PWM output
Unused
channel AX0
channel AX2
channel AX4
channel AX6
Table 6: Auxiliary port pin assignments for PWM output mode
14.5
ADXL345 bus mode
This section is currently unavailable but can be updated on request.
Pin
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
I/O
Output
Input
Output
Input
Output
Input
Output
Input
Description
ADXL345 A SPI CS
SPI CLK
ADXL345 B SPI CS
SPI DIN
ADXL345 C SPI CS
SPI DOUT
ADXL345 D SPI CS
Power enable
Table 7: Auxiliary port pin assignments for ADXL345 bus mode
14.6
UART mode
In UART mode four pins of the auxiliary port function as a configurable UART with hardware flow control.
The Bluetooth power will automatically be disabled when UART mode is enabled. Commination via the
auxiliary port UART is identical to that via the virtual serial ports enabled by the Bluetooth or USB
connection. The UART baud rate may be set to 2400, 4800, 7200, 9600, 14400, 19200, 38400, 57600, 115200,
230400, 460800 or 921600 baud in the UART baud rate register. The UART hardware flow control can be
enabled or disabled in the UART hardware flow control register.
Pin
AX0
AX1
AX2
AX3
AX4
AX5
AX6
AX7
I/O
Output
Input
Output
Input
Output
Input
Output
Input
Description
TX
Unused
RX
Unused
CTS
Unused
RTS
Unused
Table 8: Auxiliary port pin assignments for UART mode
14.6.1
UART bandwidth
It is possible for the user to define data output rates so that the amount of data being generated by the
x-IMU exceeds the bandwidth of a communication channel. If the UART bandwidth is exceed, the UART
transmit buffer will overrun and some data will be lost. When this happens a UART transmit buffer overrun
error will be generated. As this error is sent immediately after the buffer has overrun, the error will be
35
successfully transmitted. This error can be avoided by reducing the data output rates or increasing the
UART baud rate register.
All data sent to the x-IMU via UART is buffered in the UART 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
UART 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 UART receive buffer overrun error will be generated.
15
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. The API is source code is written in C# and well commented
so that porting the API (or aspects of) to another language should be a straight forward exercise.
16
Commands
Commands are executed by either sending a command packet to the x-IMU USB or Bluetooth or by pressing
the command button which may be configured to execute a specific command. Commands are sent using
the x-IMU GUI via the commands tab page. Once a command has been executed, the x-IMU will echo
the command packet back to the host as confirmation. As all communication from the x-IMU to the host
computer is logged to the SD card, 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.
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.
16.1
16.1.1
Individual commands
Null command
Command code:
Description:
16.1.2
Factory reset
Command code:
Description:
16.1.3
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.
0x0001
A factory reset command code is used to reset the x-IMU to its original state prior to
factory calibration so that all registers return to their default values. The user must press
the command button within 3 seconds of sending a factory reset command in order to
confirm the request else the x-IMU will respond with a factory reset failed error. The
x-IMU requires several seconds to reconfigure on-board components during the execution
of a factory reset.
Reset
Command code:
Description:
0x0002
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 to
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.
36
16.1.4
Sleep
Command code:
Description:
16.1.5
Reset sleep timer
Command code:
Description:
16.1.6
0x0005
The sample gyroscope axis at 200 dps command is used to calibrate the gyroscope sensitivity parameters. This command should be sent while the x-IMU rotating at either
+200◦ /s or −200◦ /s around either its x, y or z axis. The x-IMU will automatically detect
the axis and direction of rotation. The mean gyroscope output will then be measured
over approximately 8 seconds before being stored to the corresponding register. A calculate gyroscope sensitivity command will then be executed. The execution of the sample
gyroscope axis at 200 dps command will be aborted if a gyroscope axis is detected as
not being at approximately ±200◦ /s and a gyroscope axis not at 200 dps error will be
generated. See the gyroscope sensitivity calibration section for more information.
Calculate gyroscope sensitivity
Command code:
Description:
16.1.8
0x0004
The reset sleep timer command will reset the sleep timer 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 axis at 200 dps
Command code:
Description:
16.1.7
0x0003
A sleep command will put the device into sleep mode. 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 command button configured in sleep/wake mode or using the motion
triggered wake up functionality.
0x0006
The calculate gyroscope sensitivity command is used to execute the on-board gyroscope
sensitivity calibration algorithm. The algorithm uses the sampled gyroscope bias register
values previously obtained by the sample gyroscope axis at 200 dps command to update
the gyroscope sensitivity parameters registers. See the gyroscope sensitivity calibration
section for more information.
Sample gyroscope bias at temperature 1
Command code:
Description:
0x0007
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 the sampled temperature 1 registers and then trigger a calculate gyroscope
bias parameters command. The execution of the sample gyroscope bias at temperature
1 command will be aborted if the gyroscope is detected as not being stationary and
a gyroscope not stationary error will be generated. See the gyroscope bias calibration
section for more information.
37
16.1.9
Sample gyroscope bias at temperature 2
Command code:
Description:
16.1.10
Calculate gyroscope bias parameters
Command code:
Description:
16.1.11
0x0009
The calculate gyroscope bias parameters command is used to execute the on-board gyroscope bias calibration algorithm. The algorithm uses the sampled gyroscope bias register
values previously sampled by the sample gyroscope bias at temperature 1 and sample gyroscope bias at temperature 2 commands to calculate the gyroscope bias parameters and
update the gyroscope bias parameters registers. See the gyroscope bias calibration section for more information.
Sample accelerometer axis at 1 g
Command code:
Description:
16.1.12
0x0008
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 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 the sampled temperature 2 registers and then trigger a calculate gyroscope
bias parameters command. The execution of the sample gyroscope bias at temperature
2 command will be aborted if the gyroscope is detected as not being stationary and
a gyroscope not stationary error will be generated. See the gyroscope bias calibration
section for more information.
0x000A
The sample accelerometer axis at 1 g command is used to calibrate the accelerometer bias
and sensitivity parameters. This command should be sent while the x-IMU stationary
and orientated with either its x, y or z axis at either +1 g or −1 g. The x-IMU will
automatically detect the axis and direction of gravity. The mean accelerometer output
will then be measured over approximately 8 seconds before being stored to the sampled
accelerometer axis registers. A calculate accelerometer bias and sensitivity command will
then be executed. The execution of the sample accelerometer axis at 1 g command will
be aborted if a accelerometer axis is detected as not being at approximately ±1 g and a
accelerometer axis not at 1 g error will be generated. See the accelerometer calibration
section for more information.
Calculate accelerometer bias and sensitivity
Command code:
Description:
0x000B
The calculate accelerometer bias and sensitivity command is used to execute the on-board
accelerometer bias and sensitivity calibration algorithm. The algorithm uses the sampled
accelerometer axes register values previously obtained by the sample accelerometer axis
at 1 g command to calculate the accelerometer bias and sensitivity and update the
accelerometer calibration parameters registers. See the accelerometer calibration section
for more information.
38
16.1.13
Measure magnetometer bias and sensitivity
Command code:
Description:
16.1.14
Algorithm initialise
Command code:
Description:
16.1.15
0x000F
The algorithm clear tare command is used to clear the tare quaternion registers and
return the datum orientation to alignment with the Earth coordinate frame. See the
IMU and AHRS algorithms section for more information.
Algorithm initialise then tare
Command code:
Description:
17
0x000E
The algorithm tare command is used to set the algorithm datum orientation and store
the reference quaternion to the tare quaternion registers. These registers may be then
be cleared using the algorithm clear tare command. See the IMU and AHRS algorithms
section for more information.
Algorithm clear tare
Command code:
Description:
16.1.17
0x000D
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 and AHRS
algorithms section for more information.
Algorithm tare
Command code:
Description:
16.1.16
0x000C
The measure magnetometer bias and sensitivity command is used to run an on-board
magnetometer calibration algorithm. The x-IMU uses 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
and bias registers and then automatically updated. This command should be used each
time the magnetometer full-scale range is changed. The execution of this command will
be aborted if a magnetometer axis saturates and a magnetometer saturation error will
be generated. See the magnetometer calibration section for more information.
0x0010
The algorithm initialise then tare command will perform an algorithm initialise and then
algorithm tare once the initialisation is complete. See the IMU and AHRS algorithms
section for more information.
Errors
Error are sent by the x-IMU to warn the user or host software of any internal errors that have occurred.
Error data is sent in error packets. The x-IMU GUI will display these errors in message boxes for user
acknowledgment. As all data packets generated by the x-IMU are logged to the SD card, the SD card will
contain a record off errors.
17.1
17.1.1
Individual errors
No error
Error code:
Description:
0x0000
No error. This error code is used within internal processes and will never appear to the
user.
39
17.1.2
Factory reset failed
Error code:
Description:
17.1.3
Low battery
Error code:
Description:
17.1.4
0x0004
A USB 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.
The x-IMU 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. See the USB
bandwidth section for more information.
Bluetooth receive buffer overrun
Error code:
Description:
17.1.7
0x0003
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. See the USB bandwidth section for more information.
USB transmit buffer overrun
Error code:
Description:
17.1.6
0x0002
A low battery error is sent when the low battery voltage detection detects that the battery
voltage has fallen below the specific level defined in the battery shutdown voltage register.
This message is sent immediately before the x-IMU enters sleep mode. See the low battery
voltage detection section for more information.
USB receive buffer overrun
Error code:
Description:
17.1.5
0x0001
A factory reset failed error is sent if the user fails to press the command button within 3
seconds of sending a factory reset command and the execution of the command was aborted.
0x0005
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.
Bluetooth transmit buffer overrun
Error code:
Description:
0x0006
A Bluetooth 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 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.
40
17.1.8
SD card write buffer overrun
Error code:
Description:
17.1.9
Too few bytes in packet
Error code:
Description:
17.1.10
0x000C
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 to users developing
their own communication software and not using the x-IMU API or x-IMU GUI.
Invalid register address
Error code:
Description:
17.1.15
0x000B
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 to 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:
17.1.14
0x000A
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 to users developing their
own communication software and not using the x-IMU API or x-IMU GUI.
Unknown packet header
Error code:
Description:
17.1.13
0x0009
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 to users developing their own
communication software and not using the x-IMU API or x-IMU GUI.
Invalid checksum
Error code:
Description:
17.1.12
0x0008
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 to 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:
17.1.11
0x0007
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 indicates SD card activity, if this LED behaviour
approaches that of being solidly on then it is likely that the this error is occurring.
0x000D
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 to users developing their own communication software and not using the x-IMU API or x-IMU GUI.
Register read-only
Error code:
Description:
0x000E
A register read-only error will be sent if the write register packet represents an attempt to
write a read-only register.
41
17.1.16
Invalid register value
Error code:
Description:
17.1.17
Invalid command
Error code:
Description:
17.1.18
0x0013
A accelerometer axis not at 1g error will be sent if an axis is detected as not being at
approximately ±1 g during the execution of a sample accelerometer axis at 1 g command
and the execution of the command was aborted. See the accelerometer calibration section
for more information.
Magnetometer saturation
Error code:
Description:
17.1.22
0x0012
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 commands and the execution of
the command was aborted. See the gyroscope bias calibration section for more information.
Accelerometer axis not at 1g
Error code:
Description:
17.1.21
0x0011
A gyroscope axis not at 200 dps error will be sent if an axis is detected as not being at
approximately ±200◦ /s during the execution of a sample gyroscope axis at 200 dps command
and the execution of the command was aborted. See the gyroscope sensitivity calibration
section for more information.
Gyroscope not stationary
Error code:
Description:
17.1.20
0x0010
An invalid command error will be sent if the command code within the command packet is
not valid. This error is only relevant to users developing their own communication software
and not using the x-IMU API or x-IMU GUI.
Gyroscope axis not at 200 dps
Error code:
Description:
17.1.19
0x000F
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 to users developing their
own communication software and not using the x-IMU API or x-IMU GUI.
0x0014
A magnetometer saturation error will be sent if the measurements taken during the execution of the measure magnetometer bias and sensitivity command 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:
0x0015
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 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 for more information.
42
17.1.23
UART receive buffer overrun
Error code:
Description:
17.1.24
UART transmit buffer overrun
Error code:
Description:
18
0x0016
A UART receive buffer over error will be sent if the UART 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. See the UART bandwidth section for more
information.
0x0017
A UART transmit buffer overrun error will be sent if the UART 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 UART 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. See the UART bandwidth section for more information.
Registers
All x-IMU settings are stored within a bank of registers in non-volatile flash memory and loaded each time
the x-IMU starts up. Each register has a 16-bit address and 16-bit value. These values may be viewed,
modified, read, written and backed up to file using the x-IMU GUI via the Registers tab page.
18.1
Reading registers
Any register may be read by sending a read register packet containing register address to be read. The xIMU will respond with a register write packet containing the register address and value. If the read register
packet contains an invalid register address then the x-IMU will respond with an invalid register address
error. The x-IMU will automatically send all register values on start up so that settings are stored as the
first packets written to the SD card.
18.2
Writing registers
A register 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 confirmed value. If the value written is different from the current register value then the x-IMU
will save the new value to the flash memory and perform any required actions (e.g. reconfigure the IMU-3000
for a different gyroscope full-scale range. If the write register packet contains an invalid register address then
the x-IMU will respond with an invalid register address error. If the register write packet contains a register
value that is invalid for the specified address then the x-IMU will respond with an invalid register value
error. If a register write packet contains a register address that is read-only then the x-IMU will respond
with a register read-only error.
18.3
18.3.1
Individual registers
Firmware version major number
Address:
Value:
Description:
0x0000
0 to 65534. Read-only.
The major number of the current firmware version loaded on the x-IMU.
43
18.3.2
Firmware version minor number
Address:
Value:
Description:
18.3.3
Device ID
Address:
Value:
Description:
18.3.4
Description:
0x0005
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the battery ADC in lsb. See parameter bv in the battery voltmeter
section. The typical calibrated value is 0 lsb.
Thermometer sensitivity
Address:
Value:
Description:
18.3.8
0x0004
Q11.5 signed fixed point value between −1024 and +1023.969.
Calibrated sensitivity of the battery ADC in lsb/V. See parameter sv in the battery voltmeter section. The typical calibrated value is 621 lsb/V.
Battery voltmeter bias
Address:
Value:
Description:
18.3.7
0x0003
0x0000 = Disabled
0x0001 = Reset command
0x0002 = Sleep/wake up
0x0003 = Algorithm initialise command
0x0004 = Algorithm tare command
0x0005 = Algorithm initialise then tare command
The command to be executed when the command button is pressed. See the commands
section for more information and details of individual commands.
Battery voltmeter sensitivity
Address:
Value:
Description:
18.3.6
0x0002
0x0000 to 0xFFFF. Read-only.
The 4 digit hexadecimal ID of the x-IMU taken as the last 2 bytes of the Bluetooth MAC
address.
Button mode
Address:
Value:
18.3.5
0x0001
0 to 65534. Read-only.
The minor number of the current firmware version loaded on the x-IMU.
0x0006
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the thermometer in lsb/◦ C. See parameter sτ in the thermometer
section. The typical calibrated value is provided as 280 lsb/◦ C in the IMU-3000 datasheet.
Thermometer bias
Address:
Value:
Description:
0x0007
Q16.0 signed fixed point value between −32768 and +32677.
Calibrated bias of the thermometer in lsb. See parameter bτ in the thermometer section.
The typical calibrated value is provided as −23, 000 lsb in the IMU-3000 datasheet.
44
18.3.9
Gyroscope full-scale
Address:
Value:
Description:
18.3.10
Gyroscope x-axis sensitivity
Address:
Value:
Description:
18.3.11
0x000B
Q9.7 signed fixed point value between −256 and +255.9922.
Calibrated sensitivity of the gyroscope z-axis in lsb/◦ /s. See parameter sgz in the gyroscope section. The value of the parameter can be accurately evaluated through calibration
using the calculate gyroscope sensitivity command. See the gyroscope sensitivity calibration
section for more information.
Gyroscope sampled x-axis at +200 dps
Address:
Value:
Description:
18.3.14
0x000A
Q9.7 signed fixed point value between −256 and +255.9922.
Calibrated sensitivity of the gyroscope y-axis in lsb/◦ /s. See parameter sgy in the gyroscope section. The value of the parameter can be accurately evaluated through calibration
using the calculate gyroscope sensitivity command. See the gyroscope sensitivity calibration
section for more information.
Gyroscope z-axis sensitivity
Address:
Value:
Description:
18.3.13
0x0009
Q9.7 signed fixed point value between −256 and +255.9922.
Calibrated sensitivity of the gyroscope x-axis in lsb/◦ /s. See parameter sgx in the gyroscope section. The value of the parameter can be accurately evaluated through calibration
using the calculate gyroscope sensitivity command. See the gyroscope sensitivity calibration
section for more information.
Gyroscope y-axis sensitivity
Address:
Value:
Description:
18.3.12
0x0008
0x0000 = ±250◦ /s
0x0001 = ±500◦ /s
0x0002 = ±1000◦ /s
0x0003 = ±2000◦ /s
Full-scale range of the gyroscope. Each full-scale range will have different associated sensitivity and bias values. The gyroscope should therefore be recalibrated when the full-scale
range is changed. See the gyroscope calibration section for more information.
0x000C
Q16.0 signed fixed point value between −32, 768 and +32, 767.
Sampled gyroscope x-axis output in lsb when rotating at +200◦ /s, obtained through the
execution of the sample gyroscope axis at 200 dps command. This value is used by the
gyroscope sensitivity calibration algorithm to calculate the gyroscope x-axis sensitivity. See
the gyroscope sensitivity calibration section for more information.
Gyroscope sampled y-axis at +200 dps
Address:
Value:
Description:
0x000D
Q16.0 signed fixed point value between −32, 768 and +32, 767.
Sampled gyroscope y-axis output in lsb when rotating at +200◦ /s, obtained through the
execution of the sample gyroscope axis at 200 dps command. This value is used by the
gyroscope sensitivity calibration algorithm to calculate the gyroscope y-axis sensitivity. See
the gyroscope sensitivity calibration section for more information.
45
18.3.15
Gyroscope sampled z-axis at +200 dps
Address:
Value:
Description:
18.3.16
Gyroscope sampled x-axis at -200 dps
Address:
Value:
Description:
18.3.17
0x0011
Q16.0 signed fixed point value between −32, 768 and +32, 767.
Sampled gyroscope z-axis output in lsb when rotating at −200◦ /s, obtained through the
execution of the sample gyroscope axis at 200 dps command. This value is used by the
gyroscope sensitivity calibration algorithm to calculate the gyroscope z-axis sensitivity. See
the gyroscope sensitivity calibration section for more information.
Gyroscope x-axis bias at 25 degrees Celsius
Address:
Value:
Description:
18.3.20
0x0010
Q16.0 signed fixed point value between −32, 768 and +32, 767.
Sampled gyroscope y-axis output in lsb when rotating at −200◦ /s, obtained through the
execution of the sample gyroscope axis at 200 dps command. This value is used by the
gyroscope sensitivity calibration algorithm to calculate the gyroscope y-axis sensitivity. See
the gyroscope sensitivity calibration section for more information.
Gyroscope sampled z-axis at -200 dps
Address:
Value:
Description:
18.3.19
0x000F
Q16.0 signed fixed point value between −32, 768 and +32, 767.
Sampled gyroscope x-axis output in lsb when rotating at −200◦ /s, obtained through the
execution of the sample gyroscope axis at 200 dps command. This value is used by the
gyroscope sensitivity calibration algorithm to calculate the gyroscope x-axis sensitivity. See
the gyroscope sensitivity calibration section for more information.
Gyroscope sampled y-axis at -200 dps
Address:
Value:
Description:
18.3.18
0x000E
Q16.0 signed fixed point value between −32, 768 and +32, 767.
Sampled gyroscope z-axis output in lsb when rotating at +200◦ /s, obtained through the
execution of the sample gyroscope axis at 200 dps command. This value is used by the
gyroscope sensitivity calibration algorithm to calculate the gyroscope z-axis sensitivity. See
the gyroscope sensitivity calibration section for more information.
0x0012
Q13.3 signed fixed point value between −4096 and +4095.875.
Calibrated bias of the gyroscope x-axis at 25 ◦ C in lsb. See parameter bgx in the gyroscope
section. The value of the parameter can be accurately evaluated through calibration using the Calculate gyroscope bias parameters command. See the gyroscope bias calibration
section for more information.
Gyroscope y-axis bias at 25 degrees Celsius
Address:
Value:
Description:
0x0013
Q13.3 signed fixed point value between −4096 and +4095.875.
Calibrated bias of the gyroscope y-axis at 25 ◦ C in lsb. See parameter bgy in the gyroscope
section. The value of the parameter can be accurately evaluated through calibration using the Calculate gyroscope bias parameters command. See the gyroscope bias calibration
section for more information.
46
18.3.21
Gyroscope z-axis bias at 25 degrees Celsius
Address:
Value:
Description:
18.3.22
Gyroscope x-axis bias temperature sensitivity
Address:
Value:
Description:
18.3.23
0x0017
Q5.11 signed fixed point value between −16 and +15.99951.
Calibrated bias temperature sensitivity of the gyroscope z-axis in lsb/◦ C. See parameter fz
in the gyroscope section. The value of the parameter can be accurately evaluated through
calibration using the Calculate gyroscope bias parameters command. See the gyroscope bias
calibration section for more information.
Gyroscope sample 1 - Temperature
Address:
Value:
Description:
18.3.26
0x0016
Q5.11 signed fixed point value between −16 and +15.99951.
Calibrated bias temperature sensitivity of the gyroscope y-axis in lsb/◦ C. See parameter fy
in the gyroscope section. The value of the parameter can be accurately evaluated through
calibration using the Calculate gyroscope bias parameters command. See the gyroscope bias
calibration section for more information.
Gyroscope z-axis bias temperature sensitivity
Address:
Value:
Description:
18.3.25
0x0015
Q5.11 signed fixed point value between −16 and +15.99951.
Calibrated bias temperature sensitivity of the gyroscope x-axis in lsb/◦ C. See parameter fx
in the gyroscope section. The value of the parameter can be accurately evaluated through
calibration using the Calculate gyroscope bias parameters command. See the gyroscope bias
calibration section for more information.
Gyroscope y-axis bias temperature sensitivity
Address:
Value:
Description:
18.3.24
0x0014
Q13.3 signed fixed point value between −4096 and +4095.875.
Calibrated bias of the gyroscope z-axis at 25 ◦ C in lsb. See parameter bgz in the gyroscope
section. The value of the parameter can be accurately evaluated through calibration using the Calculate gyroscope bias parameters command. See the gyroscope bias calibration
section for more information.
0x0018
Q8.8 signed fixed point value between −128 and +127.9961.
Sampled temperature of gyroscope in ◦ C, obtained through the execution of the Sample
gyroscope bias at temperature 1 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
Gyroscope sample 1 - x-axis bias
Address:
Value:
Description:
0x0019
Q13.3 signed fixed point value between −4096 and +4095.875.
Sampled gyroscope x-axis output in lsb, obtained through the execution of the Sample
gyroscope bias at temperature 1 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
47
18.3.27
Gyroscope sample 1 - y-axis bias
Address:
Value:
Description:
18.3.28
Gyroscope sample 1 - z-axis bias
Address:
Value:
Description:
18.3.29
0x001D
Q13.3 signed fixed point value between −4096 and +4095.875.
Sampled gyroscope x-axis output in lsb, obtained through the execution of the Sample
gyroscope bias at temperature 2 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
Gyroscope sample 2 - y-axis bias
Address:
Value:
Description:
18.3.32
0x001C
Q8.8 signed fixed point value between −128 and +127.9961.
Sampled temperature of gyroscope in ◦ C, obtained through the execution of the Sample
gyroscope bias at temperature 2 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
Gyroscope sample 2 - x-axis bias
Address:
Value:
Description:
18.3.31
0x001B
Q13.3 signed fixed point value between −4096 and +4095.875.
Sampled gyroscope z-axis output in lsb, obtained through the execution of the Sample
gyroscope bias at temperature 1 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
Gyroscope sample 2 - Temperature
Address:
Value:
Description:
18.3.30
0x001A
Q13.3 signed fixed point value between −4096 and +4095.875.
Sampled gyroscope y-axis output in lsb, obtained through the execution of the Sample
gyroscope bias at temperature 1 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
0x001E
Q13.3 signed fixed point value between −4096 and +4095.875.
Sampled gyroscope y-axis output in lsb, obtained through the execution of the Sample
gyroscope bias at temperature 2 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
Gyroscope sample 2 - z-axis bias
Address:
Value:
Description:
0x001F
Q13.3 signed fixed point value between −4096 and +4095.875.
Sampled gyroscope y-axis output in lsb, obtained through the execution of the Sample
gyroscope bias at temperature 2 command. This value is used by the gyroscope bias calibration algorithm in the calculation the gyroscope bias parameters. See the gyroscope bias
calibration section for more information.
48
18.3.33
Accelerometer full-scale
Address:
Value:
Description:
18.3.34
Accelerometer x-axis sensitivity
Address:
Value:
Description:
18.3.35
0x0023
Q12.4 signed fixed point value between −2048 and +2047.938.
Calibrated sensitivity of the accelerometer z-axis in lsb/g. See parameter saz in the accelerometer section. The value of the parameter can be accurately evaluated through calibration using the calculate accelerometer bias and sensitivitycommand. See the accelerometer calibration section for more information.
Accelerometer x-axis bias
Address:
Value:
Description:
18.3.38
0x0022
Q12.4 signed fixed point value between −2048 and +2047.938.
Calibrated sensitivity of the accelerometer y-axis in lsb/g. See parameter say in the accelerometer section. The value of the parameter can be accurately evaluated through calibration using the calculate accelerometer bias and sensitivitycommand. See the accelerometer calibration section for more information.
Accelerometer z-axis sensitivity
Address:
Value:
Description:
18.3.37
0x0021
Q12.4 signed fixed point value between −2048 and +2047.938.
Calibrated sensitivity of the accelerometer x-axis in lsb/g. See parameter sax in the accelerometer section. The value of the parameter can be accurately evaluated through calibration using the calculate accelerometer bias and sensitivitycommand. See the accelerometer calibration section for more information.
Accelerometer y-axis sensitivity
Address:
Value:
Description:
18.3.36
0x0020
0x0000 = ±2 g
0x0001 = ±4 g
0x0002 = ±8 g
Full-scale range of the accelerometer. Each full-scale range will have different associated
sensitivity and bias values. The accelerometer must therefore be recalibrated when the
full-scale range is changed. See the accelerometer calibration section for more information.
0x0024
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the accelerometer x-axis in lsb. See parameter bax in the accelerometer
section. The value of the parameter can be accurately evaluated through calibration using
the calculate accelerometer bias and sensitivitycommand. See the accelerometer calibration
section for more information.
Accelerometer y-axis bias
Address:
Value:
Description:
0x0025
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the accelerometer y-axis in lsb. See parameter bay in the accelerometer
section. The value of the parameter can be accurately evaluated through calibration using
the calculate accelerometer bias and sensitivitycommand. See the accelerometer calibration
section for more information.
49
18.3.39
Accelerometer z-axis bias
Address:
Value:
Description:
18.3.40
Accelerometer sampled x-axis at +1 g
Address:
Value:
Description:
18.3.41
0x0028
Q12.4 signed fixed point value between −2048 and +2047.938.
Sampled accelerometer y-axis output in lsb when orientated to measure +1g, obtained
through the execution of the sample accelerometer axis at 1 g command. This value is used
by the accelerometer calibration algorithm to calculate the value of the accelerometer y-axis
sensitivity and accelerometer y-axis bias. See the accelerometer calibration section for more
information.
Accelerometer sampled z-axis at +1 g
Address:
Value:
Description:
18.3.43
0x0027
Q12.4 signed fixed point value between −2048 and +2047.938.
Sampled accelerometer x-axis output in lsb when orientated to measure +1g, obtained
through the execution of the sample accelerometer axis at 1 g command. This value is used
by the accelerometer calibration algorithm to calculate the value of the accelerometer x-axis
sensitivity and accelerometer x-axis bias. See the accelerometer calibration section for more
information.
Accelerometer sampled y-axis at +1 g
Address:
Value:
Description:
18.3.42
0x0026
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the accelerometer z-axis in lsb. See parameter baz in the accelerometer
section. The value of the parameter can be accurately evaluated through calibration using
the calculate accelerometer bias and sensitivitycommand. See the accelerometer calibration
section for more information.
0x0029
Q12.4 signed fixed point value between −2048 and +2047.938.
Sampled accelerometer z-axis output in lsb when orientated to measure +1g, obtained
through the execution of the sample accelerometer axis at 1 g command. This value is
used by the accelerometer calibration algorithm to calculate the value of the accelerometer
z-axis sensitivity and accelerometer z-axis bias. See the accelerometer calibration section for
more information.
Accelerometer sampled x-axis at -1 g
Address:
Value:
Description:
0x002A
Q12.4 signed fixed point value between −2048 and +2047.938.
Sampled accelerometer x-axis output in lsb when orientated to measure -1g, obtained
through the execution of the sample accelerometer axis at 1 g command. This value is
used by the accelerometer calibration algorithm to calculate the value of the accelerometer
x-axis sensitivity and accelerometer x-axis bias. See the accelerometer calibration section
for more information.
50
18.3.44
Accelerometer sampled y-axis at -1 g
Address:
Value:
Description:
18.3.45
Accelerometer sampled z-axis at -1 g
Address:
Value:
Description:
18.3.46
Description:
0x002D
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
Full-scale range of the magnetometer. Each full-scale range will have different associated
sensitivity and bias values. The magnetometer therefore must be recalibrated when the
full-scale range is changed. See the magnetometer bias and sensitivity calibration section
for more information.
Magnetometer x-axis sensitivity
Address:
Value:
Description:
18.3.48
0x002C
Q12.4 signed fixed point value between −2048 and +2047.938.
Sampled accelerometer z-axis output in lsb when orientated to measure -1g, obtained
through the execution of the sample accelerometer axis at 1 g command. This value is
used by the accelerometer calibration algorithm to calculate the value of the accelerometer
z-axis sensitivity and accelerometer z-axis bias. See the accelerometer calibration section for
more information.
Magnetometer full-scale
Address:
Value:
18.3.47
0x002B
Q12.4 signed fixed point value between −2048 and +2047.938.
Sampled accelerometer y-axis output in lsb when orientated to measure -1g, obtained
through the execution of the sample accelerometer axis at 1 g command. This value is
used by the accelerometer calibration algorithm to calculate the value of the accelerometer
y-axis sensitivity and accelerometer y-axis bias. See the accelerometer calibration section
for more information.
0x002E
Q12.4 signed fixed point value between −2048 and +2047.938.
Calibrated sensitivity of the magnetometer x-axis in lsb/G. See parameter smx in the magnetometer section. The value of the parameter can be accurately evaluated through calibration
using the Measure magnetometer bias and sensitivity command. See the magnetometer bias
and sensitivity calibration section for more information.
Magnetometer y-axis sensitivity
Address:
Value:
Description:
0x002F
Q12.4 signed fixed point value between −2048 and +2047.938.
Calibrated sensitivity of the magnetometer y-axis in lsb/G. See parameter smy in the magnetometer section. The value of the parameter can be accurately evaluated through calibration
using the Measure magnetometer bias and sensitivity command. See the magnetometer bias
and sensitivity calibration section for more information.
51
18.3.49
Magnetometer z-axis sensitivity
Address:
Value:
Description:
18.3.50
Magnetometer x-axis bias
Address:
Value:
Description:
18.3.51
0x0033
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the magnetometer z-axis in lsb. See parameter bmz in the magnetometer
section. The value of the parameter can be accurately evaluated through calibration using
the Measure magnetometer bias and sensitivity command. See the magnetometer bias and
sensitivity calibration section for more information.
Magnetometer x-axis hard-iron bias
Address:
Value:
Description:
18.3.54
0x0032
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the magnetometer y-axis in lsb. See parameter bmy in the magnetometer
section. The value of the parameter can be accurately evaluated through calibration using
the Measure magnetometer bias and sensitivity command. See the magnetometer bias and
sensitivity calibration section for more information.
Magnetometer z-axis bias
Address:
Value:
Description:
18.3.53
0x0031
Q8.8 signed fixed point value between −128 and +127.9961.
Calibrated bias of the magnetometer x-axis in lsb. See parameter bmx in the magnetometer
section. The value of the parameter can be accurately evaluated through calibration using
the Measure magnetometer bias and sensitivity command. See the magnetometer bias and
sensitivity calibration section for more information.
Magnetometer y-axis bias
Address:
Value:
Description:
18.3.52
0x0030
Q12.4 signed fixed point value between −2048 and +2047.938.
Calibrated sensitivity of the magnetometer z-axis in lsb/G. See parameter smz in the magnetometer section. The value of the parameter can be accurately evaluated through calibration
using the Measure magnetometer bias and sensitivity command. See the magnetometer bias
and sensitivity calibration section for more information.
0x0034
Q5.11 signed fixed point value between −16 and +15.99951.
Calibrated hard-iron bias affecting the magnetometer x-axis in G. See parameter hx in the
magnetometer section. 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. See
the magnetometer hard-iron calibrations section for more information.
Magnetometer y-axis hard-iron bias
Address:
Value:
Description:
0x0035
Q5.11 signed fixed point value between −16 and +15.99951.
Calibrated hard-iron bias affecting the magnetometer y-axis in G. See parameter hx in the
magnetometer section. 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. See
the magnetometer hard-iron calibrations section for more information.
52
18.3.55
Magnetometer z-axis hard-iron bias
Address:
Value:
Description:
18.3.56
Algorithm mode
Address:
Value:
Description:
18.3.57
0x0039
Q1.15 signed fixed point value between 0 and +0.9999695.
Algorithm integral feedback gain in units of 1/1000. The integral gain governs the rate at
which the algorithm compensates for gyroscope bias drift. In most situations it is recommended that users ensure accurate gyroscope bias temperature sensitivity calibration and
use an integral feedback gain of 0 to avoid algorithm output oscillations and instabilities.
See the IMU and AHRS algorithms section for more information.
Algorithm initial proportional gain
Address:
Value:
Description:
18.3.60
0x0038
Q5.11 signed fixed point value between 0 and +15.99951.
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; lower values ‘trust’ the gyroscope data more and the accelerometer and magnetometer
less and higher values will ’trust’ the gyroscope less and the accelerometer and magnetometer more. See the IMU and AHRS algorithms section for more information.
Algorithm gain Ki
Address:
Value:
Description:
18.3.59
0x0037
0x0000 = Disabled
0x0000 = IMU
0x0001 = AHRS
IMU and AHRS algorithm mode. See the IMU and AHRS algorithms section for more
information. The algorithm will automatically re-initialise when the value of this register
is changed. If the algorithm is not required then the algorithm mode can be set to Disabled
to reduce power consumption.
Algorithm gain Kp
Address:
Value:
Description:
18.3.58
0x0036
Q5.11 signed fixed point value between −16 and +15.99951.
Calibrated hard-iron bias affecting the magnetometer z-axis in G. See parameter hx in the
magnetometer section. 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. See
the magnetometer hard-iron calibrations section for more information.
0x003A
Q5.11 signed fixed point value between 0 and +15.99951.
Initial algorithm proportional feedback gain used during algorithm initialisation. The effective proportional gain will ramp down from the algorithm initial proportional gain to the
algorithm proportional gain over the algorithm initialisation period. See the IMU and AHRS
algorithms section for more information.
Algorithm initialisation period
Address:
Value:
Description:
0x003B
Q5.11 signed fixed point value between 0 and +15.99951.
Algorithm initialisation period in seconds. The effective proportional gain will ramp down
from the algorithm initial proportional gain to the algorithm proportional gain over the algorithm initialisation period. See the IMU and AHRS algorithms section for more information.
53
18.3.61
Algorithm minimum valid magnetic field magnitude
Address:
Value:
Description:
18.3.62
Algorithm maximum valid magnetic field magnitude
Address:
Value:
Description:
18.3.63
0x0040
Q1.15 signed fixed point value between −1 and +0.9999695.
Quaternion stored to compute the algorithm output after a tare operation has been preformed. The tare quaternion can be set using the algorithm tare command and cleared using
the clear tare command. See the IMU and AHRS algorithms section for more information.
Tare quaternion (element 3)
Address:
Value:
Description:
18.3.67
0x003F
Q1.15 signed fixed point value between −1 and +0.9999695.
Quaternion stored to compute the algorithm output after a tare operation has been preformed. The tare quaternion can be set using the algorithm tare command and cleared using
the clear tare command. See the IMU and AHRS algorithms section for more information.
Tare quaternion (element 2)
Address:
Value:
Description:
18.3.66
0x003E
Q1.15 signed fixed point value between −1 and +0.9999695.
Quaternion stored to compute the algorithm output after a tare operation has been preformed. The tare quaternion can be set using the algorithm tare command and cleared using
the clear tare command. See the IMU and AHRS algorithms section for more information.
Tare quaternion (element 1)
Address:
Value:
Description:
18.3.65
0x003D
Q5.11 signed fixed point value between 0 and +15.99951.
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 and AHRS algorithms section for more information.
Tare quaternion (element 0)
Address:
Value:
Description:
18.3.64
0x003C
Q5.11 signed fixed point value between 0 and +15.99951.
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 and AHRS algorithms section for more information.
0x0041
Q1.15 signed fixed point value between −1 and +0.9999695.
Quaternion stored to compute the algorithm output after a tare operation has been preformed. The tare quaternion can be set using the algorithm tare command and cleared using
the clear tare command. See the IMU and AHRS algorithms section for more information.
Sensor data mode
Address:
Value:
Description:
0x0042
0x0000 = Raw ADC results
0x0001 = Calibrated measurements
Data output mode of on-board sensors. See the sensors section for more details.
54
18.3.68
Date/time data output rate
Address:
Value:
Description:
18.3.69
Battery and thermometer data output rate
Address:
Value:
Description:
18.3.70
0x0043
0x0000 = Disabled (sent on reset/wake 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
0x000A = 512 Hz
Output rate of the date/time data packets. Data rates can be reduced or disabled to reduce
power consumption.
0x0044
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
0x000A = 512 Hz
Output rate of the battery and thermometer data packets. Data rates can be reduced or
disabled to reduce power consumption.
Inertial and magnetic data output rate
Address:
Value:
Description:
0x0045
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
0x000A = 512 Hz
Output rate of the inertial and magnetic data packets. Data rates can be reduced or disabled
to reduce power consumption.
55
18.3.71
Quaternion data output rate
Address:
Value:
Description:
18.3.72
SD card new file name
Address:
Value:
Description:
18.3.73
0x0049
0 to 65535
Sleep timer value in seconds. Once this period has elapsed, the x-IMU will enter sleep
mode. A value of 0 seconds will disable the sleep timer. See the sleep timer section for more
information.
Motion trigger wake up
Address:
Value:
Description:
18.3.76
0x0048
Q4.12 signed fixed point value between 3.5 and +7.999756.
Minimum voltage threshold for the device to shutdown. See the low battery voltage detection section for more information.
Sleep timer
Address:
Value:
Description:
18.3.75
0x0047
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.
Battery shutdown voltage
Address:
Value:
Description:
18.3.74
0x0046
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
0x000A = 512 Hz
Output rate of the quaternion data packets. Data rates can be reduced or disabled to reduce
power consumption.
0x004A
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.
Bluetooth power
Address:
Value:
Description:
0x004B
0x0000 = Disabled
0x0001 = Enabled
Enables or disables Bluetooth. The Bluetooth can be disabled to reduce power consumption.
56
18.3.77
Auxiliary port mode
Address:
Value:
Description:
18.3.78
Digital I/O direction
Address:
Value:
Description:
18.3.79
0x004D
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.
Digital I/O data output rate
Address:
Value:
Description:
18.3.80
0x004C
0x0000 = Disabled
0x0001 = Digital I/O
0x0002 = Analgoue input
0x0003 = PWM output
0x0004 = ADXL345 bus
Sets the auxiliary port mode. See the auxiliary port section for more information.
0x004E
0x0000 = Disabled (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
0x000A = 512 Hz
Output rate of the digital I/O data packets. Data rates can be reduced or disabled to reduce
power consumption.
Analogue input data mode
Address:
Value:
Description:
0x004F
0x0000 = Raw ADC results
0x0001 = Calibrated measurements
Data output mode of analogue input. See the analogue input section for more information.
57
18.3.81
Analogue input data output rate
Address:
Value:
Description:
18.3.82
Analogue input sensitivity
Address:
Value:
Description:
18.3.83
0x0052
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the battery ADC in lsb. The typical value is 0 lsb. See the analogue
input section for more information.
PWM frequency
Address:
Value:
Description:
18.3.85
0x0051
Q12.4 signed fixed point value between −2, 048 and +2047.938.
Calibrated sensitivity of the analogue input ADC in lsb/V. The typical value is 1241.188
lsb/V. See the analogue input section for more information.
Analogue input bias
Address:
Value:
Description:
18.3.84
0x0050
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
0x000A = 512 Hz
Output rate of the analogue input packets. Data rates can be reduced or disabled to reduce
power consumption. See the analogue input section for more information.
0x0053
3 to 65535
Frequency of the PWM output in Hz. See the PWM section for more information.
ADXL345 bus data mode
Address:
Value:
Description:
0x0054
0x0000 = Raw ADC results
0x0001 = Calibrated measurements
Data output mode of ADXL345 bus.
58
18.3.86
ADXL345 bus data output rate
Address:
Value:
Description:
18.3.87
ADXL345 A x-axis sensitivity
Address:
Value:
Description:
18.3.88
0x0059
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 A x-axis in lsb. The typical value is 0 lsb.
ADXL345 A y-axis bias
Address:
Value:
Description:
18.3.92
0x0058
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 A z-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 A x-axis bias
Address:
Value:
Description:
18.3.91
0x0057
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 A y-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 A z-axis sensitivity
Address:
Value:
Description:
18.3.90
0x0056
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 A x-axis in lsb/g. The typical value is 256 lsb/g.
The typical value is 256 lsb/V.
ADXL345 A y-axis sensitivity
Address:
Value:
Description:
18.3.89
0x0055
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
0x000A = 512 Hz
Output rate of the ADXL345 bus data packets. Data rates can be reduced or disabled to
reduce power consumption.
0x005A
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 A y-axis in lsb. The typical value is 0 lsb.
ADXL345 A z-axis bias
Address:
Value:
Description:
0x005B
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 A z-axis in lsb. The typical value is 0 lsb.
59
18.3.93
ADXL345 B x-axis sensitivity
Address:
Value:
Description:
18.3.94
ADXL345 B y-axis sensitivity
Address:
Value:
Description:
18.3.95
0x0063
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 C y-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 C z-axis sensitivity
Address:
Value:
Description:
18.3.102
0x0062
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 C x-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 C y-axis sensitivity
Address:
Value:
Description:
18.3.101
0x0061
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 B z-axis in lsb. The typical value is 0 lsb.
ADXL345 C x-axis sensitivity
Address:
Value:
Description:
18.3.100
0x0060
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 B y-axis in lsb. The typical value is 0 lsb.
ADXL345 B z-axis bias
Address:
Value:
Description:
18.3.99
0x005F
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 B x-axis in lsb. The typical value is 0 lsb.
ADXL345 B y-axis bias
Address:
Value:
Description:
18.3.98
0x005E
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 B z-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 B x-axis bias
Address:
Value:
Description:
18.3.97
0x005D
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 B y-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 B z-axis sensitivity
Address:
Value:
Description:
18.3.96
0x005C
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 B x-axis in lsb/g. The typical value is 256 lsb/g.
0x0064
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 C z-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 C x-axis bias
Address:
Value:
Description:
0x0065
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 C x-axis in lsb. The typical value is 0 lsb.
60
18.3.103
ADXL345 C y-axis bias
Address:
Value:
Description:
18.3.104
ADXL345 C z-axis bias
Address:
Value:
Description:
18.3.105
0x006B
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 D x-axis in lsb. The typical value is 0 lsb.
ADXL345 D y-axis bias
Address:
Value:
Description:
18.3.110
0x006A
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 D z-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 D x-axis bias
Address:
Value:
Description:
18.3.109
0x0069
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 D y-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 D z-axis sensitivity
Address:
Value:
Description:
18.3.108
0x0068
Q10.6 signed fixed point value between −512 and +511.9844.
Calibrated sensitivity of the ADXL345 D x-axis in lsb/g. The typical value is 256 lsb/g.
ADXL345 D y-axis sensitivity
Address:
Value:
Description:
18.3.107
0x0067
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 C z-axis in lsb. The typical value is 0 lsb.
ADXL345 D x-axis sensitivity
Address:
Value:
Description:
18.3.106
0x0066
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 C y-axis in lsb. The typical value is 0 lsb.
0x006C
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 D y-axis in lsb. The typical value is 0 lsb.
ADXL345 D z-axis bias
Address:
Value:
Description:
0x006D
Q8.8 signed fixed point value between −256 and +127.9961.
Calibrated bias of the ADXL345 D z-axis in lsb. The typical value is 0 lsb.
61
18.3.111
UART baud rate
Address:
Value:
Description:
18.3.112
0x006E
0x0000 = 2400 baud
0x0001 = 4800 baud
0x0002 = 7200 baud
0x0003 = 9600 baud
0x0004 = 14400 baud
0x0005 = 19200 baud
0x0006 = 38400 baud
0x0007 = 57600 baud
0x0008 = 115200 baud
0x0009 = 230400 baud
0x000A = 460800 baud
0x000B = 921600 baud
Baud rate of the auxiliary port UART. See the UART section for more information.
UART hardware flow control
Address:
Value:
Description:
0x006F
0x0000 = Disabled
0x0001 = Enabled
Hardware flow control enable/disable of the auxiliary port UART. See the UART section
for more information.
62
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