X-IO x-IMU3 User manual

x-IMU3 User Manual v1.7
January 5, 2024
x-IMU3 User Manual
v1.7
January 5, 2024
x-io Technologies
1

x-IMU3 User Manual v1.7
January 5, 2024
Contents
1 Overview 6
2 Hardware 7
2.1 Board ................................................ 7
2.1.1 Serial header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Housing............................................... 9
2.2.1 IP67 rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Technical specification 10
3.1 Mechanical ............................................. 10
3.1.1 Board ........................................... 10
3.2 Temperature............................................. 10
3.2.1 No battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.2 With battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 Sensors............................................... 11
3.3.1 Gyroscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.2 Accelerometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.3 Magnetometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.4 High-g accelerometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3.5 Temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.4 AHRS ................................................ 13
3.4.1 Update rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.4.2 Static accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.5 Data logger capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.5.1 8 GB microSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.5.2 32 GB microSD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Calibration 15
4.1 Inertial sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Magnetometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3 Calibration certificate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5 Power button 16
6 LED 16
6.1 Wireless disabled (green) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2 Wi-Fi client (cyan) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3 Wi-Fi AP (magenta) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.4 Bluetooth (blue) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.5 Error(red).............................................. 18
6.6 Low battery and charging (orange) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.7 Usercontrol............................................. 19
7 Data logger 19
7.1 Start and stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.2 Filename .............................................. 19
7.3 File contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.4 Maximum file size and period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.5 Downloading files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8 Communication protocol 20
8.1 Command messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1.1 Read setting command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1.2 Write setting command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1.3 Default command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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x-IMU3 User Manual v1.7
January 5, 2024
8.1.4 Apply command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1.5 Save command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1.6 Read time command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1.7 Write time command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.8 Ping command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.9 Ping response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.10 Reset command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.11 Shutdown command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.12 Strobe command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.13 Colour command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1.14 Initialise AHRS command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1.15 Heading command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1.16 Serial accessory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1.17 Note command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1.18 Format command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1.19 Self-test command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1.20 Self-test response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1.21 Bootloader command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1.22 Factory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1.23 Erase command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1.24 Error response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.2 Data messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.2.1 Byte stuffing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.2.2 Inertial message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.2.3 Magnetometer message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.2.4 Quaternion message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.2.5 Rotation matrix message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.2.6 Euler angles message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.2.7 Linear acceleration message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.2.8 Earth acceleration message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.2.9 AHRS status message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.2.10 High-g accelerometer message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.2.11 Temperature message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.2.12 Battery message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.2.13 RSSI message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.2.14 Serial accessory message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.2.15 Notification message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.2.16 Error message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9 Sample rates, message rates, and timestamps 34
9.1 Sample rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9.2 Message rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9.3 Sample averaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
9.4 Timestamps............................................. 35
9.5 Synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
10 Network announcement message 36
11 Device settings 36
11.1 Individual settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
11.1.1 Calibration date (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
11.1.2 Gyroscope misalignment (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11.1.3 Gyroscope sensitivity (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11.1.4 Gyroscope offset (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11.1.5 Accelerometer misalignment (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . 37
11.1.6 Accelerometer sensitivity (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
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x-IMU3 User Manual v1.7
January 5, 2024
11.1.7 Accelerometer offset (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11.1.8 Soft iron matrix (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
11.1.9 Hard iron offset (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
11.1.10 High-g accelerometer misalignment (read-only) . . . . . . . . . . . . . . . . . . . . . 38
11.1.11 High-g accelerometer sensitivity (read-only) . . . . . . . . . . . . . . . . . . . . . . . 38
11.1.12 High-g accelerometer offset (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . 38
11.1.13 Device name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
11.1.14 Serial number (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.1.15 Firmware version (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.1.16 Bootloader version (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.1.17 Hardware version (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.1.18 Serial mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.1.19 Serial baud rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
11.1.20 Serial RTS/CTS enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.21 Serial accessory number of bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.22 Serial accessory termination byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.23 Serial accessory timeout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.24 Wireless mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.25 Wireless firmware version (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1.26 External antennae enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1.27 Wi-Fi region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1.28 Wi-Fi MAC address (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1.29 Wi-Fi IP address (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1.30 Wi-Fi client SSID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
11.1.31 Wi-Fi client key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
11.1.32 Wi-Fi client channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
11.1.33 Wi-Fi client DHCP enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
11.1.34 Wi-Fi client IP address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
11.1.35 Wi-Fi client netmask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
11.1.36 Wi-Fi client gateway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
11.1.37 Wi-Fi AP SSID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
11.1.38 Wi-Fi AP key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
11.1.39 Wi-Fi AP channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
11.1.40 Wi-Fi AP IP address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
11.1.41 TCP port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
11.1.42 UDP IP address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.1.43 UDP send port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.1.44 UDP receive port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.1.45 UDP low latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.1.46 Synchronisation enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
11.1.47 Synchronisation network latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
11.1.48 Bluetooth address (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
11.1.49 Bluetooth name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
11.1.50 Bluetooth pin code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
11.1.51 Bluetooth discovery mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
11.1.52 Bluetooth paired address (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1.53 Bluetooth paired link key (read-only) . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1.54 Data logger enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1.55 Data logger file name prefix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1.56 Data logger file name time enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1.57 Data logger file name counter enabled . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1.58 Data logger max file size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
11.1.59 Data logger max file period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
11.1.60 Axes alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
11.1.61 Gyroscope offset correction enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
11.1.62 AHRS axes convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
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x-IMU3 User Manual v1.7
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11.1.63 AHRS gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
11.1.64 AHRS ignore magnetometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
11.1.65 AHRS acceleration rejection enabled . . . . . . . . . . . . . . . . . . . . . . . . . . 50
11.1.66 AHRS magnetic rejection enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
11.1.67 Binary mode enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
11.1.68 USB data messages enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
11.1.69 Serial data messages enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
11.1.70 TCP data messages enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
11.1.71 UDP data messages enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
11.1.72 Bluetooth data messages enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
11.1.73 Data logger data messages enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
11.1.74 AHRS message type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
11.1.75 Inertial message rate divisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
11.1.76 Magnetometer message rate divisor . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
11.1.77 AHRS message rate divisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
11.1.78 High-g accelerometer message rate divisor . . . . . . . . . . . . . . . . . . . . . . . 54
11.1.79 Temperature message rate divisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
11.1.80 Battery message rate divisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
11.1.81 RSSI message rate divisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Glossary 57
Document version history 59
Disclaimer 62
5

x-IMU3 User Manual v1.7
January 5, 2024
1 Overview
The x-IMU3 is x-io Technologies’ third generation
Inertial Measurement Unit (IMU). It is a
high-performance and versatile measurement
device designed to accommodate a wide range of
data logging and real-time applications including
biomechanics, motion-capture, virtual reality, drones,
robotics, and industrial.
USB, Wi-Fi and Bluetooth provide connectivity
for mobile and desktop devices while serial
communication supports embedded and industrial
systems. An on-board microSD allows the x-IMU3
to function as a stand-alone data logger with the
ability to download files by USB and Wi-Fi. Multiple
x-IMU3s operating together on the same wireless
network will automatically synchronise to stream or
log synchronised measurements.
Sensors
·Gyroscope, ±2000°/s, 400 Hz
·Accelerometer, ±24 g, 400 Hz
·Magnetometer, ±2.5 uT, 20 Hz
·High-g accelerometer, ±200 g, 1600 Hz
·Temperature sensor1
Calibration
·15-parameter calibration for: axis sensitivity,
axis offset, inter-axis misalignment, and
package misalignment.
·Hard-iron and soft-iron calibration
·On-board gyroscope bias correction algorithm
AHRS
·Algorithm outputs:
- Quaternion
- Rotation matrix
- Euler angles
- Linear acceleration
- Earth acceleration
·Linear acceleration rejection
·Magnetic distortion rejection
·400 Hz update rate
·Static accuracy:
- 0.5° RMS inclination
- 1° RMS heading
Communication
·USB (CDC)
·Serial, 3.3V UART
·TCP (Wi-Fi)
·UDP (Wi-Fi)
·Bluetooth2
Wi-Fi
·Client and AP mode
·Dual band (2.4 GHz, 5 GHz)
·WPA/WPA2-Personal
·WPA/WPA2-Enterprise3
Data logging
·Supports microSDs up to 32 GB4
·Start/stop logging remotely
·USB download
·Wi-Fi download5
·CSV output
Serial accessories
·Receive data from external sensors and user
electronics, e.g. GPS, analogue/digital inputs,
application-specific sensors.
·3.3 V output to power external electronics
Battery
·Internal battery charged by USB
·20 hours data logging
·15 hours Bluetooth
·12 hours Wi-Fi client 2.4 GHz
·8 hours Wi-Fi client 5 GHz
Housing
·IP67
·Wearable strap or chassis mount
Software GUI
·Connect to multiple x-IMU3s
·Real-time data graphs and 3D view
·Log data to CSV
·Windows, macOS, Ubuntu
Software API
·Rust, C, C++, C#, Python
·Code examples for other languages available
1The temperature sensor is used for calibration and is not intended to provide an accurate measurement of ambient temperature.
2Bluetooth connectivity is currently in development and not yet supported.
3WPA/WPA2-Enterprise security is currently in development and not yet supported. Will only be supported in client mode.
4The product is supplied with an 8 GB microSD that can be upgraded by the user.
5Wi-Fi downloading is currently in development and not yet supported.
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2 Hardware
2.1 Board
Board components are annotated in Figure 1. A detailed mechanical drawing describing the board dimensions
and locations of key components is available on the product web page.
1
2
3
4
5
67
8
9
10
11
Figure 1: Board
1. Power button
2. USB-C connector
3. LED
4. Serial header
5. High-g accelerometer
6. Inertial sensor (gyroscope and accelerometer)
7. Magnetometer
8. Wireless antennae
9. U.FL connector for external wireless antennae
10. microSD socket
11. Battery connector
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2.1.1 Serial header
The serial header pinout is annotated in figure 2. The connector part number is “CLP-105-02-L-D”. The
recommend mating connector part number is “FTS-105-03-F-DV”.
1
2
3
4
5
6
7
8
9
10
Figure 2: Serial header pinout
Pin Name Type
1 3.3V Power
2 GND Power
3 VBAT Power
4 VBUS Power
5 Button Input
6 Serial override Input
7 Serial RTS Output
8 Serial CTS Input
9 Serial RX Input
10 Serial TX Output
Table 1: Serial header pinout
Warning - Incorrect connections to the serial header may cause permanent
damage. This interface should only be used by an experienced engineer.
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2.2 Housing
The housing interfaces are annotated in Figure 3. A detailed mechanical drawing describing the housing
dimensions is available on the product web page.
1
2
3
Figure 3: Housing
1. Power button
2. USB-C connector
3. LED
2.2.1 IP67 rating
The Ingress Protection 67 (IP67) rating is an international standard that describes the ability of the housing to
protect against the ingress of solid particles and water. The first digit, 6 indicates complete protection against
dust and solid particles. The second digit, 7 indicates protection from water for a maximum depth of 1 meter
for up to 30 minutes.
In practical terms, this means that the housing can be used outdoors in all weather conditions and that it
will survive accidental or temporary submersion in water. The housing should not be used in underwater
applications.
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3 Technical specification
3.1 Mechanical
3.1.1 Board
Characteristic Value Notes
Size 52 ×32 ×5 mm 1
Weight 8 g -
Table 2: Board mechanical specification
Notes
1. A detailed mechanical drawing describing the board dimensions and locations of key components is
available on the product web page.
Characteristic Value Notes
Size 55 ×50 ×14 mm 1
Weight 31 g -
Table 3: Housing mechanical specification
Notes
1. A detailed mechanical drawing describing the housing dimensions and locations of key components is
available on the product web page.
3.2 Temperature
3.2.1 No battery
Characteristic Value Notes
Operating -40°C to 85°C 1, 2
Storage -40°C to 105°C -
Table 4: Temperature specification (no battery)
Notes
1. The operating temperature of the device will always be greater than the surroundings due to heat
generated by electronics.
2. The specified accuracy of the device is not achieved over the full operating temperature range. See
Section 4 on page 15 for more information.
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3.2.2 With battery
Characteristic Value Notes
Operating (discharging) -20°C to 60°C 1, 2
Operating (charging) 0°C to 45°C 1, 2, 3
Storage -20°C to 25°C -
Table 5: Temperature specification (with battery)
Notes
1. The operating temperature of the device will always be greater than the surroundings due to heat
generated by electronics.
2. The specified accuracy of the device is not achieved over the full operating temperature range. See
Section 4 on page 15 for more information.
3. Charging at temperatures below 0°C will reduce the capacity and cycle life of the battery.
3.3 Sensors
3.3.1 Gyroscope
Characteristic Value Notes
Range ±2000°/s -
Resolution 16-bit, 0.061°/s -
Sample rate 400 Hz ±0.3% 1
Bandwidth 47 Hz 2
Noise 0.014°/s/√Hz -
Table 6: Gyroscope specification
Notes
1. Each sample includes a timestamp for a reliable measurement of time independent of the sample rate
error. See Section 9 on page 34 for more information.
2. The maximum bandwidth is achieved when the message rate is equal to the sample rate. If the message
rate is less than the sample rate then samples are averaged. See Section 9 on page 34 for more
information.
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3.3.2 Accelerometer
Characteristic Value Notes
Range ±24 g -
Resolution 16-bit, 732 µg -
Sample rate 400 Hz ±0.3% 1
Bandwidth 145 Hz 2
Noise 160 µg/√Hz (X, Y), 190 µg/√Hz (Z) -
Accuracy at 1 g ±5 mg 3, 4
Table 7: Accelerometer specification
Notes
1. Each sample includes a timestamp for a reliable measurement of time independent of the sample rate
error. See Section 9 on page 34 for more information.
2. The maximum bandwidth is achieved when the message rate is equal to the sample rate. If the message
rate is less than the sample rate then samples are averaged. See Section 9 on page 34 for more
information.
3. The accelerometer error is evaluated as the deviation of the measured magnitude of gravity for a 360°
rotation around each axis aligned to the horizontal. The magnitude is calculated as px2+y2+z2.
4. Accuracy is specified for the calibrated temperature only. See Section 4 on page 15 for more information.
3.3.3 Magnetometer
Characteristic Value Notes
Range ±1300 µT (X, Y), ±2500 µT (Z) -
Sample rate 20 Hz ±8% 1
Noise 0.3 µT -
Accuracy at 1 a.u. ±50 ma.u. 2, 3, 4
Table 8: Magnetometer specification
Notes
1. Each sample includes a timestamp for a reliable measurement of time independent of the sample rate
error. See Section 9 on page 34 for more information.
2. The calibrated magnetometer units are arbitrary units (a.u.). 1 a.u. is equal to the magnitude of the
ambient magnetic field during calibration, approximately 50 µT.
3. The magnetometer error is evaluated as the deviation of the measured magnitude of the ambient
magnetic field for a 360° rotation around each axis aligned to the vertical. The magnitude is calculated
as px2+y2+z2.
4. Accuracy is specified for the calibrated temperature only. See Section 4 on page 15 for more information.
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3.3.4 High-g accelerometer
Characteristic Value Notes
Range ±200 g -
Resolution 16-bit, 6.1 mg -
Sample rate 1600 Hz ±2% 1
Bandwidth 800 Hz 2
Noise 5 mg/√Hz -
Accuracy at 1 g ±150 mg 3, 4
Table 9: High-g accelerometer specification
Notes
1. Each sample includes a timestamp for a reliable measurement of time independent of the sample rate
error. See Section 9 on page 34 for more information.
2. The maximum bandwidth is achieved when the message rate is equal to the sample rate. If the message
rate is less than the sample rate then samples are averaged. See Section 9 on page 34 for more
information.
3. The accelerometer error is evaluated as the deviation of the measured magnitude of gravity for a 360°
rotation around each axis aligned to the horizontal. The magnitude is calculated as px2+y2+z2.
4. Accuracy is specified for the calibrated temperature only. See Section 4 on page 15 for more information.
3.3.5 Temperature sensor
Characteristic Value Notes
Range -104°C to 150°C 1
Sample rate 5 Hz ±0.3% 2, 3
Accuracy ±1°C at 25°C -
Table 10: Temperature sensor specification
Notes
1. The temperature sensor measurement range exceeds the device operating temperature range. See
Section 3.2 on page 10 for more information.
2. Each sample includes a timestamp for a reliable measurement of time independent of the sample rate
error. See Section 9 on page 34 for more information.
3. The temperature sensor is oversampled and the result decimated to the specified sample rate.
3.4 AHRS
3.4.1 Update rate
Characteristic Value Notes
Update rate 400 Hz ±0.3% 1, 2
Table 11: AHRS update rate
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Notes
1. Each update includes a timestamp for a reliable measurement of time independent of the update rate
error. See Section 9 on page 34 for more information.
2. The Attitude Heading Reference System (AHRS) update rate is fixed independent of message rate
settings. AHRS outputs are not averaged when the message rate is less than the update rate.
3.4.2 Static accuracy
Characteristic Value Notes
Inclination 0.5° RMS 1, 2
Heading 1° RMS 1, 2
Table 12: AHRS static accuracy
Notes
1. Static accuracy is specified as the Root Mean Square (RMS) error for a 360° rotation around each axis.
2. Accuracy is specified for the calibrated temperature only. See Section 4 on the following page for more
information.
3.5 Data logger capacity
3.5.1 8 GB microSD
Condition Value Notes
Default message rates 485 hours 1
Maximum message rates 37 hours 1
Table 13: Data logger capacity for 8 GB microSD
Notes
1. The data logging capacity is specified for binary data messages. Capacity will be reduced for ASCII
data messages.
3.5.2 32 GB microSD
Condition Value Notes
Default message rates 1941 hours 1, 2
Maximum message rates 149 hours 1, 2
Table 14: Data logger capacity for 32 GB microSD
Notes
1. The data logging capacity is specified for binary data messages. Capacity will be reduced for ASCII
data messages.
2. The product is supplied with an 8 GB microSD that can be upgraded by the user. The maximum
compatible microSD capacity is 32 GB.
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4 Calibration
Each x-IMU3 is calibrated during production to achieve the specified accuracy. The calibration process uses
specialist equipment and propriety algorithms to calculate calibration parameters specific to each x-IMU3.
Calibration is performed at room temperature. Accuracy will be reduced for operating temperatures that
deviate from this temperature. Please refer to the calibration certificate for specific temperature values.
4.1 Inertial sensors
The inertial sensors are the gyroscope, accelerometer, and high-g accelerometer. Each inertial sensor is
calibrated for axis sensitivity, axis offset, inter-axis misalignment, and package misalignment. The inertial
calibration model is described by Equation (1) where icis the calibrated inertial measurement obtained from
the uncalibrated inertial measurement, iu, given the misalignment matrix, M, the sensitivity diagonal matrix,
s, and the offset vector, b. The inertial calibration model is expanded as Equation (2) to express the model
as 15 scalar quantities. The units of ic,iu, and bare degrees per second for the gyroscope, and g for the
accelerometer and high-g accelerometer. Mand sare ratios and therefore have no units. The calibration
parameters M,s, and bfor each inertial sensor can be accessed as device settings.
ic=Ms(iu−b) (1)


icx
icy
icz

= 
mxx mxy mxz
myx myy my z
mzx mzy mzz

 
sx0 0
0sy0
0 0 sz

  
iux
iuy
iuz

− 
bx
by
bz

 (2)
4.2 Magnetometer
The magnetometer is calibrated for soft iron and hard-iron characteristics. Soft iron characteristics are
distortions that alter the intensity and direction of the magnetic field measured by the magnetometer.
Soft iron calibration also accounts for magnetometer axis sensitivity, inter-axis misalignment, and package
misalignment. Hard iron characteristics are unintended magnetic fields generated by the device that offset
magnetometer measurements. Hard iron calibration also accounts for the magnetometer axis offset.
The magnetometer calibration model is described by Equation (3) where mcis the calibrated magnetometer
measurement obtained from the uncalibrated magnetometer measurement, mu, given the soft iron matrix,
S, the hard iron vector, h. The magnetometer calibration model is expanded as Equation (4) to express the
model as 12 scalar quantities. The units of mc,mu, and hare a.u.. Sis a ratio and therefore has no units.
The calibration parameters S,hcan be accessed as device settings.
mc=Smu−h(3)


mcx
mcy
mcz

= 
sxx sxy sxz
syx syy sy z
szx szy szz

 
mux
muy
muz

− 
hx
hy
hz

(4)
4.3 Calibration certificate
Each x-IMU3 is supplied with a calibration certificate. The calibration certificate details all calibration
parameters, the calibration date, the ambient temperature and device temperature during calibration, and any
equipment used during the calibration process. The certificate also includes graphs verifying the accuracy
over the measurement range. Calibration certificates are provided as a Portable Document Format (PDF) file.
There are three ways to access the calibration certificate:
1. Scan the Quick Response (QR) code on the back of the x-IMU3 board or housing.
2. Open the “Calibration Certificate.html” file stored on the micro Secure Digital (microSD).
3. Enter the device serial number on the calibration certificate web page.
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5 Power button
Pressing the power button while the x-IMU3 is switched off will switch the x-IMU3 on. Pressing and holding
the power button for two seconds while the x-IMU3 is switched on will switch the x-IMU3 off.
A timestamped notification message containing the string, ”Button pressed.” is sent each time the button is
pressed. This allows the button to function as a basic user input for real-time applications or as a means for
marking events during data logging. If the button is used in this way then the user must be careful not to hold
the button for too long otherwise the x-IMU3 may be switched off unintentionally.
6 LED
The Light-Emitting Diode (LED) indicates the mode and status of the x-IMU3 using different colours and
flashing behaviours.
6.1 Wireless disabled (green)
A green LED, as shown in Figure 4 indicates that the x-IMU3 is switched on and that the wireless mode is
disabled. In this mode, the LED indicates the data logger state. Flashing indicates that the data logger is
disabled and a solid LED indicates that the data logger is enabled.
Figure 4: Green LED indicating that the x-IMU3 is switched on and that the wireless mode is disabled
6.2 Wi-Fi client (cyan)
A cyan LED, as shown in Figure 5 on the following page indicates that the x-IMU3 is switched on and in Wi-Fi
client mode. Slow flashing (once per second) indicates that x-IMU3 is not connected to an Access Point (AP),
fast flashing (five times per second) indicates that the x-IMU3 is connected to an AP but has not yet obtained
an Internet Protocol (IP) address, and a solid LED indicates that the x-IMU3 is connected to an AP and has
an IP address.
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Figure 5: Cyan LED indicating that the x-IMU3 is switched on and in Wi-Fi client mode
6.3 Wi-Fi AP (magenta)
A magenta LED, as shown in Figure 6 indicates that the x-IMU3 is switched on and in Wi-Fi AP mode. The
LED will flash during the initialisation of the Wi-Fi network. Once the network has been created, the LED will
remain solid.
Figure 6: Magenta LED indicating that the x-IMU3 is switched on and in Wi-Fi AP mode
6.4 Bluetooth (blue)
A blue LED, as shown in Figure 7 on the following page indicates that the x-IMU3 is switched on and in
Bluetooth mode. Slow flashing (once per second) indicates that Bluetooth is not connected and the x-IMU3 is
not discoverable, fast flashing (five times per second) indicates that Bluetooth is not connected and the x-IMU3
is discoverable, and a solid LED indicates that Bluetooth is connected. The x-IMU3 is not discoverable while
Bluetooth is connected.
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Figure 7: Blue LED indicating that the x-IMU3 is switched on and in Bluetooth mode
6.5 Error (red)
A red LED, as shown in Figure 8 indicates an error. The LED will interrupt it’s normal behaviour to blink red
each time an error message is sent by the x-IMU3.
Figure 8: Red LED indicating an error
6.6 Low battery and charging (orange)
An orange LED, as shown in Figure 9 on the following page indicates either a low battery the x-IMU3 is
switched on, or the charging status if the x-IMU3 is switched off. The LED will interrupt it’s normal behaviour
to blink orange once a second to indicate that the battery is low. If the x-IMU3 is switched off and USB power
is connected then the LED will remain solid while the x-IMU3 is charging and blink once every four seconds
once charging is complete.
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Figure 9: Orange LED indicating low battery or charging status
6.7 User control
The LED can be controlled by the user using the strobe and colour commands. See Section 8.1.12 on page 22
and Section 8.1.13 on page 23 for more information.
7 Data logger
The x-IMU3 can function as a stand-alone data logger by streaming real-time data to a file on the microSD.
Files created by the data logger use the .ximu3 extension and can be downloaded from the x-IMU3 to be
converted to Comma-Separated Values (CSV) files using the product software.
The data logger will create a new file in the “Data Logger” directory on the microSD each time logging starts.
Files will never be overwritten or deleted by the data logger. If the microSD becomes full then the data logger
will stop and the x-IMU3 will indicate an error.
7.1 Start and stop
The data logger is enabled or disabled in the device settings. If the data logger is enabled then logging will
start when the x-IMU3 is switched on and stop when the x-IMU3 is switched off. Alternatively, an application
can start and stop logging remotely by enabling and disabling the data logger while the x-IMU3 is switched
on.
7.2 File name
The file name format is “prefix YYYY-MM-DD hh-mm-ss CCCC.ximu3” where where ”prefix” is a user-defined
label configured in the device settings, “YYYY-MM-DD hh-mm-ss” is the time that the file was created, and
“CCCC” is a counter. If the prefix is left blank then the device serial number will be used with the format
“XXXXXXXX”. The time and counter parts of the file name can be individually enabled or disabled in the
device settings. For example, if the counter was disabled and the prefix left blank for an x-IMU3 with the
serial number “01234567” then a file created at 3.30 p.m. on January 20, 2025 would have the name
“01234567 2025-01-20 15-30-00.ximu3”.
The counter is a four digit number between 0000 and 9999 that increments each time it is used. If a file name
using the counter already exists then the counter will increment until the file name is available. Incrementing
beyond 9999 will cause the counter to wraparound to 0000. If the counter part of the file name is disabled and
the file name already exists then the counter will used automatically to create an available file name.
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7.3 File contents
The contents of the file is a byte stream as per the communication protocol described in Section 8. Each file
starts with a preamble of the following messages, in order.
1. Ping response
2. Write time command
3. Write setting command for each setting
7.4 Maximum file size and period
A maximum file size and maximum file period can be configured in the device settings. The data logger will
start a new file each time the file size reaches the maximum file size, or the period since the start of the file
reaches the maximum file period.
7.5 Downloading files
Data logger files can be download by Universal Serial Bus (USB) or Wi-Fi. The microSD appears as an
external drive when USB is connected. The microSD cannot be accessed while the data logger is enabled.
The contents of the “Data Logger” directory on the microSD can be accessed by Wi-Fi by typing in the
x-IMU3’s IP address to a browser. This directory cannot be accessed while the data logger is enabled.
8 Communication protocol
All communication interfaces use the same communication protocol. The byte stream is therefore identical
for USB, serial, Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Bluetooth, and the files
created by the data logger. The communication protocol consists of two message types:
·Command messages
·Data messages
All messages are terminated by a Line Feed (LF) control character. This termination byte will not appear
anywhere else in a message and so can be used to divide a byte stream into individual messages. Table 15
describes the different ways that the control character LF may be referred to throughout this document.
Control character Abbreviation String Hex Decimal
Line Feed LF “\n” 0x0A 10
Table 15: Control characters LF representations
The first byte of a message indicates the message type. Command messages start with the character “{”
(0x7B in hex, 123 in decimal). Data messages start with either an uppercase character or a byte value
greater than 0x80 (128 in decimal) depending on the message.
8.1 Command messages
Command messages are sent to the x-IMU3 to read and write settings and execute commands. All command
messages are a JavaScript Object Notation (JSON) object containing a single key/value pair, terminated by
the control character LF. The control character LF must not appear anywhere else in a command message.
The x-IMU3 will acknowledge each received command message by sending a command message with the
same key to the host.
The key used by command messages sent to the x-IMU3 is not case sensitive and can use non-alphanumeric
characters arbitrarily. For example, “serialNumber”, “Serial Number”, and “serial number” are all valid keys for
a command message to read the device serial number.
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