Movella DOT User manual

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Movella DOT
User Manual
Document XD0502P, Revision A, July 2023

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Revision
Date
By
Changes
A
July 2023
MRA
Movella DOT rebranding.
Update the battery specifications.
Update the charger specifications.
© 2021-2023, Movella Inc. All rights reserved. Information in this document is subject to change without notice.
All other trademarks are the property of their respective owners.

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Table of Contents
1Introduction ............................................................................................................... 6
2Getting Started........................................................................................................... 7
2.1 Movella DOT set...................................................................................................................................... 7
2.2 Movella DOT sensor ................................................................................................................................ 7
2.2.1 Activate sensor................................................................................................................................ 8
2.2.2 Power ON/OFF ................................................................................................................................ 8
2.2.3 LED patterns.................................................................................................................................... 8
2.2.4 Reset sensor .................................................................................................................................... 9
2.3 Charger.................................................................................................................................................... 9
2.4 Body straps and accessories.................................................................................................................... 9
2.5 Software.................................................................................................................................................. 9
2.5.1 Supported platforms ..................................................................................................................... 10
2.5.2 Choose your software ................................................................................................................... 10
2.6 Tips for best practice............................................................................................................................. 11
2.6.1 Multiple sensors connection......................................................................................................... 11
2.6.2 Magnetic distortion....................................................................................................................... 11
2.6.3 Drift in orientation data ................................................................................................................ 12
2.6.4 Cleaning method ........................................................................................................................... 12
2.6.5 Long-term storage guidelines........................................................................................................ 13
2.7 Troubleshooting .................................................................................................................................... 14
3Movella DOT Overview..............................................................................................15
3.1 Strapdown integration .......................................................................................................................... 15
3.2 Sensor fusion algorithm and filter profiles............................................................................................ 15
3.3 Movella DOT sensor state transition..................................................................................................... 16
3.3.1 Power ON ...................................................................................................................................... 16
3.3.2 Power OFF ..................................................................................................................................... 17
3.3.3 Advertisement............................................................................................................................... 17
3.3.4 Connection .................................................................................................................................... 17
3.3.5 Synchronization............................................................................................................................. 17
3.3.6 Measurement................................................................................................................................ 18
3.3.7 Power saving ................................................................................................................................. 20
3.3.8 Button callback function ............................................................................................................... 20
3.4 Magnetic Field Mapper ......................................................................................................................... 20
3.4.1 When to perform MFM................................................................................................................. 21
3.4.2 How to perform MFM ................................................................................................................... 21
3.5 Firmware Update .................................................................................................................................. 21
3.5.1 Firmware update........................................................................................................................... 21
3.5.2 Firmware downgrade .................................................................................................................... 22
3.5.3 Firmware compatibility ................................................................................................................. 22

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3.6 Reset to factory setting......................................................................................................................... 22
4Output Specifications ................................................................................................23
4.1 Coordinate systems............................................................................................................................... 23
4.1.1 Sensor coordinate system............................................................................................................. 23
4.1.2 Orientation coordinate system ..................................................................................................... 23
4.1.3 Heading reset ................................................................................................................................ 24
4.2 Sensor data outputs.............................................................................................................................. 24
4.2.1 Calibrated delta_q and delta_v..................................................................................................... 25
4.2.2 Calibrated inertial data and magnetic field data........................................................................... 25
4.2.3 Orientation.................................................................................................................................... 25
4.2.4 Free acceleration........................................................................................................................... 26
4.2.5 Timestamp and packet counter .................................................................................................... 26
4.2.6 Status............................................................................................................................................. 26
5Physical Specifications...............................................................................................27
5.1 Sensor specifications............................................................................................................................. 27
5.2 Charger specifications ........................................................................................................................... 27
5.3 Sensor components specifications........................................................................................................ 28
5.4 Battery specifications............................................................................................................................ 28
5.5 Sensor technical drawing ...................................................................................................................... 30
5.6 Charger technical drawing .................................................................................................................... 31
6Important Notices .....................................................................................................32
6.1 Warranty and Liability........................................................................................................................... 32
6.2 Customer Support ................................................................................................................................. 32
6.3 Product Compliance .............................................................................................................................. 33

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List of references
1. Xsens DOT SDK Programming guide for Android [XD0201P]
2. Xsens DOT SDK Programming guide for iOS [XD0202P]
3. Xsens DOT BLE Services Specifications [XD0506P]
4. Magnetic Calibration Manual [MT0202P]
List of Tables
Table 1: LED patterns ................................................................................................... 8
Table 2: SDK language and supported OS ............................................................................10
Table 3: Software supported platforms ..............................................................................10
Table 4: Trouble shooting .............................................................................................14
Table 5: Filter profiles .................................................................................................16
Table 6: Synchronization accuracy....................................................................................18
Table 7: Output rates..................................................................................................18
Table 8: Delta_q and Delta_v outputs................................................................................25
Table 9: Inertial and magnetometer data outputs...................................................................25
Table 10: Orientation outputs ........................................................................................25
Table 11: Free acceleration outputs ..................................................................................26
Table 12: Status Definition ............................................................................................26
Table 13: Movella DOT sensor specifications ........................................................................27
Table 14: Orientation Performance...................................................................................27
Table 15: Charger specifications ......................................................................................27
Table 16: Gyroscope specifications ...................................................................................28
Table 17: Accelerometer specifications ..............................................................................28
Table 18: Magnetometer specifications..............................................................................28
Table 19: Alignment specifications ...................................................................................28
Table 20: Battery Specifications ......................................................................................29
List of Figures
Figure 1: Movella DOT sensors with a charger........................................................................ 6
Figure 2: Movella DOT set.............................................................................................. 7
Figure 3: Movella DOT sensor.......................................................................................... 7
Figure 4: Charger with power cable ................................................................................... 9
Figure 5: Mag Norm is constant while moving.......................................................................12
Figure 6: Mag Norm fluctuates when moving........................................................................12
Figure 7: Movella DOT signal processing architecture...............................................................15
Figure 8: Movella DOT state transition diagram .....................................................................16
Figure 9: USB power on disabled .....................................................................................16
Figure 10: USB power on enabled ....................................................................................17
Figure 11: Root and scanners in synchronization ....................................................................18
Figure 12: Movella DOT sensor coordinate system..................................................................23
Figure 13: Heading reset/revert in Movella DOT app ...............................................................24
Figure 14: Sensor technical drawing..................................................................................30
Figure 15: Charger technical drawing ................................................................................31

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1Introduction
Xsens DOT is a wearable sensor development platform which features sensor incorporating 3D accelerometer,
gyroscope and magnetometer to provide an accurate 3D orientation. The embedded processor in the sensor
handles sampling, calibration, strap-down integration of inertial data and the Xsens Kalman Filter core (XKFCore)
algorithm for sensor fusion. With wireless data transmission through Bluetooth 5.0, Xsens DOT can provide real-
time 3D orientation as well as calibrated 3D linear acceleration, angular velocity and (earth) magnetic field data
to a receiving device.
Xsens DOT is the start of a new Xsens product line bringing Xsens sensor solutions to mobile device platforms.
With simple-to-use Software-Development-Kit (SDK) and comprehensive documentation, system integrators can
easily develop their wearable applications.
The Bluetooth Low Energy (BLE) data transmission, lightweight form factor and IP68 water-proof rating widen
the application areas of Xsens DOT, making it easy and durable to use in various scenarios. Using different
combinations of 5 sensors, it’s flexible to apply Xsens DOT to customized measurement cases.
Xsens has released the 2nd generation of Xsens DOT hardware (hereinafter as v2). The hardware upgrade includes
specification improvements as well as user experience optimizations. Xsens DOT sensor and charger have been
upgraded as a drop and replaceable hardware to the existing first generation. Refer to the Product Change
Notification for the details about this upgrade. This document is applicable to v2 with the latest firmware and
software version. Refer to this link for the archived user manual for v1 hardware.
Fields of use:
1. Health and rehabilitation
2. Sports and exercise science
3. Ergonomics
Figure 1: Movella DOT sensors with a charger

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2Getting Started
2.1 Movella DOT set
A standard Movella DOT v2 set contains:
•5 Movella DOT sensors
•1 charger with power cable
•Movella DOT software package
Figure 2: Movella DOT set
The easiest way to get started with Movella DOT is to use the Movella DOT app (Android/iOS) to connect the
sensors. You can get to know the capabilities of Movella DOT and to configure the sensor according to your
needs. Refer to this BASE Article to get started quickly.
2.2 Movella DOT sensor
Movella DOT sensor provides 3D angular velocity using a gyroscope, 3D acceleration using an accelerometer and
3D earth magnetic field using a magnetometer. Combined with Xsens sensor fusion algorithms, 3D orientation
and free acceleration are provided. With the wireless nature of Bluetooth 5.0, Movella DOT sensor is an excellent
measurement unit for tracking human body motions.
Figure 3: Movella DOT sensor
On top of the sensor is the LED giving the indications of sensor states. There is a power button in the middle of
the sensor. A micro-USB port at the bottom can be used to charge the sensor.

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2.2.1 Activate sensor
When using the DOT sensors for the first time, you need to activate the sensors by connecting them to a powered
USB cable. You can directly connect to the micro-USB port at the bottom of the sensor, or place multiple sensors
in the charger and then connect the charger.
The sensors are shipped in transport mode so that they are in a minimal discharge state to maximize the battery
power and extend shelf life. Once the sensor is activated from the transport mode, it is ready for use and doesn’t
need to be activated again.
2.2.2 Power ON/OFF
The sensor can be powered on by pressing the power button for 2 seconds, and it can be turned off by pressing
the power button for over 3 seconds or through the Movella DOT app. During that, the LED will give a clear
indication by its LED patterns. Refer to section 3.3.1 and 3.3.2 for more details about power ON/OFF.
2.2.3 LED patterns
Movella DOT v2 sensor has LED patterns to indicate different sensor states.
Table 1: LED patterns
Type
LED
colour
LED patterns
Sensor state
General
states
ON for 2 seconds
Sensor is being powered on
ON for 1 second and then fade out
Sensor is being powered off
-
OFF
Power saving or off
Blink 1 time per second
Bluetooth broadcasting
Blink 1 time every 10 seconds
Ready to use (Bluetooth connected)
ON during sync period, all sensors blink (very
quick) synchronously for 3 second if sync
succeeds.
Syncing
Blink 2 times (very quick) every 2 seconds
After a successful sync and during
measurement (both streaming and
recording)
Blink 8 times (ultra-quick) and a short pause,
last for 10 seconds.
Sensor is being identified
Blink 2 times (very quick) and a long pause
Bootloader - normal state. This LED status
will briefly appear after a successful firmware
upgrade
Charging
states1
Fade in and out, 2-seconds cycle
Charging (battery ≤ 20%)
Fade in and out, 2-seconds cycle
Charging (20%< battery ≤90%)
ON
Fully charged (battery >90%)
Error states
ON
Bootloader - error state. Refer to the trouble
shooting section for further information.
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The charging state LED patterns will only be displayed if users don’t enable the “Power on via USB plug in”
option and the sensor is turned off during charging. Otherwise, sensor will show general state LED patterns as
they have higher priority. It is worth noting that this is only about LED display, as long as a powered USB cable is
connected, the sensor will be charging.

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Blink 8 times per second
Microcontroller unit (MCU) or battery
overheated during charging. Refer to the
trouble shooting section for further
information.
2.2.4 Reset sensor
In case of firmware failure and the sensor cannot respond to any operations defined in the firmware, a hardware
reset function is provided. Follow the steps below to reset the v2 sensor:
1. Press and hold the power button for a minimum of 11 seconds and then release
2. Power on the sensor again by pressing the power button for 2 seconds
2.3 Charger
The charger is a docking station for 5 sensors and includes a plastic cover shell, along with a USB power cable.
You can open the charger by holding the cover shell and pull out the docking .0 the right side.
Each docking slot features an embedded micro-USB port. Sensors can be charged by plugging them into the
respective slots. Another micro-USB port placed on the right side of the Movella DOT charger is used to power
on and charge all the sensors docked in the charger. To power this micro-USB port, an adapter of 5V/300mA is
enough but we would recommend using a 5V/500mA adapter (5 sensor loads) based on standard USB 2.0 power
supply.
Figure 4: Charger with power cable
The USB communication hub is integrated in the v2 charger. Using the Movella DOT Data Exporter software
installed on a PC, you can export the recording files from 5 sensors to the PC at the same time via the charger.
2.4 Body straps and accessories
You can check all the available straps and accessories from the webshop. Refer to this BASE article for more
information on sensor attachment.
2.5 Software
As Movella DOT serves as a wearable sensor development platform, we provide all the software needed for
different demands. The software package can be download here and includes:
•Movella DOT Software Development Kit (Android/iOS/PC)
•Movella DOT app (Android/iOS)

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•Movella DOT Data Exporter
•SDK programming guide for Android and iOS
•User manual
•BLE service specifications
2.5.1 Supported platforms
Table 2: SDK language and supported OS
Software name
Language
Supported OS
SDK for Android
Java
•Android OS 8.0 and above
•ARMv8 CPU architecture, arm64-v8a ABI (64-bit)
SDK for iOS
Objective-C
•iOS 11.0 and above
SDK for PC2
C++/C#/Python/Java
•Windows 10 or above
•Linux (Ubuntu 20.04)
Table 3: Software supported platforms
Software
Supported platforms
Movella DOT app (Android)
•Android OS 8.0 and above
•ARMv8 CPU architecture, arm64-v8a ABI (64-bit)
Movella DOT app (iOS)
•iOS 11.0 and above
Movella DOT Data Exporter
•Windows 10
Bluetooth requirements
•Best performance with BLE 5.0, DLE supported
•Compatible with Bluetooth 4.2
2.5.2 Choose your software
You can choose to use different software according to your demands. Please refer to the following instructions
on how to choose your software:
•If you focus on the motion data and want to quickly understand the data outputs and capabilities of
Movella DOT, download and install Movella DOT app. It will allow you to:
oScan and connect the sensors
oData real-time streaming
oRecord data in sensor and export to other devices
oMagnetic field mapping
oFirmware update and other functions
Refer to this BASE Article for detailed guidance on Android app and iOS app operations. Movella DOT
app tutorial video is also available.
•If you are a developer or system integrator wanting to build your own applications, download Movella
DOT Software Development Kit (SDK) for Android, iOS and PC-based applications. Download the SDK,
check out the well-written documentation and example code to get started.
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Now it’s only the first release of the PC SDK, which contains the most important features. We will be releasing
the remaining features in the coming months to make it complete.

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oAndroid example: https://github.com/MovellaTechnologies/dot_example_android
iOS example: https://github.com/MovellaTechnologies/dot_example_ios
oPC example codes are included in the SDK package.
•If the SDK does not support the language or OS that you are using, and you are familiar with Bluetooth
protocol and development, a lower level Movella DOT BLE Service Specifications is provided to enable
direct Bluetooth communication with Movella DOT. Theoretical, you can build applications via this
protocol on any platform that supports Bluetooth. An open-source project - Xsens DOT Server is
provided as a simple example code for Windows and macOS developers. You can find it here:
https://github.com/MovellaTechnologies/xsens_dot_server.
2.6 Tips for best practice
2.6.1 Multiple sensors connection
Although there is no connection limit in the Movella DOT app, SDK or BLE services, hardware and OS constraints
of the central devices have a ceiling to the maximum number of sensors that can be connected simultaneously.
For Android, MacOS and Windows, it is possible to connect up to 7 sensors. In iOS, Linux PC or Raspberry Pi, it is
possible to connect up to 11 sensors. The actual connection capability is highly dependent on the device you
choose.
However, the BLE performance cannot be guaranteed if the connection limit is reached. If big data loss or
connection failure cases are observed, reduce the sensor connection number or the transmission payload.
2.6.2 Magnetic distortion
Ferromagnetic material (iron or steel), magnets or strong electrical currents (several amperes) in the
environment near the sensor will cause disturbances to the local magnetic field. The magnetometer in Movella
DOT sensors is used as a 3D compass to determine the direction of the Earth true north (heading or yaw) and is
used as an absolute reference in the calculation of 3D orientation. For detailed information about the influence
of magnetic field on orientation, see the PhD thesis “Inertial and magnetic sensing of human movement near
ferromagnetic materials” D. Roetenberg 2006. For best results when measuring with Movella DOT, it is advised
to avoid highly magnetized areas when carrying out measurements, particularly in the beginning of the
measurement.
To check the magnetic distortion, you can use the Movella DOT app to check the Magnetic Norm
3
in magnetic
field data after connecting at least one DOT. Look at the Magnetic Norm curve while moving in the measurement
area.
•Areas for which the magnetic norm = 1 and the variation remains within ±0.2 are magnetic
homogeneous and is optimal for carrying out the measurements (see Figure 5). However, if the
measurement begins with a magnetic norm of around 2 or 3, and remains within ±0.2 of this value, the
orientation should remain accurate.
•If the Mag Norm will vary depending on the location and orientation of the device (see Figure 6), there
are magnetic distortions in the environment.
3
Magnetic Norm (Mag Norm) is the norm of all magnetic axis vectors (X, Y and Z) combined. It can be used as an
indication of magnetic distortions.

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Figure 5: Mag Norm is constant while moving
Figure 6: Mag Norm fluctuates when moving
XKFCore algorithm running in the motion processor can compensate for the magnetic disturbance caused by
short or fast fluctuating disturbances by optimally using the available sensor information and valid assumptions
about the application. However, if the disturbance is slow and large (>±0.2) or lasts for over 30s, it’s difficult for
the algorithm to compensate for and will influence heading accuracy.
If the magnetic field norm has large fluctuations, or the Movella DOT sensor is attached to an instrument or
prosthesis that influences the magnetic field (e.g. ferromagnetic object), it is best to carry out Magnetic Field
Mapping (MFM) for this DOT (see section 3.4) to recalibrate the magnetometer.
NOTES:
•Never expose sensor to strong magnetic fields. The sensor contains the absolute possible minimum of
ferromagnetic materials. Nonetheless, some minor components can be magnetized permanently by
exposure to strong magnetic fields. This will not damage the unit but will render the calibration of the
magnetometers useless, typically observed as a (large) deviation in the heading.
2.6.3 Drift in orientation data
To guarantee heading accuracy and, therefore, to avoid drift in orientation data, the sensors must be kept still at
the beginning of the measurement for 2-3 seconds.
Magnetic interferences can also affect orientation accuracy, please refer to section 2.6.2 to check the presence
of magnetic distortion and perform the MFM if needed.
2.6.4 Cleaning method
To clean the Movella DOT sensors and charger, use a moist cloth to wipe the surface.

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2.6.5 Long-term storage guidelines
Follow the recommended guidelines to preserve the battery life of the sensors:
•Operating temperature: 0°C - 50°C.
•Storage temperature: 25°C±10°C.
New sensors in transport mode
New sensors are shipped in transport mode. In this mode they can be stored for max 1 year without the need to
re-charge.
Important! Charging the sensors will move the sensors out of transport mode, thus activating the sensors.
Transport mode cannot be restored again. So if the sensors will be stored for a prolonged period of time, please
do NOT move the sensors out of transport mode unless absolutely necessary.
Sensors without transport mode
If the sensors are out of transport mode, recharge them at least every 3 months according to the following
recommended guidelines to slow the rate of battery ageing, thereby improving the battery shelf life:
1. Charge all sensors to > 90% battery level.
a. Under default circumstances, if sensor's power-on configuration has not been altered and it is
not powered on, you can know the battery level is > 90% when the LED displays solid green
during charging.
b. If the sensors are configured to be powered on by USB plug-in, or the sensors are turned on
during charging, you need to connect them to the Movella DOT app and check the battery level
to know if it’s > 90%.
2. After charging, disconnect the sensors from charger, and make sure the sensors are powered off before
storing. To turn off the sensors, press and hold the button for 3 seconds or use the Movella DOT app.
The LED will turn solid green for 1 second and then fade out, indicating that the sensor has been properly
powered off.
Stock handling advice
1. Sensors in stock should not be removed from transport mode. If handling is required before shipping
and the sensors need to be activated, it is best to do so as close to the shipping time as possible.
2. It’s advised to maintain stock level for a maximum of 6 months.
3. Manage stock according to the First In First Out principle (FIFO) to minimize the time the sensors spend
in stock.

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2.7 Troubleshooting
Table 4: Trouble shooting
Problem
Solution
Sensor LED is solid red, indicating it’s in bootloader error
state
Reset the sensor by pressing the power button over 11
seconds.
Sensor LED is blinking fast in red and lasts for more than
10 seconds, indicating overheat during charging
Stop charging the sensor and leave it for a while to see if
the LED is back to normal. If not, please try to reset the
sensor.
If the solution does not work for you, please contact our customer support. Customer support contact
information can be found in section 6.2.

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3Movella DOT Overview
The signal processing architecture of Movella DOT sensor is presented in Figure 7. The strap down integration
(SDI) and sensor fusion algorithms (XKFCore) are integrated into the firmware. You can obtain the orientation
increments and velocity increments from SDI, as well as the 3D orientation and free acceleration from XKFCore.
Figure 7: Movella DOT signal processing architecture
3.1 Strapdown integration
Strap down integration is a method used to compute orientation and velocity increments by integrating angular
velocity from gyroscope and acceleration from the accelerometer.
The angular velocity and acceleration data are sampled and calibrated at a high frequency (800 Hz) by the
embedded MCU of Movella DOT sensor to maintain accuracy under dynamic movements such as running and
jumping. Due to the high sampling frequency, the data cannot be transmitted via Bluetooth directly and would
typically present an excessive computational load on the receiving host device (e.g., mobile phone). The SDI
algorithm receives the high-rate sensor input and processes it into a lower-rate signal at 60 Hz. The main
advantage of using the SDI algorithm is that the accuracy is maintained, and information is preserved to ensure
precise orientation tracking.
The SDK data parser has built-in functions to convert SDI quantities to calibrated angular velocity (rad/s) and
acceleration (m/s2) data. Refer to data conversion sections in SDK programming guides.
3.2 Sensor fusion algorithm and filter profiles
The 3D orientation of the sensor is computed by Xsens’ latest Kalman filter core algorithm (XKFCore) for sensor
fusion, which is optimized for human motions. It uses the output from SDI to compute a statistical optimal 3D
orientation estimate of high accuracy, with no drift for both static and dynamic movements. The XKFCore uses
the measurement of gravitational acceleration and Earth magnetic north to compensate for slowly increasing
errors from the integration of the rate of turn data, and also gives out free acceleration.
As described above, the XKFCore makes assumptions on the range of acceleration and magnetic field sensed to
obtain orientation. Since those quantities can widely differ among different user applications, multiple filter
profiles are introduced to improve the orientation estimation accuracy. As a result, the XKFCore is optimised to
suit different types of movements and applications. Find below additional information on the filter profiles
available to choose which is best suited for your application.

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Table 5: Filter profiles
Name
Description
General
This filter profile is the default setting. It assumes moderate dynamics and a
homogeneous magnetic field. External magnetic distortion is considered relatively
short.
Dynamic
This filter profile assumes fast and jerky motions that last for a short time. The dynamic
filter uses the magnetometer for stabilization of the heading and assumes very short
magnetic distortions. Typical applications are when sensors are applied on subjects for
sports such as sprinting.
3.3 Movella DOT sensor state transition
Figure 8: Movella DOT state transition diagram
3.3.1 Power ON
You can power on the sensor by pressing the power button for 2 seconds. Sensor will go to advertisement mode
after powered on.
Starting with firmware version 2.0.0, there are more power on options to allow you to choose whether to power
on the sensor via USB plugin. By default, power on by USB is disabled. So, the sensor will be in charging status if
connected with USB cable. In the charging status, the sensor keeps charging until battery full and it will not do
Bluetooth advertising.
Figure 9: USB power on disabled

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You can change this setting via Movella DOT app (v2021.0 or above) or the SDK (v2021.0 or above). By enabling
USB power on, the sensor will power on immediately after the USB plugin. With this feature, you can power on
multiple sensors with the USB plugin at once.
Figure 10: USB power on enabled
3.3.2 Power OFF
Sensor will power off under 3 conditions:
1. Power button is pressed over 3 seconds
2. Receive power off command
3. Battery level is lower than 2%.
For Android users, it is possible to power off all the connected DOTs simultaneously. This function is published in
the Android Movella DOT app v2023.0.
3.3.3 Advertisement
In advertisement mode, sensors will perform operation idle detection, waiting for BLE connection from host
devices. With the default power saving settings, if there is no BLE connection detected over 10 minutes
4
during
advertisement, the sensor will enter power saving mode.
3.3.4 Connection
Once the Bluetooth connection is established, information such as MAC address, device tag name, battery level
and charging status... etc. can be retrieved from the sensor. In Movella DOT app, a reconnection will start
automatically once the connection is lost.
If no measurement is started over 30 minutes
5
during connection, sensor will enter power saving mode.
There is no sensor connection limit set in any software provided by Movella. Refer to section 2.6.1 for best
practices on connecting multiple sensors.
3.3.5 Synchronization
Each sensor has its own clock domain. So, it is important to have the measurement data time-synchronized
between different sensors, especially in scenarios where multiple sensors are required simultaneously, e.g.,
calculation of joint angles.
4
Default time threshold which can be changed in Xsens DOT app, SDK or by BLE services.
5
Default time threshold which can be changed in Xsens DOT app, SDK or by BLE services.

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All the sensors will be time-synced to a common sensor time base after synchronization. As the sensor clock
drifts, the synchronization accuracy will decrease over time (Table 4).
Table 6: Synchronization accuracy
Time
Accuracy
After 30 min
1 ppm
After 1 hour
4 ppm
A successful synchronization will take about 14 seconds. During the synchronization, one sensor will be the root
node, whereas the remaining sensors are scanners. The root node will periodically send out advertisement
messages while the scanners will receive the messages and correct their own time domain by calculating the
skew and offset of the root clock.
To achieve a better synchronization result, it is advised to put the root node in a central position of all the
scanners. In Movella DOT app, the first connected sensor will be the root node. SDK users and other developers
can set their own rules to choose the root node.
Figure 11: Root and scanners in synchronization
Synchronization should take place before the measurement so that all the sensor data are time-synced. After a
synchronization, multiple measurements can be started and stopped without additional synchronization. Refer
to this BASE article for details about synchronization in Movella DOT app.
NOTES:
•Stop the synchronization after all the measurements to prolong the battery life.
3.3.6 Measurement
Two types of measurement are available with Movella DOT. Table 7 shows the available output rates for different
types of measurement.
Table 7: Output rates
Measurement
Available output rates
Real-time streaming
1Hz, 4Hz, 10Hz, 12Hz, 15Hz, 20Hz, 30Hz and 60Hz

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Recording
1Hz, 4Hz, 10Hz, 12Hz, 15Hz, 20Hz, 30Hz, 60Hz and 120Hz
By choosing lower output rates, less data per unit time will be transmitted when compared to the standard 60Hz
output rate. As a result, this can mitigate the occurrence of data loss in Real-Time Streaming mode and less data
will be stored, thereby recording time can be extended. Conversely, the higher output rate (120Hz) is better
suited for high-dynamic applications, where a larger amount of data is needed. However, the higher output rate
is only available for Recording mode.
1.1.1.1 Real-time streaming
In real-time streaming, motion data is streamed and logged to central device (such as the mobile phone) via
constant Bluetooth connection.
Sensor fusion data, inertial data and other custom data combinations are provided in real-time streaming,
together with packet counter and timestamp. Refer to Chapter 4 for data output specifications.
NOTES:
•In the Movella DOT app, to make plotting data readable, orientation data will always be displayed in
Euler angles, whereas data in the log file will be stored in the chosen format (Euler or quaternion).
•In the Movella DOT app, to make plotting data readable, inertial data will always be displayed as
acceleration (m/s2) and angular velocity (degrees/s) whereas data in the log file will be stored in the
chosen format (high fidelity, delta quantities or rate quantities).
•Sensor will still be in streaming status even if the Bluetooth connection is lost. So stop the streaming
after every measurement to prevent battery drain.
High fidelity mode
High fidelity mode is available in real-time streaming. In this mode, Movella proprietary data format will be
transmitted via Bluetooth and parsed in Movella DOT app or SDK. The advantage of this mode is that even in the
case of transient data loss, higher frequency (800 Hz) information is still preserved with lower output data rate
(60 Hz).
High fidelity data will be parsed to delta_q, delta_v in Movella DOT app. Functions to parse high fidelity data to
delta_q, delta_v or calibrated angular velocity and acceleration are available in SDK. Refer to SDK programming
guide for detailed information.
1.1.1.2 Recording
In recording mode, motion data is stored within the sensor internal storage and can be exported for post-
processing. The internal storage of the v2 DOT is 64MB. The available recording time depends on the selected
output frequency. For example, the available recording time is around 6 hours at 60Hz. With higher output
frequency comes less available recording time.
Recording can be started and stopped using Movella DOT app and these functionalities are available in Movella
DOT SDK or BLE Service Specification manual. Bluetooth connection is not required during recording.
Recording will also stop in the following situations:
•power button is pressed for 1 second during recording.

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•time is up for timed recording sessions.
•flash memory is over 90%.
Data can be exported via Bluetooth or via USB connection. Wireless data transfer using Bluetooth is suitable for
exporting small files (a few minutes). However, when exporting large amounts of data, it is recommended to use
Movella DOT Data Exporter to export via USB on PC. Refer to this BASE article on how to use Data Exporter.
As a rule of thumb, when exporting from 5 sensors through the charger, the export speed is around 0.16Mbps.
It takes around 10 min to export 60 min’s recording at 60Hz.
When exporting data via Bluetooth, it is advised to select few sensors at a time to prevent data transmission loss
or connection failure. You can choose different types of data configurations and select recording files when
exporting.
Note that free acceleration is not included. For further information on how to calculate it from other quantities,
refer to this BASE article.
3.3.7 Power saving
In power-saving mode, sensors will turn off the signal pipeline and BLE connection, put the MCU in a sleep state
to ensure minimum power consumption. In this state, sensors cannot be discovered by host devices.
The default time thresholds to enter power saving mode is set to 10 min in advertisement mode and 30 min in
connection mode. Power saving mode can be disabled and the time thresholds can be adjusted in Movella DOT
app, SDK or by BLE services.
Sensors will exit power saving mode when:
•Power button is pressed
•Acceleration is detected by accelerometer
Once the sensor enters power saving mode, you can wake it up by pressing the power button or simply shaking
it. Movella DOT will return to advertisement mode when exiting power saving mode.
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3.3.8 Button callback function
If there is a single click on the power button during connection, a BLE notification will be sent with a timestamp
when this single click is applied. This function is called “Button callback”. It is further explained in the Movella
DOT SDK programming guide and the BLE Service Specification. Refer to those for more information.
3.4 Magnetic Field Mapper
When Movella DOT sensor is mounted to an object that contains ferromagnetic materials, the measured
magnetic field can become distorted, causing errors in measured orientation. To correct for known magnetic
disturbances, Magnetic Field Mapper function has been developed to allow users to remap the magnetic field of
the sensor.
The MFM can be executed in a few minutes and yields a new set of calibration values that can be written to the
Movella DOT’s non-volatile memory, which means it will not be erased by powering off or firmware updates.