WITMOTION WT901BLE BLE5.0 User Manual

Tutorial Link

Google Drive

Link to instructions DEMO:

• WITMOTION Youtube Channel
• WT901BLE Playlist

If you have technical problems or cannot find the information that you need in the provided documents, please contact the WITMOTION support team. The engineering team is committed to providing the required support necessary to ensure successful operation of AHRS sensors.

Contact

Technical Support Contact Info

Application

• AGV Truck
• Platform Stability
• Auto Safety System
• 3D Virtual Reality
• Industrial Control
• Robot
• Car Navigation
• UAV
• Truck-mounted Satellite Antenna Equipment

Contents

Tutorial Link - 2

Contact - 2

Application - 2

Contents - 3

1 Introduction - 5

• 1.1 Warning Statement - 6
• 1.2 LED Status - 6

2 Use Instructions with PC - 7

• 2.1 PC Connection - 7
• 2.1.1 Serial Connection - 7
• 2.1.2 BLE 5.0 Adapter Connection - 10
• 2.2 Software Introduction - 11
• 2.2.1 Main Menu - 11
• 2.2.2 Menu of Configuration - 12
• 2.3 Calibration - 15
• 2.3.1 Accelerometer Calibration - 15
• 2.3.2 Magnetic Field Calibration - 17
• 2.3.3 Gyroscope Automatic Calibration - 19
• 2.3.4 Reset Z-axis Angle - 19
• 2.3.5 Reset Height to 0 - 19
• 2.4 Configuration - 20
• 2.4.1 Data Recording - 20
• 2.4.2 Data Playback - 22
• 2.4.3 Placement Direction - 24
• 2.4.4 Bandwidth - 25
• 2.4.5 6-axis/ 9-axis Algorithm - 27

3 Use Instructions with Android phone - 28

• 3.1 APP Installation - 28
• 3.2 Connection - 29
• 3.3 Calibration - 31
• 3.3.1 Acceleration Calibration - 31
• 3.3.2 Magnetic Field Calibration - 32

1 Introduction

The WT901BLE BLE5.0 is a multi-sensor device detecting acceleration, angular velocity, angle, and magnetic field. Its compact size makes it suitable for industrial retrofit applications like condition monitoring and predictive maintenance. Configuration allows users to address various use cases by interpreting sensor data via smart algorithms.

The WT901BLE BLE5.0 is scientifically known as an AHRS IMU sensor. It measures 3-axis angle, angular velocity, acceleration, and magnetic field, with its strength lying in its algorithm for accurate three-axis angle calculation. It is employed where high measurement accuracy is required.

The WT901BLE BLE5.0 offers several advantages over competing sensors:

• Heated for best data availability: Features a new WITMOTION patented zero-bias automatic detection calibration algorithm that outperforms traditional accelerometer sensors.
• High precision output: Provides Roll Pitch Yaw (X Y Z axis) Acceleration + Angular Velocity + Angle + Magnetic Field data.
• Low cost of ownership: Includes remote diagnostics and lifetime technical support from the WITMOTION service team.
• Comprehensive resources: Offers developed tutorials, manuals, datasheets, demo videos, free software for Windows, Android, and iOS apps, and communication protocols for project development.
• Industry recognition: WITMOTION sensors are praised by thousands of engineers as a recommended attitude measurement solution.

(Image Description: A photograph showing the WT901BLE BLE5.0 sensor module, a small blue printed circuit board with several gold-plated pins, and two sets of header pins.)

1.1 Warning Statement

• Applying more than 5 Volts across the sensor wiring can cause permanent damage.
• Connecting VCC to GND directly will burn the circuit board.
• For proper instrument grounding, use original WITMOTION factory-made cables or accessories.
• Do not change the baud rate, as the WITMOTION BLUETOOTH sensor's baud rate is fixed.
• For secondary development or integration projects, use WITMOTION's compiled sample code.

1.2 LED Status

2 Use Instructions with PC

2.1 PC Connection

The PC software is compatible only with the Windows system. Link to download software.

2.1.1 Serial Connection

Step 1. Connect the sensor with a serial converter.

PIN Connection:

• VCC - 5V
• TX - RX
• RX - TX
• GND - GND

(When connecting with a computer, VCC-5V is recommended.)

(Diagram Description: A diagram illustrating TTL PIN Definition with color-coded wires: RED for VCC 5V, YELLOW for TX, GREEN for RX, and BLACK for GND. It shows a sensor connected via a serial converter to a USB port on a computer.)

Recommended tools:

(Image Description: A row of images showing three types of serial converters: a 3-in-1 converter, a 6-in-1 converter, and a TTL serial cable.)

Step 2. Unzip the software and install the driver CH340 or CP2102 (depending on the accessory used).

Link to tutorial of 3-in-1 serial converter/ TTL serial cable (CH340 driver)

Link to tutorial of 6-in-1 serial converter (CP2102 driver)

Step 3. Confirm the COM port in Device Manager.

(Screenshot Description: A screenshot of the Windows Device Manager showing the 'Ports (COM & LPT)' section, with 'Silicon Labs CP210x USB to UART Bridge (COM15)' detected.)

Step 4. Open the software (Minimu.exe). Data will appear after auto-search finishes.

Notice: If not successful, operate manually. Choose the COM port and baud rate 115200; data will be shown on the software.

(Screenshot Description: The WITMOTION software interface displaying real-time sensor data, including Angle X, Angle Y, and Angle Z values, along with calibration buttons and a compass-like indicator.)

2.1.2 BLE 5.0 Adapter Connection

Adapter's CP2102 driver link

Step 1. Insert the adapter into the USB port.

Step 2. Power on the sensor after the adapter's blue light flashes.

Step 3. Wait until the adapter's blue LED light stays on, indicating pairing succeeded.

Step 4. Open the software, Minimu.exe.

Step 5. Data will appear once the auto-search is finished.

(Screenshot Description: The WITMOTION software interface displaying connection status and sensor readings, similar to the serial connection setup, with a photograph showing the sensor connected via a blue USB adapter.)

2.2 Software Introduction

2.2.1 Main Menu

(Screenshot Description: The WITMOTION software interface showing the main menu with options like File, Tools, Record, 3D, Config, Help, and Auto-search, along with real-time angle readings.)

2.2.2 Menu of Configuration

(Screenshot Description: The 'Bluetooth 5.0 - Config' window of the WITMOTION software, showing various configuration options.)

System

Calibrate

Range

Communication

2.3 Calibration

Preparation: Ensure the sensor is "Online". Calibration on PC software is required for the first-time usage.

2.3.1 Accelerometer Calibration

Purpose: To remove the zero bias of the accelerometer. Before calibration, there may be bias errors; after calibration, measurements will be accurate.

Methods:

• Step 1. Keep the module horizontally stationary.
• Step 2. Click the "Acceleration" button in the "Config" menu and wait for 5 seconds.
• Step 3. Calibration is done when "OK" is displayed.
• Step 4. Check the result: Confirm if there is 1g on the Z-axis acceleration.

(Screenshot Description: The WITMOTION software's configuration window showing the 'Acceleration' calibration button highlighted, with a progress indicator and a data table displaying acceleration, angular velocity, and magnetic field values.)

2.3.2 Magnetic Field Calibration

Purpose: To remove the zero bias of the magnetic field sensor, which can otherwise cause significant measurement errors and affect heading angle accuracy.

Preparation:

1. Sensors should be at least 20cm away from magnetic and iron materials.
2. The value of H (magnetic field) must be lower than 350.

Methods:

• Step 1. Open the Config menu.
• Step 2. Click the "magnetic field" button and slowly rotate the sensor 360° around the X, Y, and Z axes accordingly.

(Screenshot Description: The WITMOTION software's configuration window showing the 'Magnetic Field' calibration button active, with instructions to rotate the sensor. A data table displays sensor readings.)

• Step 3. Click OK once the calibration is complete.
• Step 4. Place the sensor horizontally stationary, with the Y-axis pointing North.
• Step 5. Check the Z-axis angle data; it should be approximately 0°.

2.3.3 Gyroscope Automatic Calibration

The gyroscope calibration calibrates the angular velocity. The sensor calibrates automatically. It is recommended that automatic gyroscope calibration be inactivated only if the module rotates at a constant speed.

2.3.4 Reset Z-axis Angle

Note: To avoid magnetic interference, you can switch the algorithm to 6-axis to use the Z-axis angle reset function.

The Z-axis angle is an absolute angle, referencing the northeast sky. Resetting the Z-axis to 0 makes the initial angle relative to 0 degree. If the module experiences significant Z-axis drift during use, it can be recalibrated. When the module is powered on, the Z-axis will automatically return to 0.

Calibration methods: First, keep the module static, then click "Reset Z-axis Angle" in the "Config" menu. The Z-axis angle in the module data bar should return to 0 degree.

2.3.5 Reset Height to 0

This function is only available for modules with a built-in barometer, such as the WT901B, HWT901B, WTGAHRS1, and WTGAHRS2.

2.4 Configuration

2.4.1 Data Recording

The sensor module does not have internal memory; data can be recorded and saved on the computer.

Method: Click "Record" and then "Start" to save the data as a TXT file. The saved file is located in the upper computer program's directory as Data.tsv. The beginning of the file contains values corresponding to the data.

(Screenshot Description: The WITMOTION software interface with the 'Record' button highlighted, ready to start data logging.)

It is highly recommended to paste the data into an Excel file for better organization and readability.

(Screenshot Description: A view of the software displaying recorded data in a table format, followed by a screenshot showing raw hexadecimal data and structured data in a text editor or spreadsheet.)

2.4.2 Data Playback

New function: Each time a recorded file is created, a BIN file is generated in the record file folder within the installed software path. This allows for recorded data playback.

Recorded data playback method:

• Step 1: Disconnect the sensor.
• Step 2: Click the "File" button and then click "Load".

(Screenshot Description: The WITMOTION software interface with the 'File' menu open, showing the 'Load' option highlighted, and a file explorer window displaying a list of recorded BIN files.)

• Step 3: Choose the original path of the software installation and load the BIN file.
• Step 4: Click "Run". The binary file will play back, and the playback rate can be edited.

(Screenshot Description: The WITMOTION software interface showing the playback function with a file selection dialog, followed by the main interface displaying playback data and an editable rate control.)

2.4.3 Placement Direction

The default installation direction of the module is horizontal. For vertical installation, the setting can be changed.

• Step 1: Rotate the module 90 degrees around the X-axis.
• Step 2: Place the sensor 90 degrees vertically.
• Step 3: Click "Vertical" for install directions in the "Config" menu.

(Screenshot Description: The WITMOTION software configuration window showing the 'Install Direction' setting changed to 'Vertical'.)

2.4.4 Bandwidth

The default bandwidth is 20Hz.

Explanation:

1. A higher bandwidth setting leads to greater fluctuation in the data waveform. Conversely, a lower bandwidth results in smoother data. For example, a bandwidth of 50Hz with an output rate of 5Hz produces a very steady waveform.

(Screenshot Description: The WITMOTION software configuration window showing the 'Band Width' dropdown menu with various frequency options.)

A bandwidth of 256Hz with an output rate of 50Hz will show more fluctuation.

(Screenshot Description: Two waveform graphs illustrating data fluctuation at different bandwidth and output rate settings.)

2. A higher bandwidth setting helps resolve data-repeating issues. For instance, if the bandwidth is set to 20Hz and the retrieval rate is 50Hz, there will be 5 repeating data points. To avoid repeating data, increase the bandwidth to more than 50Hz.

2.4.5 6-axis/ 9-axis Algorithm

6-axis algorithm: Z-axis angle is primarily calculated based on angular velocity integral, which may introduce calculated error on the Z-axis angle.

9-axis algorithm: Z-axis angle is mainly calculated and analyzed based on the magnetic field, resulting in minimal drift. The default algorithm for WT901BLECL is 9-axis.

If magnetic field interference is present in the installed environment, switching to the 6-axis algorithm is recommended for angle detection.

Method:

• Step 1: Switch to the "6-axis" algorithm on the "Config" menu.
• Step 2: Proceed with "Accelerometer calibration" and "Reset Z-axis angle" calibration.

After calibration, the sensor can be used normally.

(Screenshot Description: The WITMOTION software configuration window showing the 'Algorithm' setting changed to '6-axis'.)

3 Use Instructions with Android phone

For APP configuration details, please refer to Chapter 2.2.

3.1 APP Installation

Install the APK file and grant permissions for Location and Storage.

(Screenshot Description: A mobile app installation screen showing permission requests for Storage and Location, with options to grant or deny.)

APP download link

About Android APP:

1. It is required to allow application positioning (Always allowed) and enable the positioning function and Bluetooth.
2. Note: Paired devices can be searched without positioning enabled, but according to Google's requirements, if an app is installed on a higher version of Android (6.0+), positioning must be allowed when using Bluetooth.
3. After turning on Bluetooth, it takes approximately one minute to search for authorization to find Bluetooth.

3.2 Connection

• Step 1. Install the APK file and grant permissions for Location and Storage.
• Step 2. Open the APP and choose "BLE 5.0 Series" as the sensor series.

(Screenshot Description: The WITMOTION mobile app interface showing a "Select Module Type" screen with options including "BLE 5.0 Series".)

• Step 3: Power on the sensor and scan for the device.

(Screenshot Description: The WITMOTION mobile app displaying a list of scanned Bluetooth devices, such as WT901BLE57 and WT901BLE56, with their RSSI values.)

Step 4. When pairing is complete, the sensor's blue LED will flash for about one second. After a few seconds, data will display automatically.

(Screenshot Description: The WITMOTION mobile app showing real-time data charts for Angles and Angle Velocity, along with numerical values for Angle X, Angle Y, Angle Z, and T.)

3.3 Calibration

Link to calibration demo

3.3.1 Acceleration Calibration

• Step 1. Keep the module horizontally stationary.
• Step 2. Click the "Calibration" menu.
• Step 3. Click "Acceleration Calibration" and wait for 3 seconds.
• Step 5. Check the result: Confirm if there is 1g on the Z-axis acceleration.

(Screenshot Description: The WITMOTION mobile app showing the calibration menu with "Acceleration Calibration" in progress.)

3.3.2 Magnetic Field Calibration

• Step 1. Click the "Calibration" menu.
• Step 2. Click the "Magnetic calibration" button.
• Step 3. Slowly rotate the module 360° around the X, Y, and Z axes accordingly.
• Step 4. After rotation, click "Finish".

(Screenshot Description: The WITMOTION mobile app showing the calibration menu with "Magnetic calibration" in progress, followed by a screen indicating completion.)

Check the result: The Z-axis angle will have less drift than before.

Notice: If calibration is not successful, stay away from objects that may create magnetic field interference.