USER MANUAL WT901 Inclinometer Sensor WT901 | manual v0513 | http://wiki.wit-motion.
Tutorial link Google Drive Link to instructions DEMO: WITMOTION Youtube Channel WT901 Playlist If you have technical problems or cannot find the information that you need in the provided documents, please contact our support team. Our engineering team is committed to providing the required support necessary to ensure that you are successful with the operation of our AHRS sensors.
Contents Tutorial link.................................................................................................................... - 2 Contact............................................................................................................................ - 2 Application...................................................................................................................... - 2 Contents...........................................................................................
2.4.8 Bandwidth......................................................................................... - 29 2.4.9 Restore Factory Setting............................................................... - 31 2.4.10 Set IIC Address............................................................................ - 32 2.4.11 Set Extended Port....................................................................... - 33 2.4.12 6-axis/ 9-axis Algorithm...........................................................- 34 2.4.
1 Introduction The WT901 is a multi-sensor device detecting acceleration, angular velocity, angle as well as magnetic filed. The small outline makes it perfectly suitable for industrial retrofit applications such as condition monitoring and predictive maintenance. Configuring the device enables the customer to address a broad variety of use cases by interpreting the sensor data by smart algorithms. WT901’s scientific name is AHRS IMU sensor.
1.1 Warning Statement Putting more than 5 Volt across the sensor wiring of the main power supply can lead to permanent damage to the sensor. VCC cannot connect with GND directly, otherwise it will lead to the burning of the circuit board. For proper instrument grounding: use WITMOTION with its original factory-made cable or accessories. For secondary developing project or integration: use WITMOTION with its compiled sample code. WT901 | manual v0513 | http://wiki.wit-motion.
2 Use Instructions with PC 2.1 Connection Method PC software is only compatible with Windows system. Link to WT901’s demo video 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 computer, VCC-5V is recommended.) WT901 | manual v0513 | http://wiki.wit-motion.
Recommended tools: 3 in-1 converter 6-in-1 converter TTL serial cable Step 2. Unzip the software and install the driver CH340 or CP2102 (Depending on which accessory for usage.) 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. Plugin the converter to computer and confirm the “com port” in device manager Step 4. Open the software(Minimu.
2.2 Software Introduction Link to download software 2.2.1 Main Menu Main Menu of software Button Function File Launch recorded HEX file (Bin format) Tools Hide or display tools box on left side Record Record function 3D 3D DEMO Config Configuration setting Help Language English or Chinese Bluetooth Set Binding device or unbind Firmware update Option for firmware update About Minimu Info about Minimu.
2.2.2 Menu of Configuration Menu of Configuration Button Function Read Config Reading the current configuration Lock Lock the sensor Unlock Unlock the sensor Calibrate Time Calibration time of chip Save Config Save configuration WT901 | manual v0513 | http://wiki.wit-motion.
Menu of System Button Function Reset Reset to factory setting Sleep Sleep function Alarm Alarm function Algorithm 6-axis algorithm or 9-axis Installation Direction Vertical or horizontal installation Instruction Start-up Instructions sending to start-up the sensor Instruction Start-up: This function is used to prevent the data sent by the module after connecting to the computer to conflict with the mouse, causing the mouse to jump.
Menu of Range Button Function Acceleration Acceleration measurement range Gyro Gyroscope measurement range Band Width Bandwidth range GPS Time Zone GPS positioning of time zone Menu of Communication Button Function Baud Rate Baud rate selection Output Rate Return rate selection Device Address IIC address Menu of Content Option Function Time Time data output Acceleration Acceleration data output Velocity Angular velocity data output Angle Angle data output Magnetism Magnetic fiel
Quaternion Quaternion data output Positioning Accuracy Option for GPS positioning accuracy output, including Satellite quantity, PDOP, HDOP, VDOP data, only for GPS IMU series, such as WTGAHRS1, WTGAHRS2 GPS Original Only output GPS raw data, only for GPS IMU series, such as WTGAHRS1, WTGAHRS2 Menu of Port D0 Model Extended port D0 D1 Model Extended port D1 D2 Model Extended port D2 D3 Model Extended port D3 Pulse width Pulse width of PWM Cycle Cycle of PWM WT901 | manual v0513 | http://w
2.3 Calibration Preparation: Make sure the sensor is “Online”. Calibration on PC software： It is required to calibrate for the first time usage. 2.3.1 Accelerometer Calibration Purpose: The accelerometer calibration is used to remove the zero bias of the accelerometer. Before calibration, there will be different degrees of bias error. After calibration, the measurement will be accurate. Methods: Step 1. Keep the module horizontally stationary Step 2. Click the accelerometer calibration Step 3.
Step 4. Click “Complete Calibration” Step 5. Judge the result--confirm if there is 1g on Z-axis acceleration After 1 ~ 2 seconds, the three axial acceleration value of the module is about 0, 0,1, the X and Y axis Angle is around 0°. After calibration, the x-y axis Angle is accurate. Note: When putting the module horizontal, there is 1g of gravitational acceleration on the Z-axis. WT901 | manual v0513 | http://wiki.wit-motion.
2.3.2 Magnetic Field Calibration Purpose: Magnetic calibration is used to remove the zero bias of the magnetic field sensor. Usually, the magnetic field sensor will have a large zero error when it is manufactured. If it is not calibrated, it will bring a large measurement error, which will affect the accuracy of the measurement of the z-axis Angle of the heading Angle.
Step 3. Slowly rotate the module 360° around X, Y, Z, 3-axis accordingly WT901 | manual v0513 | http://wiki.wit-motion.
Step 4. After rotation, click “End calibration” Successful result: Most of data dots will be within the ellipse. If not successful, please stay away from the objective that can create magnetic field interference. 2.3.3 Gyroscope Automatic Calibration The gyroscope calibration is to calibrate the angular velocity, and the sensor will calibrate automatically. It is recommended that the automatic calibration of gyroscopes can be inactivated only if the module rotates at a constant speed.
2.3.4 Reset Z-axis Angle Note：If you want to avoid magnetic interference, you can change the algorithm to Axis 6,then you can use reset function of “ Reset Z-axis angle”. The z-axis angle is an absolute angle, and it takes the northeast sky as the coordinate system can not be relative to 0 degree. Z axis to 0 is to make the initial angle of the z axis angle is relative 0 degree.
2.4 Configuration It is required to click “Unlock” before setting configurations. 2.4.1 Return Content Setting method: The content of the data return can be set according to user needs, click the configuration option bar, and check the data content to be output. Taking WT901 as an example, the default output of the module is acceleration, angular velocity, angle, and magnetic field. Notice: If choosing the GPS Original, there will be no other data output. WT901 | manual v0513 | http://wiki.
2.4.2 Output Rate The default return rate of the module is 10Hz, the highest return rate supports 200Hz. 10Hz refers to 10 packets returned every second. There contain 44bytes in a data packet in default. Byte Calculation: 11bytes * types of return content Default return content includes acceleration, gyro, angle, mag. That is, 4*11, 44bytes in data packet in default.
2.4.3 Baud Rate The module supports multiple baud rates, and the default baud rate is 9600. To set the baud rate of the module, you need to select the baud rate to be changed in the communication rate drop-down box in the configuration bar based on the correct connection between the software and the module. Note: After the change, the module will no longer output data at the original baud rate. The data will be output only when the baud rate that has been changed is selected on the PC software again.
2.4.4 Data Recording Method are as follows: Step 1: Click “Record” and “Begin” Step 2: Click “Stop” WT901 | manual v0513 | http://wiki.wit-motion.
Step 3: Extract the data as “txt” file Notice: If there is repeated “TIME” of data, that’s caused by low-resolution of the Windows system’s time. The changes in other data is correct. It is highly recommended that data can be pasted to an Excel file. In this way, all data will be shown in order. Time represents time, ax ay az represents the acceleration in the three axes of x y z, wx wy wz represents the angular velocity in the three axes of x y z.
2.4.5 Data Playback New function: When creating recorded file each time, there will a BIN file created in the folder of record file in path of installed software meanwhile. Recorded data playback method: Step 1: Disconnect the sensor Step 2: Click “File” Button and then click “Load” Step 3: Choose the original path of software installation and load the Bin file WT901 | manual v0513 | http://wiki.wit-motion.
Step 4: Click “Run” and the Binary file will be playback When playback, the rate can be editable. WT901 | manual v0513 | http://wiki.wit-motion.
2.4.6 Standby and Wake Up Sleep: The module paused working and entered the standby mode. Power consumption is reduced after sleeping. Wake up: The module enters the working state from the standby state. The module defaults to a working state, in the“Config”of the software, click “Sleep”option to enter the sleep state, click“Sleep”again to release sleep. WT901 | manual v0513 | http://wiki.wit-motion.
2.4.7 Placement Direction The default installation direction of the module is horizontal. When the module needs to be installed vertically, the vertical installation can be set. Step 1: Rotate the module 90 degrees around the X-axis Step 2: Place the sensor 90 degrees vertically Step 3: Click “Vertical” as install directions on “Config” menu WT901 | manual v0513 | http://wiki.wit-motion.
2.4.8 Bandwidth Default bandwidth is 20Hz. Function: 1. The higher rate of bandwidth setting will lead to the higher fluctuation in data waveform. Conversely, the lower rate of bandwidth, data will become more fluent. For example: Bandwidth as 20Hz, Output rate as 10Hz. The waveform is very steady. WT901 | manual v0513 | http://wiki.wit-motion.
Bandwidth as 256Hz, Output rate as 10Hz. The waveform will show more fluctuation. 2. The higher rate of bandwidth will solve the data-repeating problem. For example, if the bandwidth setting is 20Hz, retrieval rate as 100Hz, there will be 5 repeating data. If you prefer there is no repeating data, it is required to increase the bandwidth more than 100Hz. WT901 | manual v0513 | http://wiki.wit-motion.
2.4.9 Restore Factory Setting There are two ways to restore the factory settings, the short circuit method and the command method. Short-circuit method: short-circuit the D2 pin and VCC pin of the module with wires, and then power on the module. The LED of the module is on continuously for about 2 seconds. The LED is off, and the factory reset operation is completed.
2.4.10 Set IIC Address The module's default IIC address is 0x50, which can be changed by software. Change the IIC address only when the module connect to PC program successfully, and enter the new 16 hexadecimal IIC address and click the “change” button. Reminder: The IIC address of the module will not be changed immediately, and it will take effect when the module restart. WT901 | manual v0513 | http://wiki.wit-motion.
2.4.11 Set Extended Port The WT901 module has 4 multiple function extended ports, which can be set to different functions according to the need. Set extended port only when the module connects to the PC software successfully. The extended port supports analog input mode, digital input mode, digital output mode, PWM output mode. D1 port also supports GPSRX mode, port state by default is analog input mode.
2.4.12 6-axis/ 9-axis Algorithm 6-axis algorithm: Z-axis angle is mainly calculated based on angular velocity integral. There will be calculated error on Z-axis angle. 9-axis algorithm: Z-axis angle is mainly calculated and analyzed based on the magnetic field. Z-axis angle will have few drift. The default algorithm of WT901 is 9-axis. If there is magnetic field interference around installed environment, it is recommended to switch to 6-axis algorithm to detect the angle.
2.4.13 Set Alarm Status Through the alarm setting of the PC software, the following pins can be set as the alarm status output port. Take the following settings as an example. Normally, the four ports output low level (0V), and when the X-axis angle value is greater than 10 ° or less than -10 °, the corresponding port will output high level (3.3V).
3 Use Instructions with Android Phone For APP configuration introduction, please referring to the Chapter 2.2 3.1 APP Installation Install the APK file, give permission of Location and Storage Link to download Android APP WT901 | manual v0513 | http://wiki.wit-motion.
3.2 Hardware Preparation Connecting with Android smartphone requires a serial cable and a Type-C converter or OTG converter according to phone’s interface. WT901 | manual v0513 | http://wiki.wit-motion.
3.3 Connection Step 1. Install the APK file, give permission of Storage. Step 2: Connect the sensor with TTL cable. Then connect the cable with type-c converter. Plug in the device “type-c converter” to the phone. Notice: 1. After successful connection, there will be a notification reminding that “Choose an APP for the USB device”, which means that the device has been detected. Choose “WitMotion”, “ JUST ONCE” or “ALWAYS” is optional. 2. Only CH340 driver can be detected via WitMotion APP.
Step 3. Open APP and choose “9-axis Series” as sensor series WT901 | manual v0513 | http://wiki.wit-motion.
Step 4. Select the baud rate- 9600. WT901 | manual v0513 | http://wiki.wit-motion.
After selection and wait for a few seconds, the data will show automatically. WT901 | manual v0513 | http://wiki.wit-motion.
3.4 Calibration WT901 Playlist 3.4.1 Acceleration Calibration Step 1. Keep the module horizontally stationary Step 2. Click the “Calibration” menu Step 3. Click the “Acceleration Calibration” and wait for 3 seconds Step 5. Judge the result--confirm if there is 1g on Z-axis acceleration WT901 | manual v0513 | http://wiki.wit-motion.
3.4.2 Magnetic Field Calibration Step 1. Click "Calibration" menu Step 2. Click the "Magnetic calibration" button Step 3. Slowly rotate the module 360° around X, Y, Z, 3-axis accordingly Step 4. After rotation, click “Magnetic Calibration Finish” Check the result: The Z-axis angle will have fewer drift than before. Notice: If not successful, please stay away from the objective that can create magnetic field interference. WT901 | manual v0513 | http://wiki.wit-motion.
4 MCU Connection Link to download all sample code Link to sample code instructions demo Notice: There is no sample code provided for Linux or Python system at present. 4.1 Arduino Download link Arduino UNO3 Demo Link 4.2 STM32 Download link 4.3 Raspberry pi Tutorial link 4.4 C# DEMO link WT901 | manual v0513 | http://wiki.wit-motion.
4.5 C++ DEMO link 4.6 Matlab Receive Sample Code Dataplot DEMO WT901 | manual v0513 | http://wiki.wit-motion.
5 IIC Connection The WT901 module can be connected to the MCU through the IIC interface. The connection method is shown in the figure below. Note: 1. In order to connect multiple modules on the IIC bus, the IIC bus of the module is an open-drain output. When the MCU is connected to the module, the IIC bus needs to be pulled up to VCC through a 4.7K resistor. 2. VCC is 3.3V, it must be connected to the power supply.
