WT901BLECL Attitude Angle Sensor

SPECIFICATION

Model ：WT901BLECL

Description: 10-axis Bluetooth 4.0 attitude angle sensor with battery

Production Standard

Enterprise quality system standard: ISO9001:2016

Tilt switch production standard：GB/T191SJ 20873-2016

Criterion of detection：GB/T191SJ 20873-2016

Revision date：2018.06.20

Version Update content Author Date

V1.0 Release Sharlene 20180620
 Catalog
1 Description....................................................................................................................................... 3
2 Product Size...................................................................................................................................... 3
3 Features............................................................................................................................................ 4
4 Axial Diron........................................................................................................................................ 4
5 Method............................................................................................................................................. 4
5.1 Connect App.......................................................................................................................... 4
5.2Module Calibration.................................................................................................................5
5.2.1Accelerometer Calibration.......................................................................................... 5
5.2.2 Magnetic Calibration..................................................................................................7
5.2.3 Calibration by Instruction...........................................................................................7
5.3 Restore Factory Setting......................................................................................................... 8
5.4 Sleep/ Wake up..................................................................................................................... 8
6 Communication Protocol..................................................................................................................8
6.1 Module to APP.......................................................................................................................9
6.1.1 Acceleration, Angular velocity, Angle, Data pack(default)........................................ 9
6.1.2 Single Return Register Data Packet..........................................................................10
6.2 APP to Module.....................................................................................................................12
6.2.1 Read register value...................................................................................................12
6.2.2 Accelerometer Calibration and Magnetic Calibration............................................. 12
6.2.3 Save Settings............................................................................................................ 13
6.2.4 Set Return Rate........................................................................................................ 13
6.2.5 Set Port D0............................................................................................................... 13
6.2.6 Set Port D1............................................................................................................... 13
6.2.7 Set Port D2............................................................................................................... 14
6.2.8 Set Port D3............................................................................................................... 14
6.3 Register address.................................................................................................................. 14
7 Application Area............................................................................................................................. 16
1 Description

 Module integrates high-precision gyroscopes, accelerometer, mpu9250

geomagnetic sensor, high-performance microprocessors and advanced dynamics solves
dynamic Kalman filter algorithm to quickly solve the current real-time movement of the
module attitude .
 The use of advanced digital filtering technology, can effectively reduce the
measurement noise and improve measurement accuracy.
 Integrates gesture solver, with dynamic Kalman filter algorithm, can get the
accurate attitude in dynamic environment, attitude measurement precision is up to 0.05
degrees with high stability, performance is even better than some professional Inclinometer!
 Integrate voltage stabilization circuit, working voltage is 3.3v ~ 5v, pin level
compatible 3.3V and 5V embedded system .
 High-performance cortex-M0 core processor runs at up to 48MHz, taking into
account low power consumption and high performance.
 BLE4.0 wireless transmission, transmission stability, distance greater than 10
meters.
 Low power consumption, long standby time, self-contained battery.

2 Product Size
3 Features

1、Voltage：3.3V~5V

2、Consumption current：<16mA ( normal) Standby current：<0.1mA

3、Volume：51.3mm X 36mm X 15mm

4、Measuring dimensions:
Acceleration: X Y Z
Angular velocity: X Y Z
Attitude angle:X Y Z
Magnetic field：X Y Z
Atmospheric pressure:YES
6、Range: Acceleration: ± 16g, Angular velocity: ± 2000 ° / s,Angle:X Z ±180° Y ±90°
7、Stability: Acceleration: 0.01g, Angular speed 0.05° / s.

8、Attitude measurement stable:X Y 0.05° Z :1°

9、Data output: Acceleration, Angular velocity, Angle,Magnetic field, Pressure,Height, Port status

10、 The data output frequency: 0.1Hz ~50Hz (10Hz default)

11、Data Interface: UART(TTL , Baud rate 115200)

12、Expansion port function： Analog input（0~VCC, Digital input, Digital output)
13、Bluetooth transmission distance：>10m
14、BLE4.0：Support Android /IOS

4 Axial Diron

As shown in the figure above, the coordinates of the module are indicated, and the upper is the
X-axis, the left is Y axis, the Z axis is perpendicular to the surface of the paper to yourself. The
direction of rotation is defined by the right hand rule. that is, the thumb of the right hand is pointed
to the axial direction, and the four is the direction of the bending of the right hand.

5 Method

5.1 Connect App

1.Connect USB-micro data line (Ignore when the battery is powered)

2、Turn on the phone APP, click “scan” and then search the Bluetooth which is called
WT901BLE.

3、Click the Bluetooth and then you can get the data.

5.2Module Calibration

The module need to be calibrated before the module is used. The calibration of
WT901BLECL includes accelerometer calibration and magnetic calibration.

5.2.1Accelerometer Calibration
The accelerometer calibration is used to remove the zero bias of the accelerometer. When the
sensor is out of the factory, there will be different degrees of bias error. After manual calibration,
the measurement will be accurate.
 1、Methods as below: Firstly keep the module horizontally stationary, click “Acceleration”,
after 1~2s the acceleration X Y Z value will at 0 0 1. X Y angle: 0°. After calibration the value
will be accurate.

2、Accelerometer Calibration L, Accelerometer Calibration R

In the case that the surface is not very flat, and the data is still in error after the calibration, the
calibration L and R can be used for re-calibration. Methods as below：
The module is still at left, click on the calibration L, 2S after and then put the module to the right
and click on the calibration R, so that the X Y-axis angle is accurate when used after two
calibrations.
 Accelerometer Calibration L Accelerometer Calibration R

5.2.2 Magnetic Calibration

Magnetic field calibration is used to remove the magnetic field sensor's zero offset. Usually,
the magnetic field sensor will have a large zero error when it is manufactured. If it is not calibrated,
it will bring about a large measurement error and affect the accuracy of the Z-axis angle
measurement of the heading angle.
Calibration methods as follow:
1. When calibrating, first connect the module and the computer, and place the module in a
place far away from the disturbing magnetic field (ie, more than 20 CM away from magnets and
iron, etc.), and then open the upper computer software.
2. Click the “Magnetic Field Calibration”and rotate 360° around the X axis of the module
( you can rotate around the Y axis or the Z axis first). Rotate a few turns, then turn 360° around
the Y axis. Then turn 360° around the Z axis, then turn a few turns at random, then click the
“Finish” to complete the calibration.

Note: The data displayed on the APP will not change when the calibration is completed. After the
calibration is completed, the data will continue to be transmitted back. When the calibration is
added, the module should be stationary. When the magnetic field is calibrated and used, it must be
kept away from the magnetic field interference.

5.2.3 Calibration by Instruction

1.Instruct Accelerometer Calibration:

First keep the module horizontal and still, send the instruction: FF AA 01 01 00, after
1~2s the acceleration X Y Z value will at 0 0 1. X Y angle: 0°. After calibration the value will be
accurate.
2. Accelerometer Calibration L/R:
Keep the module is still at left, send the instruction L: FF AA 01 05 00
After 2s, turn the module to the right side and send the instruction R: FF AA 01 06 00
Calibrate two times the data will be accurate.
3. Instruct Magnetic Calibration:
When calibrating, place the module in a place far away from the disturbing magnetic field (ie,
more than 20 CM away from magnets and iron, etc.). Send the instruction: FF AA 01 07 00
Rotate 360° around the X axis of the module ( you can rotate around the Y axis or the Z axis first).
Rotate a few turns, then turn 360° around the Y axis. Then turn 360° around the Z axis, then turn a
few turns at random, then click the “Finish” to complete the calibration.

Send the instruction: FF AA 01 00 00 to finish the calibration.

Send the instruction: FF AA 00 00 00 to save the Configuration.

5.3 Restore Factory Setting

Method: After connecting the WT901BLECL and APP via Bluetooth, click the
“Resume” .Reconnect the module after recovery.

5.4 Sleep/ Wake up

Enter the sleep mode right two methods. One is to disconnect the Bluetooth connection directly,
and the module will go directly to sleep mode. The other is to send a serial port command, the
instruction content is 5 hexadecimal data: 0xff 0xaa 0x67 0x01 0x00
There are two ways to wake up the module. One is to directly search for and connect to Bluetooth.
The module will wake up automatically and start working. The other is wake-up from the serial
port. Any serial port command can be sent to wake up the module.

6 Communication Protocol
6.1 Module to APP

Module upload Flag=0x61 (Angle,Angular velocity, Acceleration) data default.

Flag=0x71(Magnetic field, Air pressure and altitude, Port status) need to send the corresponding
register instruction.
Bluetooth upload data: Bluetooth uploads up to 20 bytes per data.

6.1.1 Acceleration, Angular velocity, Angle, Data pack(default)

Packet Flag bit axL axH ……. YawL YawH

header 1Byte
1Byte
0x55 Flag 0xNN 0xNN ……. 0xNN 0xNN
Note: 0xNN is a accurate value you received. Data return sequence: Acceleration X Y Z Angular
velocity X Y Z Angle X Y Z , low byte first, high byte last.
Flag = 0x61 Data content: 18Byte is Acceleration, Angular velocity, Angle.
0x55 Packet header
0x61 Flag bit
axL X Acceleration low 8 byte
axH X Acceleration high 8 byte
ayL Y Acceleration low 8 byte
ayH Y Acceleration high 8 byte
azL Z Acceleration low 8 byte
azH Z Acceleration high 8 byte
wxL X Angular velocity low 8 byte
wxH X Angular velocity high 8 byte
wyL Y Angular velocity low 8 byte
wyH Y Angular velocity high 8 byte
wzL Z Angular velocity low 8 byte
wzH Z Angular velocity high 8 byte
RollL X Angle low 8 byte
RollH X Angle high 8 byte
PitchL Y Angle low 8 byte
PitchH Y Angle high 8 byte
YawL Z Angle low 8 byte
YawH Z Angle high 8 byte
Acceleration calculation method: Unit: g
ax=((axH<<8)|axL)/32768*16g(g is Gravity acceleration, 9.8m/s2)
ay=((ayH<<8)|ayL)/32768*16g(g is Gravity acceleration, 9.8m/s2)
az=((azH<<8)|azL)/32768*16g(g is Gravity acceleration, 9.8m/s2)
Calculation method: Unit: °/s
wx=((wxH<<8)|wxL)/32768*2000(°/s)
wy=((wyH<<8)|wyL)/32768*2000(°/s)
 wz=((wzH<<8)|wzL)/32768*2000(°/s)
Calculation method: Unit: °
Roll（x axis）Roll=((RollH<<8)|RollL)/32768*180(°)
Pitch（y axis）Pitch=((PitchH<<8)|PitchL)/32768*180(°)
Yaw angle（z axis）Yaw=((YawH<<8)|YawL)/32768*180(°)
Note:
1. Attitude angle use the coordinate system for the Northeast sky coordinate system, the X
axis is East,the Y axis is North, Z axis toward sky. Euler coordinate system rotation
sequence defined attitude is z-y-x, first rotates around the Z axis. Then, around the Y axis,
and then around the X axis.
2. In fact, the rotation sequence is Z-Y-X, the range of pitch angle (Y axis) is only ±90
degrees, when the pitch angle (Y axis) is bigger than 90 degrees and the pitch angle (Y
axis) will become less than 90 degrees. At the same time, the Roll Angle(X axis) will
become larger than 180 degree. Please search on Google about more information of
Euler angle and attitude information.
3. Since the three axis are coupled, the angle will be independent only when the angle is
small. It will be dependent of the three angle when the angle is large when the attitude
angle change, such as when the X axis close to 90 degrees, even if the attitude angle
around the X axis, Y axis angle will have a big change, which is the inherent
characteristics of the Euler angle.
Explanation:
1. The data is sent in hexadecimal format, not ASCII code.
2. Each data is transmitted in descending order of high byte and high byte, and the two are
combined into one signed short type of data.
X axis acceleration data Ax: AxL is low byte, AxH is high byte, conversion method as below:
Presume Data is a real data, DataH is high byte, DataL is low byte, so:
Data=((short)DataH<<8)|DataL. Please note that DataH need to transform a signed short type of
data and then shift. The Data type has a signed short type, so that it display negative number.

6.1.2 Single Return Register Data Packet

Single Return Data Packet need to send register instruction first:

FF AA 27 XX 00
--XX is register number. The register number please refer to 7.3. Example as below:
Function Instruction
Read magnetic field FF AA 27 3A 00
Read air pressure and altitude FF AA 27 45 00
Read port status FF AA 27 41 00
Read quaternion FF AA 27 51 00
Read temperature FF AA 27 40 00
After send instruction, the module turn back a data packet 0x55 0x71. There are register address
and 7 registers data (Fixed upload 8 registers). Return data format as below:
Start register(2 byte) + register data(16 byte, 8 registers)
 Start Start Start(No.1) Start(No.1) .... No.8 No.8
Packet Sign register register register register .. register register
header low high data low data high data low data high
byte byte byte byte byte byte
0x55 0x71 RegL RegH 0xNN 0xNN .... 0xNN 0xNN
..
Note: 0xNN is a accurate value, low byte first, high byte last.

1. Magnetic field output

0x71 0x3A 0x00 HxL HxH HyL HyH HzL HzH ......
Calculated formular：Unit: mG
Magnetic field（x axis）Hx=(( HxH<<8)| HxL)
Magnetic field（y axis）Hy=(( HyH <<8)| HyL)
Magnetic field（z axis）Hz =(( HzH<<8)| HzL)
EX: Send instruction to read magnetic field in APP: FF AA 27 3A 00 (Please refer
to 7.2.8) The module return data to APP: 55 71 3A 00 68 01 69 00 7A 00 00 00 00 00 00 00 00
00 00 00 Total: 20 bytes.
Calculate the no.5 to no.10 bytes as described above, magnetic field x=360，y=105,z=122
2. Air pressure and altitude output
0x55 0x71 0x45 0x00 P0 P1 P2 P3 H0 H1 H2 H3 ......
Calculated formular：
Air pressure P = (( P3<<24)| ( P2<<16)| ( P1<<8)| P0 （Pa）
Atitude output H = (( H3<<24)| ( H2<<16)| ( H1<<8)| H0 （cm）
EX: Send instruction to read Air pressure and altitude data in APP: FF AA 27 45 00
(Please refer to 7.2.8) The module return data to APP: 55 71 45 00 E2 88 01 00 56 18 00 00 00
00 00 00 00 00 00 00 Total: 20 bytes.
Calculate the no.5 to no.12 bytes as described above, p=100578 pa,H=6230 cm
3. Port status data output
0x55 0x71 0x41 0x00 D0L D0H D1L D1H D2L D2H D3L D3H ......
Calculated formular：
D0 = (D0H<<8)| D0L
D1 = (D1H<<8)| D1L
D2 = (D2H<<8)| D2L
D3 = (D3H<<8)| D3L
Explanation:
When the port mode is set to analog input, the port status data represents the analog voltage. The
actual voltage is calculated according to the following formula:
U=DxStatus/1024*Uvcc
Uvcc is chip supply voltage, there is LDO in it, If the module supply voltage > 3.5V, Uvcc is 3.3V.
If the module supply voltage <3.5V, Uvcc=voltage-0.2V.
When the port mode is set to digital input, the port status data indicates the digital level status of
the port, with a high level of 1 and a low level of 0.
The port status data is 1 when the port mode is set to high output mode.
The port status data bit is 0 when the port mode is set to low output mode.
4, Quaternion output
0x55 0x71 0x51 0x00 Q0L Q0H Q1L Q1H Q2L Q2H Q3L Q3H ......
Calculated formular：
Q0=((Q0H<<8)|Q0L)/32768
Q1=((Q1H<<8)|Q1L)/32768
Q2=((Q2H<<8)|Q2L)/32768
Q3=((Q3H<<8)|Q3L)/32768
Checksum：
Sum=0x55+0x59+Q0L+Q0H+Q1L +Q1H +Q2L+Q2H+Q3L+Q3H
4. Temperature output
0x55 0x71 0x40 0x00 TL TH ......
Calculated formular：
T=((TH<<8)|TL) /100 ℃

6.2 APP to Module

Send instruction:

6.2.1 Read register value

FF AA 27 XX 00 Read register value

--XX is register.
EX: Read magnetic field：FF AA 27 3A 00
Read air pressure and altitude：FF AA 27 45 00
Read port status：FF AA 27 41 00
Read quaternion：FF AA 27 51 00
Read temperature：FF AA 27 40 00
After send instruction, the module turn back a data packet 0x55 0x71. There are register address
and 7 registers data (Fixed upload 8 registers). Return data format please refer to 7.1.2.

6.2.2 Accelerometer Calibration and Magnetic Calibration

FF AA 01 01 00 Accelerometer Calibration
FF AA 01 05 00 Accelerometer Calibration L
FF AA 01 06 00 Accelerometer Calibration R
FF AA 01 07 00 Magnetic Calibration
FF AA 01 00 00 Magnetic Calibration Finish
 6.2.3 Save Settings

FF AA 00 SAVE 00 Save Settings

SAVE：Set
0：Save current configuration
1：Restore default configuration and save

6.2.4 Set Return Rate

FF AA 03 RATE 00 Set return rate

RATE：return rate
0x01：0.1Hz
0x02：0.5Hz
0x03：1Hz
0x04：2Hz
0x05：5Hz
0x06：10Hz（default）
0x07：20Hz
0x08：50Hz
0x09：100Hz

6.2.5 Set Port D0

FF AA 0E D0MODE 00 Set port D0

D0MODE：D0
0x00：Analog input（default）
0x01：Digital input
0x02：Output digital high level
0x03：Output digital low level

6.2.6 Set Port D1

FF AA 0F D1MODE 00 Set port D1

D1MODE：D1
0x00：Analog input（default）
0x01：Digital input
0x02：Output digital high level
0x03：Output digital low level
6.2.7 Set Port D2

FF AA 10 D2MODE 00 Set port D2

D2MODE：D2
0x00：Analog input（default）
0x01：Digital input
0x02：Output digital high level
0x03：Output digital low level

6.2.8 Set Port D3

FF AA 11 D3MODE 00 Set port D3

D3MODE：D3
0x00：Analog input（default）
0x01：Digital input
0x02：Output digital high level
0x03：Output digital low level
Note: After the above settings are completed, you must send a save command to save.

6.3 Register address

Address Symbol Mean

0x00 SAVE Save current configuration

0x01 CALSW Calibration
0x02 KEEP
0x03 RATE Return rate
0x04 BAUD UART Baud rate
0x05 AXOFFSET X Acceleration zero offset
0x06 AYOFFSET Y Acceleration zero offset
0x07 AZOFFSET Z Acceleration zero offset
0x08 GXOFFSET X Angular velocity zero offset
0x09 GYOFFSET Y Angular velocity zero offset
0x0a GZOFFSET Z Angular velocity zero offset
0x0b HXOFFSET X Magnetic field zero offset
0x0c HYOFFSET Y Magnetic field zero offset
0x0d HZOFFSET Z Magnetic field zero offset
0x0e D0MODE D0
0x0f D1MODE D1
0x10 D2MODE D2
0x11 D3MODE D3
0x12 KEEP
0x13 KEEP
0x14 KEEP
0x15 KEEP
0x16 KEEP
0x17 KEEP
0x18 KEEP
0x19 KEEP
0x1a KEEP
0x1b KEEP
...... ...... ......
0x30 YYMM Year, Month
0x31 DDHH Date, Hour
0x32 MMSS Minute, Second
0x33 MS Millisecond
0x34 AX X Acceleration
0x35 AY Y Acceleration
0x36 AZ Z Acceleration
0x37 GX X Angular velocity
0x38 GY Y Angular velocity
0x39 GZ Z Angular velocity
0x3a HX X Magnetic field
0x3b HY Y Magnetic field
0x3c HZ Z Magnetic field
0x3d Roll X Angle
0x3e Pitch Y Angle
0x3f Yaw Z Angle
0x40 TEMP Module temperature
0x41 D0Status D0 Status
0x42 D1Status D1 Status
0x43 D2Status D2 Status
0x44 D3Status D3 Status
0x45 PressureL Pressure low byte
0x46 PressureH Pressure high byte
0x47 HeightL Height low byte
0x48 HeightH Height high byte
0x49 KEEP
0x4a KEEP
0x4b KEEP
0x4c KEEP
0x4d KEEP
0x4e KEEP
0x4f KEEP
0x50 KEEP
 0x51 Q0 Quaternion Q0
0x52 Q1 Quaternion Q1
0x53 Q2 Quaternion Q2
0x54 Q3 Quaternion Q3

7 Application Area

Agricultural machinery Internet of things

Solar energy Power monitoring

Medical instruments Construction machinery

 Geological monitoring

深圳维特智能科技有限公司
WitMotion ShenZhen Co., Ltd

WT901BLECL Attitude Angle Sensor

TEL : (+86) 755-33185882

E-mail : wit@wit-motion.com
Website : www.wit-motion.com
Aliexpress : https://witmotion.aliexpress.com
Alibaba : https://witmotion.en.alibaba.com
Wit-wiki : https://wiki.wit-motion.com/english
Address : Honghai building 1306 Songgang town Baoan District Shenzhen
Guangdong Province China