Kevin Jia Syst & Apps engineer

Transcription

1 Kevin Jia Syst & Apps engineer Freescale, the Freescale logo, AltiVec, C-5, CodeTEST, CodeWarrior, ColdFire, ColdFire+, C-Ware, the Energy Efficient Solutions logo, Kinetis, mobilegt, PowerQUICC, Processor Expert, QorIQ, Qorivva, StarCore, Symphony and VortiQa are trademarks of Freescale Semiconductor, Inc., Reg. U.S. Pat. & Tm. Off. Airfast, BeeKit, BeeStack, CoreNet, Flexis, MagniV, MXC, Platform in a Package, QorIQ Qonverge, QUICC Engine, Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. 212 Freescale Semiconductor, Inc..

2 What are magnetic sensors? Magnetic sensor s application Typical challenges to use magnetic sensor Ideal environment for magnetic sensor Source of interference on board Tilt compensation Freescale s magnetic sensor promotion 2 Freescale, the Freescale logo, AltiVec, C-5, CodeTEST, CodeWarrior, ColdFire, C-Ware, the Energy Efficient Solutions logo, mobilegt, PowerQUICC, QorIQ, StarCore and Symphony are trademarks of Freescale Semiconductor, Inc., Reg. U.S. Pat. & Tm. Off. BeeKit, BeeStack, ColdFire+, CoreNet, Flexis, Kinetis, MXC, Platform in a Package, Processor Expert, QorIQ Qonverge, Qorivva, QUICC Engine, SMAROS, TurboLink, VortiQa and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. 211 Freescale Semiconductor, Inc.

3 Devices that sense the presence of a magnetic field that can: Measure earth s magnetic field vector magnitude and direction Detect the presence of ferromagnetic objects by change in magnetic field Complement accelerometers with Earth s field for navigation and compassing 3 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

4 SI NAN CHE SI NAN 4 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

5 T= Tesla G=Gauss 1T = 1, G 1 G = 1, ut Some typical values of magnetic field that you might expect to encounter would be: Item being measured cgs Units SI Units Geomagnetic field at zip code (Tempe, Arizona) on 1/1/ G 48.2 ut typical refrigerator magnet 5 G 5, ut small iron magnet 1 G 1, ut small neodymium-iron-boron (NIB) magnet 2 G 2, ut 5 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

6 The strength of the field at the Earth's surface ranges from less than 3 ut(.3g) in an area including most of South America and South Africa to over 6 ut(.6g) around the magnetic poles in northern Canada and south of Australia, and in part of Siberia. 6 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

7 GPS tell you where you are but not accurate velocity and heading, especially when you are in slow motion, or standing and walking (ie. Pedestrian Navigation) Magnetics provides heading what are you facing? Indoor navigation is a great interest for Location Based Services. Personal Navigation is the hot product Car, Phone, Watch, GPS receiver will have increasingly advanced navigation features. Applications: Location Based Services, Pedestrian Navigation Gartner predicts the worldwide mobile advertising market will grow from $895 million in 27 to $14.6 billion in Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

8 Mobile phones Next Gen User Interface Electronic compass (ecompass) Map orientation GPS assist with dead-reckoning Location tracking assist in mobile applications Flip/display position Gaming Virtual, low-cost gyroscope replacement 3D motion control and heading Remote Controls / 3D Pointer Virtual, low-cost gyroscope replacement 3D motion control and heading Navigation Electronic compass (ecompass) Map orientation GPS backup with dead-reckoning Location tracking in mobile applications Smartbooks / ereaders / Netbooks / Laptops Location tracking assist in mobile applications User interface 8 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

9 Low strength of Earth s geomagnetic field is what we are trying to measure Magnetometer measures the sum of the geomagnetic field plus magnetic interference generated by ferromagnetic components on the smartphone PCB. Hard Iron distortion: permanent ferromagnets (in speakers or buzzers) Soft Iron distortion: induced fields (in sheet steel). Other distortions: fields generated by current flows Magnitude of hard iron and soft iron interference can exceed 1μT and saturate the magnetometer if care is not taken to minimize the use of ferromagnetic components Development of Calibration Algorithm to estimate and remove the soft iron and hard iron distortions Development of Tilt Compensation Algorithm for roll and pitch angles 9 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

10 Put a magnets next to sensor, the pointing direction will be changed. Put ferromagnetic materials next to sensor, the pointing direction will be changed too. Reasons: 1. Geomagnetic field is very weak, its strength less than 1 gauss(1 ut) 2. The sensor just detect the magnetic field at that position 1 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

11 Assume : Geomagnetic B is parallel B to sensor s X,Y platform, vertical to Z axis Y z Rotate the board 1 cycle alone Z axis, get a circle on X/Y platform which Bz =, R=B=R1, Sensor s output on X/Y/Z = R1cos R1sin 11 R1 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All X

12 Slightly tilt the Z axis and makes it have an angle with B Y z R2 Rotate the board 1 cycle alone Z axis, get a circle on X/Y platform which Bz, R=R2, R2 < R1 Sensor s output on X/Y/Z = R2cos R2sin B z 12 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All X

13 Continue to tilt Z axis then rotate, we can get another circle,bz and R Draw all these circles in a unified coordinate system, get a sphere which origin at (,,) 13 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

14 So the direction heading can be easily expressed by: Y B s horizontal component arctan( x y ) X Condition: the phone is placed on flat plane Phone s heading 14 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

15 Actually, we can not get such ideal environment on board, there exists 3 source of interference: Hard iron material Permanent ferromagnets Soft iron material Easy to be magnetized, magnetic will disappear after remove away the source of interference. Fields generated by current flows Power supply tracks, coils 15 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

16 Problem: Distortion of the magnetic field due to the presence of hard iron Hard iron is basically a permanent magnet in the system fixed in location and orientation with respect to our sensor that acts as a DC Offset. Examples: - speakers/camera/mic have magnets - holsters have magnets to secure the device A permanent magnet fixed relative to the sensor simply adds an offset to the origin of the ellipsoid. Y o( x, y) V 2-D to 3-D X x y 16 V x y z Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

17 Problem: Distortion of the magnetic field due to the presence of soft iron. Multiple components on a PCB or in a product can create soft iron interference. For example, Steel provides a lower resistance path to the magnetic field than does the surrounding air. So it s natural for the field to be diverted. b Y a Steel, Nickel, etc. i.e. EMI shields, screws and battery contacts X 2-D to 3-D M cos a sin b sin a cos b Soft iron effects distort the measured field 17 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

18 The magnetic field B r at distance r from the PCB trace is gaven in Teslas by: B r.21 r 6 I 1mA 3mm.67uT 5mA 7mm 1.43uT 1mA 18mm 1.11uT 2mA >=25mm 1.6uT 18 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

19 Although hard/soft iron can be removed by software, designer should not assume that the calibration software will always correct for a poor layout. Component selection and layout should therefore be optimized to reduce the interfering fields as much as possible. Notice : external magnetic field outside board can not be removed!! 19 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

20 Compass s pointing direction is computed by horizontal component of geomagnetic field When the board(phone) tilt, sensor s X/Y axis output is not the horizontal component of geomagnetic field Thus, need an accelerometer to get the tilt angle B cosd d B g 2 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

21 With the board/phone flat and pointing northwards G r g (1) B r cos d B sin d (2) 21 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

22 Can be modeled as resulting from rotations in yaw, pitch and roll applied to a starting position G p R x R y R z G r (3) B p R x R y R z B r (4) 22 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

23 R x 1 cos sin sin cos (5) R y cos sin 1 sin cos (6) R z cos sin sin cos 1 (7) 23 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

24 Equation 4 becomes: B p R x R R y z B r V R x R R y z cos d B sin d V V V x y z (8) 24 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

25 25 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All Pre-multiplying (3) by the inverse roll and pitch rotation matrices giving: g g R G G G R R z pz py px x y - - G - R - R p x y (9)

26 Expanding (9) gives: cos sin 1 sin 1 cos cos sin G sin G cos G px py pz g (1) cos sin sin sin cos cos sin sin cos G sin G cos cos G px py pz g (11) 26 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

27 From equ(11),we can get: G py tan (12) G pz tan G py G px sin G pz cos (13) 27 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

28 From equ(8),we can get: R z R y B cos d B sin d R B V x sin p cos sin cos B cos d 1 B sin d (14) 28 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

29 expanding equ(14), cosb cos d sinb cos d Bsin d cos sin 1 sin 1 cos cos sin sin cos B B B px py pz V V V x y z (15) 29 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

30 expanding right side of equ(15), B px Vx cos Bpy Vy sin sin Bpz Vz sin cos B fx Bpy Vy cos Bpz Vz sin B fy B V sin B V cos sin B V cos cos B px x py y (16) B fx, Bfy, B represent the components of the magnetic fz sensor after correcting for the hard iron offset and after derotating to the flat plane where pz z fz 3 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

31 The x,y components of (15) and(16) give, tan B B B cos d B sinb cos d B fx cos (17) fy B pz Vz sin Bpy Vy cos Bpx Vx cos Bpy Vy sin sin Bpz Vz sin cos fx fy (18) (19) 31 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

32 32 2x2x.85mm DFN-1 Features 1.95V to 3.6V supply voltage High accuracy compass function Magnetometer resolution of.1ut Output data rates (ODR) from 2.5Hz to 8Hz Maximum field of 1G (1 ut) Multiple Selectable Oversampling Options Current Consumption as low as 24uA at 1.25Hz Standby Mode Current Consumption 2uA typ I²C digital interface Extended temperature range of -4 C to +85 C. Applications Electronic Compass Enhanced User Interface Dead-reckoning GPS assist for Location Based Services Enhanced Gaming Interface 32 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

33 Features Specification Benefits Wide Dynamic Range +/- 1 μt Allows operation in PCBs with high extraneous magnetic fields and flexibility in PCB placement. High resolution in full dynamic range.1 μt Allows for the full specification resolution in all ranges Low Noise (at 8 Hz ODR) Power Consumption Sample rate Supply voltage.25 μt RMS Normal Mode: 24 μa at 1.25 Hz 8 Hz maximum 1.95 to 3.6 V Enables high resolution applications with low averaging requirements for decreased latency Lower power for significant battery savings Increased bandwidth to provide higher data rates Wide range for various applications Freescale s MAG311 magnetometer has phenomenal performance due to the combination of R (Tunnel Magneto Resistive) technology, high resolution analog design and dedicated embedded logic 33 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

34 High Sensitivity Across a Wide Range: The MAG311 provides a linear, high sensitivity output across a high field range to accurately measures changes, relative to the earth s field. Low Noise: The MAG311 provides high resolution with a fast response and stable reading. External filters are not needed, thus reducing board level costs Automatically Calibrated: The MAG311 is calibrated and factory trimmed for sensitvity. Some version of software calibration is always needed. First generation products required a Figure 8 motion. Next generation versions will run calibration in the background. Contact Freescale for an evaluation license. Small Footprint: The MAG311 is in a 2x2mm udfn package for all 3 axis of magnetic sensing to allow for flexibility of placement on PCB due to extremely small size Easy to Use: The MAG311 has a I2C Interface with configurable registers. It has development tools to get a user started out of the box such as with the RD4247MAG311 development tool which interfaces directly to a PC serial port with easy-to-use demonstration software. Temperature Compensated: The MAG311 has a temperature sensor on board and is trimmed to reduce effects of temperature inherent to magnetoresistive devices High Reliability: MAG311 is developed on solid state silicon wafers allowing for all the high reliability and high quality that Freescale provides. 34 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

35 LFSTBEB311 Sensor Toolbox Kit Includes a self identifying MAG311 magnetometer development board Works with the USB communication board Includes Sensor Toolbox demo and evaluation software Will be available at: RD4247MAG311 Sensor Toolbox Bundle This Sensor Toolbox kit comes with the MAG311 magnetometer development board and the USB board Will be available at: Xtrinsic Solution Board Includes a MAG311 magnetometer and MMA955 Accelerometer and Smart Sensor development board Works with the USB communication board Application Notes AN4246 : Accuracy of Angle Estimation in ecompass and 3D Pointer Applications AN4247: Layout Recommendations for PCBs Using a Magnetometer Sensor AN4248: Implementing a Tilt-Compensated ecompass using Accelerometer and Magnetometer Sensors RD4247MAG311 Sensor Toolbox Bundle AN4249: Accuracy of Angle Estimation in ecompass and 3D Pointer Applications 35 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

36 Differentiating Points Lowest noise gcell and mcell Embedded Functionality to allow system fast response and power savings 32 sample FIFO with burst read Product Features 1.95V to 3.6V supply voltage, I/O 1.6V 3.6V ±2g/±4g/±8g accelerometer, ±15 Gauss Field range Output data rate (ODR) from 1.563Hz to 8Hz, 4Hz hybrid 14-bit gcell data, 8 counts per Gauss Low Offset Drift:.1mG per deg 4 channel motion detect ion- FF, Pulse, Transient, HPF, Tap Vector Magnitude for mcell, gcell Typical Applications Electronic Compass Enhanced User Interface Dead-reckoning GPS assist for Location Based Services Package 3 x 3 x 1.2mm QFN Timing Alpha Samples Now Alpha Dev Tool Oct 11 Dev Tool orderable May 12 Production Jul Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

37 LFSTBEB87 Sensor Toolbox Kit Includes a self identifying FXOS87CQ 6DOF development board Works with the USB communication board Includes Sensor Toolbox demo and evaluation software Will be available May 12 at: RD4247FXOS87 Sensor Toolbox Bundle This Sensor Toolbox kit comes with the FXOS87CQ 6DOF development board and the USB board Will be available May 12 at: Application Notes to be updated to include FXOS87CQ : AN4246 : Accuracy of Angle Estimation in ecompass and 3D Pointer Applications AN4247: Layout Recommendations for PCBs Using a Magnetometer Sensor AN4248: Implementing a Tilt-Compensated ecompass using Accelerometer and Magnetometer Sensors AN4249: Accuracy of Angle Estimation in ecompass and 3D Pointer Applications RD4247FXOS87 Sensor Toolbox Bundle 37 Ready Play, SafeAssure, the SafeAssure logo, SMAROS, TurboLink, Vybrid and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All

38 THANK YOU Freescale on Kaixin Tag yourself in photos and upload your own! Weibo? Please use hashtag #FTF211# 38 Freescale, the Freescale logo, AltiVec, C-5, CodeTEST, CodeWarrior, ColdFire, C-Ware, the Energy Efficient Solutions logo, mobilegt, PowerQUICC, QorIQ, StarCore and Symphony are trademarks of Freescale Semiconductor, Inc., Reg. U.S. Pat. & Tm. Off. BeeKit, BeeStack, ColdFire+, CoreNet, Flexis, Kinetis, MXC, Platform in a Package, Processor Expert, QorIQ Qonverge, Qorivva, QUICC Engine, SMAROS, TurboLink, VortiQa and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. 211 Freescale Semiconductor, Inc.

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