Sensors on android
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This document discusses sensors on Android devices. It covers an introduction to common sensors like accelerometers and gyroscopes, how sensors are used in Android applications, tips for developing sensor applications, and porting new sensors to Android. The presentation is divided into multiple parts covering the Android sensor framework, sensor hardware, developing and debugging sensor applications, and future directions for sensors on Android.
![Porting a sensor onto Android (userspace)
Sensor-HAL
Adding
– Reference Implementation : http://goo.gl/jjF3l
– Sensor-HAL implemented in : android/device/<vendor>/<device>/libsensors
– Generates library : system/lib/hw/sensors.<TARGET_BOARD_PLATFORM>.so
Modifying
– Update sensors.cpp in sSensorList[]
– Derive a new sensor object, Include appropriate file
– Update i/p dev name in constructor
12:30 AM Sensors on Android 20](https://image.slidesharecdn.com/sensorsonandroid-111118103152-phpapp01/85/Sensors-on-android-20-320.jpg)
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Sensors on android
- 1. Sensors on Android ChinmayVS @ DroidCON-2011
- 2. cvs@droidcon$ who am i • Android >2yrs. Remember anyone? • - sensors development. 10million+ units sold. • Presently working @ PathPartnerTech.com 10:16 PM Sensors on Android 2
- 3. Sensors on Android PART1 : Introduction PART4: Sensor Application development. • Sensors on Android Sample android app (code snippets) • Famous sensor apps • Sensors in Android apps PART5: App-dev Tips and tricks • Sensor Hardware intro • Sensor callibration. 1. one-turn deserves another (axes-calib) PART2 : Android Sensor Overview 2. zero-calib • Overview • Sensor fusion (hard-way) • Porting a new sensor onto Android • Invensense (easy-way) • Kernel • Polling rate game/ui/fastest • Sensor "HAL" • When to place Wakelocks • When to register/unregister eventListener PART3 : Porting tips and tricks • No motion ≠ 0accel • Accel axes 3step calibration • Input devices & events (EV_ABS, EV_REL) 10:20 PM Sensors on Android 3
- 4. “Sense-ors” on Android A sensor (also called detector) is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. 1. ACCELEROMETER 2. GYROSCOPE 3. MAGNETIC_FIELD REAL 4. LIGHT 5. PRESSURE 6. AMBIENT_TEMP 7. RELATIVE_HUMIDITY 8. PROXIMITY VIRTUAL 9. LINEAR_ACCELERATION 10. GRAVITY 11. ROTATION_VECTOR DEPRECEATED 12. TEMPERATURE 13. ORIENTATION 10:20 PM Sensors on Android 4
- 5. “Famous” sensor apps 10:16 PM Sensors on Android 5
- 6. Sensors in Android applications • Use-cases of sensors in apps: 1. Active-Input 2. Passive-Input Application developer 3. Active-Passive 4. Auto-Rotate Android window manager 10:16 PM Sensors on Android 6
- 7. Sensors in Android applications (1/4) • Active input 10:16 PM Sensors on Android 7
- 8. Sensors in Android applications (2/4) • Passive input 10:16 PM Sensors on Android 8
- 9. Sensors in Android applications (3/4) • Active-passive 10:16 PM Sensors on Android 9
- 10. Sensors in Android applications (4/4) • Auto-rotate 10:16 PM Sensors on Android 10
- 11. Sensor Hardware Intro (1/4) • Accelerometer + ZERO drift - Relatively slower response 10:16 PM Sensors on Android 11
- 12. Sensor Hardware Intro (2/4) • Gyroscope (MEMS) + Extremely quick response - Gradual drift with time 10:16 PM Sensors on Android 12
- 13. Sensor Hardware Intro (3/4) • Compass (Magnetometer) + Obtain Yaw/Azimuth + Rotation with the device on a flat surface - Picks-up surrounding magnetic noise 10:16 PM Sensors on Android 13
- 14. Sensor Hardware Intro (4/4) • Light & Proximity 10:16 PM Sensors on Android 14
- 15. Android Sensors Frameworks Overview Android App • Use SensorManager & SensorEventListener C O Android Framework N D • SensorService & SensorManager T A R T Android sensor “HAL” O A L • Links the Kernel-Drivers to the framework Kernel Drivers • Device drivers to control and gather data from the actual hardware. 10:16 PM Sensors on Android 15
- 16. Porting a sensor onto Android Q. My board has XYZ sensor. How do I get Android to recognise it? Kernel Device-driver Board File Userspace Adding New HAL -OR- Modifying existing HAL 10:16 PM Sensors on Android 16
- 17. Porting a sensor onto Android (kernel) Device-driver Poll/Interrupt? Hybrid-approach = Workqueues Early-suspend hook input_report_abs() / input_report_rel() Board File Interrupt, GPIO, SPI/I2C-lines Axes-remap to device axes platform_data 12:15 AM Sensors on Android 17
- 18. Porting a sensor onto Android (kernel) Workqueues 12:09 AM Sensors on Android 18
- 19. Porting a sensor onto Android (kernel) Early-Suspend hook Input Events 12:13 AM Sensors on Android 19
- 20. Porting a sensor onto Android (userspace) Sensor-HAL Adding – Reference Implementation : http://goo.gl/jjF3l – Sensor-HAL implemented in : android/device/<vendor>/<device>/libsensors – Generates library : system/lib/hw/sensors.<TARGET_BOARD_PLATFORM>.so Modifying – Update sensors.cpp in sSensorList[] – Derive a new sensor object, Include appropriate file – Update i/p dev name in constructor 12:30 AM Sensors on Android 20
- 21. Sensor Fusion Advantages – Faster data samples – Less noise in data samples – More Accurate data samples – Advanced Sensor data (Gestures, Glyphs, Shake-count, Step-count) Disadvantage – Higher power consumption Implement inside App – Register multiple sensor-listeners. – Correlate-data. Implement using Custom-Library – android/device/sample/frameworks/PlatformLibrary http://goo.gl/OI8sg 12:30 AM Sensors on Android 21
- 22. Using Sensors in your app SensorEvent http://goo.gl/hWOQu SensorManager http://goo.gl/1DRUv 12:30 AM Sensors on Android 22
- 23. App-dev Tips and tricks Sensor callibration. 1. one-turn deserves another (axes-calib) 2. zero-calib Sensor fusion Hard-way Easy-way (Invensense ) http://goo.gl/bHmDe Polling rate ui/normal/game/fastest? When to register/unregister eventListener When to place Wakelocks 1:08 AM Sensors on Android 23
- 24. App-dev Tips and tricks register sensorlistener acquire wakelock release wakelock unregister sensorlistener 1:04 AM Sensors on Android 24
- 25. What Next? • Moving on… – Sensor Framework on Android 4.0 (ICS) – Sensor Drivers on Kernel 3.0 • Sensor-Fusion – App / library – Unified Kernel driver(sensors-class) • Calorie-counter/Diet Advisor “You spent 800calories since breakfast. Have a Greek-salad and a cup of milk…” • Location-fix without GPS (using sensors wink-wink) http://goo.gl/ipbrL 12:57 AM Sensors on Android 25
- 26. Thank You!! Questions? android-porting android-developers android-kernel android-platform CONTACT ME http://goo.gl/kKMOr 10:16 PM Sensors on Android 26