X/Y/Z/PITCH/ROLL/YAWGetting you started with CoreMotion

AGENDA

• Intro

•Concept

•APIs

•Experiments

INTRODUCTION

CORE MOTION WILL

• Provide raw Accelerometer & Gyroscope data

• Provide relatively High-Level filtering

• Provide separated Acceleration, Gravity, Rotation Rate, Attitude

CORE MOTION WON’T

• Give you GPS Data

• Give you Compass Data

• Allow easy management of high-level Motion Events

CONCEPTS

ACCELERO–METER

Measures 3-Axis-Gravity

Available since iPhone 1

Relatively noisy

STMicro STM33DH 3-axis accelerometer

GYROSCOPEMeasures 3-Axis-Rotation

New in iPhone 4

Relatively precise

STMicro AGD1 3-Axis-Gyroscope

Up to 2500 °/s ±0.03 °/s

X

Z

roll

yaw

pitch

Y

Accelerometer Gyroscope

X/ Y/Z Pitch/Roll/Yaw

Device Motion

Acceleration / GravityRotation Rate / Attitude

CREATIVE USES

• Steering wheel — Real Racing

•Water level — iHandy Level, etc.

• Photo stabilisation — camera+, etc.

• Instrument dynamics — GarageBand

• Can you think of something new?

API

- timestamp

CMLogItem

- pitch, roll, yaw

CMGyroData- x, y, z

CMAccelerometerData

- accel, gravity, rotationRate

CMDeviceMotion

- pitch, roll, yaw

CMAttitude

- start, stop

CMMotionManager

CMMotionManager

- is<Accelerometer|DeviceMotion|Gyro>Available

- is<…>Active

- set<…>UpdateInterval

- start<…>UpdatesToQueue:WithHandler :

- stop<…>Updates

CMMotionManager II

• Needs to be allocated & initialized only once

•Make it a (nonatomic, retain)-property

• Reference frame for attitude is fixed at initialization time!

CMLogItem

• Abstract superclass

•Only contains -timestamp property

CMAccelerometerData

X

Z

Y

typedef struct { double x; double y; double z;} CMAcceleration;

Measured in G

You aren’t going to need itroll

yaw

pitch

CMGyroData

Measured in radian

CMDeviceMotion

• CMAttitude attitude

• CMRotationRate rotationRate

• CMAcceleration gravity

• CMAcceleration userAcceleration

CMAttitude

• Yaw, Pitch, Roll

• Also as Rotation Matrix!

CAN’T TEST ON SIMULATOR

• You will need an actual iPhone 4

•One could read the Mac’s Accelerometer and send it to the iPhone via network…

• But for usability tests you’d still need an iPhone!

EXPERIMENT

DEMO

THANK YOU!

SOURCES• Core Motion Framework Reference — © Apple Inc.

/SYSTEM/LIBRARY/FRAMEWORKS/COREMOTION.FRAMEWORK

• “Get Moving with Core Motion” — © Jonathan BlocksomHTTP://WWW.SLIDESHARE.NET/JBLOCKSOM/CORE-MOTION-PRESENTATION

•MEMS Gyroscope X-Ray / SEM pictures — © Chipworks Inc.HTTP://WWW.CHIPWORKS.COM/

• iPhone 4 Teardown pictures — CC BY-NC-SA: Andrew BookholtHTTP://WWW.IFIXIT.COM/TEARDOWN/IPHONE-4-GYROSCOPE-TEARDOWN/3156/1

• iPhone 4 Gyroscope Datasheet — © ST Mikro Inc.HTTP://WWW.ST.COM/STONLINE/PRODUCTS/LITERATURE/DS/17116.PDF

FURTHER READING

• Core Motion Framework ReferenceIOS DEVELOPER LIBRARY — FRAMEWORKS — CORE SERVICES LAYER — COREMOTION

• Event Handling Guide for iOS“MOTION EVENTS” — SECTION “CORE MOTION”

•WWDC ’10 Sample Code“COREMOTIONTEAPOT”

files.ludwigschubert.de/cm.pdf