O'Reilly Media, Inc. Basic Sensors in iOS, the image of a Malay fox-bat, and . This chapter summarizes the available sensors on the iPhone and iPad platforms . Basic Sensors in IOS: Programming the Accelerometer, Gyroscope, and Magnetometer. Home · Basic Sensors in IOS: Programming the Accelerometer. Basic Sensors In Ios Programming The Accelerometer cat.p19e-6 murata manufacturing co., ltd. this is the pdf file of catalog no.p19e
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Android, iOS, mobile platform, sensor, Windows phone . Near Field Communication (NFC) share the same basic technology with RFID, but the biggest. Most smartphone accelerometers trade large value range for high precision, iPhone 4 range: ±2g, precision. g. Zeitmaschinen – Smartphone Sensors. If you're an Objective-C programmer who likes to experiment, this book explains the basics of Arduino and other hardware components you need — and lets you .
In the case of a gyroscope with two gimbals, the outer gimbal, which is the gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by the support.
This outer gimbal possesses one degree of rotational freedom and its axis possesses none. The inner gimbal is mounted in the gyroscope frame outer gimbal so as to pivot about an axis in its own plane that is always perpendicular to the pivotal axis of the gyroscope frame outer gimbal. This inner gimbal has two degrees of rotational freedom.
The axle of the spinning wheel defines the spin axis. The rotor is constrained to spin about an axis, which is always perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees of rotational freedom and its axis possesses two. The wheel responds to a force applied to the input axis by a reaction force to the output axis. The behaviour of a gyroscope can be most easily appreciated by consideration of the front wheel of a bicycle.
If the wheel is leaned away from the vertical so that the top of the wheel moves to the left, the forward rim of the wheel also turns to the left. In other words, rotation on one axis of the turning wheel produces rotation of the third axis.
A gyroscope flywheel will roll or resist about the output axis depending upon whether the output gimbals are of a free or fixed configuration.
Reflection Reflection is a Java mechanism for apps to examine or modify their runtime behaviors. Apps can use reflection to dynamically change their call targets, which could help them bypass static analysis.
To prevent apps from retrieving sensor data in this implicit way, our Instrumentor employs the same strategy in [ 16 ], that is, we hook the critical reflection function invoke 1 in class java.
Method in short, Method [ 23 , 24 ]. As stated above, when we hook a specific API, we replace the API call with a call to its corresponding wrapper function. In wrapper invoke, we check whether the function being invoked by reflection is the critical sensor-related API, i. From object method, we can retrieve the class name and method name of the method being invoked with APIs like getDeclaringClass and getName [ 24 ] and then check whether the class name is SensorManager and the method name is regsiterListener.
If they are, then we invoke wrapper reg instead of the original registration function.
Instrumentor employs the method in Aurasium [ 18 ] to hook native API calls, which examines the native shared libraries loaded by the app and replaces function pointers in their global offset table GOT.
Android apps can load a native library by calling either System. We hook these loading functions. An app can also use dlopen to open libandroid in which the sensor-related APIs are defined and use dlsym to get the function pointer. We hook both dlopen and dlsym , record the address of libandroid returned by dlopen , and check whether the app is using dlsym to resolve the address of the sensor-related APIs the abovementioned registration function and queue-polling function.
Prevent direct access to sensors As mentioned in Section 2. Hao et al. To prevent such an evasion, we hook the Binder IPC to prevent apps from accessing sensors in such a direct way.
We hook the native function ioctl in libc. On Android, all IPCs are sent through this function. We reconstruct the high-level IPC communication in ioctl using the same method in Aurasium.
When we observe an IPC of enabling a sensor, we examine the current Java and native call stacks of the app to check whether this IPC is from the public registration APIs provided by the sensor framework. If not, we deny this IPC because we do not know the customized way in which the app is retrieving and handling sensor events. Policy Manager and runtime communication Policy Manager is a standalone app running on the same Android device with the instrumented apps, which manages and deploys control policies for all the instrumented apps.
At runtime, the wrappers in the instrumented apps need to get the most up-to-date control policies from Policy Manager to decide whether the app is allowed to access sensors. This is a consideration of runtime overhead because the frequency of sensor events is quite high at least 5 Hz.
In Sensor Guardian, every app is instrumented with an internal light-weight Policy Manager that handles IPC with the external Policy Manager and caches current policies only for this app. When a sensor event is hooked, there is no need to ask the external Policy Manager for control policies through IPC.
The hooks only need to get the cached policies from the internal Policy Manager in the same process, which has lower overhead than IPC. Though this strategy may delay the new control policy to take effect, the latency is quite low, which is the time of only one IPC process.
In preparation, we implemented aforementioned API wrappers both in Java and native. The Java wrappers and the internal Policy Manager, say manager int, are compiled into a dex file called dex prep. The native wrappers and the code to hook native API calls are compiled into a native shared library, say lib prep. Note that dex prep and lib prep only need to be generated once for all apps because these preparations do not depend on any details about a specific app.
As a result, the time to generate these two preparations is not included in the measurement of instrumentation time in Section 4. Java Instrumentation takes dex prep, manifest orig, and dex orig as its input and generates an instrumented dex file dex instrumented as output.
In order to ensure that manager int can get the available policies at the start of an app, we implemented manager int as a subclass of android.
Application and modified the application tag in manifest orig to set manager int as the first class to be instantiated. At last, we repackage dex instrumented, lib prep, and the modified manifest file into the original APK file to generate the instrumented APK file.
And we sign the instrumented APK file with a new certificate.
When an APK file is modified and repackaged, its signature is inevitably destroyed and we cannot recover its original signing key. This is a problem in all static instrumentation techniques [ 16 — 18 ].
We adopt the method in [ 18 ], in which we generate a new certificate for each app we have encountered and keep the relationship between the certificate and the app.
Add the code highlighted below to the accelerometer: Save your changes again and click on the Run button to compile and deploy the application to your device. Apple provides convenience methods to determine whether the current device orientation is portrait:.
These methods return YES if the device is in portrait or landscape mode respectively; otherwise they return NO. If the change in angular velocity between successive data points is large then the algorithm determines that a UIEventSubtypeMotionShake has occurred, and the motionBegan: Conversely, if the change in angular velocity is small and a shake event has been triggered, the motionEnded: The iPhone is better at detecting side-to-side rather than front-to-back or up-and-down motions.
Take this into account in the design of your application. There are three motion delegate methods, mirroring the methods for gesture handling: The first indicates the start of a motion event, the second the end of this event. You cannot generate a new motion event for a second or two following the first event.
The final delegate method is called when a motion is interrupted by a system event, such as an incoming phone call. Save your changes and click on the AccelerometerViewController.
The easiest way to ensure that the view controller receives motion events is to promote it to First Responder in the viewDidAppear: Remember to make the controller resign as first responder when the view goes away. Add the viewDidAppear: Use the canBecomeFirstResponder method to indicate that the view controller can indeed become the First Responder:.
Save your changes and return to the AccelerometerViewController. Save your changes and click on the Run button in the Xcode toolbar. After the application is built and deployed to your device, try shaking the phone. Stay ahead with the world's most comprehensive technology and business learning platform. With Safari, you learn the way you learn best.
Get unlimited access to videos, live online training, learning paths, books, tutorials, and more. Start Free Trial No credit card required. Using the Accelerometer. Note While it should in theory be possible to change the operating mode of the accelerometer, there is currently no published API that allows you to do so within the SDK.
About the Accelerometer. Note Yaw , pitch , and roll refer to the rotation of the device in three axes. Writing an Accelerometer Application. Warning The raw accelerometer data can also be accessed using the Core Motion framework, which was new in iOS 4. Connecting the UI elements to your code in Interface Builder. We declare that this class is the delegate for the UIAccelerometer.