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Android Hardware Interfacing with the BeagleBone Black
Android Hardware Interfacing with the BeagleBone Black

Android Hardware Interfacing with the BeagleBone Black: Design and implement Android apps that interface with your own custom hardware circuits and the BeagleBone Black

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Profile Icon Andrew Henderson Profile Icon Prakash
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Full star icon Full star icon Full star icon Full star icon Half star icon 4.5 (6 Ratings)
Paperback Feb 2015 134 pages 1st Edition
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Mex$179.99 Mex$442.99
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Mex$553.99
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Arrow left icon
Profile Icon Andrew Henderson Profile Icon Prakash
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Free Trial
Full star icon Full star icon Full star icon Full star icon Half star icon 4.5 (6 Ratings)
Paperback Feb 2015 134 pages 1st Edition
eBook
Mex$179.99 Mex$442.99
Paperback
Mex$553.99
Subscription
Free Trial
eBook
Mex$179.99 Mex$442.99
Paperback
Mex$553.99
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Free Trial

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Android Hardware Interfacing with the BeagleBone Black

Chapter 2. Interfacing with Android

In the last chapter, you installed Android on your BBB. You also gathered all of the hardware and components that you will need to try out the exercises in this book. Now that you have a working Android system and the hardware needed to explore it, it is time to dive into Android and find out how to prepare it to interface with custom hardware.

Most people would not consider Android and Linux to be very similar, but the two have more in common than you might realize. Underneath the polished UIs and a wide variety of apps, Android is secretly Linux. Android's filesystem layout and services are quite different from those of a typical Linux system, so there are certainly many differences between the two in terms of user space (where apps and other processes execute). In terms of kernel space (where device drivers execute and resources are allocated to each running process), they are almost identical in functionality. Understanding how the BBB...

Understanding the Android HAL

An Android kernel contains a few additional features that aren't found in a typical Linux kernel, such as Binder IPC and the low-memory killer, but otherwise it is still Linux. This provides you with one very big advantage when interfacing hardware with Android, that is, if a Linux driver already exists in the kernel used for an Android system, then you already have an Android driver for that device.

Android apps must interact with the hardware of an Android device by generating video and audio data, receiving button and touchscreen input events, and receiving sensor events from cameras, accelerometers, and other devices that gather information from the outside world. Leveraging existing Linux drivers for these devices makes Android support much easier. Unlike a traditional Linux distribution, which grants applications permission to directly access many different device files (by directly opening files in the /dev filesystem), Android dramatically limits...

Installing PacktHAL

All of the various pieces of PacktHAL are located in the PacktHAL.tgz file, which is available for download from Packt's website (http://www.packtpub.com/support). This is a compressed tar file that contains all of the source code and configuration files required to modify BBBAndroid to use PacktHAL and include PacktHAL support in your apps.

Preparing PacktHAL under Linux

Once you have downloaded the PacktHAL.tgz file, you must decompress and untar it. We will assume that you have copied PacktHAL.tgz to your home directory after downloading it and will decompress it from there. We will refer to your home directory as $HOME.

Use the Linux tar command to decompress and untar the file:

$ cd $HOME
$ tar –xvf PacktHAL.tgz

A directory named PacktHAL now exists in your $HOME directory. All of the PacktHAL files are located in this directory.

Preparing PacktHAL under Windows

Once you have downloaded the PacktHAL.tgz file, decompress and untar it. We will assume that you...

Setting up the Android NDK for PacktHAL

Unfortunately, the Android Native Development Kit (NDK) is missing a kernel header file that is needed to build PacktHAL. The missing header describes the interface between user space apps and the generic SPI driver (spidev, which you will use in Chapter 5, Interfacing with High-speed Sensors Using SPI). It is not the fault of the NDK that this header file is missing, as usually apps will never need direct access to the spidev driver.

As you are using an app to talk directly talk to the hardware, you will need to copy this missing header into your NDK installation.

Tip

For your convenience, we have included a copy of this header file in the PacktHAL source tarball. You only need to copy the file into your NDK installation prior to building PacktHAL.

BBBAndroid is 4.4.4 KitKat, and API level 19 is the highest level supported by this version. You will be building all of the examples in this book for API level 19. Each API level has a different set of headers...

Multiplexing the BBB pins

As accessing hardware resources follows the same process under Android as it does under Linux, it is important to understand how the Linux kernel configures device drivers and allocates them to particular pieces of hardware. It is also necessary to understand how these kernel drivers provide user space interfaces that PacktHAL can interact with.

The BBB's AM3359 processor offers a wide variety of signals on its hundreds of pins. These signals include many different, specialized interface buses and sensor inputs. There are far too many potential signals for the number of pins available to supply these signals to the outside world. To select which signals are available on the pins, the pins are multiplexed, or muxed, to specific signals.

Several of the processor's pins are wired to the connections of the BBB's P8 and P9 headers. The muxing of these particular pins is of great interest to BBB users, as the muxing determines which processor signals and...

Summary

In this chapter, we explained how Android uses a HAL to allow Android managers to provide hardware access to apps. We introduced you to PacktHAL that can be used to interface with all of the examples throughout this book. You configured your BBBAndroid image to use PacktHAL, and you modified your NDK installation to build PacktHAL into your apps.

We also showed which pins of the BBB's P8/P9 headers can be multiplexed, what the Device Tree is and how it is used to multiplex pins, and how the capemgr loads Device Tree overlays to dynamically mux the BBB's pins.

In the next chapter, you'll put PacktHAL to work and build your first hardware-interfacing app using GPIOs.

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Description

If you are an Android app developer who wants to experiment with the hardware capabilities of the BeagleBone Black platform, then this book is ideal for you. You are expected to have basic knowledge of developing Android apps but no prior hardware experience is required.

What you will learn

  • Install Android on your BeagleBone Black Explore the three primary hardware interfaces of the BeagleBone Black-GPIO, SPI, and I2C Construct circuits that interface the BeagleBone Black with high-speed sensors, external memory chips, and more Discover the advantages and disadvantages of using GPIO, I2C, and SPI components in your interfacing projects Modify Android to recognize and interface with your own custom and prototype hardware Develop multithreaded apps that communicate directly with custom circuitry

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Length: 134 pages
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Table of Contents

8 Chapters
1. Introduction to Android and the BeagleBone Black Chevron down icon Chevron up icon
2. Interfacing with Android Chevron down icon Chevron up icon
3. Handling Inputs and Outputs with GPIOs Chevron down icon Chevron up icon
4. Storing and Retrieving Data with I2C Chevron down icon Chevron up icon
5. Interfacing with High-speed Sensors Using SPI Chevron down icon Chevron up icon
6. Creating a Complete Interfacing Solution Chevron down icon Chevron up icon
7. Where to Go from Here Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

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Full star icon Full star icon Full star icon Full star icon Half star icon 4.5
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4 star 16.7%
3 star 16.7%
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Daxter Apr 21, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Is complicated, if you are a novice watch out, get ready for a real challenge. But there is plenty of good info.
Amazon Verified review Amazon
Wilhelm Löffler Apr 10, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
The mobile evolution is changing rapidly. Communication is now carried out over the Internet between the mobile devices (not only e-mail or telephone). I can send commands to the destination device (miniPC with android OS), that is starting an application to do the job, which is in the command.Now the mini PC (Beaglebon Black) can operate with the android OS and can communicate to the outside world with several interfaces (I2C, SPI, Can, GPIO ..) for carrying out a specific task. The user can use it on a device to send commands to the destination device. With this system in place, the world in automation is really stableSee the website baggerautomatik.selfhost.eu to get the idea what we are going to do.This book helps you learn the concepts I just explained and provides practical Android app examples that will help the users to create Android controlled devices that will use BeagleBone as hardware.
Amazon Verified review Amazon
billy Feb 20, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I don't have this book but I do know Andy and everything he does is solid gold! If you are looking for a book on BeableBone/Android interfacing, this is the one!
Amazon Verified review Amazon
Vicky Singh Mar 05, 2015
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One of the best Do it yourself books for Android.
Amazon Verified review Amazon
Jeffrey Smith Mar 17, 2015
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
Before you decide to purchase this book, please understand that the scope of this book is more appropriate for prototyping or hacking versus implementing a production grade BBB Android hardware product. In order to use the resources, e.g. PacktHAL, you must loosen up the security on the device files at the driver level. This is fine for prototyping, but would almost never be done in a real product. These limitations are called out in the text, but the book description does not really indicate this fact. With a bit more effort, the book could have presented a very simple example HAL and device driver that more completely follows the Android hardware interfacing model. Granted, detailed discussion of Linux device drivers is beyond the scope of this book, so additional references are appropriate. The book is well written for what it is intended to cover and there is probably still a good deal of benefit from applying the techniques laid out in it. I gave it 4 stars for that reason alone.
Amazon Verified review Amazon
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