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:

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 have copied PacktHAL.tgz to the root directory of the C: drive after downloading it and will use WinRAR to decompress it from there.

Tip

Where should I unpack PacktHAL.tgz?

You can decompress and untar PacktHAL.tgz on the desktop or wherever else you wish, but you will be performing some command-line commands to copy files around later. It is much simpler to perform these operations if PacktHAL.tgz is decompressed and untarred in the root directory of the C: drive, so we will assume that you are performing these operations from there.

Perform the following steps to extract the PacktHAL.tgz file:

1. Open a file explorer window and navigate to the root of the C: drive.
2. Right-click on the PacktHAL.tgz file in file explorer and select Extract Here.

A directory named C:\PacktHAL now exists. All of the PacktHAL files are located in this directory.

The PacktHAL directory structure

The PacktHAL directory has the following structure:

The cape subdirectory contains the source code and build script for building a Device Tree overlay that enables all of the hardware features that PacktHAL needs. You will learn more about Device Tree overlays later in this chapter. The jni subdirectory contains the source code files that implement PacktHAL. These source files will be added to your projects in later chapters to build PacktHAL support into your apps. The prebuilt directory contains a few premade files that must be added to your BBBAndroid image and Android NDK to build and use PacktHAL. You will install the files in the prebuilt directory to their required locations in the next few sections.

Preparing Android for PacktHAL

Before using PacktHAL with any apps, you have to prepare your BBBAndroid installation. By default, Android is very restrictive on the permissions that it assigns to hardware devices. To use PacktHAL, you must lessen the permission restrictions and configure Android for the hardware that you will interface with. These actions require copying some prebuilt files into your Android system to make a few configuration changes that relax various Android permissions and configure the hardware properly for PacktHAL's use.

You will use the ADB tool to push (push) the necessary files over to your running BBB system. Prior to pushing the files, boot Android on the BBB and connect the BBB to your PC using the USB cable that came with your BBB. Once you have reached this point, continue with the instructions.

Pushing PacktHAL files under Linux

The following steps are used in order to publish PacktHAL files under Linux:

1. Before you get started, make sure that ADB can see your BBB by using the adb devices command. The BBB will report as having a serial number of BBBAndroid. Execute the following command: $ adb devices List of devices attached BBBAndroid device
2. If you are missing the adb command, install the android-tools-adb package via apt-get: $ sudo apt-get install android-tools-adb

   Tip

   
   

   Why can't Linux find my BBB?

   If adb is installed on your system and you are unable to see the BBB, you might need to add a udev rule to your system and perform some additional troubleshooting. Google provides directions for adding this rule and some troubleshooting steps if you run into any difficulty, and this can be found at http://developer.android.com/tools/device.html.

   BBBAndroid reports the USB device ID of its ADB interface as 18D1:4E23, which is the device ID of a Google Nexus S, so the USB vendor ID for the BBB is 18D1 (the device ID for Google devices).

3. Once you have verified that adb can see the BBB, change into the PacktHAL directory, shell into Android via adb, and remount the read-only rootfs filesystem as read-write: $ cd $HOME/PacktHAL/prebuilt $ adb shell root@beagleboneblack:/ # mount rootfs rootfs / rw root@beagleboneblack:/ # exit
4. Now, push the necessary files into Android's rootfs filesystem: $ adb push BB-PACKTPUB-00A0.dtbo /system/vendor/firmware $ adb push init.genericam33xx\(flatteneddevicetr.rc / $ adb chmod 750 /init.genericam33xx\(flatteneddevicetr.rc
5. Finally, shell into Android's rootfs filesystem to sync it and remount it as read-only: $ adb shell root@beagleboneblack:/ # sync root@beagleboneblack:/ # mount rootfs rootfs / ro remount root@beagleboneblack:/ # exit
6. You have now prepared your BBBAndroid image for PacktHAL under Linux. Remove the power supply cable and USB cable from your BBB to shut it down.
7. Then, power up the BBB to verify that Android boots properly with the modifications that you have just made.

Pushing PacktHAL files under Windows

You must locate where your adb.exe file is located. It is part of the platform tools in the Android SDK. In the following instructions, we are assuming that you installed the Eclipse ADT in the c:\adt-bundle directory, making the full path to adb to be c:\adt-bundle\sdk\platform-tools\adb.exe.

The following steps are used in order to publish PacktHAL files under Windows:

1. Before you get started, make sure that adb can see your BBB by using the adb devices command. The BBB will report as having a serial number of BBBAndroid: $ adb devices List of devices attached BBBAndroid device

   Tip

   
   

   Why can't Windows find my BBB?

   It can be notoriously difficult to get adb to see Android devices under Windows. This is because each hardware manufacturer that creates an Android device provides its own Windows ADB device driver that Windows uses to talk to that device. BBBAndroid reports the USB device ID of its ADB interface as 18D1:4E23, which is the device ID of a Google Nexus S. This device is one of the (many) USB devices that are supported by Koushik Dutta's excellent Universal ADB driver for Windows. If adb can't find your BBB, install the Universal ADB driver and then try again. You can download the driver from http://www.koushikdutta.com/post/universal-adb-driver.

2. Once you have verified this, adb can see the BBB, shell into Android via adb, and remount the read-only rootfs filesystem as read-write: $ adb shell root@beagleboneblack:/ # mount rootfs rootfs / rw root@beagleboneblack:/ #...