Embedded Android: Android beyond the smartphone

Embedded Android
Android beyond the smartphone
Chris Simmonds, 2net Ltd
Hitex ARM User Conference, 2017
Embedded Android 1 Copyright © 2017, 2net Ltd

About Chris Simmonds
• Consultant and trainer
• Author of Mastering Embedded Linux Programming
• Working with embedded Linux since 1999
• Android since 2009
• Speaker at many conferences and workshops
"Looking after the Inner Penguin" blog at http://2net.co.uk/
https://uk.linkedin.com/in/chrisdsimmonds/
https://google.com/+chrissimmonds

Mainstream Android
• Android from Google comes in several ﬂavours:
• Android, for smartphones and tablets (approx. 2 billion of them)
• Android Things, for IoT
• Android Wear, for smart watches
• Android TV
• Android Automotive

Why Embedded Android?
• It’s free (open source)
• Has a familiar UI
• There are many developers who can write
Android apps
• Has good development tools
• It’s still Linux underneath
• You can customise it to suit your needs

Example 1: marine navigation
• Furuno NavNet TZtouch2
• Navigation system for small boats
• i.MX6 platform

Example 2: point of sale
• Leaf, leaf.me
• Tablet-based POS terminal
• Credit card reader

Example 3: digital signage
• Many companies provide use Android
for signage
• The example shown is from
www.allsee-tech.com
• Player based on Rockchip RK3188
(Quadcore Cortex A9, Mali 400 GPU)

How open is Android?
• Need to distinguish between the open part:
• AOSP
• And the proprietary part:
• Google Mobile Services
• GMS consists of extension libraries that implement the Google APIs,
such as maps, in-app payment, Gmail and so on
• Let’s take a closer look at the architecture ...

Architecture of AOSP
Android Java libraries (android.*)
Android Java API
Applications
System services
"Glue" libraries
Native
servers
HAL
libraries
Other
libraries
Linux
Binder
JNI
Android
framework
Native
layer
Kernel
App
layer

The four layers
• Applications: stock AOSP apps and 3rd party apps
• Framework, consisting of
• The android.* libraries, which dispatch messages via binder to ...
• ... System services, which use JNI to call down to ...
• ... "Glue" libraries written in C++
• Native
• The init program, various native servers (daemons) and libraries
• Kernel
• A Linux kernel customised for the platform

Google Mobile Services
AOSP
Android apps
Google Mobile
Services
Google apps

Google Mobile Services
• Plain Android apps use only the APIs published within the AOSP
• AOSP aps include Launcher, Browser, Email, Gallery, Keyboard
• GMS is a set of services that provide Google proprietary APIs
• Most user-facing features require GMS, including popular Google apps
such as Play Store, Chrome browser, Google Now, etc.
• Requires a license from Google
• (You can grab it unofﬁcially (and illegally) via the gapps zip ﬁle - google
for it)

What do you need to run Android?
• Hardware from one of the supported architectures
• ARM, x86 or MIPS, in 32 or 64 bit varieties
• Capable of running Linux
• At least 512 MiB RAM
• At least 512 MiB ﬂash storage
• Touchscreen or external display (optional, but desirable)
• GPU with OpenGL ES libraries (optional, but desirable)

Beware the binary blob
• Although AOSP and Linux are open source, you will need proprietary
binary blobs to make a working system
• Firmware for the processor and peripherals
• Kernel modules for some hardware
• GPU driver and OpenGL libraries
• These are only available from the manufacturer
• Chip vendors with good support include NXP, Qualcomm, HiSilicon

Dev boards 1/3
DragonBoard 410c
• Qualcomm Snapdragon 410E quad-core ARM
Cortex-A53
• 1 GiB RAM
• 8 GiB eMMC ﬂash storage
• Wi-Fi 802.11 b/g/n
• Adreno 306 GPU
• Expansion headers: 1 x UART, 2 x i2c, 12 x
GPIO
https://developer.qualcomm.com/hardware/dragonboard-410c

Dev boards 2/3
Wandboard
• NXP i.MX6 single, dual or quad core ARM
Cortex-A9
• 512 MiB, 1 GiB or 2 GiB RAM
• Ethernet and WiFi
• Vivante 880 GPU
• Expansion headers: 2 x UART, 3 x i2c, 8 x GPIO
http://www.wandboard.org

Dev boards 3/3
HiKey
• HiSilicon Kirin 620 eight-core ARM Cortex-A53
• 1 GiB RAM
• 8 GiB eMMC ﬂash storage
• WiFi b/g/n
• Expansion headers: 1 x UART, 2 x i2c, 12 x
GPIO
www.lenovator.com/product/86.html

SBC and SoM support for Android
Many SBC and SoM vendors offer Android BSPs
Here is a non-exhaustive list:
• Phytec phytec.com
• DAVE dave.eu
• Digi digi.com
• Toradex toradex.com
And many more...

Locking down the UI
• Also known as kiosk mode
• Main app replaces the Launcher as the home screen
• Runs in full screen mode
• Calls startLockTask() to enter Lock Task mode, which
• Disables the status bar
• Disables Home, Back, Recents navigation
• Optionally, you may want to disable screen dimming and blanking
• ... and add hardware keys for easy navigation

Hardware interfacing
• Android has support for the hardware you would expect in a
smartphone
• UI: touchscreen, HDMI monitor, keyboard, mouse, gamepad
• Network: mobile data, WiFi, Ethernet
• Sensors: accelerometer, magnetometer, ambient light, etc.
• But, embedded applications have more diverse needs ...
• Serial, i2c, digital and analog I/O

Direct access
• In Linux, everything is a file
• Serial ports: /dev/tty*
• I2C host controllers: /dev/i2c-*
• GPIO pins: /sys/class/gpio
• LEDs: /sys/class/leds
• PWM: /sys/class/pwm
• Normally these files are not accessible from application code
• But, you can change the permissions files, /ueventd*.rc, and the
SELinux policy to permit access

Custom system service
• Better still, encapulate the
hardware interface as a system
service
• Enforces correct permissions
• Runs in its own SELinux domain
GPIO extension
library
GPIO service
GPIO hardware
control library
Android app
Java function call
Binder AIDL interface
JNI function call
Java library (jar ﬁle)
Java service, part of
Android framework
C/C++ library
(.so ﬁle)
/sys/class/gpio

What next?
• Get a dev board
• Start to play
• Learn how to build Android from scratch
• Begin tinkering with hardware
• Keep on learning

Android4Beagle
• My pet project to run Android on the
BeagleBone Black
• Makes a good platform for learning
about AOSP
• I use it as the example device in my
training courses
github.com/csimmonds/android4beagle

Courses in Android and Linux
• 2net offers a number of 4-day instructor-led classes, including
• Embedded Android
• Android Porting
• Mastering Yocto Project
• Embedded Linux device drivers
• Open access or on-site
• Details at 2net.co.uk/training.html
• Contact: email training@2net.co.uk or chris@2net.co.uk

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