Building Android for Raspberry Pi 3B

General notes

This is project experimental; it is not guaranteed to build on all possible systems and it is not guaranteed to run on all Raspberry Pi configurations. You need a fair amount of knowledge of Linux and Android to get this to work. Be warned.

My build system:

• Ubuntu 16.04

My Raspberry Pi configuration:

• Raspberry Pi 3B or 3B+
• 7" HDMI touch screen 1024x600. There are many available. The one I use is from Elecrow

Preparation

Make sure that you have a system capable of building AOSP in a reasonable amount of time, as described here: http://source.android.com/source/building.html.

Then set it up following the steps given here: http://source.android.com/source/initializing.html

Then install these extra packages

$ sudo apt install bmap-tools

Download AOSP

Choose a directory for the AOSP source, e.g. $HOME/aosp:

$ export ANDROID_BUILD_TOP=$HOME/aosp
$ mkdir $ANDROID_BUILD_TOP && cd $ANDROID_BUILD_TOP

Select the version of AOSP you want:

$ repo init -u https://android.googlesource.com/platform/manifest -b android-10.0.0_r25

If you want to reduce the size of the download and you don't care too much about the git history you can do a shallow clone by setting the depth to 1:

$ repo init --depth=1 -u https://android.googlesource.com/platform/manifest -b android-10.0.0_r25

Get the Raspberry Pi code and sync

$ git clone https://github.com/csimmonds/a4rpi-local-manifest .repo/local_manifests -b android10
$ repo sync -c

Install a Linaro toolchain

You need this to build U-Boot and the kenel

Download https://releases.linaro.org/components/toolchain/binaries/7.4-2019.02/arm-linux-gnueabihf/ gcc-linaro-7.4.1-2019.02-x86_64_arm-linux-gnueabihf.tar.xz

Un-tar it somewhere convenient, for example your $HOME directory

Build U-Boot

$ cd $ANDROID_BUILD_TOP/u-boot
$ PATH=$HOME/gcc-linaro-7.4.1-2019.02-x86_64_arm-linux-gnueabihf/bin:$PATH
$ export ARCH=arm
$ export CROSS_COMPILE=arm-linux-gnueabihf-
$ cp $ANDROID_BUILD_TOP/device/rpiorg/rpi3/u-boot/rpi_3_32b_android_defconfig configs
$ make rpi_3_32b_android_defconfig
$ make

Build the kernel

$ PATH=$HOME/gcc-linaro-7.4.1-2019.02-x86_64_arm-linux-gnueabihf/bin:$PATH
$ export ARCH=arm
$ export CROSS_COMPILE=arm-linux-gnueabihf-
$ cd $ANDROID_BUILD_TOP/kernel/rpi
$ scripts/kconfig/merge_config.sh arch/arm/configs/bcm2709_defconfig \
kernel/configs/android-base.config kernel/configs/android-recommended.config
$ make -j $(nproc) zImage
$ cp arch/arm/boot/zImage $ANDROID_BUILD_TOP/device/rpiorg/rpi3
$ make dtbs
$ croot

Build AOSP

Start a new shell

$ source build/envsetup.sh
$ lunch aosp_rpi3-eng
$ m

The command 'm' is a wrapper for 'make', with the additional benefit that it will use all available CPU cores (see \filePath{build/soong/ui/build/config.go).

Even so, the build will take an hour or two...

Write to SD card

You will need a micro SD card of at least 4 GB. Ideally it should be class 10 or better.

Plug the card into your card reader. Run command lsblk to find which device it is. Then run the script below, giving the device name as the parameter. For example, if the card reader is /dev/mmcblk0, the command would be:

$ scripts/write-sdcard-rpi3.sh mmcblk0

Note: I use bmap-tool to write the card because it is faster and safer than dd. If you don't want to use bmap-tool, go ahead and edit the script to switch back to dd.

When done, plug the card into your Raspberry Pi and boot up

ADB

Because the Raspberry Pis up to and including 3 do not have a USB OTG port, the only way to connect ADB is via Ethernet. Plug your Raspberry Pi into your Ethernet LAN and wait for it to be given an IP address. Then from $ANDROID_BUILD_TOP type this command:

$ adb connect Android.local:5555