Embedded Linux Development on Raspberry PI using Buildroot – part1

By | June 15, 2016

Let us automate embedded Linux development using buildroot.

In this post, I’m going to describe the procedure to create a complete Embedded Linux software for Raspberry Pi using buildroot. We will be configuring buildroot to create a complete package which includes following components

  • Rpi-firmware
  • Kernel
  • zImage
  • Device tree
  • Rootfs
  • Cross compiler

These components are pretty much necessary to boot Raspberry Pi board. Only sad part here is, Rpi buildroot default configuration won’t generate u-boot bootloader, which is a conventional embedded Linux component. In fact, Rpi demos doesn’t come with u-boot.

So, in the part-2, we will customize the buildroot and add support for u-boot.

Development Environment :

Nothing much required for buildroot setup.

  • Software
    • Ubuntu 14.04
  • Others
    • Internet to download buildroot and packages

Required Ubuntu tools and dependencies:

Common tools are required such as, minicom, git, ncurses etc… Run below commands as a root user to install in your Ubuntu computer.

$ sudo apt-get install minicom git ncurses-dev gedit flex bison 
$ sudo apt-get install texinfo g++ gettext u-boot-tools autoconf

Raspberry Pi BSP development with Buildroot:

Let’s get started with buildroot setup.

1.  Run below command to clone mainline buildroot source.

$ git clone git://git.buildroot.net/buildroot

2. Change directory to buildroot

$ cd buildroot/

3. Checkout a particular git tag or git branch. To verify available buildroot tags, run below command.

$ git tag

Now checkout a particular tag or branch based on the requirement. Say latest 2016 tag.

$ git checkout 2016.02 -b 2016.02

4. Once done with checkout process,  have a glance at buildroot folder structure.

$ ls

5. Now, you need to identify and apply the raspberry pi board specific configuration.

In the buildroot, configuration files are available in the ‘./configs’ folder. Run below command to verify the list of available configuration files.

$ ls configs/

6. In particular, to find raspberry configuration run below command.

$ ls configs/raspberrypi*

You will get terminal messages as shown below.

$ ls configs/raspberrypi*
 configs/raspberrypi2_defconfig  configs/raspberrypi_defconfig

So, there are two configuration files available. Since, there is a change in the ARM core of rpi previous versions and Rpi-2,3, its is required to have two different configuration files.

raspberrypi2_defconfig – This configuration is for raspberry pi 2 and later versions of boards

raspberrypi_defconfig – This configuration is for raspberry pi cm, raspberry pi b, raspberry pi b+ boards and other earlier versions.

7. Now apply desired configuration file.

For raspberry Pi A/B A+/B+ boards, run this command

$ make raspberrypi_defconfig

For Raspberry PI 2 run this command

$ make raspberrypi2_defconfig

8. No compile the buildroot.

$ make -j4

Compilation process takes several hours based on in the Internet speed and type of host machine. You may also get build errors during compilation . So try to monitor the build process.

9. Once done with the compilation, final images will be stored in the below path.

$ ls output/images/

RPI Buildroot

bcm2708-rpi-b-plus.dtb  - Rpi B+ and A + device tree
bcm2708-rpi-b.dtb       - Rpi B and A  device tree 
bcm2708-rpi-cm.dtb      - Rpi Computer module device tree
rootfs.ext4             - Root filesystem 
├── bootcode.bin        - Second stage bootloader
├── cmdline.txt         - For Boot parameter
├── config.txt          - System configuration file 
├── fixup.dat           - For SDRAM configuration b/w CPU and GPU
└── start.elf           - GPU firmware
zImage                  - Kernel image

sdcard.img              - Disk image for SD cards

10. Other important component is cross compiler, which can be found in the below path.

$ ls output/host/usr/bin/arm-buildroot-linux-uclibcgnueabihf-*

Now, you are done with basic buildroot setup for Raspberry PI boards. We will be using this buildroot setup for future development.

Create bootable SD card:

Disk image makes our life more easier. Follow below post and flash sdcard.img to a SD card.

win32diskimager: How to write raw disk image to removable storage device

In the upcoming post, we will see the procedure to boot till Linux prompt.

3 thoughts on “Embedded Linux Development on Raspberry PI using Buildroot – part1

  1. Pingback: Embedded Linux Development on Raspberry PI using Buildroot – part2 - EmbeddedForU

  2. Pingback: How to compile mainline u-boot for Raspberry Pi ? - EmbeddedForU

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