Embedded Linux

Alex J Lennon (ajlennon@dynamicdevices.co.uk)

https://slides.com/ajlennon/embedded-linux

Overview

 

• A bit about me / Arcom & Embedded Linux
• A brief history of Embedded Linux
• What do I need to build Embedded Linux?
• Demo - Building with Yocto / OpenEmbedded
• Demo - Talking about 'recipes' (if time allows)
• Demo - Using Mono .NET with Linux (if time allows)
• Thoughts on the future
• Questions (& perhaps some answers!)

Arcom & Embedded Linux

• Started at Arcom Control Systems in Cambridge in '96
• 188EB / 386EX target boards,
• Mainly C & Assembler code (Borland Turbo C!)
• Bare Metal, DOS, RTOSses (QNX, pSOS, VxWorks)

AIM104-386EX ('98)

Target 188EB ('96)

AIM104-MULTI-IO

AIM104-ADC16-IN8

AIM104-RELAY8-IN8

AIM104-SER4

Stackable PC/104 I/O

First Linux Capable Board!

SBC104 (1996)

• 25MHz 386
• BIOS
• 2MB or 4MB DRAM
• 1MB or 4MB Internal FLASH

• Support for M-SYSTEMS Disk On Chip
• RTC, Floppy/IDE Interface, LPP/SPPx2

Disk-On-Module

Linux is going to be BIG !!!

Nah!!!

The proof!

http://www.infradead.org/pipermail/linux-mtd/2001-April/002219.html

SBC-MediaGX (1999)

• 233MHz x86 CPU
• EBX Form Factor
• <= 128MB RAM
• <= 16MB onboard Flash
• FDD/HDD interface

Viper ('2003)

• 400MHz PXA255 ARM XScale
• PC/104 bus
• <= 64MB RAM
• <= 16MB onboard Flash
• USB/CF/Serial/GPIO

Arcom Embedded Linux (AEL)

Development Kits with Free Tux Penguin!!!

And Now?

A Brief History of Embedded Linux

Timeline

• 1995 - BusyBox created. Debian installer on 1.44 FDD
• 1997 - LRP (Linux Router Project) created
• 1999 - ARM support, MTD layer work starts (block flash), ucLibC work starts

     *** People are rolling their own embedded distros.

Linux goes Mobile ***

• 2001 - BuildRoot project starts for cross-compilation
• 2001 - Sharp creates Zaurus SL-500D running Linux, OpenZaurus project created
• 2003 - OpenEmbedded created from OpenZaurus, Familiar Linux, OpenSIMpad
• 2004 - Poky Linux created based on OpenEmbedded, OpenWRT created for LinkSys WRT54G
• 2010 - Intel Spin out Poky Linux as the Yocto Project

(Thanks to Chris Simmonds' "A timeline for embedded Linux" for this)

Today?

• More than 2 billion monthly active Android devices (running Embedded Linux)
  ref: https://www.macrumors.com/2017/05/17/2-billion-active-android-devices

ref: https://www.linux.com/news/embedded-linux-keeps-growing-amid-iot-disruption-says-study

What do I need to build Embedded Linux?

 

Should I cross compile or build on the target?

Cross compilation is

• faster (usually)
• replicable (if we archive sources)
• retargetable (we can change target)

What do I need to cross compile Embedded Linux?

• A host PC to do my build
   
• A target board with a supported architecture (e.g. ARM) to run my build
   
• A build system to manage the cross compilation of packages, dependencies between packages, and creation of an image I can run on the target 
  • Buildroot (https://buildroot.org)
    • May be easier to get started
    • Has a following. I haven't used this myself.

What do I need to cross compile Embedded Linux?

• A build system to manage the cross compilation of packages, dependencies between packages, and creation of an image I can run on the target ​
  • LTIB (http://ltib.org)
    • I have had trouble with this
    • Limited support for packages
  • Yocto (https://www.yoctoproject.org)
    • There is a learning curve, but it is a comprehensive flexible build environment with lots of package support

What are the components of Yocto?

• "BitBake is a make-like build tool with the special focus of distributions and packages for embedded Linux cross compilation, although it is not limited to that."

 

• Meta-data to describe how to build an image, there is some core data, and the rest is provided in layers (BSP etc.)
  
  https://layers.openembedded.org

Where do I get Yocto?

• Some vendors, such as NXP, provide their own tested release for their own reference boards.

• Alternatively follow the Yocto Project Quick Start and download the community sources.
  
  Use a release branch or master if you are feeling brave.

Yocto Releases

https://wiki.yoctoproject.org/wiki/Releases

Sumo	2.5	April 2018		Not started	19.0	1.38
Rocko	2.4	Fall 2017		Development	18.0	1.36
Pyro	2.3	May 2017	2.3.1	Stable	17.0	1.34
Morty	2.2	Nov 2016	2.2.1	Stable	16.0	1.32
Krogoth	2.1	Apr 2016	2.1.3	Community	15.0	1.30
Jethro	2.0	Nov 2015	2.0.3	Community	14.0	1.28
Fido	1.8	Apr 2015	1.8.2	Community	13.0	1.26
Dizzy	1.7	Oct 2014	1.7.3	Community	12.0	1.24
Daisy	1.6	Apr 2014	1.6.3	Community	11.0	1.22
Dora	1.5	Oct 2013	1.5.4	Community	10.0	1.20
Dylan	1.4	Apr 2013	1.4.3*	Community	9.0	1.18
Danny	1.3	Oct 2012	1.3.2	Community	8.0	1.16
Denzil	1.2	Apr 2012	1.2.2	Community	7.0	1.15
Edison	1.1	Oct 2011?	1.1.2	Community	6.0	1.13
Bernard	1.0	??? 2011?	1.0.2	Community	5.0	1.11
Laverne	0.9	??? 2010?			4.0	1.11
Purple	N/A	??? ????			3.2
Pinky	N/A	??? ????			3.1
Blinky	N/A	??? ????			3.0
Clyde	N/A	??? ????			2.0
Inky	N/A	??? ????			1.0

Yocto Layers

https://layers.openembedded.org

Building with Yocto / OpenEmbedded

From Yocto Project Quick Start

    http://www.yoctoproject.org/docs/2.1/yocto-project-qs/yocto-project-qs.html

 

Ubuntu and Debian

     $ sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib build-essential chrpath socat libsdl1.2-dev xterm

Initialize the Build Environment: Run the oe-init-build-env environment setup script to define the OpenEmbedded build environment on your build host.

     $ source oe-init-build-env

 

Start the Build: Continue with the following command to build an OS image for the target, which is core-image-sato in this example:

     $ bitbake core-image-sato

Simulate Your Image Using QEMU: Once this particular image is built, you can start QEMU and run the image:

     $ runqemu qemux86

Demo

• A look at the configuration files
• A look at simple recipes
• A look at how layers work
   
• Creating recipes [if time allows]
• Using Mono .NET with Linux [if time allows]

Thoughts for the Future?

• Virtual Build environments - Docker
  • Replicable builds, archived and versioned
  • Potential for cloud CPU rental for build
• Virtual Deployment environments - Resin.io
  • Push code to a repository
  • Resin.io builds and pushes code deltas to target
  • Virtual channel to device (even if behind NAT)

Questions ?

Resources

OpenEmbedded ​

https://www.openembedded.org/wiki/Main_Page

Yocto Project ​

https://www.yoctoproject.org/

Yocto Quickstart

http://www.yoctoproject.org/docs/2.1/yocto-project-qs/yocto-project-qs.html

Building your own recipes from first principles

https://wiki.yoctoproject.org/wiki/Building_your_own_recipes_from_first_principles

Building and running embedded Linux .NET applications from first principles​

https://wiki.yoctoproject.org/wiki/Building_and_running_embedded_Linux_.NET_applications_from_first_principles