MOVING INTO ARM EMBEDDED LINUX DEVELOPMENT

Welcome  



Joe Nicholson Software consultant & embedded developer Rufilla Ltd.  www.rufilla.com  [email protected]

“Moving Into” 



This topic can take some time to get started with A fast way of getting to a basecamp

“ARM”  

Excellent platform for Embedded Linux ARM Cortex-A8 based TI  System

On Chip  Very few additional components required, true embedded system  Powerful  Uses very little power

“Embedded Linux”   

Brief history of Linux What the difference is: Desktop/Embedded Why put Linux inside devices?

“Development”  

Specific focus on application development No longer need to make a distro or understand the kernel to get started…  Wide

range of training boards available  Range of pre-built embedded Linuxes available 

So, need to know how to use it  NOT

how to build it

Using DS-5  



From ARM Combines all the tools required for development in a single installation Runs under Windows  No

need to learn Desktop Linux

 Go

straight in!

At the end of this session you will..   

Get an overview of Embedded Linux Get a bird’s eye view of DS-5 Go through the simplest example – flashing a light!

Origins of Linux



HANDS UP ALL C PROGRAMMERS!  …You

think!

are more closely linked with Linux than you

Origins of Linux     



Linux is a Unix-Like OS Unix is old Bell Labs, 1969 Ken Thompson, PDP-7 Originally coded in Assembler Ken Thompson was also designer of programming language B

Origins of Linux 

Dennis Ritchie  Colleague

of Ken Thompson  Took Ken’s B and created C 

By 1973 Unix was rewritten in C  First



portable operating system

Unix and Linux have stayed in C A

gift for embedded developers

Linux - A Free Unix 

Linux is actually composed of two major components:  GNU

part  Linux part 

Some therefore have called it GNU/Linux  But

it mainly just tends to be called Linux

The GNU Part 

Richard Stallman  Worked



1983 – GNU Operating System  “GNU’s



at MIT’s AI laboratory Not Unix!”

Created the GPL  Free

software licence  Protect the freedom and openness of the source code 

Created ALMOST all of a UNIX system

Almost, but not quite… 

GNU created:  Compilers,

linkers, debuggers  Command shell  Unix programming tools  etc., etc. 

Missed one important part  Kernel

– The core interface to hardware, scheduler, etc.  This bit is running late…

Linux 

1991 - Linus Torvalds  Student

at University of Helsinki  Working on a terminal emulator to access Unix servers at the University  Kept developing this… “suddenly realised” he’d essentially written an operating system kernel

Embedded Linux 

Linux almost entirely in C  So

portable  Ported to a wide range of processors 

Originally in high-end embedded space  Headless

PCs  File servers, etc. 

Needs memory management unit (MMU)  µClinux

attempt to create a version without this requirement

Embedded Linux (2) 

Needs megabytes of memory to run Requirements have become easier to achieve



Greater demands on embedded devices



Play MP3s  Connect to servers or devices using TCP/IP 



System On Chips 



Single chip systems capable of running embedded Linux

…Now Is The Time!

Why Embedded Linux?  

No licence fees or royalties An inexpensive means of incorporating advanced features: 



TCP/IP, FTP, telnet, Web servers, SSL encryption

Tools are: Often standard  Rugged and secure  Tested and supported by a wide community 



Similar components for RTOS kind can be nonstandard and very expensive

Embedded Linux Advantages 

Mature  Unix

 

 Linux  Embedded Linux

Sophisticated Extensible  100,000s

projects

 Many

work out of the box cross compiled onto embedded platform



Community  Hundreds

of thousands of developers  Often talk direct to the key developer

Embedded Linux: The Challenge 

HARD to get started!



Challenges:  Thousands

of differing approaches  Many, many tools  Desktop Linux normally required as development platform  Linux command line interface complex though sophisticated  Culture which can focus on detail

Enter ARM DS-5  

Tools by ARM… firmly in embedded space DS-5 first Embedded Linux offering

DS-5 Advantages 

ARM approach Embedded Linux from an embedded developer’s viewpoint  Complete

development package  Single Windows installation  Simulator  Debugger  Example programs to try out-of-the-box 

I consider this attitude refreshing in Embedded Linux space

So, What is DS-5? 



Combination of open source tools and ARM’s own Main components are all standard  GCC

compiler

 Running

under Windows using Cygwin

 Eclipse

IDE  GDB debugger, with ARM front end 

ARM Profiler

Version of DS-5

Downloading and Installing

Downloading and Installing

Main DS-5 Features     

IDE Compiler Debugger Simulator Profiler

Menu Bar Toolbars

Editor

Views

Views

Perspective s

Debugger

Simulator 

Gnometris example running under simulator

Profiler

Target Hardware 

DS-5 is compatible with: A

range of ARM-based system-on-chip devices.  A range of prototype boards and development platforms.

A Typical Development Path  

Out-of-the-box Linux development with DS-5 Dev board with out-of-the-box Linux distro  E.g.

  

Emtrion

Develop product on dev board Use in prototype Use in final unit  If

low volume or high value

A Typical Development Path (2)   

Base hardware on board or reference design Some changes Alter kernel board support  Rufilla



An Example: Hello GPIO   

Let’s flash an LED! Use the kernel GPIO driver We need to look at a concept…

“Everything in Linux is A File” 

…everything? 



So, programs are files? 



That’s how you see them, yes.

So how do I light an LED? 



Yep, obviously.

And… device drivers are files? 



Yes.

You write the state of the LED to a file.

What?! A real file? That’s just WEIRD! 

No, but it looks like one: it’s a virtual file in a virtual filesystem, in this case sysfs.

Setting the state of an LED static void set_led_state(int led_state) { /* fd_led: File handle for LED's brightness file */ int fd_led; /* led_val: The value to write to the brightness file */ char led_val = '0'; /* Open the LED's brightness file in binary for writing */ if ((fd_led = open("/sys/class/gpio/gpio40/value", O_WRONLY)) == -1) { printf("Cannot open LED brightness file.\n"); exit(1); } /* Set the state of the pin */ led_val = led_state ? '1' : '0'; /* Write this to the brightness file */ write(fd_led, &led_val, sizeof(char)); close(fd_led); }

Let’s Do This

Let’s Do This (2)

Let’s Do This (3)

Summary  

Embedded Linux is relevant NOW DS-5 Provides a clear path for development

Thank you for coming! 

Any questions?