A cross compiler is fundamentally used to separate the build environment from the target environment, which is very useful for embedded systems. Within embedded systems devices often have extremely limited recourses.
In this case Yocto is going to be used as development environment. Which also contains a cross compiler, because Yocto needs a lot of processing power and memory.
This means that it is not possible to run Yocto from an embedded system. Therefore this cross compiler is needed to be able to compile the Linux kernel, kernel drivers and eventually software applications.
First this chapter will give a brief introduction to the Yocto Project, after this introduction it contains information about how to configure Yocto to build an architecture specific cross compiler for an ARM Cortex-M3.
2.1 Introducing the Yocto Project
The Yocto Project is a complete embedded Linux development environment. That provides templates, tools and methods to help creating custom Linux-based systems for embedded products regardless of the hardware architecture.
This paragraph contains information about the basic Yocto fundamentals.
2.1.1 Yocto layers
Yocto uses layers to add customizations. A layer is a logical collection of recipes representing the kernel, a Board Support Package (BSP) or an application. All layers have a priority and are able to override the policy and configuration settings of the layers beneath it.
Figure 2 1 gives a graphical representation of the Yocto layer priorities. The lower OpenEmbedded and Yocto layers have the lowest priority and are able to be overruled by the higher level BSP and developer layers.
2.1.2 Yocto hardware configuration
In order to add a machine configuration to a Yocto layer, you need to add several...
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...rce and to start using Yocto in combination with an external binary tool chain.
2.2.3 External tool chain
The external binary tool chain could be retrieved from Mentor Embedded, and since Mentor Embedded does already have a Yocto layer to support their binary tool chains. The external tool chain could be implemented very easily.
Unfortunately the Mentor Embedded Yocto layer gives an example for a GNU Linux external tool chain, instead of an uCLinux external tool chain. And where Yocto normally builds dynamic libraries, the external tool chain with uCLinux for MMU less processor support, does not support dynamic libraries, and is only able to use static libraries.
To change the dynamically build packages to build static libraries, the Yocto variable ‘EXTRA_OECONF’ could be used to set configuration and build variables such as ‘--disable-shared’ and ‘--enable-static’.
Open source software development is taking place all over the world where part of the community develops individual modules, becoming necessary to establish standards and common definitions for open source software. These standards are established to define interaction between modules to insure interoperability of software. Software components which follow specific open standards can be replaced with other standard-compliant product, which allows the user more freedom to choose the component best suited to his needs and is not bound to a particular product, as with commercial software (Chauhan)
Yossarian can be seen as an anti-hero. Many of his actions could be considered immoral or cowardly. For example, in the hospital, he forged and tampered with letters he censored. Whenever he was overwhelmed by the horrors of war and by memories of his friends' deaths, he created symptoms that got him admitted to hospitals. He also made repeated attempts to be judged as certifiably insane so that he could be discharged. In the end, Yossarian deserted the Army and fled to Sweden, the only place he knew to be safe and sane.
...t is undeniably embracing open source more and more, ... Microsoft Building Hybrid Open Source Software Development Model ... Jun 11, 2008 ...
Embedded platforms were initially composed of separate discrete components. The processor was a separate component with just a memory bus interface, and all peripherals were attached to this bus. As integration levels increase, more and more logic is added to the processor die, creating families of application-specific service processors. The term system on chip (SOC) is often used to describe these highly integrated processors. These SOCs include much of the logic and interfaces that are required for a range of specific target applications. The silicon vendors that develop these SOC devices often create families of SOCs all using the same processor core, but with a wide range of integrated capabilities.
Next, the 8-bit Arduino Mega from ATMEL(R) provides several unique and interesting challenges. The AVR is disparate from all other platforms that Xinu presently operates on. For instance...
Yo-Good is one of four franchise options offered by ‘Fresh & Healthy Brands, LLC”, a corporation based in Burnaby, British Columbia (Serving Up Healthy Choices in New Franchise Opportunities, 2011). The company’s mission is to “offer a delicious and healthy combination of non-fat frozen yogurt with a dazzling variety of fresh toppings” (Yo-Good: Frozen Yogurt with an Important Difference, 2011) in an all-natural way without the use of artificial sweeteners. Our goal is to bring a Yo-Good franchise to the city of Halifax; a city that we believe is in dire need of great tasting healthy alternatives.
The application layer is the OSI layer closest to the user. It differs from the other layers because it does not provide services to any other OSI layer, but rather to application processes lying outside the scope of the OSI model. Examples include spreadsheet programs, word-processing programs, banking terminal programs, etc. The application layer identifies and establishes the availability of intended communication partners, synchronizes cooperating applications, and establishes agreement on procedures for error recovery and control of data integrity. Also, the application layer determines whether sufficient resources for the intended communication exist.
Mac OS X is a powerful development platform; it supports multiple development technologies like UNIX, Java, Cocoa and Carbon. It also is host to many open source, web, scripting, database and development technologies. It was build around the integrated stack of graphics and media technologies such as QuickTime, Quartz, Core Image and Core Audio. Mac OS X is based on the Mach Kernel and the BSD implementation of UNIX which were originally incorporated into the NEXTSTEP operating system. Many aspects of the Mac OS X architecture are derived from OPENSTEP / NEXTSTEP which was designed to be an easy transition from one platform to another. At the core of this system is Darwin, an open source UNIX like operating system built around the XNU kernel with standard UNIX facilities available from a command line interface.
“One of the primary advantages of this system is that the compiler has to do very little work to translate a high-level language statement into assembly. Because the length of the code is relatively short, very little RAM is required to store instructions. The emphasis is put on building complex instructions directly into the hardware.”(www.cs.stanford.edu.com) .This is a major advantage for CISC and its examples of CISC processors are IBM 370/168, MicroVAX II.
Most computer languages use different versions of compilers for different types of computers or operating systems; so one language may have different compilers for personal computers (PC) and Apple Macintosh computers. Many different manufacturers often produce versions of the same programming language, so compilers for a language may vary between manufacturers.
For UNIX truly to be an open system, The Open Group provides certification and standardization for UNIX-like operating system, thus regardless of different UNIX-like environment the standards set by The Open Group are the same, therefore it helps eliminate confusion and achieve consensus among the various interests of the members of the standards-forming bodies. Several standards have come about as the direct result of computer users’ desire to see UNIX standardized and to see it evolve in a direction compatible with present use as well as future needs. Standards are at the basis of the concept of open systems (Dunphy 1991, 44).
The ability of a reference architecture to provide guidance so that future developers understand how to program future applications in a domain is a primary motivation for the generation of a reference architecture. The guidance provided by a reference architecture can reduce development costs.
When company called IBM (International business machine) started selling computers in the 1960s which was one of the first computer machines, they introduced some free software. These softwares were easy to modify and can be shared among different users. After some time IBM gain more success in the Community by launching some software which were written in an assembly language named as “Cobol”. (R.W.Bemer)
The final or resulting functionalities can be delivered with ease since the code is being developed with smaller fragments and thoroughly tested. So the resulting implementation does not tend to be complex. [1]
Surran, M. (2003). Making the Switch to Open Source Software. T.H.E. Journal Online. Retrieved September 16, 2003 from T.H.E. Journal Online website: