L4/Iguana Learning

There is a lot of buzz going around for virtualization systems where a base system (for example L4 based micro-kernel) supporting other real-time operating systems such as Linux variants, WinCE, Symbian, REX etc.

The primary reason is to provide more secure and highly reliable systems to the manufacturer of embedded systems. The GPL license makes a bit difficult for the manufacturers to adopt for open systems as they have to expose their firmware to the public. NICTA initiate is the response to address the smilar issues and provide a high end systems to the market.

http://markustips.blogspot.com

GCC C __attribute__ feature

Most of compilers support optimization level in which each level has special significance to optimize the source in terms of size, performance etc. This can be enabled by specified command line arguments, mostly known as options.

Moreover GCC compiler has a special characteristic additionally – declaring attributes of a function. The source can be optimized at programming level. While writing the source, the programmer has a chance to instruct the compiler to what should be taken care.

__attribute__ keyword is used when a function (declared only) is a declared and the corresponding instruction/s is/are mentioned with it.  There are many ways to do nasty things with it found here.

In the embedded system, the code is nicely put together in different sections according to the design/requirements.  The code goes into the text section. It happens that while starting the OS, it is so better to gather the initialization code together that as soon as the initialization is over, the related code can be removed from the main memory.  This can be achieved by combining initialization code into init section i.e  __attribute__ section(“.init”). This is where my journey has started for attribute feature.

This function attibute has been widely used in L4 micro-kernel, which provides a secured approach for embedded systems facilitating the hardware manufactures to protect their patents/innovation without exposing to the outside world.

There are many things can be done using Linux and GCC pair, but today this is enough to start with.

Nucleus – Interrupt Handling

In most of RTOS, whenever an interrupt arrives, the interrupt vector table’s corresponding routine is invoked to execute some piece of code to take the required action for that interrupt.

Nucleus RTOS had peculiar interrupt handling mechanism which is not found in some of those RTOS mechanism. Nucleus interrupts are handled in two phases called LISR (Low level ISR-Interrupt Service Routine) and HISR (High level ISR) parts.

The LISR routine is similar to existing RTOS’s ISR, but the important difference is if required more processing, it activates the corresponding HISR.  During LISR processing, only limited system calls are allowed and minimal processing is done. This ensures to respond to interrupt in very quick manner and reduces the latency for the same.

The HISR are scheduled similar to the task. They have priority 0 to 2 that are the highest priority levels defined by Nucleus. The remaining 3 to 255 priority levels are given to the tasks.  The lower the priority value, the higher the chances of task or HISR to get scheduled. The HISR can access most of the system calls.

Moreover, whenever the scheduler runs, it checks any activated HISR first. If found, it schedules all HISR before any of the task is scheduled.  This allows to perform the required extra processing in HISR after LISR is executed without spending much time in ISR.

UML Introduction (1)

UML – Unified Modeling Language

Why UML?

There were many modeling and methodologies available out there before 1994 to design the software systems. There was need to have a common understanding about the visual representation of the software system. The pioneering works is done in Rational through Booch, Rumbaugh and Jacobson who combined their visual modeling languages and methodologies to present the world with UML.

What are the building blocks of UML?

The next step – Customization

Recently we had an opportunity to listen to two great thinkers expert in their own domain. Let me describe what is coming up there in next 5-10 years from now.

Brian Levy, CTO, HP

He was emphasizing about mass customization. What is it?

Previous technology had been developed in view of fitting to all. There was no personalization about the technology. No demograhy, age brackets were considered for making the products. The most of the users have no choice.

The present technological changes have proved that this cannot sustain for long time because human needs are different. The device world is transforming to personal world. Now most of the people wants to be connected anytime and anywhere to their family, work and community. The present era tells us that “connectivity is everything”

There are four places in which the breakthrough is expected

- My Persona
- My Entertainment
- My Community
- My Communication

These are the four dimensions of the diamond. The individual is interwoven across this dimensions.

The basic gist of the presentation is to connect human rather than devices.

He also highlighted the trust paradigm which represents the center of trust is different for different geographies. Those are network service providers within those geographies in whom people trust for the future services and connectivity.

David J Farber, The GodFather of IP Network

His perspective was toward the future of telecommunication industry, current research challenges and opportunities and the business.

He speaks in typical professor language so sometimes difficult to follow, but he really shared a good ideas with us.

The current IP network cannot support gigabit speed network, so there is a need to develop a completely new kind of protocol or enhanced the existing one. In doing so, there are many things down the line have to be changed.

He is looking forward to photonic networks in the future.

He also talked a little bit about “Snow Crash” authored by Neal Stephenson. The book is really interesting and one should read it.

And he talked a lot about federal laws for bandwidth allocation and current scenario for the same as there is a sale of 700 MHz radio.