Field Programmable Gate Arrays (FPGAs)

Most Integrated Circuits (ICs) are given a defined function during manufacturing. However, some parts can be configured after manufacturing. One such family of parts are FPGAs.

FPGAs were introduced by Xilinx in 1985, but are now also available from other vendors such as Actel and Altera.

FPGAs consists of programmable logic blocks, and re-configurable interconnects that can be programmed, to “wire” together the logic blocks in the required way to suit the application. Logic blocks can act as simple gates, or can be connected together to perform combinatorial functions. Logic blocks also contain memory elements, allowing sequential and memory functions to be implemented.

So called hard core blocks have also become available, which implement a more defined function such as a processor or analogue-to-digital converter within the FPGA. This combined with the configurable sections of the part, allow full systems-on-a-chip (SOC) to be created using FPGA technology.

The FPGA function and routing memories are initialised either on power-up from an external non-volatile memory, or it can be initialised after power-on using software.

For more information, explore the following links:

Overview 1
Overview 2
Overview 3

And some suppliers

            Xilinx
            Altera
            Actel

And a slightly controversial topic ASIC-v-FPGA?

Digital Signal Processors (DSPs)

Computers process information as discrete numbers, whereas information (signals) in the real world is almost always continuous and changing. Converting the real world to numbers that can be dealt with digitally, often gives greater stability to signal processing, as in this form the signal is less vulnerable to noise, and more complex error detection and correction techniques can be applied.

Many signal processing applications have constraints on latency, which means that an operation must be completed in some fixed time, and any delay in processing is not possible.

A Digital Signal Processor (DSP) is a specialised computer chip with an optimised set of architectural features for the fast operational needs of signal processing applications.

Most standard microprocessors can excute DSP algorithms, but a specialised DSP can carry out these tasks with lower cost, lower power needs, better performance, and improved latency. This can be critical in many lower power products, such as mobile phones, PDAs etc.

The most prevalent use of DSPs is in mobile telephony, where the RF interface is handled by the DSP, and other aspects of the phone are handled by a standard microprocessor. This combination gives the greatest performance, at the lowest cost and at the lowest power.

Tutorial

On-Line Book

TI DSPs

DSP Directory from EDN

Analog Devices DSP


Embedded Linux

An Operating System (OS) is a computer program which manages the resources of a computer system—memory, files, printers, network, etc. We are all familiar with the PC OS Windows. But there are others such as the Apple’s MAC OS and Linux. An embedded OS is used to manage computer devices such as mobile phones, media players and set-top boxes. And Linux is often a common choice.

Linux is an open source OS, which means it can be easily modified, and is available free of charge. This gives great flexibility, and also makes it attractive for low cost devices where other OS’s would add an additional cost for each unit shipped.

The core of the Linux OS, called the kernel, was initially developed by a Finnish student Linus Torvalds in 1991. However, it is now maintained by thousand of programmers worldwide. Tools and libraries for Linux are also available as open source and are maintained by the GNU project.

Linux is also now in widespread use in applications right through from PC’s, to supercomputers, to mobile phones. Some studies place it market share at >1%.

The open source nature of Linux makes it ideal for embedded devices, as it can easily be optimised to suit the nature of the particular application, thus eliminating unneeded code which can drive down the operating efficiencies of a product. And what’s more it’s free.

General Linux Links
            Linux Foundation
            GNU Project
            www.linux.org
            www.linux.com
Embedded Linus Links
            Wiki for Embedded Linux
            Linux for Devices