Introduction to Embedded Systems

Outline What is an embedded system Characteristics and Classification of Embedded Systems Systems-on-a-Chip Distributed Systems Internet-of-Things Embedded Systems Design Challenges Real-Time Embedded Systems

Microprocessors for Embedded systems Computing systems are everywhere Most of us think of “desktop” computers PC’s Laptops Mainframes Servers But there’s another type of computing system Far more common...

Embedded systems overview Embedded computing systems Computing systems embedded within electronic devices Hard to define. Nearly any computing system other than a desktop computer Billions of units produced yearly, versus millions of desktop units Perhaps 50 per household and per automobile A lot more programming is done for embedded systems than desktop computers or servers Computers are in here... and here... and even here... Lots more of these, though they cost a lot less each.

A “short list” of embedded systems Anti-lock brakes Auto-focus cameras Automatic teller machines Automatic toll systems Automatic transmission Avionic systems Battery chargers Camcorders Cell phones Cell-phone base stations Cordless phones Cruise control Curbside check-in systems Digital cameras Disk drives Electronic card readers Electronic instruments Electronic toys/games Factory control Fax machines Fingerprint identifiers Home security systems Life-support systems Medical testing systems Modems MPEG decoders Network cards Network switches/routers On-board navigation Pagers Photocopiers Point-of-sale systems Portable video games Printers Satellite phones Scanners Smart ovens/dishwashers Speech recognizers Stereo systems Teleconferencing systems Televisions Temperature controllers Theft tracking systems TV set-top boxes VCR’s, DVD players Video game consoles Video phones Washers and dryers And the list goes on and on

Definitions Broad definition: Narrow definition: Any computer system that is not a general-purpose computer That would include robots, and all portable devices Narrow definition: A computer system (software and hardware) that interacts with its physical environment, mainly without human intervention That would exclude printers, modems, portable devices such as dvd and mp3 players, etc.

Some common characteristics of embedded systems Single-functioned Executes a single program, repeatedly Tightly-constrained Low cost, low power, small, fast, etc. Reactive and real-time Continually reacts to changes in the system’s environment Must compute certain results in real-time without delay

Considerations in embedded system design An embedded system receives input from its environment through sensors, processes this input and acts upon its environment through actuators Besides the usual software and hardware design issues the embedded system designer must consider the properties of the sensors and actuators and the environment itself The ultimate test of an embedded systems are the laws of physics

Classification of Embedded Systems Centralized vs distributed Real-time vs non real-time Hard deadline Failsafe Fail-operational Soft deadline Firm deadline Battery powered vs mains powered System-on-Chip vs discrete element

What is real-time? Is there any other kind? A real-time computer system is a computer system where the correctness of the system behavior depends not only on the logical results of the computations, but also on the physical time when these results are produced. By system behavior we mean the sequence of outputs in time of a system.

Real-time means reactive A real-time computer system must react to stimuli from its environment The instant when a result must be produced is called a deadline. If a result has utility even after the deadline has passed, the deadline is classified as soft, otherwise it is firm. If severe consequences could result if a firm deadline is missed, the deadline is called hard. Example: Consider a traffic signal at a road before a railway crossing. If the traffic signal does not change to red before the train arrives, an accident could result.

Fail-Safe hard-deadline RT systems If a safe state can be identified and quickly reached upon the occurrence of a failure, then we call the system fail-safe. Failsafeness is a characteristic of the controlled object, not the computer system. In case a failure is detected in a railway signaling system, it is possible to set all signals to red and thus stop all the trains in order to bring the system to a safe state. In failsafe applications the computer system must have a high error-detection coverage. Often a watchdog, is required to monitor the operation of the computer system and put it in safe state.

Fail-Operational hard-deadline RT systems In fail-operational applications, threre is no safe state a flight control system aboard an airplane. The computer system must remain operational and provide a minimal level of service even in the case of a failure to avoid a catastrophe

Typical Embedded System Components Sensors: Allow the system to “read” the environment Processing Elements: Control of the embedded system Actuators: Allow the system to act on its environment Network Connection: Local or internet, allowing exchange of information

An embedded system example – Digital camera Microcontroller CCD preprocessor Pixel coprocessor A2D D2A JPEG codec DMA controller Memory controller ISA bus interface UART LCD ctrl Display ctrl Multiplier/Accum Digital camera chip lens CCD Single-functioned -- always a digital camera Tightly-constrained -- Low cost, low power, small, fast Reactive and real-time -- only to a small extent

A System-on-a-Chip: Example Courtesy: Philips

Design at a crossroad System-on-a-Chip RAM 500 k Gates FPGA + 1 Gbit DRAM Preprocessing Multi- Spectral Imager mC system +2 Gbit DRAM Recog- nition Analog 64 SIMD Processor Array + SRAM Image Conditioning 100 GOPS Embedded applications where cost, performance, and energy are the real issues! DSP and control intensive Mixed-mode Combines programmable and application-specific modules Software plays crucial role

The Future of Embedded Systems In the past an embedded system was more or less isolated In the past decade Wireless Sensor Networks have changed that Today embedded systems + internet connection = Internet of Things ! Near future: Embedded systems + internet + mobile devices + cloud computing + artificial intelligence + ? = smart environment

IoT forecasts Global Internet of Things (IoT) market reached USD 598.2 Billion in 2015 is expected to reach USD 724.2 Billion by 2023 the market is projected to register a CAGR of 13.2% The number of connected IoT (Internet of Things) devices, sensors and actuators will reach over 46 billion in 2021

IoT Embedded system with internet connection Not quite as simple as it sounds Increased need for security Safety issues Direct machine to machine (M2M) communication