Definition, Characteristics, and History of Embedded Systems
– Combination of computer processor, memory, and input/output peripheral devices
– Dedicated function within a larger mechanical or electronic system
– Often controls physical operations and has real-time computing constraints
– Used in various devices and industries
– Optimized for size, cost, reliability, and performance
– Origins trace back to MOS integrated circuit in the early 1960s
– MOS chips led to large-scale integration and the development of microprocessors
– First multi-chip microprocessors and single-chip microprocessor (Intel 4004)
– Early mass-produced embedded systems: Apollo Guidance Computer and Autonetics D-17
– Decrease in price, increase in processing power, and functionality over time
– Dramatic rise in processing power and functionality
– Integration of memory, input/output, and processor into microcontrollers
– Microcontrollers replace expensive analog components with buttons or knobs
– Cost reduction and increased prevalence of embedded systems
– Design effort focused on software rather than additional hardware components
Applications and Range of Embedded Systems
– Commonly found in consumer, industrial, automotive, aerospace, and military applications
– Telecommunications systems, computer networking, and consumer electronics
– Household appliances, HVAC systems, and home automation
– Transportation systems, avionics, and electric motors
– Medical equipment, imaging systems, and automotive safety systems
– Range in size from portable personal devices to large machines and installations
– Low complexity with a single microcontroller chip to high complexity with multiple units and networks
– Embedded systems can be customized and networked together
– Can be found in equipment racks or across large geographical areas
– Offer cost-effective solutions compared to traditional circuit-based designs.
Characteristics of Embedded Systems
– Embedded systems are designed for specific tasks, unlike general-purpose computers.
– Some embedded systems have real-time performance constraints, while others have low performance requirements.
– Embedded systems can be standalone devices or part of a larger device.
– Firmware, the program instructions for embedded systems, is stored in read-only or flash memory.
– Embedded systems run with limited hardware resources, such as memory and keyboard/screen.
Processors and Peripherals in Embedded Systems
– Embedded computers have properties like low power consumption, small size, rugged operating ranges, and low cost.
– Microcontrollers are commonly used in embedded systems, while general-purpose microprocessors require more support circuitry.
– PC/104 and PC/104+ are standards for ready-made computer boards used in embedded systems.
– Some embedded systems use components compatible with general-purpose x86 PCs.
– System-on-a-chip (SoC) processors are integrated into small modules for high volume manufacturing.
– Serial communication interfaces like RS-232, RS-422, and RS-485 are commonly used.
– Synchronous Serial Interfaces (I2C, SPI, SSC) and USB provide additional communication options.
– Media cards (SD cards, CompactFlash) and network interfaces (Ethernet, WiFi) are used for data storage and networking.
– Fieldbuses like CAN bus and PROFIBUS are used for industrial communication, and timers provide precise timing control.
Tools, Debugging, Tracing, and Reliability in Embedded Systems
– Compilers, assemblers, and debuggers are used by embedded system designers.
– In circuit debuggers or emulators are used to debug embedded system software.
– Utilities can be used to add a checksum or CRC to a program for validation.
– Computational notebooks are used for simulating mathematics in systems using digital signal processing.
– System-level modeling and simulation tools help designers construct simulation models for power vs. performance trade-offs, reliability analysis, and bottleneck analysis.
– Interactive resident debugging, software-only debuggers, external debugging, in-circuit debuggers, and in-circuit emulators are used for debugging embedded systems.
– Real-time operating systems often support tracing of operating system events.
– Trace recording can be performed in software or by the RTOS or by special tracing hardware.
– Reliability in embedded systems is achieved through careful development and testing of software, avoiding unreliable mechanical moving parts, using techniques like watchdog timers and trusted computing base architecture, and using hypervisors designed for embedded systems.
– Software tools for embedded systems can come from software companies specializing in the embedded market or be ported from the GNU software development tools.
– High-volume embedded systems focus on minimizing cost, while low-volume systems prioritize flexibility.
– Different types of software architecture are commonly used in embedded systems, including single-board computers, numerical controllers, and event-based controllers.
– Simple control loop and interrupt-controlled system are two common architectures for embedded systems. Source: https://en.wikipedia.org/wiki/Embedded_computer
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is embedded as part of a complete device often including electrical or electronic hardware and mechanical parts. Because an embedded system typically controls physical operations of the machine that it is embedded within, it often has real-time computing constraints. Embedded systems control many devices in common use. In 2009[update], it was estimated that ninety-eight percent of all microprocessors manufactured were used in embedded systems.[needs update]
Modern embedded systems are often based on microcontrollers (i.e. microprocessors with integrated memory and peripheral interfaces), but ordinary microprocessors (using external chips for memory and peripheral interface circuits) are also common, especially in more complex systems. In either case, the processor(s) used may be types ranging from general purpose to those specialized in a certain class of computations, or even custom designed for the application at hand. A common standard class of dedicated processors is the digital signal processor (DSP).
Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase its reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.
Embedded systems range in size from portable personal devices such as digital watches and MP3 players to bigger machines like home appliances, industrial assembly lines, robots, transport vehicles, traffic light controllers, and medical imaging systems. Often they constitute subsystems of other machines like avionics in aircraft and astrionics in spacecraft. Large installations like factories, pipelines and electrical grids rely on multiple embedded systems networked together. Generalized through software customization, embedded systems such as programmable logic controllers frequently comprise their functional units.
Embedded systems range from those low in complexity, with a single microcontroller chip, to very high with multiple units, peripherals and networks, which may reside in equipment racks or across large geographical areas connected via long-distance communications lines.
