Embedded software is computer

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

, written to control machines or devices that are not typically thought of as computers, commonly known as

embedded systems 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 ...

. It is typically specialized for the particular hardware that it runs on and has time and memory constraints. This term is sometimes used interchangeably with

firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...

A precise and stable characteristic feature is that no or not all functions of embedded software are initiated/controlled via a human interface, but through machine-interfaces instead. Manufacturers build embedded software into the electronics of

cars A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...

, telephones, modems,

robot A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. A robot can be guided by an external control device, or the control may be embedded within. Robots may be c ...

s, appliances, toys, security systems,

pacemaker An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or pacemaker is a medical device that generates electrical impulses delivered by electrodes to the chambers of the heart eith ...

s, televisions and set-top boxes, and

digital watches A watch is a portable Clock, timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, atta ...

, for example. This software can be very simple, such as lighting controls running on an

8-bit In computer architecture, 8-bit Integer (computer science), integers or other Data (computing), data units are those that are 8 bits wide (1 octet (computing), octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) arc ...

microcontroller A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable i ...

with a few

kilobytes The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix ''kilo'' as 1000 (103); per this definition, one kilobyte is 1000 bytes.International Standard IEC 80000-13 Quantitie ...

of memory with the suitable level of processing complexity determined with a Probably Approximately Correct Computation framework (a methodology based on

randomized algorithm A randomized algorithm is an algorithm that employs a degree of randomness as part of its logic or procedure. The algorithm typically uses uniformly random bits as an auxiliary input to guide its behavior, in the hope of achieving good performan ...

s). However, embedded software can become very sophisticated in applications such as routers, optical network elements，

airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spe ...

missile In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...

s, and

process control An industrial process control in continuous production processes is a discipline that uses industrial control systems to achieve a production level of consistency, economy and safety which could not be achieved purely by human manual control. I ...

systems.

Operating systems

Unlike standard computers that generally use an operating systems such as

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

, embedded software may use no operating system. When they do use one, a wide variety of operating systems can be chosen from, typically a

real-time operating system A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...

. Code for embedded software is typically written in C or

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

, but various

high-level programming languages In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ''elements'', be easier to use, ...

, such as

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

and

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of Website, websites use JavaScript on the Client (computing), client side ...

, are now also in common use to target microcontrollers and embedded systems.

Assembly language In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...

s are often used too, especially in booting and

interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...

handling.

Ada Ada may refer to: Places Africa * Ada Foah, a town in Ghana * Ada (Ghana parliament constituency) * Ada, Osun, a town in Nigeria Asia * Ada, Urmia, a village in West Azerbaijan Province, Iran * Ada, Karaman, a village in Karaman Province, ...

is used in some military and aviation projects.

Differences from application software

Most consumers are familiar with

application software Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

that provide functionality on a computer. However embedded software is often less visible, but no less complicated. Unlike application software, embedded software has fixed hardware requirements and capabilities, and addition of third-party hardware or software is strictly controlled. Embedded software needs to include all needed

device driver In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...

s at manufacturing time, and the device drivers are written for the various hardware devices. These device drivers, called BSP (

Board support package In embedded systems, a board support package (BSP) is the layer of software containing hardware-specific boot firmware and device drivers and other routines that allow a given embedded operating system, for example a real-time operating system (RT ...

), form the layer of software containing hardware-specific drivers and other routines that allow a particular operating system (traditionally a real-time operating system, or RTOS) to function in a particular hardware environment (a computer or CPU card), integrated with the RTOS itself. The software is highly dependent on the CPU and specific chips chosen. Most embedded software engineers have at least a passing knowledge of reading

schematic A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the sc ...

s, and reading data sheets for components to determine usage of registers and communication system. Conversion between

decimal The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...

hexadecimal In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, hexa ...

and

binary Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that t ...

is useful as well as using

bit manipulation Bit manipulation is the act of algorithmically manipulating bits or other pieces of data shorter than a word. Computer programming tasks that require bit manipulation include low-level device control, error detection and correction algorithms, ...

. Web applications are often used for managing hardware, although XML files and other output may be passed to a computer for display. File systems with folders are typically used, however SQL databases are often absent. Software development requires use of a

cross compiler A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is running. For example, a compiler that runs on a PC but generates code that runs on an Android smartphone is a cross ...

, which runs on a computer but produces executable code for the target device. Debugging requires use of an

in-circuit emulator In-circuit emulation (ICE) is the use of a hardware device or in-circuit emulator used to debug the software of an embedded system. It operates by using a processor with the additional ability to support debugging operations, as well as to carr ...

, and debugging hardware such as

JTAG JTAG (named after the Joint Test Action Group which codified it) is an Technical standard, industry standard for verifying designs and testing printed circuit boards after manufacture. JTAG implements standards for on-chip instrumentation in ele ...

or SWD debuggers. Software developers often have access to the complete kernel (OS) source code. Size of the storage memory and RAM can vary significantly. Some systems run in 16 KB of Flash and 4 KB of RAM with a CPU operating at 8 MHz, other systems can rival contemporary computers. These space requirements lead to more work being done in C or embedded C++, instead of C++. Interpreted languages like

BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

(while e.g.

Parallax Propeller The Parallax P8X32A Propeller is a multi-core processor parallel computer architecture microcontroller chip with eight 32-bit reduced instruction set computer (RISC) central processing unit (CPU) cores. Introduced in 2006, it is designed and sold ...

can use compiled BASIC) and

(Java ME Embedded 8.3 is available for e.g.

ARM Cortex-M4 The ARM Cortex-M is a group of 32-bit RISC ARM processor cores licensed by Arm Holdings. These cores are optimized for low-cost and energy-efficient integrated circuits, which have been embedded in tens of billions of consumer devices. Though ...

Cortex-M7 The ARM Cortex-M is a group of 32-bit RISC ARM processor cores licensed by Arm Holdings. These cores are optimized for low-cost and energy-efficient integrated circuits, which have been embedded in tens of billions of consumer devices. Thou ...

microcontrollers and older

ARM11 ARM11 is a group of 32-bit RISC ARM processor cores licensed by ARM Holdings. The ARM11 core family consists of ARM1136J(F)-S, ARM1156T2(F)-S, ARM1176JZ(F)-S, and ARM11MPCore. Since ARM11 cores were released from 2002 to 2005, they are no lon ...

used in

Raspberry Pi Raspberry Pi () is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in association with Broadcom. The Raspberry Pi project originally leaned towards the promotion of teaching basic ...

and

Intel Galileo Intel Galileo is the first in a line of Arduino-certified development boards based on Intel x86 architecture and is designed for the maker and education communities. Intel released two versions of Galileo, referred to as Gen 1 and Gen 2. Th ...

Gen. 2) are not commonly used; while an implementation of the interpreted

3 language

MicroPython MicroPython is a software implementation of a programming language largely compatible with Python 3, written in C, that is optimized to run on a microcontroller. MicroPython consists of a Python compiler to bytecode and a runtime interpreter of ...

is however available expressly for microcontroller use, e.g.

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...

ARM In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...

-based (such as BBC micro:bit) and

16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...

PIC microcontroller PIC (usually pronounced as ''"pick"'') is a family of microcontrollers made by Microchip Technology, derived from the PIC1650"PICmicro Family Tree", PIC16F Seminar Presentation originally developed by General Instrument's Microelectronics ...

Communication protocols

Communications between processors and between one processor and other components are essential. Besides direct memory addressing, hardware level common protocols include

I²C I2C (Inter-Integrated Circuit, ), alternatively known as I2C or IIC, is a synchronous, multi-controller/multi-target (master/slave), packet switched, single-ended, serial communication bus invented in 1982 by Philips Semiconductors. It is wide ...

, SPI,

serial port In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. ...

1-Wire 1-Wire is a device communications bus system designed by Dallas Semiconductor Corp. that provides low-speed (16.3 kbit/s) data, signaling, and power over a single conductor. 1-Wire is similar in concept to I²C, but with lower data rates and ...

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

s, and

USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...

. Communications protocols designed for use in

are available as

closed source Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and inte ...

from companies including InterNiche Technologies and

CMX Systems CMX Editing Systems (also known as CMX Systems) was a company founded jointly by CBS and Memorex; with help from many individuals such as Ronald Lee Martin, who later became a head of Universal Studios; that developed some of the very first comput ...

Open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

protocols stem from uIP,

lwip lwIP (lightweight IP) is a widely used open-source TCP/IP stack designed for embedded systems. lwIP was originally developed by Adam Dunkels at the Swedish Institute of Computer Science and is now developed and maintained by a worldwide networ ...

, and others.

Notes

References

* Edward A. Lee, "Embedded Software", ''Advances in Computers'' (

Marvin Victor Zelkowitz Marvin Victor Zelkowitz (born 7 August 1945) is an American computer scientist and engineer. Zelkowitz earned a degree in mathematics from Rensselaer Polytechnic Institute in 1967 and a master's degree and doctorate in computer science at Cornel ...

, editor) 56, Academic Press, London, 2002. {{Embedded systems Computing terminology Embedded systems

Operating systems

Differences from application software

Communication protocols

See also

Notes

References