Embedded software

Embedded software is computer software, written to control machines or devices that are not typically thought of as computers, commonly known as embedded systems. It is typically specialized for the particular hardware that it runs on and has time and memory constraints.[1] This term is sometimes used interchangeably with firmware.[2]

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.[3]

Manufacturers build embedded software into the electronics of cars, telephones, modems, robots, appliances, toys, security systems, pacemakers, televisions and set-top boxes, and digital watches, for example.[4] This software can be very simple, such as lighting controls running on an 8-bit microcontroller with a few kilobytes of memory with the suitable level of processing complexity determined with a Probably Approximately Correct Computation framework[5] (a methodology based on randomized algorithms), or can become very sophisticated in applications such as airplanes, missiles, and process control systems.[6]

Operating systems

Unlike standard computers that generally use an operating systems such as OS X, Windows or GNU/Linux, embedded software may use no operating system, or when they do use, a wide variety of operating systems can be chosen from, typically a real-time operating system. This runs from small one-person operations consisting of a run loop and a timer, to LynxOS, VxWorks, BeRTOS, ThreadX, to Windows CE or Linux (with patched kernel). Others include OpenWrt, PikeOS, eCos, Fusion RTOS, Nucleus RTOS, RTEMS, INTEGRITY, uC/OS, QNX, FreeBSD and OSE. Code is typically written in C or C++, but various high-level programming languages, such as Python and JavaScript, are now also in common use to target microcontrollers and embedded systems.[7] Ada is used in some military and aviation projects.

Differences from application software

Most consumers are familiar with application software 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 drivers at manufacturing time, and the device drivers are written for the specific hardware. The software is highly dependent on the CPU and specific chips chosen. Most embedded software engineers have at least a passing knowledge of reading schematics, and reading data sheets for components to determine usage of registers and communication system. Conversion between decimal, hexadecimal and binary is useful as well as using bit manipulation.[8]

Web applications are rarely used, although XML files and other output may be passed to a computer for display. File systems with folders are typically absent as are SQL databases.

Software development requires use of a cross compiler, which runs on a computer but produces executable code for the target device. Debugging requires use of an in-circuit emulator, JTAG or SWD. 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.[9] These space requirements lead to more work being done in C or embedded C++, instead of C++. Interpreted languages like BASIC (while e.g. Parallax Propeller can use compiled BASIC) and Java (Java ME Embedded 8.3[10] is available for e.g. ARM Cortex-M4, Cortex-M7 microcontrollers and older ARM11 used in Raspberry Pi and Intel Galileo Gen. 2) are not commonly used; while an implementation of the interpreted Python 3 language – MicroPython – is however available expressly for microcontroller use, e.g. 32-bit ARM-based (such as BBC micro:bit) and 16-bit PIC microcontrollers.

Communication protocols

Communications between processors and between one processor and other components are essential. Besides direct memory addressing, common protocols include I²C, SPI, serial ports, and USB.

Communications protocols designed for use in embedded systems are available as closed source from companies including InterNiche Technologies and CMX Systems. Open-source protocols stem from uIP, lwip, and others.

gollark: What if we create AR glasses which blot out all people on tracks and in similar situations so nobody has responsibility?
gollark: I mean, a laser powerful enough to stop the train would probably create more problems for the people on the tracks than just the molten or vaporized or whatever metal.
gollark: The real solution is a very powerful laser. Not only will it slow down via radiation pressure, but when the front of the train ablates it'll slow down further.
gollark: That reminds me! AutoBotRobot function will be restored SOON™
gollark: Via WASM usually.

References
  • Edward A. Lee, "Embedded Software", Advances in Computers (M. Zelkowitz, editor) 56, Academic Press, London, 2002.
  1. "Stroustrup on C++ for embedded (bottom p.2)" (PDF). Retrieved 9 December 2012.
  2. Emilio, Maurizio Di Paolo (2014-09-01). Embedded Systems Design for High-Speed Data Acquisition and Control. Springer. ISBN 978-3-319-06865-7.
  3. "I.C.S. on embedded software". Archived from the original on 22 March 2013. Retrieved 22 July 2013.
  4. "Embedded Systems Methods and Technologies". Archived from the original on 29 October 2013. Retrieved 9 December 2012.
  5. Alippi, Cesare (2014), Intelligence for Embedded Systems, Springer, ISBN 978-3-319-05278-6.
  6. http://ptolemy.eecs.berkeley.edu/publications/papers/02/embsoft/embsoftwre.pdf
  7. Mazzei, Daniele; Montelisciani, Gabriele; Baldi, Giacomo; Fantoni, Gualtiero (2015). Changing the programming paradigm for the embedded in the IoT domain. Internet of Things (WF-IoT), 2015 IEEE 2nd World Forum on. Milan: IEEE. pp. 239–244. doi:10.1109/WF-IoT.2015.7389059.
  8. "Stroustrup on embedded software". Archived from the original on 3 February 2013. Retrieved 9 December 2012.
  9. "Example of embedded CPU". Retrieved 9 December 2012.
  10. "Java ME Embedded". Oracle Technology Network.

See also
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