COMP1321 Digital Infrastructure Richard Henson November 2015

Week 7: Devices and Embedded Systems n Objectives:  Explain what an embedded system is and what it consists of  Explain the diversity of use of embedded systems in modern day life, and how this has transformed our society

What is an “Embedded System? n “A computer on a chip” n Could be an i/o control device n Needs programming to control a peripheral n Requirements:  CPU and RAM  ROM to store control program(s)

Feedback Loops n Biggest challenge in a control system is to get data transferred quickly enough to change parameters in sufficient time n Obviously not possible to control a rocket remotely if out in space…  embedded systems the only way…

Embedded Digital Systems for control n To control movement in machines  parameters for feedback loops need to be controlled IN REAL TIME n Nothing new… been happening for centuries in analogue systems

Analogue Control… n The Steam Engine… control of Steam to move piston. Feedback loop?  Q Q Q   n The Petrol Engine… control of Spark for Igniting Petrol. Feedback loop? 

Digital Control… n The same effect can be created digitally using a transistor as electronic switch:  TYVhQ TYVhQ TYVhQ n What is the feedback loop in this digital system?

History of Embedded Digital Systems n Not possible before integrated circuits went into production (mid-1960s) n Started with Apollo Project:  President Kennedy’s plan to land a man on the moon by end of 1969…  first commercial production for US defence (1966)… »“Minuteman” intercontinental ballistic missile

Early SciFi view of a “control” computer: HAL (1968) n One that controls a space ship, and gets “out of control…” =ARJ8cAGm6JE

And has to be turned off… n ?v=OuEN5TjYRCE ?v=OuEN5TjYRCE ?v=OuEN5TjYRCE

Programming of Apollo guidance system n Written in Fortran language  Formula Translation  most popular engineering/technology language before “C” n Later showed to have an almost fatal flaw  Apollo 13 near catastrophe…

“Moon Lander” Program n Retro rockets of falling LEM vehicle n Balanced against moon gravity n Limited amount of fuel… n Version written for BASIC n Most popular early microcomputer game

What happened to “Moon Lander”? n In reality…  start of the embedded system revolution  “A small step for man… a giant step for mankind” can be interpreted more broadly n In virtual reality…  versions available to present day  great introduction to real-time control

Economics of Embedded Systems n Huge initial development cost!! n Once “chips” go into production, cost falls dramatically…  e.g. First Apollo guidance program cost $1000 per chip to implement  as soon as mass production started, unit cost was $3  economic driving force behind “Silicon Valley”….

BBC, 1977 “The Chips are Down”… Silicon Valley, California ch?v=HW5Fvk8FNOQ

Early Microprocessors n n Two main rival companies:   Intel (world’s first, 4004)   Motorola (pushed efficiency, through larger bus size…) n n CPU not much of a system on its own…   still needed lots of “external” support

Microcontrollers n Mass produced in late 1980s  responsible for “computerisation” of electrical appliances  programs held on ROM n Further development of microprocessor & components… n Whole system on a chip…  truly an embedded system

Programming a Microcontroller n Assembly language cumbersome n Fortran shown to be deficient  Apollo 13 failure caused by variable not being reinitialised to zero – other languages enable this by default n “C” seen as the way forward:  perfected by 1978

Components of a Microcontroller n e.g. Intel 8048 (1977):  CPU  RAM  Timer chip  ROM of some kind  i/o capability

Uses of Microcontrollers n Automatically controlled products and devices:  car engine control systems  implantable medical devices  remote controls  office machines  Appliances  power tools, toys, etc.

Why are embedded systems so popular? n Reduced size/cost compared to designs that using separate microprocessor, memory, and input/output devices  became economical to digitally control ever more devices and processes »embedded systems networkable »even configurable via network… »“intelligent” products now leave the factory with an IP address…

The Internet of things n Networks often have embedded systems n Why not the Internet…?  logical extension of giving each digital device or system a MAC address »generate IP address from this!  is this wise with intelligent devices?  especially with 3D printers? 

Networking Embedded Devices n Two ways to network:  Peer-peer »Internet uses peer-peer  Client-server »better for centralised control… n How about IoT? »