1. COMP1321 Digital Infrastructure
Richard Henson
November 2017

2. Week 7: Devices and Embedded Systems
Objectives:
Explain how control (e.g. of temperature) is achieved traditionally (analogue)
Explain digital control, sensors and embedded systems
Explain the diversity of use of embedded systems in modern day life, and how this has transformed our society

3. Traditional Systems developed for control
“Control” using machines is not at all new… been happening for centuries with analogue systems
secret is to develop a system that can provide feedback IN REAL TIME
system can then respond to make a change… e.g. of temperature

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

5. Control and Feedback Loops
A typical example of a control system is a temperature sensor & associated heater
triggered to turn on…
when the sensor detects a temperature drop below a certain value
triggered to turn off…

6. Analogue Control…
The Steam Engine… control of Steam using pressure to move piston. Feedback loop?
The Petrol Engine… control of Spark for Igniting Petrol. Feedback loop?

7. Digital Control…
The same effect can be created digitally using integrated circuits and sensors:
What is the feedback loop in this digital system?

8. What is an “Embedded System?
“A computer on a chip”
Usually an i/o control device
programming for control stored on ROM
CPU and RAM needed on same circuit board as ROM to process instructions
Getting smaller and smaller…
e.g. Arduino board
now very cheap <£5.

9. History of Embedded Digital Systems
Not possible before integrated circuits went into production (mid-1960s)
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

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

11. And has to be turned off…

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

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

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

15. Economics of Embedded Systems
Huge initial development cost!!
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”….

16. BBC, 1977 “The Chips are Down”… Silicon Valley, California

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

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

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

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

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

22. Why are embedded systems so popular?
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 even configurable via network…
“Intelligent” products now leave the factory with an IP address…

23. The Internet of things
A logical extension of giving digital devices IP addresses
is this wise with intelligent devices?
especially with 3D printers
Is this wise… (lol)

24. Linking of Devices Two fundamentally different arrangements:
Peer-peer
Internet uses peer-peer
Client-server
better for centralised control…
How about IoT?