Embedded Systems

1
Embedded Systems
Ning Wang Dept of Biosysems and Agricultural
Engineering Oklahoma State University Naiqian
Zhang Dept of Biological and Agricultural
Engineering Kansas State University At South
China Agricultural University November, 2014
2
What are embedded systems?

• An embedded system is a computer system with a
  dedicated function within a larger mechanical or
  electrical system, often with real-time computing
  constraints. It is embedded as part of a complete
  device often including hardware and mechanical
  parts. 
• - Wikipedia
• ?????(Embedded system),???????????????????????????
  ??,?????????????????????????????????????,?????????
  ???????,?????????????????????????????????

• An embedded system is a computer system with a
  dedicated function within a larger mechanical or
  electrical system, often with real-time computing
  constraints. It is embedded as part of a complete
  device often including hardware and mechanical
  parts.  - Wikipedia
• ?????(Embedded system),???????????????????????????
  ??,?????????????????????????????????????,?????????
  ???????,?????????????????????????????????

Keywords??
3
Examples Embedded system
4
IMPACT

• The global embedded systems market was valued at
  USD 140.32 billion in 2013, expected to grow at a
  rate of 8.1 from 2014 to 2020, to reach USD
  214.39 Billion.
• Many more embedded processors per person are used
  than general purpose processors
• A cell phone may up to eight core processors.
• Value of embedded electronics in Automobiles 25
  of total cost, to rise to 35 by 2015
• Embedded market is 50 times the desktop market.
• Application Domains
• Automotive, Avionics, Industrial Automation,
  Telecommunication, Consumer Electronics, Medical,
  IT hardware
• Cutting edge
• Multicore processors, Network-on-Chip,
  System-on-chip

5
Embedded Systems

• An Embedded System is an information processing
  system that is
• application domain specific (not general
  purpose)
• tightly coupled to its environment

Application domains e.g. automotive, cellphone,
multimedia. Environment type and properties of
input/output information. Tightly coupled The
environment dictated what the systems response
behavior must be.
Constrains real-time, speed, resource, power
consumption, cost, efficiency
6
Embedded Systems
An embedded system performs computation that is
subject to physical constraints, interaction with
a physical environment, and execution on a
physical (implementation) platform.

• In summary, an embedded system
• Is a special purpose unit.
• Is a computer device which has a CPU, memory and
  programs that control mainly physical devices.
  The program is preinstalled and may not be
  changed easily.
• Has limited processing power and limited
  electrical power and limited data storage.
• Has intelligence, thus can be configured,
  personalized, programmed.

7
Schematic
8
Embedded Systems

• Embedded systems design is not a straightforward
  extension of either hardware (computer/electrical
  engineering) or software (computer science)
  design.
• They have functional requirements (expected
  services), and extra-functional requirements
  (performance/cost, robustness).
• Computer Science provides (software)
  functionality for Instruction Set Architectures
  (ISA) which are characterized by an instruction
  set and an organization (program counter,
  register file).
• Computer/Electrical Engineering deals with
  logical implementation and physical realization.
• An Embedded Systems design discipline needs to
  combine these two approaches from the beginning
  of the design.

9
Embedded System Engineers
Embedded systems engineer is a relatively new
job classification that merges electrical
engineering and computer science. These computer
engineers work on hardware and software designs
for electronic medical equipment, industrial and
military control systems, mobile communications
devices, appliances, and remote controls. They
need at least a bachelor's degree in a relevant
field, and some schools now offer certificate and
undergraduate and graduate degree programs in
embedded systems engineering. - A job
recruiting company (2014)
Skills Strong software coding and debugging
skills, some hardware integration knowledge, and
strong problem solving skills
10
As you have learned embedded system, let us do
some real tests!
11
Schematic
12
MP3 player simple system

• Function Large flash memory to store songs
• Songs (audio) stored in digital form, then
  compressed to a set of numbers that are of the
  MP3 format
• Processing CPU runs program in main memory
• Decompresses audio and generates raw digital
  audio
• Gets user input from button
• Displays information on screen
• Input/Output Digital-Analog converter generates
  audible sound waves and sends to
  speaker/headphones
• Interfaces touch screen, buttons,

13
GPS Navigator more complicated

• Components
• GPS Radio
• GPS signal processor
• Map database
• Processor to control display and compute routes,
  locations, points of interest
• Video image processor to control actual screen
• May contain several different CPUs in one
  package

14
GPS Radio

• Receives data from several satellites, converts
  RF to digital signals
• Separate for each satellite

A set of at least 24 Medium Earth Orbit
satellites that transmit precise microwave
signals, A GPS receiver can determine its
location, speed, direction, and time.
Radio receiver circuitry
Digital signals
15
GPS Signal Processor

• Correlates satellite signals
• Computes timing differences
• triangulates location

GPS dataprocessor
Current location in latitude and longitude
Digital Signals
16
GPS Navigator

• The user interface show location on map and
  provide useful other information

GPS Processor
Display Processor
GPS signals
MAP database
Touch Sensor
17
Automobile Computers

• Engine control computer
• Advanced diagnostics
• Simplification of the manufacture and design of
  cars
• Reduction of the amount of wiring in cars
• New safety features collision avoidance,
  blind-spot detection, back up camera,
• New comfort and convenience features

It would be easy to say the modern car is a
computer on wheels, but its more like 30 or more
computers on wheels, said Bruce Emaus, the
chairman of SAE Internationals embedded software
standards committee. - NY Times
18
Engine Control Computer (ECU)

• Read sensors (temp, pedal position, exhaust) and
  control fuel injector timing and spark timing
• Control engine fan and other actuators
• Handle the CAN (Control Area Network) that is
  becoming common in cars.

• Interface with climate and other passenger
  controls
• Provide diagnostics

19
Other computers in car

• There are more processors in the car other than
  ECU
• ABS system
• Climate control
• Cruise control
• Radio
• Dashboard
• Automatic doors, lights and such
• Cars also have networks for simplified wiring
  as well as automotive control networks CAN Bus!

20
Simplified Wiring
OLD
NEW
Switches signal encoders
Lamps signal decoders
LAMPS
SWITCHES
One wire runs all over the vehicle and carries
power and signal
Many connecting wires
21
Automobile Networking

• As multiple computing units get into cars, a
  networking standard is being used
• CAN 2.0 is predominant
• Functions
• Communicate between subsystems
• Reduce wires
• Multiplexing standard
• Network addressing
• multiple networks coming in the future

22
Design approach

• Phase 1 Design flow of embedded system begins
  with design specifications and constraints,
  including both cost and processing time.

http//arxiv.org/ftp/arxiv/papers/1005/1005.0931.p
df
23
What are Specifications?

• A design specification provides explicit
  information about the requirements for a product
  and how the product is to be put together.
• - Wikipedia

Leikr GPS Watch
24
What are Specifications?

• Develop specifications (specs) for every
  component in the embedded system.
• Specs for sensors
• Specs for controls
• Specs for computer systems (speed, memory,
  channels.)
• Specs of sensors, controllers, and computer many
  include
• Desired measurement accuracy, resolution,
  sensitivity, linearity, dynamic performance,
  consistency, reliability, etc.
• Environment condition temperature, humidity,
  pressure, external fields (radiation, electric,
  magnetic,)
• Compatibility with existing instruments
• Cost Closely related with the performance
• Durability Life of an instrument
• Maintenance requirements

25
Sensor Specifications (datasheet)

• Example 1 Infrared Temperature Sensor
• Example 2 Soil Sensor (Conductivity,
  temperature, and moisture)
• Example 3 Distance Sensor

26
Find Out Information on a Sensor


Telaire 7001 CO2 Sensor

• Read specifications!
• Questions to be answered
• Parameters to be measured
• Range
• Accuracy
• Resolution
• Time response
• Output signal
• Other information
• Working environment
• Power supply

Measurement Range  0 to 2500 ppm when using
the CABLE-CO2 and a U12 or ZWOperating Range
32F to 122F (0C to 50C), 0 to 95 RH,
Display Resolution 1 ppm  Accuracy 50 ppm or
5 of reading, whichever is greater  Repeatability
 20 ppm  Temperature Dependence 0.1 of
reading per C or 2 ppm per C, whichever is
greater, referenced at 25C.  Pressure
Dependence 0.13 of reading per mmHg (corrected
via user input for elevation)  Response Time lt60
seconds for 90 of step change  Warm-Up Time lt60
seconds at 72F (22C)  Calibration Interval 12
months Full factory calibration available Battery
Type Four AA batteries (not included)  Battery
Operation 80 hours (alkaline)  External Power
Supply Specifications  AC/DC adapter
(included)  Output 6 VDC, 500mA output. 
Power Connector Round barrel with 2.5mm ID ,
5.5mm OD, 12mm long, center positive (6 VDC),
outer shell ground.
27
Performance Parameters

• Range
• Input range The limits between which input can
  vary.
• Input Range Inputmax - Inputmin
• Output range The limits between which output can
  vary.
• Output Range Outputmax Outputmin
• Example A load cell can measure a force within
  the range of 0-50kN a thermocouple can measure
  temperatures within the range of 0-100C.

28
Performance Parameters

• Errors
• Absolute error measured value true value
• Relative error
• Example A sensor might give a resistance change
  of 10.2 ? when the true change is 10.5 ?. The
  error is -0.3 ? the relative error is 2.9.

29
Performance Parameters

• Accuracy
• An accuracy of a sensor is an indication of the
  possible measurement error. A temperature sensor
  specified as having an accuracy of 2?C means
  that the reading given by the system may lie
  within plus or minus 2 ?C of the true value.
• An accuracy is often expressed as a percentage of
  the full range output or full-scale deflection.
• Example A temperature sensor
• Range 0 to 200 ?C
• Accuracy 5 of full-range output
• Error 5 x 200 ?C 10 ?C

30
Performance Parameters

• Sensitivity
• Sensitivity indicates the change in output per
  unit change in input.
• The static sensitivity is a measure relating the
  change in the output associated with a given
  change in a static input.
• Example a resistive thermometer has a
  sensitivity of 0.5 ?/?C.

Slope!
31
Performance Parameters

• Resolution
• The smallest scale increment or the least count
  (least significant digit) of the measured value.
• Example Hobo Temperature Data logger Resolution
  U10-001 0.1 ?C at 25 ?C

Resolution 1/100 of a second
Resolution 1/10 of a second
Image Resolution
32
Performance Parameters

• Precision the fineness to which an instrument
  can be read repeatedly and reliably.
• Accuracy vs. Precision

Low Accuracy, Low Precision
Low Accuracy, High Precision
High Accuracy, Low Precision
High Accuracy, High Precision
Accuracy actual vs. True value
Precision Repeatability
33
Performance Parameters

• Hysteresis error
• A sensor/transducer may give different readings
  between an upscale sequential test and a
  downscale sequential test.
• eh (y)upscale (y)downscale
• Maximum hysteresis error

where r0 is the full output range.
34
Performance Parameters

• Non-linear error
• Most transducers have a linear relationship
  between the input and the output over the working
  range.
• An error occurs when this linear relationship can
  not be maintained.

Non-linearity error using (a) end-range values,
(b) best-fit straight line for all values, (c)
best-fit straight line through zero point
35
Performance Parameters

• Repeatability
• Describe the sensors capability to give the same
  output for repeated measurements of the same
  input value.
• The error resulting from the same output not
  being given with repeated measurements is
  expressed as a percentage of the full range
  output
• Example A transducer for the measurement of
  angular velocity typically quoted as having a
  repeatability of 0.01 of the full range at a
  particular angular velocity.

36
Performance Parameters

• Overall Instrument Error Combining all known
  errors

37
Performance Parameters

• Other issues
• Stability
• Describes the sensors capability to give the
  same output when used to measure a constant input
  over a period of time.
• drift describes the changes in output that
  occur over time.
• Zero drift describes the changes that occur
  in output when there is zero input.
• Dead band/time
• Dead band A range of input values within which
  there is no output.
• Dead time the length of time from the beginning
  of the measurement to the time the output begins
  to respond and change.

38
Performance Parameters

• Working conditions
• Temperature range
• Humidity
• Dust
• Climate
• Maintenance
• Warranty
• Life cycle
• Tech support

39
Static and Dynamic Characteristics

• A calibration applies known input values to a
  measurement system to observe the system output
  values. The goal of calibration process is to
  establish the relationship between the input and
  output values.
• Static Calibration
• Values of the variables involved do not vary with
  time and space.
• Only magnitudes of the known input and measured
  output are important.
• By applying a range of known input values and
  observing the system output values, a direct
  calibration curve can be developed for the
  measurement system.

40
Static and Dynamic Characteristics
The static calibration curve describes the static
input-output relationship for a measurement
system and indicates how the output can be
interpreted by a measurement.
41
Static and Dynamic Characteristics

• Dynamic Behavior
• Response time
• The time which elapses after a step input is
  applied to a sensor up to the point at which the
  sensor gives output to some specified percentage,
  e.g. 95, of the value of the input.

42
Specifications (datasheet)
Re-catch

• Campbell Scientific Datalloger CR3000

43
Design approach

• Phase 2-4 Design and development
• Functions by HW
• Functions by SW
• Integration
• Considerations
• Application needs
• Cost
• Speed/throughput
• User-friendliness

A considerable amount of iteration and
optimization occurs within phases and between
phases.
Phase 4 HW/SW Integration
http//arxiv.org/ftp/arxiv/papers/1005/1005.0931.p
df
44
Design approach

• Phase 5 Testing
• Calibration
• Lab/indoor testing
• Practical testing
• Evaluation criteria
• Specifications
• Modifications
• Phase 6 Maintenance and Upgrade
• Plan for maintenance and upgrade
• Tech support

Phase 4 HW/SW Integration
http//arxiv.org/ftp/arxiv/papers/1005/1005.0931.p
df
45
Design Project

• eXploration Habitat (X-Hab) 2015 Academic
  Innovation Challenge
• Deployable Greenhouse for food production on
  long-duration exploration missions

46
Design tasks

• Deployable mechanism
• Architecture design
• Greenhouse controls
• Environment control
• Water management
• Plant management
• Waste management
• Power system

47
Design an Embedded system for greenhouse control
a class project

• Oral Presentation
• Wednesday
• Use Powerpoint
• 10 min/team
• In Chinese

• Select one of the five Greenhouse controls
  tasks.
• Phase 1 Define system specifications and
  constraints
• System specifications need to be clearly
  defined
• System functions
• Performance parameters
• Goals
• Design constraints need to be clearly
  identified
• Payload (lt5 kg)
• Environment (temperature, relative humidity,
  ambient light)
• Cost
• Processing speed (throughput, dynamic response)

48
Design an Embedded system for greenhouse control
a class project

• Phase 2-4 System design (HW SW)
• Hardware
• microcontroller
• sensors
• actuators
• power supply
• harness
• Off-the-shelf products need to be selected based
  on specifications.
• A Block diagram is required.
• Software
• control flow
• algorithms
• user interface
• A flow chart is required.
• Integration
• possible networking
• communications
• Communications (protocols and directions) need to
  be shown in the block diagram.

49
Design an Embedded system for greenhouse control
a class project

• Phase 5 Testing
• sensor calibrations
• system laboratory tests
• system field tests
• Procedures for the tests are required.
• Phase 6 Maintenance and Upgrade sensor
  calibrations
• A system maintenance schedule is required (Think
  about the maintenance schedule for cars.)
• Possible future system upgrading needs to be
  discussed.

• Oral Presentation
• Wednesday
• Use Powerpoint
• 10 min/team
• In Chinese