- 1 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Simplified design flowfor embedded systems
- 2 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Embedded System Hardware
Embedded system hardware is frequently used in a loop(„hardware in a loop“):
Embedded system hardware is frequently used in a loop(„hardware in a loop“):
actuators
- 3 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Many examples of such loops
Heating Lights Engine control Power supply … Robots
Heating Lights Engine control Power supply … Robots
Show robot movie
- 4 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Sensors
Processing of physical data starts with capturing this data.
Sensors can be designed for virtually every physical and
chemical quantity• including weight, velocity, acceleration, electrical current,
voltage, temperatures etc.• chemical compounds.
Many physical effects used for constructing sensors.
Examples:• law of induction (generation of voltages in an electric field),• light-electric effects.
Huge amount of sensors designed in recent years.
Processing of physical data starts with capturing this data.
Sensors can be designed for virtually every physical and
chemical quantity• including weight, velocity, acceleration, electrical current,
voltage, temperatures etc.• chemical compounds.
Many physical effects used for constructing sensors.
Examples:• law of induction (generation of voltages in an electric field),• light-electric effects.
Huge amount of sensors designed in recent years.
- 5 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Example: Acceleration Sensor
Courtesy & ©: S. Bütgenbach, TU Braunschweig
- 6 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Charge-coupled devices (CCD) image sensors
Based on charge transfer to next pixel cellBased on charge transfer to next pixel cell
- 7 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
CMOS image sensors
Based on standard production process for CMOS chips, allows integration with other components.
Based on standard production process for CMOS chips, allows integration with other components.
- 8 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Comparison CCD/CMOS sensors
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- 9 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Example: Biometrical Sensors
Example: Fingerprint sensor (© Siemens, VDE):Example: Fingerprint sensor (© Siemens, VDE):
Matrix of 256 x 256 elem.Voltage ~ distance. Resistance also computed. No fooling by photos and wax copies.Carbon dust?
Integrated into ID mouse.
- 10 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Artificial eyes
© Dobelle Institute(www.dobelle.com)
- 11 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Artificial eyes (2)
He looks hale, hearty, and healthy — except for the wires. They run from the laptops into the signal processors, then out again and across the table and up into the air, flanking his face like curtains before disappearing into holes drilled through his skull. Since his hair is dark and the wires are black, it's hard to see the actual points of entry. From a distance the wires look like long ponytails.
© Dobelle Institute(www.dobelle.com)
- 12 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Other sensors
Rain sensors for wiper control(„Sensors multiply like rabbits“ [IIT automotive])
Pressure sensors Proximity sensors Engine control sensors Hall effect sensors
Rain sensors for wiper control(„Sensors multiply like rabbits“ [IIT automotive])
Pressure sensors Proximity sensors Engine control sensors Hall effect sensors
- 13 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Discretization of time
Vx is a sequence of values or a mapping ℤ ℝ Vx is a sequence of values or a mapping ℤ ℝ
In this course: restriction to digital information processing; Known digital computers can only process discrete time series. Discrete time; sample and hold-devices.
Ideally: width of clock pulse -> 0
In this course: restriction to digital information processing; Known digital computers can only process discrete time series. Discrete time; sample and hold-devices.
Ideally: width of clock pulse -> 0
Ve is a mapping ℝ ℝVe is a mapping ℝ ℝ
- 14 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Aliasing
Impossible to reconstruct fast signals after slow sampling:multiple fast signals share same sampled sequence; Example: Signal: 5.6 Hz; Sampling: 9 Hz
-1.5
-1
-0.5
0
0.5
1
1.5
More info at end of chapter.[http://www.cise.ufl.edu/~prabhat/Teaching/cis6930-f04/comp1.ppt]
- 15 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Discretization of values: A/D-converters1. Flash A/D converter
Parallel comparison with reference voltage
Speed: O(1)
Hardware complexity: O(n)
with n= # of distin-guished voltage levels
Parallel comparison with reference voltage
Speed: O(1)
Hardware complexity: O(n)
with n= # of distin-guished voltage levels
Digital computers require digital form of physical valuesA/D-conversion; many methods with different speeds.Example: 1. Flash A/D converter:
Digital computers require digital form of physical valuesA/D-conversion; many methods with different speeds.Example: 1. Flash A/D converter:
- 16 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Discretization of values2. Successive approximation
Key idea: binary search:Set MSB='1'if too large: reset MSBSet MSB-1='1'if too large: reset MSB-1
Key idea: binary search:Set MSB='1'if too large: reset MSBSet MSB-1='1'if too large: reset MSB-1
Speed: O(ld(n))Hardware complexity: O(ld(n))with n= # of distinguishedvoltage levels;slow, but high precision possible.
Speed: O(ld(n))Hardware complexity: O(ld(n))with n= # of distinguishedvoltage levels;slow, but high precision possible.
- 17 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Successive approximation (2)
1100
1000
1010
1011
t
V
Vx
V-
- 18 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Application areas for flash and successive approximation converters
[Gielen et al., DAC 2003]
Effective number of bits at bandwidth
(using single bit D/A-converters;common for high quality audio equipments)[http://www.beis.de/Elektronik/DeltaSigma/DeltaSigma.html]
(Pipelined flash converters)
(used in multimeters)
- 19 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Quantization Noise
N = (approximated - real signal) called quantization noise.Example: quantization noise for sine wave
N = (approximated - real signal) called quantization noise.Example: quantization noise for sine wave
* [http://www.beis.de/Elektronik/DeltaSigma/DeltaSigma.html]
- 20 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Quantization noise for audio signal
Signal to noise for ideal n-bit converter : n * 6.02 + 1.76 [dB]
e.g. 98.1 db for 16-bit converter, ~ 160 db for 24-bit converter
voltage noise effective
voltage signal effective log 20 [db] (SNR) ratio noise to signal
Additional noise for non-ideal converters Source: [http://www.beis.de/Elektronik/ DeltaSigma/DeltaSigma.html]
e.g.: 20 log(2)=6.02 decibels
- 21 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Communication
- 22 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Communication:Hierarchy
Inverse relation between volume and urgency quite common: Inverse relation between volume and urgency quite common:
Sensor/actuator busses
- 23 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Communication- Requirements -
Real-time behavior
Efficient, economical(e.g. centralized power supply)
Appropriate bandwidth and communication delay
Robustness
Fault tolerance
Maintainability
Diagnosability
Security
Safety
Real-time behavior
Efficient, economical(e.g. centralized power supply)
Appropriate bandwidth and communication delay
Robustness
Fault tolerance
Maintainability
Diagnosability
Security
Safety
- 24 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Basic techniques:Electrical robustness
Single-ended vs. differential signalsSingle-ended vs. differential signals
Voltage at input of Op-Amp positive '1'; otherwise '0'
Combined with twisted pairs; Most noise added to both wires.
ground
Local groundLocal ground
- 25 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Evaluation
Advantages: Subtraction removes most of the noise Changes of voltage levels have no effect Reduced importance of ground wiring Higher speed
Disadvantages: Requires negative voltages Increased number of wires and connectors
Applications: USB, FireWire, ISDN Ethernet (STP/UTP CAT 5 cables) differential SCSI High-quality analog audio signals
Advantages: Subtraction removes most of the noise Changes of voltage levels have no effect Reduced importance of ground wiring Higher speed
Disadvantages: Requires negative voltages Increased number of wires and connectors
Applications: USB, FireWire, ISDN Ethernet (STP/UTP CAT 5 cables) differential SCSI High-quality analog audio signals
- 26 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Real-time behavior
Carrier-sense multiple-access/collision-detection (CSMA/CD, Standard Ethernet) no guaranteed response time.
Alternatives: token rings, token bussesCarrier-sense multiple-access/collision-avoidance
(CSMA/CA)• WLAN techniques with request preceding transmission• Each partner gets an ID (priority). After each bus transfer,
all partners try setting their ID on the bus; partners detecting higher ID disconnect themselves from the bus. Highest priority partner gets guaranteed response time; others only if they are given a chance.
Carrier-sense multiple-access/collision-detection (CSMA/CD, Standard Ethernet) no guaranteed response time.
Alternatives: token rings, token bussesCarrier-sense multiple-access/collision-avoidance
(CSMA/CA)• WLAN techniques with request preceding transmission• Each partner gets an ID (priority). After each bus transfer,
all partners try setting their ID on the bus; partners detecting higher ID disconnect themselves from the bus. Highest priority partner gets guaranteed response time; others only if they are given a chance.
- 27 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Other basic techniques
Fault tolerance:error detecting and error correcting bus protocols
Privacy:encryption, virtually private networks
Fault tolerance:error detecting and error correcting bus protocols
Privacy:encryption, virtually private networks
- 28 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Sensor/actuator busses
1. Sensor/actuator busses: Real-time behavior very important; different techniques:
1. Sensor/actuator busses: Real-time behavior very important; different techniques:
Many wires less wires expensive & flexible
- 29 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Field busses: Profibus
More powerful/expensive than sensor interfaces; mostly serial. Emphasis on transmission of small number of bytes.
Examples:
1.Process Field Bus (Profibus) Designed for factory and process automation.Focus on safety; comprehensive protocol mechanisms.Claiming 20% market share for field busses.Token passing.≦93.75 kbit/s (1200 m);1500 kbits/s (200m);12 Mbit/s (100m)Integration with Ethernet via Profinet.
More powerful/expensive than sensor interfaces; mostly serial. Emphasis on transmission of small number of bytes.
Examples:
1.Process Field Bus (Profibus) Designed for factory and process automation.Focus on safety; comprehensive protocol mechanisms.Claiming 20% market share for field busses.Token passing.≦93.75 kbit/s (1200 m);1500 kbits/s (200m);12 Mbit/s (100m)Integration with Ethernet via Profinet.
[http://www.profibus.com/]
- 30 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Controller area network (CAN)
2. Controller area network (CAN) Designed by Bosch and Intel in 1981; used in cars and other equipment; differential signaling with twisted pairs, arbitration using CSMA/CA, throughput between 10kbit/s and 1 Mbit/s, low and high-priority signals, maximum latency of 134 µs for high priority signals, coding of signals similar to that of serial (RS-232) lines of
PCs, with modifications for differential signaling. See //www.can.bosch.com
2. Controller area network (CAN) Designed by Bosch and Intel in 1981; used in cars and other equipment; differential signaling with twisted pairs, arbitration using CSMA/CA, throughput between 10kbit/s and 1 Mbit/s, low and high-priority signals, maximum latency of 134 µs for high priority signals, coding of signals similar to that of serial (RS-232) lines of
PCs, with modifications for differential signaling. See //www.can.bosch.com
- 31 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Time-Triggered-Protocol (TTP)
3. The Time-Triggered-Protocol (TTP) [Kopetz et al.]for fault-tolerant safety systems like airbags in cars.
3. The Time-Triggered-Protocol (TTP) [Kopetz et al.]for fault-tolerant safety systems like airbags in cars.
- 32 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
FlexRay
4. FlexRay: developed by the FlexRay consortium(BMW, Ford, Bosch, DaimlerChrysler, General Motors, Motorola, Philips).Combination of a variant of the TTP and the Byteflight [Byteflight Consortium, 2003] protocol.Specified in SDL.
• Improved error tolerance and time-determinism• Meets requirements with transfer rates >> CAN std.
High data rate can be achieved:– initially targeted for ~ 10Mbit/sec;– design allows much higher data rates
• TDMA (Time Division Multiple Access) protocol:Fixed time slot with exclusive access to the bus
4. FlexRay: developed by the FlexRay consortium(BMW, Ford, Bosch, DaimlerChrysler, General Motors, Motorola, Philips).Combination of a variant of the TTP and the Byteflight [Byteflight Consortium, 2003] protocol.Specified in SDL.
• Improved error tolerance and time-determinism• Meets requirements with transfer rates >> CAN std.
High data rate can be achieved:– initially targeted for ~ 10Mbit/sec;– design allows much higher data rates
• TDMA (Time Division Multiple Access) protocol:Fixed time slot with exclusive access to the bus
- 33 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
TDMA in FlexRay
Cycle subdivide into a static and a dynamic segment.Exclusive bus access enabled for short time in each case.Dynamic segment for transmission of variable length information.Bandwidth used when it is actually needed.
Cycle subdivide into a static and a dynamic segment.Exclusive bus access enabled for short time in each case.Dynamic segment for transmission of variable length information.Bandwidth used when it is actually needed.
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Static segment
Channel 1
Channel 2
Channel 1
Channel 2
Communication cycle
Dynamic segment
- 34 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Structure of Flexray networks
Bus guardian protects the system against failing processors, e.g. so-called “babbling idiots”
Bus guardian protects the system against failing processors, e.g. so-called “babbling idiots”
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- 35 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Other field busses
• MAP:MAP is a bus designed for car factories.• EIB:The European Installation Bus (EIB) is a bus designed
for smart homes. European Installation Bus (EIB)Designed for smart buildings; CSMA/CA; low data rate.
• IEEE 488: Designed for laboratory equipment.• Attempts to use standard Ethernet.
However, timing predictability remains a serious issue.
• MAP:MAP is a bus designed for car factories.• EIB:The European Installation Bus (EIB) is a bus designed
for smart homes. European Installation Bus (EIB)Designed for smart buildings; CSMA/CA; low data rate.
• IEEE 488: Designed for laboratory equipment.• Attempts to use standard Ethernet.
However, timing predictability remains a serious issue.
- 36 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Wireless communication
- 37 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Wireless communication: Examples
IEEE 802.11 a/b/g UMTS DECT Bluetooth
IEEE 802.11 a/b/g UMTS DECT Bluetooth
- 38 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Wireless communication: Example HomeRF
© //www.palowireless.com
Focus on integrating phone connections.
Incorporates DECT.
Competes with different extensions to IEEE 802.11
- 39 - P. Marwedel, Univ. Dortmund, Informatik 12, 04/05
Universität Dortmund
Summary
Hardware-in-the loop Sensors (robots) Discretization
• Sample-and-hold (S/H) circuit• A/D-converters
– Flash converter– Successive approximation– Other converters– Discretization noise
Communication• Requirements• Sensor/actor-busses• Field busses
Hardware-in-the loop Sensors (robots) Discretization
• Sample-and-hold (S/H) circuit• A/D-converters
– Flash converter– Successive approximation– Other converters– Discretization noise
Communication• Requirements• Sensor/actor-busses• Field busses
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