- 1 - Embedded Systems – sensors-comm Simplified design flow for embedded systems

- 2 - Embedded Systems – sensors-comm Embedded System Hardware Embedded system hardware is frequently used in a loop (“hardware in a loop”): actuators

- 3 - Embedded Systems – sensors-comm 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.

- 4 - Embedded Systems – sensors-comm Example: Acceleration Sensor Courtesy & ©: S. Bütgenbach, TU Braunschweig

- 5 - Embedded Systems – sensors-comm Charge-coupled devices (CCD) image sensors Based on charge transfer to next pixel cell

- 6 - Embedded Systems – sensors-comm CMOS image sensors Based on standard production process for CMOS chips, allows integration with other components.

- 7 - Embedded Systems – sensors-comm Example: Biometrical Sensors 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.

- 8 - Embedded Systems – sensors-comm Artificial eyes © Dobelle Institute (

- 9 - Embedded Systems – sensors-comm 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

Embedded Systems – sensors-comm Discretization of time V x 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 V e is a mapping R  R

Embedded Systems – sensors-comm Discretization of values: A/D-converters 1. 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 values  A/D-conversion; many methods with different speeds. Example: 1. Flash A/D converter: Digital computers require digital form of physical values  A/D-conversion; many methods with different speeds. Example: 1. Flash A/D converter:

Embedded Systems – sensors-comm Discretization of values 2. Successive approximation Key idea: binary search: Set MSB='1' if too large: reset MSB Set MSB-1='1' if too large: reset MSB-1 Key idea: binary search: Set MSB='1' if too large: reset MSB Set MSB-1='1' if too large: reset MSB-1 Speed: O(ld(n)) Hardware complexity: O(ld(n)) with n= # of distinguished voltage levels; slow, but high precision possible. Speed: O(ld(n)) Hardware complexity: O(ld(n)) with n= # of distinguished voltage levels; slow, but high precision possible.

Embedded Systems – sensors-comm Successive approximation (2) t V VxVx V-V-

Embedded Systems – sensors-comm Application areas for flash and successive approximation converters [Gielen et al., DAC 2003] Effective number of bits at bandwidth

Embedded Systems – sensors-comm Communication

Embedded Systems – sensors-comm Communication: Hierarchy Inverse relation between volume and urgency quite common: Sensor/actuator busses

Embedded Systems – sensors-comm Communication - Requirements - Real-time behavior Efficient, economical (e.g. centralized power supply) Appropriate bandwidth and communication delay Robustness Fault tolerance Maintainability Diagnosability Security Real-time behavior Efficient, economical (e.g. centralized power supply) Appropriate bandwidth and communication delay Robustness Fault tolerance Maintainability Diagnosability Security

Embedded Systems – sensors-comm Basic techniques: Electrical robustness Single-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 ground

Embedded Systems – sensors-comm 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

Embedded Systems – sensors-comm Real-time behavior Carrier-sense multiple-access/collision-detection (CSMA/CD, Standard Ethernet) no guaranteed response time. Alternatives: token rings, token busses Carrier-sense multiple-access/collision-avoidance (CSMA/CA) –WLAN techniques with request preceeding 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 busses Carrier-sense multiple-access/collision-avoidance (CSMA/CA) –WLAN techniques with request preceeding 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.

Embedded Systems – sensors-comm 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

Embedded Systems – sensors-comm Sensor/actuator busses 1.Sensor/actuator busses: Real-time behavior very important; different techniques: Many wires less wires expensive & flexible

Embedded Systems – sensors-comm Field busses More powerful/expensive than sensor interfaces; serial busses preferred. Examples: 1. Process Field Bus (Profibus) (see // Token passing; 9.6 kbit/s (1200 m) to 500 kbits/s (200m); to slow to be used for hard time constraints. More powerful/expensive than sensor interfaces; serial busses preferred. Examples: 1. Process Field Bus (Profibus) (see // Token passing; 9.6 kbit/s (1200 m) to 500 kbits/s (200m); to slow to be used for hard time constraints.

Embedded Systems – sensors-comm Field busses (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 // 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 //

Embedded Systems – sensors-comm Field busses (3) The Time-Triggered-Protocol (TTP) [Kopetz et al.] for fault-tolerant safety systems like airbags in cars. FlexRay: TDMA (Time Division Multiple Access) protocol, 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. - Designed to meet key automotive requirements - Complements the major in-vehicle networking standards - A high data rate can be achieved: initially targeted for a data rate of approximately 10Mbit/sec; however, the design of the protocol allows much higher data rates to be achieved. The Time-Triggered-Protocol (TTP) [Kopetz et al.] for fault-tolerant safety systems like airbags in cars. FlexRay: TDMA (Time Division Multiple Access) protocol, 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. - Designed to meet key automotive requirements - Complements the major in-vehicle networking standards - A high data rate can be achieved: initially targeted for a data rate of approximately 10Mbit/sec; however, the design of the protocol allows much higher data rates to be achieved.

Embedded Systems – sensors-comm Field busses (4) 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. 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.

Embedded Systems – sensors-comm Wireless communication

Embedded Systems – sensors-comm Wireless communication: Examples IEEE a/b/g UMTS DECT Bluetooth UWB IEEE a/b/g UMTS DECT Bluetooth UWB