Chapter 3: Node Architecture Outline ." The Sensing Subsystem! ." Analog-to-Digital Converter! ." The Processor Subsystem ! ." Architectural Overview! ." Microcontroller! ." Digital Signal Processor! ." Application-specific Integrated Circuit! ." Field Programmable Gate Array! ." Comparison! ." Communication Interfaces! ." Serial Peripheral Interface! ." Inter-Integrated Circuit! ." Summary! ." Prototypes! ." The IMote Node Architecture! ." The XYZ Node Architecture! ." The Hogthrob Node Architecture! Fundamentals of Wireless Sensor Networks: Theory and Practice 2! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Node Architecture ." Wireless sensor nodes are the essential building blocks in a wireless sensor network! ." sensing, processing, and communication! ." stores and executes the communication protocols as well as data processing algorithms! ." The node consists of sensing, processing, communication, and power subsystems! ." trade-off between flexibility and efficiency – both in terms of energy and performance! Fundamentals of Wireless Sensor Networks: Theory and Practice 3! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. 1! Node Architecture Figure 3.1 Architecture of a wireless sensor node Fundamentals of Wireless Sensor Networks: Theory and Practice 4! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Outline ." The Sensing Subsystem! ." Analog-to-Digital Converter! ." The Processor Subsystem ! ." Architectural Overview! ." Microcontroller! ." Digital Signal Processor! ." Application-specific Integrated Circuit! ." Field Programmable Gate Array! ." Comparison! ." Communication Interfaces! ." Serial Peripheral Interface! ." Inter-Integrated Circuit! ." Summary! ." Prototypes! ." The IMote Node Architecture! ." The XYZ Node Architecture! ." The Hogthrob Node Architecture! Fundamentals of Wireless Sensor Networks: Theory and Practice 5! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. The Sensing Subsystem ." The sensing subsystem integrates! Application Sensor! Sensed Event! Explanation! Area! 2D and 3D acceleration of Accelerometer! AVM! Volcano activities! movements of people and objects! SHM! Stiffness of a structure! Stiffness of bones, limbs, joints; Motor Health care! fluctuation in Parkinson#s disease! Irregularities in rail, axle box or wheels of a Transportation! train system! SCM! Defect of fragile objects during transportation! Acoustic Elastic waves generated by the Measures micro-structural changes or emission SHM! energy released during crack displacements! sensor! propagation! Acoustic Transportation Vehicle detection; Measure structural Acoustic pressure vibration! sensor! & Pipelines! irregularities; Gas contamination! Capacitance sensor! PA! Solute concentration! Measure the water content of a soil! Fundamentals of Wireless Sensor Networks: Theory and Practice 6! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. 2! The Sensing Subsystem Application! Sensor! Sensed Event! Explanation! Area! ECG! Health care! Heart rate! EEG! Brain electrical activity! EMG! Muscle activity! Electrical capacitance or inductance ! Measure of nutrient contents and ! Electrical sensors! PA! affected by the composition of ! distribution! tested soil! Gyroscope! Health care! Angular velocity! Detection of gait phases! Humidity sensor! PA & HM! Relative and absolute humidity! Concussive acoustic waves – ! Infrasonic sensor! AVM! earth quake or volcanic eruption! Presence, intensity, direction,! Presence, speed and density of a ! Magnetic sensor! Transportation! rotation and variation of a magnetic! vehicle on a street; congestion! field! Blood oxygenation of patient's ! Cardiovascular exertion and trending! Oximeter! Health care! hemoglobin! of exertion relative to activity! Indicates the acid and alkaline! Pipeline ! pH sensor! Concentration of hydrogen ions! content of a water measure of! (water)! cleanliness! Fundamentals of Wireless Sensor Networks: Theory and Practice 7! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. The Sensing Subsystem Application Sensor! Sensed Event! Explanation! Area! Photo acoustic Pipeline! Gas sensing! Detects gas leak in a pipeline! spectroscopy! A leak produces a high frequency Piezoelectric noise that produces a high Pipeline! Gas velocity! cylinder! frequency noise that produces vibration! Soil moisture sensor! PA! Soil moisture! Fertilizer and water management! Temperature sensor! PA & HM! Pressure exerted on a fluid! Passive infrared Health care & Infrared radiation from objects! Motion detection! sensor! HM! Measure primary and secondary seismic Seismic sensor! AVM! Detection of earth quake! waves (Body wave, ambient vibration)! Amount and proportion of oxygen in the Oxygen sensor! Health care! blood! The Doppler shift of a reflected ultrasonic Blood flow sensor! Health care! wave in the blood! Fundamentals of Wireless Sensor Networks: Theory and Practice 8! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Outline ." The Sensing Subsystem! ." Analog-to-Digital Converter! ." The Processor Subsystem ! ." Architectural Overview! ." Microcontroller! ." Digital Signal Processor! ." Application-specific Integrated Circuit! ." Field Programmable Gate Array! ." Comparison! ." Communication Interfaces! ." Serial Peripheral Interface! ." Inter-Integrated Circuit! ." Summary! ." Prototypes! ." The IMote Node Architecture! ." The XYZ Node Architecture! ." The Hogthrob Node Architecture! Fundamentals of Wireless Sensor Networks: Theory and Practice 9! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. 3! Analog-to-Digital Converter ." ADC converts the output of a sensor - which is a continuous, analog signal - into a digital signal. It requires two steps:! 1." the analog signal has to be quantized ! ." allowable discrete values is influenced :! ! ! (a) by the frequency and magnitude of the signal! ! ! (b) by the available processing and storage resources! 2. the sampling frequency! ." Nyquist rate does not suffice because of noise and transmission error! ." resolution of ADC - an expression of the number of bits that can be used to encode the digital output! ." where Q is the resolution in volts per step (volts per output code); Epp is the peak-to-peak analog voltage; M is the ADC#s resolution in bits! Fundamentals of Wireless Sensor Networks: Theory and Practice 10! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Outline ." The Sensing Subsystem! ." Analog-to-Digital Converter! ." The Processor Subsystem ! ." Architectural Overview! ." Microcontroller! ." Digital Signal Processor! ." Application-specific Integrated Circuit! ." Field Programmable Gate Array! ." Comparison! ." Communication Interfaces! ." Serial Peripheral Interface! ." Inter-Integrated Circuit! ." Summary! ." Prototypes! ." The IMote Node Architecture! ." The XYZ Node Architecture! ." The Hogthrob Node Architecture! Fundamentals of Wireless Sensor Networks: Theory and Practice 11! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. The Processor Subsystem ." The processor subsystem ! ." interconnects all the other subsystems and some additional peripheries! ." its main purpose is to execute instructions pertaining to sensing, communication, and self-organization! ." It consists of! ." processor chip ! ." nonvolatile memory - stores program instructions! ." active memory - temporarily stores the sensed data! ." internal clock Fundamentals of Wireless Sensor Networks: Theory and Practice 12! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. 4! Outline ." The Sensing Subsystem! ." Analog-to-Digital Converter! ." The Processor Subsystem ! ." Architectural Overview! ." Microcontroller! ." Digital Signal Processor! ." Application-specific Integrated Circuit! ." Field Programmable Gate Array! ." Comparison! ." Communication Interfaces! ." Serial Peripheral Interface! ." Inter-Integrated Circuit! ." Summary! ." Prototypes! ." The IMote Node Architecture! ." The XYZ Node Architecture! ." The Hogthrob Node Architecture! Fundamentals of Wireless Sensor Networks: Theory and Practice 13! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Architectural Overview ." The processor subsystem can be designed by employing one of the three basic computer architectures! ." Von Neumann architecture! ." Harvard architecture! ." Super-Harvard (SHARC) architecture! Fundamentals of Wireless Sensor Networks: Theory and Practice 14! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Von Neumann Architecture ." Von Neumann architecture ! ." provides a single memory space - storing program instructions and data! ." provides a single bus - to transfer data between the processor and the memory! ." Slow processing speed - each data transfer requires a separate clock! Fundamentals of Wireless Sensor Networks: Theory and Practice 15! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. 5! Von Neumann Architecture Fundamentals of Wireless Sensor Networks: Theory and Practice 16! Waltenegus Dargie and Christian Poellabauer © 2010 John Wiley & Sons Ltd. Harvard Architecture ." Harvard architecture ! ." provides separate memory spaces - storing program instructions and data! ." each memory space is interfaced with the processor with a separate data bus! ." program instructions and data can be accessed at the same time! ." a special single instruction,