Signals Instruments and Signals, Instruments, and Systemsy

School of Architecture, Civil and Environmental EngineeringEnvironmental Engineering

EPFL, SS 2012-2013EPFL, SS 2012 2013

http://disal.epfl.ch/teaching/signals_instruments_systems/

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Signals, Instruments, and Systems – W1Part I: Course Organization,

Team and ContentTeam, and Content

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Team beyond this courseDi ib d I lli S d Al i h L b

http://disal.epfl.chDistributed Intelligent Systems and Algorithms Laboratory:

l h i i li• Instructor: Alcherio Martinoli• Guest lecturers: Alexander Bahr, William C. Evans, Sven Gowal, Steven

Roelofsen, Milos Vasic • Teaching assistants:• Teaching assistants:

– Alexander Bahr (head TA, postdoctoral fellow)– Steven Roelofsen (TA, PhD student)– Milos Vasic (TA PhD student)Milos Vasic (TA, PhD student)– Fabian Baerenbold (help TA, master student)– Adrien Gaudard (help TA, master student)

• Support staff:pp– Ezequiel Di Mario (PhD student)– Bahar Haghighat (PhD student)– Inaki Navarro Oiza (postdoctoral fellow)– Jorge Soares (PhD student)– Zeynab Talebpour (PhD student)

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Course Rationale Content Course Rationale, Content, and Prerequisites

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Typical Field Instrumentation f E i t l M it ifor Environmental Monitoring

Ultrasound anemometer Laser based disdrometerUltrasound anemometer Laser-based disdrometer

Integrated compact weather station (temperature, humidity, anemometer disdrometer) Data logger 5

Local Climate MonitoringFeatures:- Very low sampling frequency < 1Hz- Very low power consumption: 25mW- Solar panel- Radio communicationRadio communication

Sensors:Air Temperature and Humidity- Air Temperature and Humidity

- Infrared Surface Temperature- Anemometer- Solar Radiation- Pluviometer- Soil moistureSo o s u e- Soil pressure

Visit http://sensorscope.epfl.ch for further details! 6

Permafrost MonitoringPermafrost Monitoring

• What is measured:– rock temperaturerock temperature– rock resistivity– crack widthcrack width– earth pressure

water pressure– water pressure

Pictures: courtesy of Permasense7

Seismic Event Monitoring• 38 strong-motion seismometers in 17-story steel-frame Factor Building.38 strong motion seismometers in 17 story steel frame Factor Building.• 100 free-field seismometers in UCLA campus ground at 100-m spacing

1 km Source: D. Estrin, UCLA 8

Ecosystem MonitoringScience• Understand response of wild populations (plants and animals) to habitats

tiover time.• Develop in situ observation of species and ecosystem dynamics.

TechniquesTechniques• Data acquisition of physical and chemical properties, at various

spatial and temporal scales, appropriate to the ecosystem, species and habitat.b .

• Automatic identification of organisms(current techniques involve close-range human observation).

• Measurements over long period of time,taken in-situ.

• Harsh environments with extremes in i b itemperature, moisture, obstructions, ...

Source: D. Estrin, UCLA 9

Embedded Systems at the Heart ofEmbedded Systems at the Heart of Modern Environmental Engineering

• Moving the lab to the field is “in”!• Most of the applications require large spatialMost of the applications require large spatial

distributions (scale of the domain >> scale of a node) → sensor networks)

• Some applications require controlled mobility → field robots

• The underlying hardware/software technology (at the single device level) share the same ( g )principles

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Rationale (1)Rationale (1)• This course must allow you to become an power user of

the key instruments in environmental/civil engineeringthe key instruments in environmental/civil engineering used nowadays (sensor networks, meteorological stations, data loggers, etc.) and in the futuregg )(exploratory and cleaning robots, robotics sensor networks, etc.)B i t l b i d d• Being a power user means not only being an advanced user but also understand enough to collaborate with EE/CS/ME engineers to design the instruments of the g gfuture in environmental/civil engineering; idea: complexity shifted more and more from hardware to software a lot of domain knowledge can besoftware → a lot of domain knowledge can be transferred to the instruments at software level

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Rationale (2)• Well-balanced course: theory, algorithms, tools and

practical exercisespractical exercises• It should prepare you to better follow a number of

master courses (especially in the new Environmentalmaster courses (especially in the new Environmental Monitoring and Modeling specialization)

• This course can be considered as an elevator to theThis course can be considered as an elevator to the master course “Distributed Intelligent Systems” for SIE/SGC students where various other sections and programs attend (past semester SIE, SGC, SIN, SSC, SEL, SMT, SGM, CSE, EMS, EDOC, 57 students)

• It should get you prepared for carrying out a design/semester/master project at DISAL 12

What this course is about• Fundamentals of signal processing:

– Analog/Digital signals, Time/Frequency domains, Filters, Converters

• Fundamentals of embedded systems:– Microprocessors, microcontrollers, memory– Sensors and actuators

B i t l t h i d t– Basic control techniques and concepts– Basic notions of communication systems

• Fundamentals of computer science (from an embedded• Fundamentals of computer science (from an embedded systems perspective):– Basics of computer architecture– UNIX (crash course)– C programming (vs Java, Matlab/Octave) 13

Course PrerequisitesCourse Prerequisites• Matlab/Octave knowledgeg• Fundamentals on structured programming

(you learned Java, you will also learn C)(you learned Java, you will also learn C)• Fundamentals on probability calculus

F d t l l i (A l i I t IV• Fundamentals on analysis (Analysis I to IV, ODE, Fourier series and analysis, transforms)

• The Introduction to Control of Dynamical System course (Mullhaupt) will help although for now not fully leveraged

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Organization of the Organization of the CourseCourse

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Credits and Workload

• 5 ECTS• 1 ECTS = 30 h workload → 150 h workload total• Rough breakdown

– 60 h lecture (including reading, exam preparation)– 45 h hwk+lab (including preparation + reporting)– 45 h course project (including implementation, reporting,

reviewing and defense)

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Grade• Final written exam, summer; 180 minutes• 60% performance during semester, 40%60% performance during semester, 40%

performance during the exam (compromise US/Europe style)

• During semester: mean performance of 9 hwk assignments (bundled into 3 series) (30%) and course project (30%)(30%) and course project (30%)

• During exam: all covered material is subject to examination, but the exam is open bookto examination, but the exam is open book (no electronic equipment allowed other than a basic, non programmable pocket

l l t )calculator)17

Lecture Notes & ReadingLecture Notes & Reading• Policy: no manuscript, but slides and your own notes• Preliminary lecture slides in pdf format available for

download on the course web site possibly before each lecture (wed evening), definitive ones after lecture (couple of days max)R di ill b dd d M dl h• Reading will be added on Moodle as the course progressesA t M dl i i i l h ld b ll t• Access to Moodle: in principle you should be all set because compulsory course and therefore automatic enrollment; if issues contact sis-ta@groupes epfl chenrollment; if issues contact sis-ta@groupes.epfl.ch

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Tools used in Exercises and Course Projects

• C programming environment• MatlabMatlab• Realistic simulator (Webots)• Real devices (desktop robots: e puck; desktop• Real devices (desktop robots: e-puck; desktop

sensor nodes: Mica-Z)OS UNIX (Li ) Ti OS• OS: UNIX (Linux), TinyOS

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MICAzMICAz• Microprocessor

8 bi i 8MH– 8 bit microprocessor, ~8MHz– 128kB program memory, 4kB SRAM– 512kB external flash (data logger)( gg )

• Transceiver– 802.15.4 (Zigbee)

• TinyOS• Sensor board

Light– Light – Temp– Microphone Acoustic – Buzzer (4 kHz Resonator)

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e-puck RobotComputation and memory

Actuators

and memoryCommunicationActuatorsSensors I/O

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Realistic Simulation

• Discrete sensor and actuators• Noise and nonlinear characteristics faithfully reproduced• Single and multi-robot simulator• Different levels of simulation (different accuracy/faithfulness trade-Different levels of simulation (different accuracy/faithfulness trade-

offs)22

Labs (1)Labs (1) • Lab session 17:15-19:00 on Mon, GR B0 01 weekly

(first lab session: next week)(first lab session: next week)• Mini-tutorial (5-10 min) by the main lab designer at the

beginning of the labbeginning of the lab• 2h lab + 0.5 h preparation

9 l b t t t l ( 22 5 h t t l)• 9 lab sets total (= 22.5 h total)• Official solution available on Moodle after the lab

isession• Office hours (biweekly + exceptions see syllabus): wed

8:15 10 am in the computer room8:15-10 am in the computer room• sis-ta@groupes.epfl.ch for ANY issue! 23

Labs (2)• Lab assignment posted on Friday of the previous week• Lab presence not compulsory but• Lab presence not compulsory but

– We do not repeat labs– If you do not come to labs you will have a hard time inIf you do not come to labs you will have a hard time in

solving the hwk and being efficient in the course project– Certain labs involve HW which we do not distribute outside

the lab sessions

• I think it is a lot of fun and really helps you d d l ffunderstand lecture stuff

• Assistants are well prepared and numerous• Dedicated feedback forms for each lab on Moodle

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Hwk (1) • Each lab is followed by an hwk but bundled submission

every 3 weeks• Effort 2.5 h per hwk assignment 22.5h total roughly• Good training for your written examg y• Deadline: 12h00 on Monday after the last lab of the three-

week series, no late submission accepted unless motivated by provable health problems

• Penalty clock start from 14h00 of the due date• Specific projectable issues in submitting a write-up should

be mentioned in advance to the TAs• Network/Moodle server problems → TAs immediately

notified 25

Hwk (2)Hwk (2) • Hwk individually reviewed, distributed in a

timely fashion (target 2 weeks after submission, commented pdf)

• No official solution of hwk distributed; TAs available during office hours for discussion g(wed morning 8h15-10h00 or, even better, upon appointment via e-mail to TA list)pp )

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Suggestions for a Successful E i S iExercise Series

From our teaching experience:• Read the assignment in advance (i.e. before the lab,

you have always a “free” evening), in this way you ill b ffi i t h th TA d fwill be more efficient when the TAs are around for

helping you on the toughest questions… B f t t h k h id f th i t• Before you start your hwk, have an idea of the point distribution: this roughly correspond to the breakdown in time you should have; if your time is tight investin time you should have; if your time is tight invest where it is worth!

• You do not have to achieve always 100/100: bonuses,You do not have to achieve always 100/100: bonuses, exam are also great opportunities to round up…

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Course Project (1)• Course project list distributed and assigned after Easter

break• 45 h effort, defenses on the first week after sem end –

date? We need about 6 h on the same day• Team of 2 students (ad hoc solution for total odd number

in class)• Will distribute HW/SW at home• Short progress report (compulsory but not graded, 1

page) and debriefing with responsible TA/staff member• Final report to be submitted (pre-established max # of

pages and format)28

Course Project (2)

• Final presentation in front of the class (10 p (minutes + 5 min questions)

• Each of the project will have another team ofEach of the project will have another team of students as reviewers

• Each of the team members has to present• Each of the team members has to present

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Suggestions for a Successful Course ProjectSuccessful Course Project

From our teaching experience:g p• Contact ASAP the responsible supervisor when

the projects will have been assigned for getting p j g g gstarted

• Plan your effort (milestone, time, etc.), y ( , , ),coordinate your team

• Arrive at the intermediate report milestone with pa clear plan, reading, tool handling, project understanding and possible some preliminary implementation behind you

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Collaboration Policy

• Lecture and exam preparation: encouraged• Course project: mandatory (student team)p j y ( )• Lab: discussion encouraged • Hwk: discussion encouraged but problemHwk: discussion encouraged but problem

solved and submitted individually! We will be very strict in penalizing too similar y p gwrite-ups copies because 30% of the grade is acquired with hwk (n copies = # of points/n)!

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Fi l N tFinal Notes

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5th Iteration at ENAC• Fourth iteration as compulsory course

A i lti l l t t f th t d t i t d l t thi• Again multiple lecturers: most of the students appreciated a lot this aspect last year (anyway impossible to teach the whole)

• More weight on the course project (and a bit less on the exam); o e we g t o t e cou se p oject (a d a b t ess o t e e a );complexity of the course project is the same but recognition of the gap in programming required for it in comparison to exercises.

• More C programming spread out after the introductory part as much as appropriate for reducing the gap above

• Hwk following up directly the lab but submission every 3 weeks as• Hwk following up directly the lab but submission every 3 weeks as last year

• No major course restructuring until the batch of SIE students with reinforced programming background will arrive (SS 2013-2014)

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Signals, Instruments, and Systems – W1Signals, Instruments, and Systems W1Part II: Linux & C

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Linux

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LinuxLinux is a free Unix based operating systemLinux is a free Unix-based operating system.

• DefinitionAn operating system is commonly abbreviated to either OS or O/S) is an interface between hardware and applications; it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer.

• Other OSs:Windows, Mac OS X, Android, etc…

Source: http://en.wikipedia.org/wiki/Operating_system 36

Linux

• Properties– Portable to most computer architectures– Multi-tasking– Multi-user

Time sharing (programs can share CPU)– Time sharing (programs can share CPU)– Plain text to store configurations (vs. ‘Registry’ of Windows)– Hierarchical file system– Command line interpreter

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Ubuntu• Ubuntu is a particular flavor of Linux• Others: SUSE, RedHat, Fedora, etc…• Ubuntu’s graphical interface:

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The TerminalA t i l ( ‘ h ll t i l’) ll t i• A terminal (or ‘shell terminal’) allows you to give command-line orders

• Applications > Accessories > Terminal• Applications > Accessories > Terminal

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Shell• The command shell is the interface which• The command shell is the interface which

interprets your commands• At the prompt commands can be entered• At the prompt, commands can be entered.

chris@disallap14:~$

• Commands represent programs.• Programs are located in the file system in foldersPrograms are located in the file system in folders.

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Directory Structure and NavigationLinux organizes its directories differently to WindowsLinux organizes its directories differently to Windows

Absolute paths:

/ Root directory. Everything is mounted on top of this directory.

/bin Bin is short for ‘binaries’. This directory contains yprograms (executables).

/home/user Your ‘home’ directory. This is where you can store your data

Relative paths:

. Here (current directory).( y)

.. Parent directory.

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Absolute vs. relative path• Absolute

– Starts with the root location: /– Examples: /bin/ps/h / / d/home/user/mydocs

• Relative– Starts with: . or ..– Examples:

/h ll ld./hello_world../../bin/ps 42

Environment Variables

• Definition: each process has its set of environment variables. By default, when a process is created it inherits a duplicate environment of its parent process

• Environment variables good to know:$PATH contains paths of executable files$ ’ h di$HOME user’s home directory

• To get the value of a variable, use:h $VARIABLE NAMEecho $VARIABLE_NAME

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$ L bl fil$PATH: Locate executable files

• When I type ps, I actually execute the program:/bin/ps

• /bin is part of the PATH

• Any program that is not located in the path must be executed by specifying its location:y p y g

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Standard commands 1l li t th t t f th t di t• ls: lists the content of the current directoryls can take several arguments:

• ls mydocs (lists the content of mydocs)• ls -a (lists the content of the current directory

incl ding hidden files)including hidden files)• ls -l (lists the content of the current directory

including rights, owner, size and date properties)g g , , p p )• ls –la mydocs

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Standard commands 2d changes the c rrent director• cd: changes the current directory

• Ex: change to directory mydocscd mydocscd mydocs

• pwd: prints the current working directory

Remark 1: The command prompt shows the current directoryRemark 2: ~ stands for /home/[username]Remark 2: ~ stands for /home/[username]

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Standard commands 3: deletes the specified file (remo es)• rm: deletes the specified file (removes)

• Ex: remove file text.txtrm text txtrm text.txt

• rm –r: deletes files recursively inside directory. Ex:rm –r mydocs

• rm –f: forces the deletion of the specified file

Y h di trm –rf ~/* Your home directoryEverything inside it

f l d fil i h i diffi l hCareful: rm doesn’t move files into “trash”– it’s difficult to recover them!

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Standard commands 4

• mv: moves/renames the specified file/folder– Ex: move text.txt into mydocsmv text.txt mydocs

– Ex: rename text.txt to file.txtmv text txt file txtmv text.txt file.txt

• cp: copies into another file (exactly like mvexcept that a copy is made)except that a copy is made)– Ex: copy text.txt and call the copy text_copy.txtcp text.txt text_copy.txt

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Standard commands 5

• mkdir: creates a new folder (make dir.). Ex:mkdir myfolder

• man: displays the manual of the specified commandE : e plain command ‘mkdir’– Ex: explain command ‘mkdir’man mkdir

– To quit man, hit qq , q

man is very useful!

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man

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Advanced commands

• ps: displays the current programs (processes) that are running (similar to the “task manager” of Windows)

• kill: stop the program with the specified PID (process ID).

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Useful things…

• [TAB] auto-completes the command that is currently being typed.

• [TAB][TAB] displays all the remaining possibilities.

[TAB][TAB]

• [TAB][TAB] without having typed anything b f di l ll th th t bbefore displays all the programs that can be run from the path. 52

Redirection• It is possible to redirect the resulting output of a

program execution into a fileE it t t f t ‘l ’ i t fil t t t– Ex: write output of commant ‘ls’ into file out.txtls > out.txt

– Useful to save and analyze the data in Matlab forUseful to save and analyze the data in Matlab for example.

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Pipes

• It is possible to use the output of a program directly as input to another program.– Ex: get values of all environment variables and find the

value of SHELL within env | grep “SHELL”env | grep SHELL

– This is quivalent to: env > out.txtgrep “SHELL” < out.txt

Remark: grep searches the input for the specified sequence.54

Programming in CProgramming in C

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Question

• What is your level in programming?– Java?Java?– Matlab?– C?C?

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What is C?

• C is a programming language just like Java: It enables the programmer to tell to the p gcomputer what it should do.

• It was developed in 1972 and is still one ofIt was developed in 1972, and is still one of the most widely-used languages in the worldworld

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What is C?

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Main differences with Java

• It is NOT object oriented. (C++ is OO)• Code is directly translated into binary thatCode is directly translated into binary that

can be directly executed by the machine. With C the programmer can directly accessWith C, the programmer can directly access machine resources (memory, processes).

• It’s not ‘safe’ (Java is ‘safe’)• It s not safe (Java is safe )• Full comparison of C vs. Java:

h //i i d /j /f / 2j h lhttp://introcs.cs.princeton.edu/java/faq/c2java.html59

How to use it?

file?

file.c

source file executable(binary)(binary)

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How to use it?• ‘gcc’ is a program, and stands for Gnu C Compiler

gcc file.c –o file

• ‘gcc’ contains all standard libraries needed to compile a basic program

object file

filefile.ofile.c

source file executablelibc

standard C library61

Example: Hello World

class myclass {public static void main(String args[]) {

In Java

public static void main(String args[]) {System.out.println("Hello World!");

}}

#include <stdio h>

In C#include <stdio.h>

int main(int argc, char *args[]){printf(“Hello World!\n”);printf( Hello World!\n );return 0;

}62

Example: Hello World• #include <stdio h>

• int main(int argc, char *args[])

• #include <stdio.h>

• Includes the declaration of printf in our C code.

– That is the entry function of any C code.– This function is called first when the

t t dprogram gets executed. #include <stdio.h>

int main(int argc, char *args[]){printf(“Hello World!\n”);

• printf(“Hello World!\n”);

Thi f ti i i th lib return 0;}

– This function is in the libc.– It is declared in the stdio.h file.

• return 0;

– main always returns an int (integer value).– The convention is to return 0 when everything went ok. 63

Variables• Just like Java there are several types of yp

variables in C:– Integers: char, short, int, longg g

– Floating point: float, double– Characters: char– There is no Boolean type.

• Variables can be either signed or unsigned:• Variables can be either signed or unsigned:– Ex.: unsigned int, signed char

Ad d i f ifi i• Advanced: integers of a specific sizeint8_t, int16_t, int32_t 64

VariablesV i bl d t b d l d b f th• Variables need to be declared before they are used.

• In correct ANSI C89, variables need to be declared at the beginning of a block (after the opening curly bracket “{”).int main() {

int a = 5;double b = 4.3;return (int)((double)a * b);

}}

Remark: A variable type can be modified with a cast.65

Controlling the execution flow

• Algorithms are all about controlling the execution flow.

• Algorithms are all about deciding how to proceed depending on some conditionalproceed depending on some conditional statements.

What are the tools we use to do this?

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ififif (condition) {

code;Def.:

;

} else if (another condition) {another code;

} l {} else {yet another code;

}

if (a >= b && a != c) {a = b;

Ex.:a b;

} else if (a == 3 || b == 3) {a = c;

} l {} else {b = 2*a;

} 67

whilewhilewhile (condition) {( ) {

code;}

do {code;

} while (condition);

• At any time, you can quit the loop with the keyword b kbreak.

• You can also skip the rest of the code in the loop with continue.continue.

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forfor

for (initialization; condition; increment) {code;

}}

for (i = 0; i < i_max; i++) {a = a + i * a;

printf(“a is equal to: %d \n”, a);

}

ti d b k l b d• continue and break can also be used.

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C l iConclusion

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Summary

• Basics in Linux:– How to navigate, how to manipulate filesHow to navigate, how to manipulate files– How to combine commands– Where to look for information (man pages)Where to look for information (man pages)

• Introduction to C:V i bl d i f ti– Variables and main function

– Basic control structures (if, while, for)

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Additional Literature – Week 1

• Nice summary on linux shell usage:http://linuxcommand.org/learning_the_shell.php

• Classical book for C programming:‘C Programming Language’, Prentice HallBrian W. Kernighan , Dennis M. Ritchie

• Popular C link:http://www.c-faq.com/

• And many more – Google is your friend

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