EKIT - Tool for Learning Signals, Circuits andElectronic Systems

Nuno Lucas, Jose Gaspar and Joao SequeiraInstituto Superior Tecnico,

Universidade Tecnica de Lisboa, Portugalnunofml@gmail.com,jag,jseq@isr.ist.utl.pt

The increase of student mobility in Europe and in other countries,and the recent attempt to harmonise European curricula at thegraduation and post-graduation levels lead towards an increasing co-operation among universities to develop educational modules witha common background [8] . With Bolonha coming into effect inmost universities the self-learning processes lead to the abolition ofmany experimental classes in the electronic graduations courses. Thispaper describes a project to help and promote the self-learning skillson signals, circuits and electronic systems. Experiments of measur-ing resistors, capacitors, DC motor parameters and Bode diagramsshow that an inexpensive USB/microcontroller device constitutes aneffective minimal equipment setup.

Keywords: Microcontroller based interfaces, Analog to digital con-version, Digital to analog conversion , e-Learning.

I. I NTRODUCTION

The self-learning processes imposed by the Bolonha process[2] left aside an important component of the basis of electronicsengineering, namely the interaction in laboratory with the most basicphysical devices. Since the signal acquisition and analysis usuallyrequires expensive hardware such as oscilloscopes, signals generators,data acquisition devices. It seems that in fact the self-learning willbe contradicting the experimental learning.

While the conventional laboratory teaching of circuits tends todecrease its prevalence, in fact the self-learning of electronics is actu-ally growing, mostly associated to hobbies as remotely commandingmodel cars or planes, or by participating in robotics competitions[1]. Some of these learning dynamics can for sure be helpful for thetransition process of the teaching and learning for circuit analysis,associated to the Bolonha process.

The main purpose of this paper is therefore to discuss a frameworkfor teaching and learning circuit theory and analysis, termed theEKit project, and to show that despite the decreasing of the time ofpresence learning in the Bolonha paradigm, a simple hardware devicestill allows realizing a comprehensive variety of the experiments thatwere standard in pre-Bolonha circuit analysis courses. The device isbased on a reconfigurable microcontroller (PIC), combined with aUSB interface to allow importing data directly to a ordinary desktopor laptop.

The structure of the paper is the following. Section 2 in-troduces a general teaching and learning framework. Section 3presents one inexpensive Hardware and Software Setup based ona USB/microcontroller device, which serves as a basis to handlethe requirements of the teaching and learning framework. Section4 details examples of experiments on electronics that can be donewith the device. Section 5 draws some conclusions.

II. L EARNING AND TEACHING FRAMEWORK

The EKit project aims to provide students enrolled in Electric,Electronics and Computer (EEC) engineering courses, the necessarytools for autonomously conducting experiments similar to the onescarried out in first courses of circuit analysis. These tools are expectedto be lent by the universities or in cases of personal interest, e.g.hobby applications, acquired by the students.

Commonly, first year EEC students have too little acquaintancewith electronic devices. The EKit project has therefore to be userfriendly in its various facets. Three very important of those facetsare (i) having the required hardware capabilities, (ii) being easy touse, and (iii) being affordable. These three facets seem at first hardto fulfill simultaneously. For example first courses on circuit analysisinvolve using power supplies, wave signal generators and oscillo-scopes, which is equipment usually not easy to use by inexperiencedusers and is definitely expensive.

However, there are two very important recent trends that changecompletely the previous scenario. The first one is that almost allstudents have their own personal computer (PC). The second wasthe introduction in the last decade of very inexpensive microcon-trollers, containing very good analog-to-digital and digital-to-analogconverters. Combining these two through a USB connection, one canobtain an almost complete solution: the microcontroller can generatesignals to simple circuits (e.g. a voltage divider), acquire the signalsof interest and send them to the PC. Then, the PC makes the role ofthe oscilloscope i.e. displays the resulting signals. Considering thatthe PC is already owned by the student, all that has to be bought isthe microcontroller with the USB interface, which is certainly underthe price of a text-book.

This is however an incomplete solution, not because of lackingcapabilities or the price, but because it is missing the easy ofuse aspect, for students and teachers. Analyzing in more detail theteaching point of view, there are two additional important aspectsto consider: (ii.a) interfacing to the students, giving diversified,constantly innovative and interesting challenges, while (ii.b) keepingacceptable the logistics within the university.

Acceptable logistics imply that the hardware must be easy to buy,maybe from various brands to be available from multiple vendors,easy to replace with novel versions, and simultaneously alwaysguaranteeing that the work done at the university for the hardwareis never lost. In other words, most of the hardware logistics can relyon commercial companies, the university just has to safeguard thatthe companies do notdeprecateits own developing efforts. Here, theuniversity just has to maintain the specifications and the softwarestandard for interfacing to the device.

Interfacing to the students implies being able to assign specificworks to the individual students and providing help. It must allowthe student to work at his own pace. As with the logistics, building

interfaces calls once more for properly designed software solutions.In summary, a significant effort must be put in building softwaresolutions. These solutions have to be flexible in the sense that copewith a variety of hardware devices, and allow doing diversified CircuitAnalysis experiments.

In the authors view, the software solutions comprise in essence: (i)designing generic drivers made public through a webpage, providingalso the installation manuals, the user interface software and anumber of typical experiments, (ii) maintaining a public forum forgeneral support and discussion, and (iii) creating e-learning tools fordistributing and automatically grading assignments [9]. In some moredetail:

• Designing a stable and generic driver interface to theUSB/microcontroller solves most of the issues related withsupporting multiple brands and upgrading the hardware withoutlosing the developed applications. Based on the driver interface,one can than builddiversified experiments.

• The discussion forum can be moderated by both teachers,and students having a prior knowledge and experience withmicrocontrollers. The forum should solve most of the supportto the students without spending too many teaching resources.

• The e-learning tools can be used to guarantee that the student isactually self-learning, as they make possible giving differenti-ated assignments though individual logins and allow gradingthem automatically. Teachers may take advantage of the e-learning to save time and to provide an extra evaluation system.

In this paper we explore the experiments diversification aspect, bylisting a variety of experiments that can be done with one hardwaredevice, comprising a USB interface and one microcontroller havingAD/DA converters. Firstly, in the next section, we detail the hardwaredevice and succinctly describe software development having in mindbuilding a generic interface.

III. H ARDWARE AND SOFTWARE SETUP

Baring in mind that the EKit project aims to provide students withthe necessary tools for conducting experiments similar to the onescarried out in first courses of circuit analysis, it was necessary to findthe appropriate hardware solutions as well as the implementation ofthe necessary software.

A. Hardware

To be able to acquire signals and send data over the USB, thefirst priority is the selection of one microcontroller having Analogto Digital Converters (ADC) and one USB adapter to communicatewith an host PC (necessary if the microcontroller does not have aUSB interface). Adding Digital to Analog Converters (DAC) to thehardware list is also necessary for generating analog signals since themost common microcontrollers in the market do not have them.

In particular we have used the USB and microcontroller moduleDLP-2232PB-G, manufactured by DLP [3], which combines alreadyone USB adapter with one 16F877A microcontroller into a singlePCB (printed circuit board). It is USB 1.1/2.0 compatible andsends/receives data over USB to a host computer at up to 2 megabitsper second. It has 16 digital I/O lines (5 can be configured as A/Dinputs).

Having a microcontroller in the device is a convenient decisionas it allows a lot of flexibility. For example the PIC 16F877Amicrocontroller provides a large number of I/O pins with eightA/D 10-bit channels [6]. It has also 8 KB of Flash EEPROM, twocomparators, two PWM of 10bit resolution, 368 bytes RAM, I2C,SPI, parallel, USART interfaces, and works at a frequency of 20MHz.

The USB adapter is the FT2232D [4], based on FTDI’s thirdgeneration chips which incorporates into a single device two func-tionalities, USB-to-UART and USB-to-parallel-FIFO as well as twoversions of royalty-free drivers, a Virtual COM Port (VCP) and aDynamic Link Library (DLL). We select the VCP way in order tokeep the device as independent as possible of the operating system.

As the 16F877A microcontroller does not have digital to analogconversion, one has to augment the module with an extra IC. Weselected the DAC MCP4822 [7] which based on aSerial PeripheralInterface(SPI) communication to the microcontroller, a synchronousserial data link, where the devices communicate in master/slave modehaving the master device initiating the data frames.

Figure 1 shows the communication of the DLP module withDAC (required for signal generation) which is made through SPIcommunication, as well as the real setup.

Fig. 1. DLP2232PB-G and DAC-4822 connections (top) and setup (bottom)

Table I shows the final working specifications of the EKit, whenthe DLP module and DAC are put together, to provide the desiredsignal acquisition and generation tool with USB interface.

device DLP-2232PB-G DAC MCP4822Power source USB 2.7 - 5.5V

Max current in I/O pins 25 mA 25mANumber of digital channels 11 (I/O) -

Converter resolution ADC 10 bits DAC 12 bitsNumber of analog channels 5 (ADC) 2 (DAC)

Signal range 0 - 5.12 V 0 - 4.096 VMax sampling frequency 10 kHz (ADC) 16 kHz (DAC)

TABLE I

EKIT SPECIFICATIONS

B. Software

The software can be divided into firmware and software on thePC side. We call firmware to the software that directly controls thehardware, in our case the microcontroller. The microcontroller isprogrammed in C and it controls the communications with the DAC.A flowchart of the generic approach to this firmware is shown infigure 2.

The software on the PC side was developed in C++ with thepurpose of building a generic software interface solution that couldapply to future projects of EKit with upgraded hardware. Thesoftware functions were divided into three groups: the communica-tion functions, the digital functions and the analog functions. The

Fig. 2. Firmware flowchart.

communication functions use the manufacturer provided drivers forthe VCP port and a few API functions to communicate with thedevice. The digital functions allow writing and reading digital inputsand outputs. The analog functions are used to acquire analog values(ADC) and to generate waves signals(DAC).

Considering conventional circuit analysis courses [5], the typicalexperiments range from resistive circuits analysis, as voltage divisionand load effect, till the analysis of dynamic systems as Resistor-Capacitor (RC) circuits or DC motors, both involving transientresponses, time constants, DC gains, frequency response, etc. In thefollowing section on experiments we want therefore to prove that asimple USB/microcontroller device can effectively touch the conceptsof most of the conventional experiments.

IV. D IDACTIC EXPERIMENTS

In these section we propose four experiments: (i) measuringresistors, using a simple voltage divider, (ii) measuring capacitiesbased on the step response function, (iii) measuring the DC gainand time constant of a DC motor using techniques similar to themeasurement of the capacities, and (iv) Bode diagram analysis.

A. Measuring resistors

Considering a voltage divider of a supply voltage,Vs through acalibrated resistor,Ri and a resistor load to measure,R, one has anexpression for the voltage at the load,Vr = VsR/(R+Ri). Hence, ifone knowsVs, Ri and measuresVr, then one can estimateR simplyas:

R = RiVr/(Vs − Vr)

Using the USB/microcontroller device, one can easily obtain thenecessary measurements. Figure 3 shows the voltage divider circuitconnected to such device.

Fig. 3. Resistor measuring circuit diagram (top) and image of the real setup(bottom).

An experiment was conducted for measuring 1K, 10K and 100Kresistors, using one calibrated 1K resistor. The experiment was re-peated 100 times for each resistor and has shown standard deviationsof 0.37%, 1.09% and 7.95%, respectively. In other words, resultsshow that the measurement noise of the device is small enough toallow using one calibrated 1K resistor to measure other resistors up-toan order of magnitude larger, within about1% accuracy.

B. Measuring capacitors

A serial RC circuit is a typical way of measuring a capacity. Forexample one can actuate the RC circuit with a step voltage source,vs and measure the voltage on the capacitor,vc(t). The voltagevc(t)allows calculating the time constant,τ of the RC circuit, and in caseof knowing precisely theR, one obtains directly the capacity,C.

Again using the USB/microcontroller device, one can easily obtainthese measurements. Figure 4 shows the device connected to theRC circuit, actuating through an output port, i.e. generatingvs andreadingvc(t).

Fig. 4. RC series setup to measure the capacityC.

There are several ways of measuring the capacity,C from the timeresponse,vc(t) of a RC circuit charged by a constant source. We willdetail here three ways of estimatingC, starting from: (i) the localincrements of the capacitor’s voltage and the integral of the current,(ii) as the previous case, but taking longer time periods, and (iii)directly the time response.

In order to apply the first two methods, one needs to estimate thecapacitor’s current,ic(t), which comes directly from the knowledgeof vs andR as:

ic(t) =vs − vc (t)

R(1)

The current flowing onto the capacitor is by definition the rate atwhich charge is being stored,ic(t) = C · dvc(t)/dt. So the chargeon the capacitor equals the integral of the current with respect to time,leading toC =

∫ t1

t0ic(t)dt/(vc(t1) − vc(t0)) and thus we arrive to

a local formula by converting the continuous to discrete time:

C(k) ∼=Ts

2

ic((k + 1)Ts) + ic(kTs)

vc((k + 1)Ts) − vc(kTs)(2)

whereTs denotes the sampling time andk the sample number.In method (ii) we consider a more dilated time interval, and thus

we need to account for all the local increments in the current:

C(k) ∼=Ts

2

k−1∑

n=0

ic((k + 1)Ts) + ic(kTs)

vc(kTs) − vc(0). (3)

Method (iii) uses the knowledge of the time response function, i.e.the capacitor’s charging functionvc(t) = vs(1 − e−t/τ ) which canbe solved explicitly forτ , and then forC sinceτ = R · C:

C(t) =−t

R · log (1 − vc(t)/vs)(4)

wheret = kTs.

−0.2 0 0.2 0.4 0.6 0.8 1 1.2

0

1

2

3

4

5

6

Vc

[V]

0 0.5 1−1

0

1

2

3x 10

−6

C [F

]

0 0.5 1−1

0

1

2

3x 10

−6

0 0.5 1−1

0

1

2

3x 10

−6

Fig. 5. Time response of the RC circuit and estimates of the capacity usingmethods (i), (ii) and (iii) (see text).

Figure 5 shows the time response of the RC circuit to the inputvoltagevs = 5.12[V ], and the estimates of a capacitor with nominalvalue C = 1µF , using each of the three methods. It is interestingto note that despite having noisy local estimates of the currentflowing on the capacitor, which has a direct impact on the estimatesof C using method (i), one can obtain good results using method(ii) provided that one takes enough integration time. The result ofmethod (ii) is smooth along time, due to its integrating nature, andis interesting even when compared to method (iii), whereC cannotbe estimated as soon asvc(t) gets too close tovs. This smoothnessproperty of (ii) is convenient for example if one does not want toimplement a detector ofvc(t) ∼= vs.

C. DC motor parameters

The experiment on a brush DC motor consists on measuring itsparameters from its response to a step input. In this section we willbe interested in finding the parameters of a didactic DC motor setup,built by Quanser, for control courses. Figure 6 shows the power driverand the motor.

Fig. 6. Power driver (left), the motor and sensors (right).

The methods for parameters estimation will follow closely the onesused for the RC circuit, since they have in essence the same model. ADC motor with the input voltage,vs and the output angular velocity,ω can be approximately described by a first order transfer functionG(s) = k0/(1 + τs), whereτ is the time constant andk0 is the DCgain (note that in the RC circuitk0 = 1). The response of the systemto the input step voltage is therefore given by:

ω(t) = vsk0

(

1 − e−t/τ)

(5)

whereω(t) is the motor speed measured as a voltage by a tachometer.This response, Eq.5 can be used as a model to estimate the motorparameters,k0 andτ .

After acquiring the motor speed (Fig. 7) the DC gain and timeconstant can be estimated by two methods, inverting the step responseand using a curve fitting algorithm.

a) Inverting the step response -:Firstly we need to estimatethe DC gain. Given that the step response is a monotonic function,we can estimate the DC gain from the maximum value of the stepresponse. In order to deal with noise, in practice we estimate the DCgain from the median of all the values in a five percent range of thetachometer maximum voltage:

k0 = medianω(t) : ω(t) ≥ 0.95 max(ω(t)) (6)

The time constant is then calculated from Eq.5:

τ(t) =−t

log (1 − ω(t)/(vsk0))(7)

In order to test the above procedure we acquired step responsesof the DC motor, using our USB/microcontroller device to generatethe reference signals (to the power driver of the motor) and readthe velocity signals generated by the tachometer. To demonstratethe potential of this microcontroller as a data acquisition device thisexperiment was made also with a National Instruments NI PCI-6221signal acquisition board. Using both devices the data acquisition wasconducted 200 times for the same input step voltage with a samplingfrequency of about 500Hz. See Fig.7(a,b).

The time constant was computed for the time samples along thelength of each experiment. Figure 7(c,d) shows that the measurementnoise led to good results only in the central time-samples. Notice thatthe uncertainty grows ast → ∞, due to the DC motor reaching thesteady state. In the case of the PIC, the uncertainty is also largein the beginning which is due to some clock inaccuracy on the PCmotivated by the operating system.

0 0.05 0.1 0.15 0.20

1

2

3

4

5PIC acquisition

time [sec]

w [v

]

0 0.05 0.1 0.15 0.20

1

2

3

4

5NI−daq acquisition

time [sec]

w [v

]

(a) (b)

0 0.05 0.1 0.15 0.20

20

40

60

80

Tau

vs

tim

e [m

sec]

0 0.05 0.1 0.15 0.20

20

40

60

80

(c) (d)

3.9 4 4.1 4.2

24

26

28

30

32

Tau

[mse

c] v

s k

0

3.9 4 4.1 4.2

24

26

28

30

32

(e) (f)

Fig. 7. 200 step responses of the DC motor (a,b). PIC (left-column) andNI board (right-column). Time constant,τ [msec] estimated using Eq.7 (c,d).Time constant vs DC gainK0 (e,f). The red circle denotes the medianτ andk0 in the 200 experiments.

Hence, in order to estimate a singleτ value for each experimentwe selectedτ := τ(t), with t the time sample where the standarddeviation of theτ(t) is a minimum considering the 200 experiments.Figure 7(e,f) shows the estimates(k0, τ) for the 200 step responses.The uncertainty of the estimates is due to some mechanical uncer-tainty (the load of DC motor implies more friction in some angles)and to the measurement noise. As expected the PIC yields somemore uncertainty due to its lesser precision of the analog to digitalconverters (10 bits, instead of the 12 bits in the NI acquisition board).Nevertheless, it should be pointed out that the difference between thetwo acquisition devices is less than 2% in both parameters,k0 andτ .

b) Optimal curve fitting -:The goal of this optimization isto find the time constant and the DC gain simultaneously so that thetheoretical model (Eq.5) fits as well as possible the measurements.The cost function used in our optimization algorithm is simply asquared distance:

(k0, τ)∗ = argk0,τ min

N∑

i=1

(

ω(ti) − vsk0(1 − e−ti/τ ))2

(8)

The non-linear optimization is done in our case with the Matlabfunction fminsearch that finds the minimum of a scalar functionof several variables, starting at an initial estimate.

Figure 8 and table II show estimates ofτ and k0 using bothacquisition devices. The estimates are noisier than the ones ofthe previous section due to the non-existence of a data selectionmechanism for removing samples not so precisely timed (timing doneby the PC) or noisier due to the analog to digital conversion process(remember thatτ in the previous section is estimated from the central,more precise measurements). The offset of about 1ms between theτ estimates obtained using both devices is justified mainly by the

timing imprecision at the PC. Note that the USB has itself a timingschedule that imposes some significant timing discretization errors.

Overall, table II shows that the NI PCI-6221 allows to obtainslightly smaller variances in the estimates. However one importantobservation is that the measurement of the DC motor parametersusing the PIC is reliable enough for many applications and a muchcheaper solution.

3.9 4 4.1 4.2

24

26

28

30

32

Tau

[mse

c] v

s k

0

3.9 4 4.1 4.2

24

26

28

30

32

(a) (b)

Fig. 8. Time constantτ vs DC gainK0 estimated using the optimizationprocedure Eq.8 based on the PIC (a) or on the NI board (b) data.The redcircle denotes the medianτ andk0 in the 200 experiments.

device PIC NI PCI-6221k0 mean 4.033 4.010k0 std 0.0311 0.0241

τ mean [msec] 28.87 27.66τ std 0.6049 0.4301

TABLE II

k0 AND τ COMPARISON ESTIMATED USING BOTH DEVICES.

D. Bode diagram

The Bode diagram provides information about the relationshipbetween the input and output of any system whose input can beset to a sine wave and whose output can be measured.

In order to build a didactic experiment concerning the acquisitionof a Bode diagram, we consider again the RC series of section IV-B,and use the DLP module and the DAC to generate a wave signalas input of the RC circuit, and acquiring both input and outputsimultaneously. Figure 9 shows both devices connected to the RCcircuit, generating the input signal wave at the DAC pin and acquiringtwo voltage’s through two ADC pins of the DLP module.

Fig. 9. Setup to obtain the Bode Diagram of an RC series circuit.

Although there is a simple model for the RC series, the goalhere is to vary the signal wave frequency so that we can measurethe magnitude gain and phase delay between input and output. Let

Vs(t) = A sin(ωt)+A, with ω the frequency inrad/sec, A the sineamplitude, andVc(t) the capacitors voltage in steady state (forcedsine-wave response). Then, the frequency response,H(jω) can beestimated in its magnitude component with:

|H(jω)|dB = 20 log10

(

max(Vc(t)) − min(Vc(t))

max(Vs(t)) − min(Vs(t))

)

and the phase component can be estimated from:

6 H(jω) = (ts − tc) × ω ×180o

2π

where ts and tc are time measurements for one correspondingmaximum of the input,Vs(t) and the output,Vc(t).

0 500 1000 1500 2000 2500 3000 3500 40000

0.5

1

1.5

2

2.5

3

3.5

4

4.5Entrada e saída de um circuito RC

Amostras

Ten

são

[V]

0 500 1000 1500 2000 2500 3000 3500 40000

0.5

1

1.5

2

2.5

3

3.5

4

4.5Entrada e saída de um circuito RC

Amostras

Ten

são

[V]

Fig. 10. Input and output of a RC circuit in response to a wave signal.

Figure 10 shows the input (blue) and output (red) voltage of the RCcircuit at 10Hz and 100Hz frequencies. We took several samples atdifferent frequencies and obtained the Bode diagram (figure 11). Themagnitude plot shows two functions, in blue we have the measureddata points and in green the curve fitting function that best fits to theseries of data points. The model used for the curve fitting functionis the frequency response of a first order system with unit gain:

H(jω) =ωc

jω + ωc

The cost function used in our optimization algorithm is:

ω∗c = argωc

min∑

i

(

|H(jωi)| −

∣

∣

∣

∣

ωc

jωi + ωc

∣

∣

∣

∣

)

2

. (9)

10−1

100

101

102

103

−30

−25

−20

−15

−10

−5

0

Bode Diagram

Frequency (rad/seg)

Mag

nitu

de (

dB)

10−1

100

101

102

103

−120

−100

−80

−60

−40

−20

0

20

Frequency (rad/seg)

Pha

se A

ngle

(º)

Fig. 11. Bode plot: phase angle(down), Magnitude of experimental sam-ples(blue) and its curve fitting curve(green) (up).

The experiment was conducted with a capacitor,C = 1µF , anda 100kΩ resistor. The cut-off frequency (at -3dB) observed in theBode diagram is about10 rad/sec. Using the curve fitting procedure ofequation 9, through the Matlab functionfminsearch, the estimatedcut-off frequency is10.44 rad/sec.

Considering that the cut-off frequency,ωc and the time constant,τ of the RC circuit have an inverse relationship:

ωc =1

τ=

1

RC

one observes that the estimated cut-off frequency has an error lessthan 5% w.r.t. the nominal cut-off frequency,ωc,nom = 1/τnom =1/(1µ × 100k) = 10rad/sec i.e. the inverse of the nominal timeconstant,τnom computed from the nominal values of the components.Noting that C = 1

ωcR, one obtains an estimate ofC, closely

matching the estimation in section IV-B. These show that the EKiteffectively allows conducting didactic experiments with dynamicsystems, in particular presenting the concepts, and estimating thevalues, of time constants and cut-off frequencies. The accuracyof the estimations allows specially to explore the time-frequencyrelationships so important in EEC.

V. CONCLUSIONS ANDFUTURE WORK

With the self-learning processes imposed by Bolonha the develop-ment of cheap and accessible tools for EEC students autonomouslylearn and experiment circuit analysis is a priority. The Ekit wasdeveloped with the DLP-2232PB-G USB Adapter and the MCP4822DAC but with generic SW programming it can be used with severalUSB data acquisition devices. The potential of these microcontrollersalong with their low cost make them a powerful and essential toolfor EEC students. The experiments conducted in this paper providefirst year students an experimental glance at electronic circuits.

Future experiments like filter identification, systems control (dig-ital displays or servomechanisms), can be accomplished with thesedevices allowing them to be useful for a wider range of EEC classes.The Ekit implemented with the PIC is an excellent and above of allcheap solution for signal generation and data acquisition. It providesquick learning processes and incentives future applications as well asadvanced signal processing and system control studies.

REFERENCES

[1] Univ. Aveiro. Robotica2008 8th portuguese robotics open. http://robotica.ua.pt/robotica2008/index-en.htm, 2008.

[2] European Commision. The bologna process towards the european highereducation area.http://ec.europa.eu/education/policies/educ/bologna/bologna_en.html, 2007.

[3] Future Technology Devices International. Dlp design - dlp-2232pb-g.http://www.ftdichip.com/Products/EvaluationKits/DIPModules.htm#DLP-2232PB-G, 2007.

[4] Future Technology Devices International. Ft2232d - dual usb uart/fifo ic.http://www.ftdichip.com/Products/FT2232C.htm, 2007.

[5] J. David Irwin. Basic Enginering Circuit Analysis. J.Wiley, 7th editionedition, 2002.

[6] Microchip. Pic16f87xa microcontroller.http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010242,2003.

[7] Microchip. Mcp4822 12-bit dacs with internal vref and spi inter-face. http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en024016, 2005.

[8] P. Ruffio. Changing the university: The supporting role of the erasmusthematic networks (a three-year perspective). Technical report, EuropeanUnion: Eucen, Brussels, Belgium, Jan. 2000.

[9] Moodle team. Moodle - a free, open source course management systemfor online learning.http://moodle.org/, 2008.