EC312 Twelve Week Exam Spring 20 21 April 2, 2021 United States Naval .

EC312 Twelve Week Exam Spring 2021April 2, 2021United States Naval AcademyElectrical and Computer Engineering DepartmentEC312 - 12 Week Midterm – Spring 20211.2.3.4.5.6.Do a page check: you should have 6 pages including this cover sheet.You have 50 minutes to complete this exam.An FE-approved calculator may be used for this exam. Calculators may not be shared.This is a closed book and closed notes exam. You may use two single-sided hand-written pages of notes.Turn in your two single-sided hand-written pages of notes with your exam.This exam may be given as a makeup exam to several midshipmen at a later time. No communication ispermitted concerning this exam with anyone who has not yet taken the exam.Name:SOLUTIONSInstructor:Page 1 of 6

EC312 Twelve Week Exam Spring 2021April 2, 2021The following diagram and tables will be used for the questions on CAN.Question 1. The CAN network diagram above shows four Micromods connected to a CAN bus. Nodes 1 and 2can each drive a motor (max speed 5000 RPM) using PWM output 0. (Assume an appropriate motor driver isused.) Nodes 3 and 4 can each control a 7-segment display using their Digital Out pins do0, do1, do7. Thedisplays are active high (i.e. logic 1 causes a segment to light up) and are wired as shown below. Note that d0 isalways 0. (For example, an input ofwould cause the display to depict the decimal “3”.)For the PWM outputs, the digital-to-analog conversion factor (from decimal value toPWM percentage) is 100/255.For each of the following cases, determine what outcome would be observed. Youranswer should take the form “Motor turns at RPM” or “Displaylights up with decimal number ”. Show all work.a) (7 pts) A node transmits a CAN message with ID 0x203 and 1 byte of data 0x7F.0x203 0 0100 0000011, i.e. Type RPDO1 digital Output, Node 0000011, i.e. #3So this is a request to Node 3 to set its digital outputs to 0x7F, i.e. 011111111.This means that d01 through d07 are all set to 1 (on), i.e. Display #3 lights up with decimal number 8.Page 2 of 6

EC312 Twelve Week Exam Spring 2021April 2, 2021b) (7 pts) A node transmits a CAN message with ID 0x301 and 8 bytes of data 0x8000800080008000.0x301 0 0110 0000001, i.e. Type RPDO2 PWM out, Node 0000001, i.e. #1So this is a request to Node 1 to set its PWM outputs to particular levels specified by the 8 bytes of data.The 8 bytes correspond to the four PWM outputs, i.e. 0x8000 for each one.Correcting for Little Endian we have 0x0080, which converts to 128 in decimal.To get PWM value, we multiply by the conversion factor, i.e. 128*(100/255) 50.1% PWMSince the max speed of the motor is 5000 RPM (at 100% PWM), we’ll have 50.1%*5000 2509 RPMMotor #1 turns at 2509 RPMc) (7 pts) A node attempts to transmit the message from part (a) at exactly the same time that another nodeattempts to transmit the message from part (b).When two nodes attempt to transmit at the same time, we use the bus arbitration process with the message ID’s.0x203 0 0100 00000110x301 0 0110 0000001Message 0x203 takes priority because the 0 beats the 1 in the bolded position. (We can also see this just by thefact that RPDO1 is higher than RPDO2 on the table.)Therefore, Display #3 lights up with decimal number 8d) (7 pts) The following binary sequence (which DOES include STUFF BITS) is observed on the CAN bus: 1111111 First we must identify and remove stuff bits, which are the bit immediately following any series of 5 bits of thesame type. These stuff bits are identified in bold in the sequence above. If we remove the stuff bits, we have thefollowing: 111 0 01000000100 000 0001 01011011 1011010001001010 1 1 1111111 SOFMSG IDDLCDataCRCEOFDecoding the message ID, this is type 0100 (i.e. RPDO1 Digital Output) intended for node 0000100, i.e.node #4. The DLC indicates that we have one byte of data, and the data field is 01011011. Since DigitalOut means we’re lighting up the 7-Segment Display #4, our data field tells us which light segments areon or off. Since only d02 and d05 are off, this would look like decimal #5.Display #4 lights up with decimal number 5.Question 2. (8 pts) Suppose a malicious node wants to use a Denial-of-Service (DOS) attack to flood the buswith messages to prevent other nodes from controlling the motors or 7-segment displays in the CAN networkfrom question 1. Which of the following COMM Object types could the malicious node use for a successful DOSattack? (Circle all that apply.)EMERGENCYRPDO3TPDO1TPDO2HEARTBEATNeed to choose messages that are higher priority than RPDO1 and RPDO2.Page 3 of 6

EC312 Twelve Week Exam Spring 2021April 2, 2021Question 3. A two-bit binary multiplier takes two 2-bit inputs and produces the 4-bit output which is the productof the two inputs. Let the first input be 𝐴𝐴0 𝐴𝐴1 and the second input be 𝐵𝐵0 𝐵𝐵1, with the output denoted as 𝑃𝑃0 𝑃𝑃1 𝑃𝑃2 𝑃𝑃3 .As an example, if 𝐴𝐴0 𝐴𝐴1 10 (decimal 2) and 𝐵𝐵0 𝐵𝐵1 11 (decimal 3), the output should be 𝑃𝑃0 𝑃𝑃1 𝑃𝑃2 𝑃𝑃3 0110(i.e. decimal 6, which is 2 3).a) (10 pts) Complete the corresponding truth table shown 11011111001b) (5 pts) Write out the Boolean expression for output 𝑃𝑃0 .There is only one 1 in output column 𝑃𝑃0 , corresponding to all inputs being 1. Therefore our expressionis:𝑷𝑷𝟎𝟎 𝑨𝑨𝟎𝟎 𝑨𝑨𝟏𝟏 𝑩𝑩𝟎𝟎 𝑩𝑩𝟏𝟏c) (5 pts) Draw a logic circuit to implement output 𝑃𝑃0 .Could also use a four-input AND gate.Page 4 of 6

EC312 Twelve Week Exam Spring 2021April 2, 2021Question 4. (10 pts) Fill out the truth table for the transistor circuit shown here, and determine what type of logicfunction it implements.VIN,XVIN,YVOUT000010100111Logic Function:ANDQuestion 5.a) (8 pts) A signal 𝑣𝑣𝑖𝑖𝑖𝑖 (𝑡𝑡) 2 sin(2𝜋𝜋50𝑡𝑡) 4 sin(2𝜋𝜋300𝑡𝑡) 3 sin(2𝜋𝜋10𝑡𝑡) 7 sin(2𝜋𝜋175𝑡𝑡) is the inputto an ideal low-pass filter with cutoff frequency 𝑓𝑓𝑐𝑐𝑐𝑐 150 𝐻𝐻𝐻𝐻. Determine the time-domain equation forthe output signal 𝑣𝑣𝑜𝑜𝑜𝑜𝑜𝑜 (𝑡𝑡). (Assume the filter doesn’t introduce any phase shift.)𝒗𝒗𝒐𝒐𝒐𝒐𝒐𝒐 (𝒕𝒕) 𝟐𝟐 ���𝟐𝟐𝟐) 𝟑𝟑 ���𝝅𝝅𝝅)(The two other sine waves are cut off because their frequencies are above the cutoff.)b) (8 pts) The periodic sawtooth wave in the figure tothe right is the input to an ideal low-pass filter withcutoff frequency 𝑓𝑓𝑐𝑐𝑐𝑐 150 𝐻𝐻𝐻𝐻. Circle which oneof the following could be the time-domain equationfor the output signal 𝑣𝑣𝑜𝑜𝑜𝑜𝑜𝑜 (𝑡𝑡).a. 𝑣𝑣𝑜𝑜𝑜𝑜𝑜𝑜 (𝑡𝑡) cos(2𝜋𝜋100𝑡𝑡) cos(2𝜋𝜋200𝑡𝑡)b. 𝒗𝒗𝒐𝒐𝒐𝒐𝒐𝒐 (𝒕𝒕) ���𝟐𝟐𝟐𝟐𝟐)c. 𝑣𝑣𝑜𝑜𝑜𝑜𝑜𝑜 (𝑡𝑡) cos(2𝜋𝜋200𝑡𝑡) cos(2𝜋𝜋400𝑡𝑡)d. 𝑣𝑣𝑜𝑜𝑜𝑜𝑜𝑜 (𝑡𝑡) cos(2𝜋𝜋150𝑡𝑡)1.5vin(t)10.50-0.5-1First note that the triangle wave has period T 0.011seconds, i.e. frequency 𝑓𝑓0 0.01 100 𝐻𝐻𝐻𝐻. Since it is aTime (s)periodic signal, the frequency domain graph would have“spikes” at 𝑓𝑓0 and at integer multiples of 𝑓𝑓0 (i.e. harmonics). But the first possible harmonic is 2𝑓𝑓0 200 𝐻𝐻𝐻𝐻,which is above the cutoff frequency, so only 𝑓𝑓0 would make it through the filter. Therefore our output must be asinusoid with frequency 100 .05Page 5 of 6

EC312 Twelve Week Exam Spring 2021April 2, 2021Question 6. The frequency domain plot below shows signals received by an AM radio receiver. As depicted,there are two different AM signals that are being transmitted from different stations.a) (6 pts) What is the carrier frequency (𝑓𝑓𝑐𝑐 )and the baseband frequency (𝑓𝑓𝑚𝑚 ) forsignal 1?𝑓𝑓𝑐𝑐 3 𝑘𝑘𝑘𝑘𝑧𝑧𝑓𝑓𝑚𝑚 3.2 𝑘𝑘𝑘𝑘𝑘𝑘 3 𝑘𝑘𝑘𝑘𝑘𝑘 0.2 𝑘𝑘𝑘𝑘𝑘𝑘 (𝑖𝑖. 𝑒𝑒. 200 𝐻𝐻𝐻𝐻)b) (6 pts) What is the carrier frequency (𝑓𝑓𝑐𝑐 )and the baseband frequency (𝑓𝑓𝑚𝑚 ) forsignal 2?𝑓𝑓𝑐𝑐 5 𝑘𝑘𝑘𝑘𝑧𝑧𝑓𝑓𝑚𝑚 5.44 𝑘𝑘𝑘𝑘𝑘𝑘 5 𝑘𝑘𝑘𝑘𝑘𝑘 0.44 𝑘𝑘𝑘𝑘𝑘𝑘 (𝑖𝑖. 𝑒𝑒. 440 𝐻𝐻𝐻𝐻)c) (6 pts) Propose a solution using an ideal filter that would allow you to tune out (i.e. attenuate) signal 1 andonly receive signal 2. Make sure to specify any cutoff frequencies.There are several different options that would work:- Band-pass filter with lower cutoff frequency between 3.2 kHz and 4.56 kHz, and upper frequency above5.44 kHz- High-pass filter with cutoff frequency between 3.2 kHz and 4.56 kHz- Band-reject filter with lower cutoff frequency between 0 kHz and 2.8 kHz, and upper cutoff frequencybetween 3.2 kHz and 4.56 kHzHONOR STATEMENT: Please write out and sign the following statement: “I have neither given norreceived unauthorized assistance on this exam.”Signed:Page 6 of 6

2. You have 50 minutes to complete this exam. 3. An FE-approved calculator may be used for this exam. Calculators may not be shared. 4. This is a closed book and closed note s exam. You may use two single-sided hand-written page s of notes. 5. Turn in your two single-sided hand-written pages of notes with your exam. 6.