# ECET 340 Week 7 HomeWork 7

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1. The movable part of the solenoid is the: +2 points

2. Why is the 6N139 optoisolator used in the interfaces to devices such as large motors? +2 points

3. Calculate the number of steps per revolution for a stepper motor with a step angle of 7.5°. +2 points

4. How is stepper motor speed controlled? State any two ways a program can do this. +2 points

5. For this problem, you should look at Figure 5A on the next page as a physical example of a stepper motor. It is an example of a stepper motor with four (4) magnetic windings which are connected via an interface circuit to the HCS12 Port T pins 4, 5, 6, & 7, with an armature (rotor) that has 12 poles (combined number of North and South magnetic poles). Notice how each step rotates the rotor 30 degrees, and notice the logic states on the Port T pins going from Step 1 to Step 2. To rotate the rotor 90 degrees, you would need three (3) steps (see figure 5A for explanation).

6. Identify 2 major kinds of devices that can be used to interface a dc motor to the HCS12. +2 points

7. Given that pulses need to be delivered to a specific dc motor at the rate of 12.5 kHz to avoid vibration, write down the C statements needed to output pulses from the HCS12 to drive the at 80% of its full drive level. +2 points

8. An HCS12 timer input capture/output compare register (TC0) holds the value 0×498 when timing the period between pulses coming in from a servomotor’s optical encoder (see Figure 8A below for setup of optical encoder). Assume the counter/timer is operating at 1.0us. The encoder wheel has 6 holes. Find the motor’s speed in RPM. Show work. +2 points

9. Unidirectional dc motors often have high-voltage diode connected for reverse-bias across the motor’s input terminals. Explain why this is done. +2 points

10. What advantages do dc motors offer over stepper motors? +2 points

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# ECET 340 Week 6 HomeWork 6

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1. What are the four main functions of the HC12 Timer unit?

2. Two input capture events occur at counts 0×1037 and 0xFF20 of the free-running counter. How many counts (in decimal) have transpired between these two events?

3. What is the maximum time possible before the free-running counter overflows when the e MHz?

4. Two input capture events occur at 0×1037 and 0x002A. If the prescaler bits PR[2:1:0] are set to 101 and the e clock is 24 MHz, how much time as transpired between the two events?

5. Calculate the count that should appear in the timer capture register TC0 if a 125 kHz rectangular wave is inputted on timer pin PT0 while TCTL4 is preset for falling edge detection. Assume a 24 MHz e-clock, TMSK2 was programmed with the value \$02, and the count of the 1st edge event has already been subtracted off from TC0.

6. Write down the name of the HC12 timer register that should be polled through software to determine whether or not an active input edge has been captured on one of the port T pins.

7. What is the duty cycle of a signal produced by the PWM when and ?

a. 28.0% b. 29.8% c. 50.0% d. 72.0%

8. What values are required for period and duty cycle to generate a 6.0 kHz, 95% duty cycle waveform using the PWM function? Assume e-clock frequency is 24 MHz.

9. What is the slowest clock signal that can be generated from the PWM output using the 16-bit counter mode with pre-scaling and scaling? Assume e-clock frequency is 24 MHz.

10. Write down the C statements needed to program PWM channel 0 to output a 12.5 kHz left-aligned wave with 30% duty cycle. Assume e-clock frequency is 24 MHz.

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# ECET 340 Week 5 iLab 5

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Scenario/Summary
This week’s lab covers two areas, conversion of digital HCS12 signals to an analog format, and the use of a Serial Peripheral Interface (SPI) to transfer data, and commands between the HCS12, and the DAC peripheral. Deliverables For this lab, the deliverables include the cover sheet, filled-in sections of the lab report, photographs (online), or instructor sign-offs (onsite), and answers to the questions. The cover sheet must be completed in typed format.

STEP 2: Predict the Results of Waveform Generation Program Study the 340_lab5_1 program and predict the performance, and outputs of the code. Answer the questions in Part A, Step 2.

STEP 3: Run the Waveform Generation  Program  Use the 340_lab5_1 program to load the Dragon12 board and verify  the operation. Photograph your circuit with an oscilloscope attached (online), or obtain your instructor’s sign-off (onsite).

STEP 4: Design Project Modify the software to produce, either a square wave, or sawtooth wave based on user input. Photograph your circuit with an oscilloscope attached to show both waveforms (online), or obtain your instructor’s sign-off (onsite).

STEP 5: Answer the Questions There are two questions that must be answered in this lab.

STEP 6: Complete the Cover Sheet, Type the required information onto the cover sheet.

STEP 7: Submit Your Deliverables  See Syllabus/Due Dates for Assignments & Exams for due date
information.

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# ECET 340 Week 5 HomeWork 5

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1. Explain, briefly, why an analog restoring filter is sometimes used at the output of a DAC.

2. Given Iref = 2 mA for a DAC1408 IC, find Iout for the input 1110 1110

3. Find the number of discrete voltages output by a 12-bit DAC. Show work.

4. Use the internet to locate the data sheet for an MC1408 DAC. From it find, for the MC1408-7 version, the following:

a. The settling time

b. Accuracy at full scale output current (1.99 mA), 25ºC

c. Output current range when -7V <vee=””>< -15v=”” is=”” used.=””>

5. Assume that an MC1408 DAC is attached to Port T of an HC12 Microprocessor as shown below. Verify that the program below outputs 8 different values to the DAC and determine the output voltage (Vout) after each output operation. Show your work in the space below

6. How does the SCI system achieve synchronization between the transmitter and receiver?

7. The SCI1 serial port is initialized for 8 data bits, 1 stop bit and 2400 baud. How much time is required to data transfer 3000 characters?

8. Why is the maximum data rate of the SPI system faster than the SCI system?

9. Discuss the advantages and disadvantages of the SCI versus SPI data transfers.

10. Provide the C language code to set the SPI to the lowest frequency.

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# ECET 340 Week 4 iLab 4

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OBJECTIVES:

To learn how to use A-to-D converters to digitize signals from analog input devices.

To learn how to write a C language program that samples the data from an analog device, digitizes it and formats it for output on an LCD.

To become more proficient in programming displays for real-time operation.

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# ECET 340 Week 4 Homework 4

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1. Determine the conversion time for an ADC0804 (8-bit), where 66 clocks per bit are required, if its clock frequency is 50 kHz.

2. If an 8-bit SAR has Vref = 10 V, what is the binary value for an input voltage of 7.28 V?

3. What is the percent error for the binary answer found in Problem #2?

4. Given an 24 MHz bus speed. Write down the line(s) of instruction which set the ATD1 unit for 2MHz conversion frequency, 10-bit resolution and 8 A-to-D clocks per sample time.

5. A single 10-bit, left justified conversion of 3.75V is complete in ATD0. Assume and

i. Name the register(s) where the result of the conversion is found

ii. What are the values in each of the 16-bits of this register after conversion is complete? Assume the result is unsigned. Show work

6. Assume that a position-sensitive potentiometer can measure up to 25 cm over a voltage range of 0 to 5 V. If an 8-bit ADC outputs a value of 0111 1010, what is the distance measured?

7. Design the basic interface circuit (using an op amp) for a temperature sensor that covers a range of 0° to 70°C if the output of the sensor is 2 mV/1°C and the ADC voltage range is 0 to 4 V.

8. Design an amplifier suitable for converting the output voltage from an LM35 temperature sensor (10 mV/°C) into a signal that makes use of the full input voltage range (0-5V) of the HCS12 ADC port pins. Assume the LM35 is to measure temperatures from 0°C up to +150°C. Show work and circuit!

9. Given a sensor with W that outputs voltage in the range +1.25V to +4.25V. Show the complete interface circuitry needed to connect it to the A/D unit built-in to the HC12 Controller.

10. Write the lines of C code needed to configure the A/D converter, start the conversion, and output a hex integer in the range 0×0000 to 0xFFFF to the variable called data1 that is proportional to airflow input (0.0 to 1.0 litre/min). No further conversion is required

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# ECET 340 Week 3 iLab 3

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OBJECTIVES:

To learn the basic operation of a keypad.

To understand how to interface a keypad to a microprocessor.

To learn how to program a keypad driver in C language.

To learn how to program a keypad activated interrupt that identifies the key being pressed and displays or otherwise returns its value to the main program.

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# ECET 340 Week 3 HomeWork 3

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1. Sketch a circuit that can be used to debounce a pushbutton and explain how it works. (4 points max)

2. In Figure 7.32 on page 339 of the Huang textbook, if the row has and the columnsare , which key is pressed? (2 points max)

3. In Figure 7.32 on page 339 of the Huang textbook, explain why the 10kΩ resistors ties to VCC are required. (2 points max)

4. Write down the lines of C code (interrupt service routine, ISR) that generates an interrupt when Port H pin 0 becomes a logic “1”. Within this ISR, disable interrupts, clear the interrupt flag, then enable interrupts, and return from routine. I also want the routine or lines of C code that initialize Port H pin 0 to be used as an interrupt (hint: think data direction register) (2 points max)

5. Write down the C statements you would need to add to the main program of the keypad driver program given in lecture and lab in order to store the key characters to a buffer area of memory called keys_entered and exit the program as soon as either seven keypresses are entered or the the “D” key is entered. (Counts as two questions) (4 points max….you need to use arrays in C code)

6. State the functions of pins RS, E and R/W in the LCD. (4 points max)

7. Give the state of RS, E and R/W~, and the command code (in hex) for the 20th location, line 2 on the 40×2 LCD described in lecture. (2 points max)

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