ECE3720 Prelabs

1Clemson ECE Laboratories

ECE 372 – Microcomputer Interfacing Laboratory

Pre-labs for ECE 372Created by Ryan Mattfeld 12/17/12

Last Updated:12/17/12


ORIENTATION


Instructor Information and Syllabus

• Instructor Name: Nilim Sarma• Email: [email protected]• Office Hours: Email to set up appointment.• Lab Manual can be found at

http://www.clemson.edu/ces/departments/ece/resources/lab_manuals.html




Introduction

Objective:• Gain a better understanding of the functionality of a

microcontroller.• Learn to interface devices with different modules on a

microcontroller.

Experiments:10 experiments involving various modules and a final

design project.


Final Design Project

• Will combine at least two of the labs performed throughout the semester in a creative way

• Worth 30% of final grade• Weekly Lab Reports for reference when making final

design• Final lab report will be given on final design project


Equipments

• The National Instruments ELVIS system .

• Freescale MCU Project Board Student Learning Kit – Prototyping board with microcontroller interface.

• Microcontroller - Freescale HCS12 Family, model MC9S12DT256.





CodeWarrior IDE.

• Text Editor for writing code.• Cross compiler to generate executables.• Loader program to load the executable on the

microcontroller.• Debugger to perform runtime debugging.

Software Development Environment.


Prerequisite

• Familiarity with C programming language.

• C tutorial available in lab manual.


Freescale Board Connector J1


Mandatory Safety Video


LABORATORY 1 – INTRODUCTION TO THE MC9S12DP256B


Laboratory 1 Program

• Program will count from 1-16 in binary using LEDs and in decimal using the LCD display.

• Download the program from our section on Blackboard under the “information” section

• Extract the program to your student (U:) drive• Open the “Lab 1” folder and open the .mpc file to edit

the program• Take a few minutes to read the code and figure out

what it should do


Laboratory 1 Program

• Make sure to turn on both power switches on the NI-ELVIS board and connect the USB cables

• Attempt to compile the code (ctrl+F7 is keyboard shortcut)

• Identify and fix the error• Hit the “debug” button (green arrow with helicopter)• Run the code and see the result• Modify the code to count backwards


Final Reminders!

• Store each lab as a separate file on your student server (copying an old lab folder and renaming it for new labs)

• This ensures all necessary files are linked and provides your access to your previous lab code when you begin your final design project.

• You can also access your student drive from any computer with internet access at:

• https://netstorage.clemson.edu/• Read over Lab 2 in the lab manual to be prepared for

next week!

https://netstorage.clemson.edu/


LABORATORY 2 – READING AND WRITING USING RAM


Device Memory Map

$0000 - $03FF – Registers.$0000 - $0FFF – 4K Bytes EEPROM.$1000 - $3FFF – 12K Bytes RAM.External Memory$FF00 - $FFFF – Vectors.

After reset the bottom 1k of the EEPROM ($0000 - $03FF) are hidden by the register space.

Refer to MC9S12DT256 Device User Guide.


Laboratory 2 Preparation

• Find the folder for Lab 1 that you used last week (stored on your student drive)

• Copy the folder and rename it for Lab 2• Open the .mpc file to edit and compile your code• In main.c, leave the header files and #pragma

statement, but delete all code in void main(void)• We will define a command to read and write to the

RAM of our microprocessor• ** We will begin writing at reading at memory

location ***insert location here***


Laboratory 2 Code

• We will create an easy method to access specific RAM memory addresses by using a #define statement

• #define _P(ADDRESS) *(unsigned char volatile *)(ADDRESS)

• This command will allow you to both read and write to a specific address in RAM.

• Conceptually, in your program, you can use • _P(**desired memory address**)• Like you would use a variable to store and use

information.


Laboratory 2 Code

• Program goal: Write **** insert phrase here **** to RAM, then read from RAM to the LCD

• At the beginning of your program, make sure you initialize the LCD using “LCDInit()”

• Then, make sure that after every 8 characters you clear the LCD using “LCDClearDisplay()”

• You can write to the LCD using the command “LCDPutChar()”

• Use loops to write the phrase• Use conditional statement to clear display


Preparations for Next Week

• Before next lab, read over Lab 3 in your lab manual, Application of a Digital Latch.


LABORATORY 3 – APPLICATION OF A DIGITAL LATCH


Lab 3 Preparation

• Find the folder for Lab 2 that you used last week (stored on your student drive)

• Copy the folder and rename it for Lab 3• Open the .mpc file to edit and compile your code• This lab combines hardware with software• Uses 74LS374 Flip-Flop chip (D Flip-Flop)


74LS374 – D Flip Flop

• Latch data from Input Pin to Output Pin when there is a rising edge on Clock Pin.


Laboratory 3 - Hardware Prep

• The Input, 1D corresponds to the output, 1Q. Reference chip diagram:

• Input: Switches (SW1 1 and SW1 2)• Output: LEDs (LED 1 and 2)• Intermediate Output (Port B LEDs) (Port B is hardwired to 4 LEDs)• Wire SW1 1 to 1D, SW1 2 to 2D• Wire 1Q to LED 1, 2Q to LED 2


Laboratory 3 – Microcontroller Comm.

• Must wire inputs to microcontroller to manipulate input with code.

• Wire SW 1 to PTT 0 (reference page 50 in lab manual for Port wiring table)

• Wire SW 2 to PTT 1• Clock Pulse Input: Pushbutton (PB1) to Port M 1• Clock Pulse Output: Port M 0 to clock of Flip-Flop

• Wiring complete!


Laboratory 3 – Software Prep

• To use input and output registers on the microcontroller, must designate them for input or output in code.

• DDR – Data Direction Register (0 for input, 1 for output)

• Will use Port T, channels 0 and 1 for input, so we will set DDRT = 0x00;

• Will use LEDs hard wired to Port B for output. • LEDs wired to Port B channels 4-7, set DDRB=0xF0;• Will use Port M channel 0 as input and Port M

channel 1 as output, set DDRM = 0x01


Laboratory 3 – Main Function

• Constantly loop, looking for switch input. Port T 0 and Port T 1 will change between 00, 01, 10, 11 based on switch configuration.

• For each possible state of Port T, light corresponding LEDs (set Port B to appropriate values)(HINT: Port B 4-7 are wired to LOW active LEDs)

• Finally, must generate clock pulse for D Flip-Flop• Check if Port M channel 1 is 0 (Push Buttons are low

active). If it is, generate clock pulse on Port M channel 0. (Set PTM = 0x01 then reset it to 0x00)


Result

• When complete, should have two displays:• 1) When you flip one of the switches, the LEDs hard

wired to Port B should immediately change• 2) When you push Pushbutton 1, the switch values

will travel through the Flip-Flop, and light the LEDs you wired your outputs to.


Flowchart



• Before next lab, read over Lab 5 in your lab manual, Keypad Interfacing


LABORATORY 5 – KEYPAD INTERFACING


Laboratory 5 Hardware Prep

• Plug in Keypads with brass side of connector facing left

• Keypad 1 Port T 1• Keypad 2 Port T 2• Keypad 3 Port T 5• Keypad 4 Port T 3• Keypad 5 Port T 6• Keypad 6 Port T 7• Keypad 7 Port T 4• Keypad 8 Port T 0


Keypad Description/Operation


Laboratory 5 software prep

• Set Port T channels 0-3 as output and channels 4-7 as input using DDRT

• New registers: PERx (Pull Enable Register) and PPSx(Polarity select Register)

• PER and PPS work together to pull desired ports either high or low.

• Pull Port T channels 4-7 high.• Enable Port T channels 4-7 for pulling(PERT = 0xF0)• Pull Port T channels 4-7 high (PPST = 0x00)

(setting PPST to 0 pulls corresponding channel high)


Laboratory 5 Software Tools

• Arrays can make keyboard interfacing easier:• unsigned char mask[16]={0xEE,0xDE,0xBE,0x7E,

0xED,0xDD,0xBD,0x7D,

0xEB,0xDB,0xBB,0x7B,

0xE7,0xD7,0xB7,0x77};• unsigned char key[16]={'D','1','2','3', 'A','4','5','6', 'B','7','8','9',

'C','*','0','#'};


Laboratory 5 Code Flow Chart

START INITIALIZE (proper header files, declarations, and definition) INITIALIZE PORT T

TURN ON 1 ROW AT A TIME

SEND THE PRESSED KEY TO THE LCD DISPLAY

DETERMINE IF A SPECIFIED COLUMN IS ACTIVE IN THE

ACTIVE ROW

No

Yes



• Before next lab, read over Lab 4 in your lab manual, Interrupts


LABORATORY 4 – INTERRUPTS


Laboratory 4 Wiring Diagram

Port P 0

Port P 1

Gnd

+5V


Laboratory 4 Software Prep

• INPUTS• Port P 0 and 1 should be used as interrupts• Port P generates interrupt vector 56 (reference lab

manual page 51 for vector interrupt table)• Registers: • DDRP = 0x00; (interrupts are inputs)• PERP = 0x03; (Enable pulling for interrupt channels)• PPSP = 0x03; (Pull low so high active button will trip

interrupt)• PIEP (Port Interrupt Enable Register) = 0x03; (This

enables Port P 0 and 1 as interrupts)



• OUTPUTS• LEDs hard wired to Port B will be outputs• DDRB = 0xF0; (Channels 4-7 are wired to the LEDs

so they should be outputs)• LCD will constantly count from 0-9• LCDInit();• LCDClearDisplay();



• LOGIC• Constantly loop to count from 0-9 on the LCD

display• Create interrupt function (using interrupt 56, the

interrupt vector corresponding to Port P)– Check PIFP to see which interrupt was triggered– Light LEDs to reflect which interrupt was

triggered– Reset Port P flags by setting the PIF(Port Interrupt

Flag) register to a 1 for each channel you want to reset


Laboratory 4 Code Flow Chart



• Before next lab, read over Lab 7 in your lab manual, Rotary Pulse Generator


LABORATORY 7 – ROTARY PULSE GENERATOR


Laboratory 7 Wiring Diagram

Port P 0

Port J 7

Rotary Pulse Generator



• INPUT• Port P 0 and Port J 7 are interrupts wired to Output A

and Output B• Rotate Right Increase position• Rotate Left Decrease position• Change in voltage produces

interrupt• Can determine which direction

Rotary Pulse Generator turnsbased on interrupt and state ofPort P 0, Port J 7



• INPUT• Interrupt Vector for Port P• Interrupt Vector for Port J• Two interrupt functions• Set Port P 0 and Port J 7 as

inputs• Set PERP and PERJ to enable

Port P 0 and Port J 7 for pulling



• OUTPUT• Port B LEDs will be used to show rotation in rotary

pulse generator• Set Port B 4-7 as output• Initialize Port B LEDs off (Low Active)



• LOGIC• Pulling registers high and low is essential• Interrupt trigger requires

voltage change• As pulse generator rotates,

voltage changes from low to high and high to low.

• Pull high if next voltage change is high low• Pull low if next voltage change is low high



• LOGIC• In each interrupt function:• Determine which position

the switch is in• Set LEDs to light such that

rotating right causes the LEDs to “scroll” up and rotating left causes the LEDs to “scroll” down


Laboratory 7 Flow Chart



• Before next lab, read over Lab 8 in your lab manual, Clock Pulse Generator


LABORATORY 8 – CLOCK PULSE GENERATOR


Laboratory 8 Hardware Preparation

• The buzzer is hardwired to Port T 0, so no wiring is required!

• (Quick note generation review)



• LOGIC• Introduction to the Enhanced Capture Timer• Input Capture• *Output Compare*• Enable ECT: TSCR1 (Timer System Control

Register 1) Bit 7 (Enable bit) set to 1• TIOS (Timer Input capture/Output compare Select)

Set to 1 for Output Compare



• LOGIC• Initialize: DDRT (Port T 0 is our output to the buzzer)• TCNT holds current clock time• TC1 holds our target clock time (when time is

reached, flag is tripped)• TFLG1_C1F is our flag• TFLG1 = TFLG1_C1F_MASK; resets timer flag• Invert voltage from Port T 0 when timer flag is

tripped• Allows control based on real time



• LOGIC• Initialize our target time (TC1) to the current time

(TCNT)• For a certain note length (quarter note, eighth note, etc)• Add the note’s period (in microseconds) to target time• Wait until timer flag is tripped• Invert signal to buzzer (through Port T 0)


Laboratory 8 Software Flow Chart



• Before next lab, read over Lab 11 in your lab manual, Pulse Width Modulation


LABORATORY 11 – PULSE WIDTH MODULATION


Laboratory 11 PWM Lab Description

• Pulse Width Modulation allows us to control the duty cycle of a signal

• Can be used to control motor rotation speeds• Using our board, we must amplify the current in order

to power our motor (current driver chip)• Control speed of our motor using interrupts to control

duty cycle• Display duty cycle on LCD


Laboratory 11 PWM Description


Laboratory 11 PWM Registers

• PWMEx – Pulse Width Modulation Enable• PWMPOLx – PWM Polarity Register (one for each

PWM channel, if 1 - starts high at each period, if 0 – starts low)

• PWMCLKx – PWM Clock Select Register (1- SA or SB, 2- A or B) --- Note: channels 0,1,4,5 use A/SA and channels 2,3,6,7 use B/SB

• PWMCAEx – PWM Center Align Enable Register (1- Center Aligned, 0- Left Aligned)


Laboratory 11 PWM Registers

• PWMPRCLK – PWM Prescale Clock Select Register (6-4 select prescaler for B, 2-0 select prescaler for A)

• PWMSCLA – PWM Scale A Register • (Clock SA = Clock A/(2*PWMSCLA))• PWMPERx – PWM Channel Period Registers• (PWMx Period = Channel Clock Period*(2*PWMPERx)• (HINT: bus clock = 25 MHz)


Laboratory 11 PWM Final Registers

• PWMDTYx = PWM Duty Register • If Polarity (PWMPOL) = 1, • Duty Cycle = (PWMDTYx/PWMPERx)*100• If Polarity (PWMPOL) = 0,• Duty Cycle = ((PWMPERx-PWMDTYx)/PWMPERx)*100


Laboratory 11 Hardware Preparation

• 62003 Current Amplifier• Wire GND to ground and Common to +5V• Output of current amplifier goes to the black motor wire• Red wire from motor goes to 3.3V on NI-ELVIS board• Wire PWM1 (pin can be located in chart on page 50 of

manual) tothe input ofcurrent amp


Laboratory 11 Software Preparation

• Initializations• Port P 1 (which corresponds to PWM 1) set to output• Port J 7 will be the interrupt used to control duty

cycle• PIEJ set to turn on Port J 7 as interrupt• PERJ, PPSJ set to pull Port J 7 to high voltage (push

buttons are low active)• EnableInterrupts;• LCDInit(); (will display motor duty cycle on LCD)


Laboratory 11 Software Goals

• When interrupt detected (pushbutton pressed)– Increment duty cycle by 25%– When duty passes 100%, reset it to 0%

• Display current duty cycle on LCD display



• Before next lab, read over Lab 6 in your lab manual, Serial Communications (SCI)


LABORATORY 6 – SERIAL COMMUNICATIONS (SCI)


Laboratory 6 Description

• Serial Communication Simulation (no communication with NI-ELVIS board at all)

• Will use simulation to read in keyboard entry, alter it in code, and send it back out to terminal

• Simulation can accurately simulate registers with proper set up.

• Create structures and definitions to make register simulation easier


Laboratory 6 Definitions

#define SCI_ADDR 0x00C8Typedef struct{

unsigned char SCIBDH;unsigned char SCIBDL;unsigned char SCICR1;unsigned char SCICR2;unsigned char SCISR1;unsigned char SCISR2;unsigned char SCIDRH;unsigned char SCIDRL;

} SCIStruct;#define SCI (*((SCIStruct*)(SCI_ADDR)))


Laboratory 6 Initializations

• SCIBDH and SCIBDL – SCI Baud Rate High and Baud Rate Low registers (used to set baud rate)

• SCI baud rate = SCI module clock/(16*BR)• BR = total of 12 bits from SCIBDH and SCIBDL:

0000 HHHH LLLL LLLL• Question: If module clock has speed of 8MHz, what

should SCIBDH and SCIBDL be to produce a target baud rate of 9600 Hz.


Laboratory 6 Initializations

• SCICR1 = 0x00• SCICR2 = 0x0C (sets transmitter enable bit (bit 3)

and receiver enable bit (bit 2))• SCISR1 is used to detect when data is sent and

received. • SCISR1 bit 7 Transmit Data Register Empty Flag• SCISR1 bit 5 Receive Data Register Full Flag• SCIDRH and SCIDRL store data for transmitting and

receiving. Because we set SCICR1 to 0x00, we only have 8 bits of data (SCIDRH is not used)


Laboratory 6 Software

• Create two functions, one to write to the terminal and one to read keyboard input:

• Char TERMIO_GetChar(void)– Wait until data received (using SCISR1)– Return received character (using SCIDRL)

• Void TERMIO_PutChar(char ch)– Wait until ready to transmit (using SCISR1)– Send character to terminal (using SCIDRL)

• In main, convert received character from lowercase to uppercase (use ASCII table)



• Before next lab, read over Lab 10 in your lab manual, A/D and D/A Conversion


LABORATORY 9/10 – A/D AND D/A CONVERSION


Laboratory 9/10 Description

• We will read in an analog signal from the function generator and read it into our microprocessor through a built in Analog to Digital Converter

• The ATD Converter converts the signal by sampling it at a specified rate and estimating the value by quantizing it

• We then send the digital signal out and use an external Digital to Analog converter to send the signal to the oscilloscope


Laboratory 9/10 Hardware Preparation


Laboratory 9/10 SPI Registers

• SPI (Serial Parallel Interface) allows communication with external devices (DTA converter, here)

• SPICR1 = 0x50; (Sets SPI Control Register 1 bits 6 and 4. Bit 6 enables SPI, Bit 4 sets SPI as master)

• SPICR2 = 0x0000; (disables a number of unneeded features)

• SPI1BR = 0x00; (SPI Baud Rate Register)


Laboratory 9/10 ATD Registers

• ATD0CTL2 = 0x80 (enables internal ATD converter)• ATD0CTL3 = 0x40 (Sets to take 8 conversions per

sequence)• ATD0CTL4 = 0x0000 (Sets 10 bit resolution and sets

sample rate as high as possible)


Laboratory 9/10 Software

• Port M channel 0 is used as a sync pin for the DTA converter chip. (Will be used as output)

• Set DDRM = 0x03;• Create main loop to constantly read in data, convert it

for writing, and then write it to the DTA converter.• While loop

– Prepare ATD for data • ATD0CTL5 = ATD0CTL5_DJM_MASK;

– Wait until data is read (Sequence Complete Flag)• While(ATD0STAT0_SCF == 0);

– Prepare and Send Data



• Preparing Data• Data Received as 10 bits from ATD

ATD0DR0H ATD0DR0L0000 00AB CDEF GHIJ

• Data Trasmitted through SCI as 12 bits, so desired output looks like this:0000 ABCD EFGH IJ00

• In order to maintain uppermost bits, must shift bits.<< (shift bits left) >> (shift bits right)& (binary AND) | (binary OR)



• Sending Datavolatile char temp;void write_dac(char upperbyte, char lowerbyte){ PTM = 0x00; SPI1DR = upperbyte & 0x0F; while(SPI1SR_SPTEF == 0); SPI1DR = lowerbyte; while(SPI1SR_SPTEF == 0); temp = SPI1SR; temp = SPI1DR; PTM = 0x03;}


Laboratory 9/10 Function Generator



• Next week begins Final Design Project week. It will help to prepare your code before working on your design project next week.


References

• Images provided from ECE 372 lab manual and user’s manual for MC9S12DT256 and from personal notes.


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ECE3720 Prelabs

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