EC7451: MICROPROCESSOR AND … V- Microcontroller...Dr. V. SATHIESH KUMAR Department of Electronics...

EC7451: MICROPROCESSOR AND MICROCONTROLLER

Dr. V. SATHIESH KUMAR Department of Electronics Engg., MIT 1

Presentation Slides:

www.sathieshkumar.com/tutorials

Unit V: MICROCONTROLLER BASED SYSTEM DESIGN 1. Interfacing to: matrix display 2. (16x2) LCD 3. High power devices 4. Optical motor shaft encoder 5. Stepper Motor 6. DC Motor speed Control using PWM 7. RTC and EEPROM interface using I2C protocol TEXT BOOK Muhammad Ali Mazidi, Janice Gillispie Mazidi and Rolin D. McKinley, "The 8051 Microcontroller and Embedded Systems", Second Edition, Pearson Education 2008. Fifth impression 2011

Presented By,

Dr. V. Sathiesh Kumar Department of Electronics Engg.,

MIT-Anna University


8051 Microcontroller: Stepper Motor Interfacing

Translates electrical pulses into mechanical movement.

Applications: Disk drives, Dot matrix printers, robotics

Shaft is a permanent magnet rotor, surrounded by a four stator windings that are

paired with a centre-tapped common. This type of motors are termed as four phase or

unipolar stepper motors.

The center tap allows a change of current direction in each of two coils when a

winding is grounded, thereby resulting in a polarity change of the stator.

MICROPROCESSOR AND MICROCONTROLLER UNIT V – Microcontroller Based System Design



A

B

A

B

Control Word (Clockwise)

0 1 1 1 0x07

1 0 1 1 0x0B

1 1 0 1 0x0D

1 1 1 0 0x0E




A

B

A

B

Control Word (Clockwise)

0 0 1 1 0x03

1 0 0 1 0x09

1 1 0 0 0x0C

0 1 1 0 0x06




Step angle is determined by the internal construction of the motor, in particular the

number of teeth on the stator and the rotor.

The step angle is the minimum degree of rotation associated with a single step.

Steps per revolution is the total number of steps needed to rotate one complete

rotation or 360 degrees.

rpm Steps per revolution Steps per second=

60




In a 4-step switching sequence, after four steps the same two windings will be “ON”.

How much movement is associated with these four steps?

After completing every four steps, the rotor moves only one tooth pitch.

Therefore, in a stepper motor with 200 steps per revolution, the rotor has 50

teeth because 4x50=200 steps are needed to complete one revolution.

Minimum step angle is always a function of the number of teeth on the rotor.

In other words, the smaller the step angle, the more teeth the rotor passes.

Motor Speed: Measured in steps per second (steps/s), is a function of switching rate

(By changing the length of the time delay loop, we can achieve various rotation speeds).

Holding torque: With the motor shaft at standstill or zero rpm condition, the amount

of torque, from an external source, required to break away the shaft from its holding

position. This is measured with rated voltage and current applied to the motor. The unit

of torque is ounce-inch or kg-cm.




Three common types of stepper motor interfacing: universal, unipolar and bipolar.

They can be identified by the number of connections to the motor.

A universal stepper motor has eight, while the unipolar has six and the bipolar

has four.

The universal stepper motor can be configured for all three modes, while the

unipolar can be either unipolar or bipolar. Obviously the bipolar cannot be

configured for universal nor unipolar mode.



8051 Microcontroller: Stepper Motor Interfacing – 4 Step Sequence/Biphase

ORG 0000H

MOV A, #66H ; load step sequence

BACK: MOV P1, A ; issue sequence to motor

RR A ; rotate right clockwise

ACALL DELAY ; wait

SJMP BACK ; continue loop

DELAY: MOV R2, #100

H1: MOV R3, #255

H2: DJNZ R3, H2

DJNZ R2, H1

RET



8051 Microcontroller: Stepper Motor Interfacing – 8 Step Sequence

ORG 0000H

START: MOV R0, #08H ; initialize count for data

MOV DPTR, #0200H ; Load DPTR with 0200H

RPT: CLR A ; clear A

MOVC A, @A+DPTR ; load data to A

MOV P1, A ; send value to port 1

CALL DELAY ; wait

INC DPTR ; increment DPTR to next data

DJNZ R0, RPT ; decrement count

SJMP START ; continue loop

ORG 0200H

DB 09H, 08H, 0CH, 04H, 06H, 02H, 03H, 01H



8051 Microcontroller: Stepper Motor Interfacing – 8 Step Sequence

DELAY: MOV R2, #100

H1: MOV R3, #255

H2: DJNZ R3, H2

DJNZ R2, H1

RET



ADC0808 Interface with 8051

•It is a monolithic CMOS device with an 8-bit analog to digital convertor.

•It has 8 channel multiplexer to interface with the microprocessor.

• The 8-bit A/D convertor uses successive approximation as the conversion technique.

•The ADC0808, ADC0809 offers high speed, high accuracy, minimal temperature

dependence, excellent long-term accuracy, repeatability, and consumes minimal

power.

•One of the main advantage of this chip is that it does not require any external zero

and full scale adjustment, only +5V DC supply is sufficient.



ADC0808 Interface with 8051: Architecture



ADC0808 Interface with 8051: Pin Details



ADC0808 Interface with 8051:

• The device contains an 8-channel single-ended analog signal multiplexer.

•A particular input channel is selected by using the address decoder.

•The address is latched into the decoder on the low-to-high transition of the address

latch enable (ALE) signal.



ADC0808 Interface with 8051: Typical Application

Potentiometer connected to IN1




ALE BIT P2.4

OE BIT P2.5

SC BIT P2.6

EOC BIT P2.7

ADDR_A BIT P2.0

ADDR_B BIT P2.1

ADDR_C BIT P2.2

MYDATA EQU P1

ORG 0000H

MOV MYDATA, #0FFH ; make P1 an input

SETB EOC ; make EOC an input

CLR ALE ; clear ALE - output

CLR SC ; clear WR - output

CLR OE ; clear OE - output




BACK: CLR ADDR_C ; C=0

CLR ADDR_B ; B=0

SETB ADDR_A ; A=1 (Select Channel 1)

ACALL DELAY ; Wait till address becomes stable

SETB ALE ; latch address

ACALL DELAY ;

SETB SC ; Start the Conversion

ACALL DELAY ;

CLR ALE ;

CLR SC ;

HERE1: JNB EOC, HERE1 ; wait until conversion complete

SETB OE ; enable RD

ACALL DELAY ; wait




MOV A, MYDATA ; read data

CLR OE ; clear RD for next acquisition

SJMP BACK

DELAY: MOV CX, 07FFH //Delay Subroutine

LOOP1: NOP

NOP

DEC CX

JNE LOOP1

RET



DAC0808 Interface with 8051:

DAC 0808 is a 8-bit Digital to Analog Convertor.

Binary weighted DAC and R/2R ladder type

DAC0808 (8-bit) provides 256 discrete voltage or current levels of output

7 6 5 3 04 2 1( )2 4 8 16 32 64 128 256

out ref

D D D D DD D DI I

2refI mA



DAC0808 Interface with 8051: Square waveform generation

START: MOV A, #00H // Low logic level

MOV P1, A

CALL DELAY

MOV A, #FFH // High logic level

MOV P1, A

CALL DELAY

JMP START

DELAY: MOV CX, 07FFH //Delay Subroutine

LOOP1: NOP

NOP

DEC CX

JNE LOOP1

RET



DAC0808 Interface with 8051: Sawtooth waveform generation

MOV A, #00H // Low logic level

MOV P1, A

BACK: INC A

SJMP BACK



16X2 LCD Displays:

LCD replacing LEDs (Seven-segment LEDs or other multi-segment LEDs) due to

following reasons:

1. Declining prices of LCDs

2. The ability to display numbers, characters and graphics. This is in contrast to LEDs,

which are limited to numbers and few characters.

3. Incorporation of a refreshing controller into the LCD, thereby relieving the CPU of the

task of refreshing the LCD. IN contrast, the LED must be refreshed by the CPU (or in

some other way) to keep displaying the data.

4. Ease of programming for characters and graphics.



16X2 LCD Displays:



16X2 LCD Displays:

Vcc and Vss provide +5V and ground respectively.

VEE is used for controlling the LCD contrast.

Register Select (RS) is used to select the command code register or data register

(RS=0: command code register, RS=1: data register).

Read/Write (R/W) input allows the user to write information to the LCD or read

information from it (R/W=0: Write, R/W=1: Read).

Enable (E) pin is used by the LCD to latch information presented to its data pin.

When data is supplied to data pins, a high-to-low pulse must be applied to the E pin

in order for the LCD to latch in the data present at the data pins. This pulse must be a

minimum of 450 ns wide.

D0-D7 is 8-bit data pins are used to send information to the LCD or read the contents

of the LCD’s internal registers.



16X2 LCD Displays:

To display letters and numbers, we send ASCII codes for the letters A-Z, a-z and

numbers 0-9 to these pins while making RS=1.

There are two ways to send characters (command/data):

1. use a delay before sending the next one

2. use the busy flag (D7 bit of command register, R/W=1, E=L to H pulse) to see if

the LCD is ready for the next one.

Code(Hex) Function Code(Hex) Function

1 Clear display screen C Display on, Cursor off

4 Decrement Cursor E (or) F Display on, Cursor Blinking

6 Increment Cursor 80 Beginning of 1st line

5 Shift Display Right C0 Beginning of 2nd line

7 Shift Display Left 90 Beginning of 3rd line

8 Display off, Cursor off D0 Beginning of 4th line

A Display off, Cursor on 2 Return Home

LCD command codes



16X2 LCD Displays:



40X2 LCD Displays: Addressing



16X2 LCD Displays:



16X2 LCD Displays:

P1.0 – P1.7 are connected to LCD data pins D0 – D7

P2.0 is connected to RS pin of LCD

P2.1 is connected to R/W* pin of LCD

P2.2 is connected to E pin of LCD

ORG 0000H

MOV A, #38H ; initialize LCD 16 X 2

ACALL COMD ; call command subroutine

ACALL DELAY ; give LCD some time

MOV A, #0EH ; display on, cursor on



MOV A, #01H ; clear LCD





16X2 LCD Displays:

MOV A, #06H ; shift cursor right



MOV A, #84H ; cursor at line 1, position 4



MOV A, #’N’ ; display letter N

ACALL DATA ; call display subroutine


MOV A, #’O’ ; display letter O

ACALL DATA ; call display subroutine

AGAIN: SJMP AGAIN ; stay here



16X2 LCD Displays:

COMD: MOV P1, A ; copy reg A to port 1

CLR P2.0 ; RS=0 for command

CLR P2.1 ; R/W*=0 for write

SETB P2.2 ; E=1 for high pulse


CLR P2.2 ; E=0 for High to Low pulse

RET

DATA: MOV P1, A ; copy reg A to port 1

SETB P2.0 ; RS=1 for data

CLR P2.1 ; R/W*=0 for write

SETB P2.2 ; E=1 for high pulse


CLR P2.2 ; E=0 for High to Low pulse

RET



16X2 LCD Displays:

DELAY: MOV R3, #50 ; 50 or higher for fast CPUs

HERE2: MOV R4, #255 ; R4=255

HERE: DJNZ R4, HERE ; stay until R4 becomes 0

DJNZ R3, HERE2 ;

RET

END



Summary

1.Stepper Motor Interfacing

2.ADC and DAC interfacing

3.LCD Interfacing

MICROPROCESSOR AND MICROCONTROLLER UNIT IV & V – Microcontroller & it Applications

EC7451: MICROPROCESSOR AND … V- Microcontroller...Dr. V. SATHIESH KUMAR Department of Electronics...

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