INTERFACING HARDWARE WITH

MICROCONTROLLER

P.Raghavendra PrasadFinal Yr EEE

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What is a Microcontroller ?What is a Microcontroller ?

A i t ll ( MCU) i t hi ItA microcontroller (or MCU) is a computer-on-a-chip. Itis a type of microprocessor emphasizing self-sufficiency and cost-effectiveness in contrast to asufficiency and cost effectiveness, in contrast to ageneral-purpose microprocessor (the kind used in aPC). The only difference between a microcontroller anda microprocessor is that a microprocessor has threeparts - ALU, Control Unit and registers (like memory),

h l h ll h dd l l l kwhile the microcontroller has additional elements likeROM, RAM etc.

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ATMEGA32/ATMEGA32Lh f A 8 b M llHigh-performance, Low-power AVR 8-bit Microcontroller

Up to 16 MIPS Throughput at 16 MHz32K Bytes of In-System Self-Programmable Flashy y g1024 Bytes EEPROM2K Byte Internal SRAMTwo 8-bit Timer/Counters One 16-bit Timer/CounterTwo 8-bit Timer/Counters, One 16-bit Timer/CounterIn-System Programming by On-chip Boot ProgramFour PWM Channels8 h l 10 bi ADC8-channel, 10-bit ADCProgrammable Serial USARTInternal Calibrated RC OscillatorExternal and Internal Interrupt SourcesPower-on Reset32 Programmable I/O Lines

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32 Programmable I/O Lines

ATMEGA32/32L ATMEGA16/16LATMEGA32/32L ATMEGA16/16L

32K Bytes of Flash memory 16K Bytes of Flash memory

1024 Bytes EEPROM

2K Byte Internal SRAM

512 Bytes EEPROM

1K Byte Internal SRAM2K Byte Internal SRAM 1K Byte Internal SRAM

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ATMEGA32/16 ATMEGA32L/16LATMEGA32/16 ATMEGA32L/16L

Operating Voltage 4.5 - 5.5 V

Operating Voltage 2.7 - 5.5 V

Speed Grades Speed GradesSpeed Grades0 – 16 MHz

Speed Grades0 – 8 MHz

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Pin Diagram

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COMPUTER

cC - CODE COMPILER HEX - CODE

MICRO CONTROLLER

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STK200 CableSTK200 Cable

Configuring PORT PINS

Each PORT consists of three registers

DDRX (Data Direction Register)

PORTX

PINXPINX

Where X = A, B, C, D

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DDRX

The DDXn bit in the DDRx Register selects the direction of pin n.g pIf DDXn is written logic one, PXn is configured as an output pin.If DDXn is written logic zero, PXn is configured as an input pin.

Where n = 0 1 2 7Where n = 0,1,2 - - - ,7

For Example

If DDRA = 0x0F ( 0000 1111)

The Lower bytes of PORTA are configured as output pins The Higher bytes of PORTA are configured as input pins

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PORTX

When PORTXn is configured as Input Pin

Writing logic ONE to this pin, activates pull-up resistor.Writing logic ZERO to this pin, deactivates pull-up resistor

When PORTXn is configured as Output Pin

Writing logic ONE to this pin, drives the port pin HIGHWriting logic ZERO to this pin, drives the port pin LOW

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PINX

PINXn is used to read the value of particular port pin

Independent of the setting of Data Direction bit DDRXn, the port pin can be read through the PINXn Register bit

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ICCAVR

ICCAVR, the ImageCraft’s C Development Environment is aprogram for developing AVR microcontroller applications usingthe ANSI standard C language

Full featured 30-day demo program can be downloaded from the ImageCraft web site

fwww.image-craft.com

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Getting Started with ICCAVR

1. Project>New2 Project name and path2. Project name and path3. Project>Options4. In the Compiler options, check “Accept C++ Comments” and “Intel HEX” as the “output format”the output format5. In the Target options, select “ATmega32/Atmega16” under “Device Configuration”6. Write the source code7. Add the source file to the project by selecting “Project>Add File(s)” and select the file just written8. Compile by selecting “Project>Make Project” or by clicking on the “build” icon9. Open AVR ISP and download the hex file generated by ICCAVR , It is stored under the project name.

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Sample program to generate Square wave on PORTA of ATMEGA32

#include<iom32v.h>#include<macros.h>Void delay(unsigned int i)

{{unsigned int k;While(i--)For(k=0;k<=500;k++);

}}Void main()

{DDRA = 0xFF; // Configures PORTA Pins as Output pinsDDRA 0xFF; // Configures PORTA Pins as Output pins

While(1){PORTA=0xFF;D l (500)Delay(500);PORTA=0x00;Delay(500);

} }

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} }

Interfacing with Microcontrollerg

LED

Switches

DC Motor

Sensors

S MStepper Motor

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LED – Light Emitting Diode

M i t ti l d LED Maximum potential drop across LED will be approximately 2V.

Maximum current tat can be allowed through am LED is approximately 30ma.

Resistor should be added in series h l h h hwith LED to limit the current through it.

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Calculating LED resistor value g

R = (Vs – VL )/I

Vs = supply voltage VL = Voltage drop across LED VL = Voltage drop across LED

( around 2V)I = 15 to 30 ma

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LED’s connected to 1. PORTA02.PORTB0

LED BLINK PROGRAMLED BLINK PROGRAM

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DC Motor

DC Motors are small, inexpensive and powerful motors used widely.

These are widely used in robotics for their small size and high energy out.

A typical DC motor operates at speeds that are far too high speed to be useful, and torque that are far too low.

Gear reduction is the standard method by which a motor is made useful .useful .

Gear’s reduce the speed of motor and increases the torque

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Choosing a DC Motor

DC Motor with Gear headOperating voltage 12VSpeed Depends on our applicationDepends on our application

Some available speeds in market30 RPM60 RPM60 RPM

100 RPM150 RPM350 RPM1000 RPM

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Drive basics of DC MotorDrive basics of DC Motor

Red wire Black wire Direction of rotation

Positive Negative Clock wise

Negative Positive Anti clock wiseg

Logic Logic Direction

1 0 Clock

0 A0 1 Anti clock

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Bi Direction control of DC MotorBi-Direction control of DC Motor

H-Bridge Ckt using transistors for bidi ti l d i i f DC t

Direction Pulse to

bidirectional driving of DC motor

Clock wise A and C

Anti Clock wise B and D

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H-Bridges in IC’s to reduce the drive circuit complexity H Bridges in IC s to reduce the drive circuit complexity

Th t l d H B id L293D d The most commonly used H-Bridges are L293D and L298L293D has maximum current rating of 600maL293D has maximum current rating of 600maL298 has maximum current rating of 2ABoth has 2 H-Bridges in themThese are designed to drive inductive loads such as relays, solenoids

C b d d 2 CCan be used to drive 2 DC motors or 1 stepper motor

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DRIVING OF DC MOTORDRIVING OF DC MOTOR

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Switches

Active LowWhen pressed shorts the corresponding pin to ground

Active highWhen pressed shorts the corresponding pin to Vcc

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Active lowActive lowActive high

INTERFACING SWITCHES

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Sensors

Commonly used sensors in the field of robotics areCommonly used sensors in the field of robotics are

IR Digital sensors

IR analog sensors

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IR Digital sensors

TransmitterIR led connected to 38KHz oscillator

ReceiverTSOP1738

IR Analog sensors

TransmitterIR LED

ReceiverReceiverIR Photodiode

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IR Analog sensor

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STEPPER MOTOR

STEPPER MOTOR is a brushless DC motor whose rotor rotates in discrete angular increments when its stator windings are energized in a programmed manner energized in a programmed manner.

Rotation occurs because of magnetic interaction between rotor poles and poles of sequentially energized stator windings.

/The rotor has no electrical windings, but has salient and/or magnetized poles.

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4 – Lead stepper 5 – Lead stepper

6 – Lead stepper 8 – Lead stepper

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Full Step driving of Stepper Motor

Full step wave drive

4 3 2 14 3 2 1

1 0 0 0

0 1 0 0

0 0 1 0

0 0 0 1

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Full Step driving of Stepper Motor

Full step 2 phases active

4 3 2 1

1 1 0 0

0 1 1 0

0 0 1 10 0 1 1

1 0 0 1

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Half Step driving of stepper motor

4 3 2 1

1 0 0 0

1 1 0 0

0 1 0 00 1 0 0

0 1 1 0

0 0 1 0

0 0 1 1

0 0 0 1

1 0 0 11 0 0 1

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Choosing a Stepper motor

12 V operating voltage1 8 degree step1.8 degree step6 Lead 250 t0 500 ma of current

orCoil resistance of 20 ohms to 40 ohmsSize and shape depends on applicationp p ppIn most of the robotics cube shaped motors are

preferred with frame size of 3.9 to 4 cm

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Commonly used IC’s for driving Stepper motor

ULN2803• It has 8 channels• It has 8 channels• It channel has maximum current rating of 500ma• can be used to drive 2 unipolar stepper motors

L293d

L297 & L298

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ULN2803

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Bi – Polar driving of Stepper Motor

A B C D

1 1 0 0

0 1 1 0

0 0 1 10 0 1 1

1 0 0 1

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DRIVING STEPPER MOTOR

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Line Follower

sensor1L2

Leftmotorsensor1

sensor2

293D

motor

RightM t

Microcontrollersensor3

Motor

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You can download this presentation atYou can download this presentation atwww.raghu.co.nr

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