AVR I/O programming Atmega 64 uNiboard ThinkLABS maaniq

Embedded SystemsBe Ready for Tomorrow…

By,

PL.Manicka Raja,Embedded & Robotics Engineer,ThinkLABS Techno Solutions Pvt Ltd,SINE, IIT-Bombay, [email protected]

mailto:[email protected]

What is Embedded Systems?

© 2013, www.thinklabs.in 2




About Microcontroller

ATmega64

AT - ???

Mega - ???

64 - ???


KEY Notes

REGISTERS…?

Types of Registers

General Purpose Registers

Special Registers


GENERAL PURPOSE – I/ODDRx …..

PORTx

PINx

Where X represents A,B,C,D….F,G.


Special PurposeUART

TIMERS

ADC

SPI

I2C

EEPROM© 2013, www.thinklabs.in 9

8 - BIT REGISTER ACCESSING

7 6 5 4 3 2 1 0

MSB…… …..LSB



Output Step 1 : Configuration or Initialization

DDRx = 1 – Output, 0 – input

Step 2 : Status

PORTx = 1 – Logic High ( 5 volts) 0 – Logic Low (0 volts)

Where X represents A,B,C,D….F,G.






BLINK LED - Program#include<avr/io.h>void main(){

DDRC=OxFF; // Configuration

PORTC=OxOO; // All LEDS - ON, Active Low

PORTC=OxFF; // All LEDS - OFF,

}


BLINK LED - Program#include<avr/io.h>

void main(){

DDRC=OxFF; // Configurationwhile(1) // super loop{PORTC=OxOO; // All LEDS - ON, Active Low

PORTC=OxFF; // All LEDS - OFF,

}}


BLINK LED - Program#include<avr/io.h>#include<util/delay.h>void main(){

DDRC=OxFF; // Configurationwhile(1) // super loop{PORTC=OxOO; // All LEDS - ON, Active Low_delay_ms(1000);PORTC=OxFF; // All LEDS - OFF,_delay_ms(1000);

}}


INPUT


INPUT


INPUT

© 2013, www.thinklabs.in

Vcc

22

INPUT


Vcc

23

INPUT


Vcc

24


Functions of PORTx Register in GPIO

Output Input

DDRx 1 0

PORTx

1 0 1 0

Logic High Logic Low Enable Internal Pull-Up

Disable Internal Pull-Up

5 volts 0 volts Stable state - 1 Floating state ( 0 or 1)



Input Step 1 : Configuration or Initialization

DDRx =

Step 2 : Pull – Up

PORTx =

1 – Enable Pull – UP

0 – Disable Pull – UP

Step 3 : Checking

1 – Switch is not pressed

0 – Switch is pressed

Switches are Active Low, When pressed , it gives 0.© 2013, www.thinklabs.in 28







MSB……….LSB = Big Endian.


•7654 3210

•1010 1010

• (1<< position )

• (1<<4)

BIT WISE OPERATIONS

35

BIT WISE OPERATIONSWhy we need BITWISE operations…?

To change only our desired bit without affecting any other Bits in the REGISTER.

When Individual Accessing is required

When the port is both Input & Output.



BIT WISE OPERATIONS

SET BIT

To make the desired position as LOGIC 1 (ONE)

CLEAR BIT

To make the desired position as LOGIC 0 (ZERO)

CHECK BIT

To know whether the desired position is 0 or 1(Without affecting any other bits)


SET Bit - Explanation a = 0110 1010;

Desired Position is 4 So, OR function

0 1 1 O 1 0 1 0 is a0 0 0 1 0 0 0 0 is (1<<pos) ….(1<<4)-----------------------

0 1 1 1 1 0 1 0 is a= a|(1<<pos); x=x+5;

----------------------- a|=(1<<pos); x+=5;

Important Note : Rest of the BITS are not affected


One’s complement• 0001 0000 is (1<<4)

• One’s Complement…?

• 1110 1111 is one’s complement of (1<<4)

•~ is negation , used to produce one’s complement of a number.

• 11101111 is ~(1<<4)


CLEAR Bit - Explanation a = 0110 1010;

Desired Position is 5

So, AND function

0 1 1 0 1 0 1 0 is a

1 1 0 1 1 1 1 1 is ~(1<<pos) or ~(1<<5)

-----------------------

0 1 0 0 1 0 1 0 is a= a&~(1<<pos); x=x+5;

----------------------- a&=~(1<<pos); x+=5;

Important Note : Rest of the BITS are not affected

© 2013, www.thinklabs.in41

SET BIT

REGISTER |= (1<<pos)

|= OR Equal to


CLEAR BIT

REGISTER &=~ (1<<pos)

&= ~AND equal to negation


CHECK BIT(REGISTER & (1<<pos))== ?

& AND is only for checking, not for assingning EQUAL ‘=’ is for assigning, BUT here we don’t assign

anything, Just checking the Status of the BIT


Multiple SET BITREGISTER |= ( refer below)

|= ((1<<7) | (1<<5) | (1<<2))


Multiple CLEAR BITREGISTER &=~ ( refer below)

&=~ ((1<<7) | (1<<5) | (1<<2))


Switch Program#include<avr/io.h>#include<util/delay.h>void main(){

DDRC=OxFF; // ConfigurationDDRD&=~(1<<6); // PORTD 6th pin is SW1PORTD|=(1<<6); //PULL – UP resistorwhile(1) // super loop{

if( (PIND & (1<<6)) == O ){PORTC=OxOO; // All LEDS - ON, Active Low_delay_ms(1000);}

}} © 2013, www.thinklabs.in 47

Switch Program#include<avr/io.h>#include<util/delay.h>#define SW1 (PIND & (1<<6)) // macro for SW1

void main(){

DDRC=OxFF; // ConfigurationDDRD&=~(1<<PD6); // PD6 is already #defined as 6 @ avr/ io.hPORTD|=(1<<PD6); //PULL – UP resistorwhile(1) // super loop{

if( SW1 == O ){PORTC=OxOO; // All LEDS - ON, Active Low_delay_ms(1000);}



Direct OPERATION for REGISTERS 7..4 – o/p

3...0 – i/pDDRC = 0b11110000;

(or)

DDRC = 0xF0;

0 – input

1- output


Bitwise OPERATION for REGISTERS 7..4 – o/p

3...0 – i/pDDRC |=

((1<<7)|(1<<6)|(1<<5)|(1<<4));

(and also)

DDRC &=~((1<<3)|(1<<2)|(1<<1)|(1<<0));


Key Notes for An Embedded Developer

What is a Compiler?

What is a Cross–Compiler..?

Diff B/W uC & uP

CISC & RISC…?

Architecture…?

= Program memory & Data Memory


Compiler The process of converting high level language to the

machine level language

For the SAME processor.

Example : Turbo C, Dev C

Programs are compiled &

Output is viewed on the SAME System


Cross -Compiler The process of converting high level language to the

machine level language

For the TARGET processor.

Example : winAVR, KeilC, AVR Studio

Programs are compiled in a system &

Output is viewed on ANOTHER System


5 Golden Rules for Programming also called as Cross Compilation

1. Make New Separate folder for Each & Every Program

2. Only Makefile and .c (dot C) file…?

3. ‘M ‘of Makefile should be in Capital.

4. Target name in Makefile & some changes

5. Those three Switches in your uNiBoard



Tools to Remember

To Compile

Tools Make All

To Program

Tools Make Program


ReCap X= 6;

Right to Left Operation in C.

So, We are passing the value 6 to X,

Similarly,

DDRx=OxFF, and PORTx=OxFF;

So, We are (passing) Writing an 8 bit Value to REGISTER

But, in PINx , we are just only reading from it.

PINx & (1<< pos )


R/W - Registers

DDRx - Write Only

PORTx - Write Only

PINx - Read Only


THANK U…

Contact

[email protected]

www.linkedin.com/in/maaniq

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Date post:	16-Jul-2015
Category:	Education
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AVR I/O programming Atmega 64 uNiboard ThinkLABS maaniq

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