Atmega AVR Programming Basics

Program an AVR manually


DDRX = DATA DIRECTION REGISTER X [1=output/0=input] where X is the letter of the register
eg. DDRC |= _BV(7);    set pin 7 of register C as output

PORTX = 1;
eg.  PORTC ^= (1<<1);  set pin 1 of register C to HIGH (5v) until otherwise set

    DDRB = 0b00000110;
  PORTB = 0b00000100;

Set a bit :

_BV() is a macro, BV = bit value

#define _BV(bit)  (1 << (bit))

_BV(7) = (1<<7)   

a |= (1<<position) or
a |=_BV(position)

example :
a = 00000000
a |= (1<<3)  =>  a = a|(1<<3) => a=(0000000)|(00000100) => a=00000100
a |= _BV(3)

Set a bit :
a |= (1<<2);
a |= _BV(2);

Clear a bit :
a &= ~(1<<2);
a &= ~_BV(2);

uint8_t (same as: unsigned char)
int8_t (same as: signed char)

uint16_t (same as: unsigned int)
int16_t (same as: int)

Hello world program in microcontroller world = Blink program :

#define F_CPU 1000000UL  // set proc speed to 1MHz
#include <avr/io.h>
#include <util/delay.h>

int main (void)
{
    DDRD |= _BV(6);  // pin D6 set as output
   
    while(1)
    {
        PORTC |=_BV(6);
        _delay_ms(1000);
       PORTC &= ~_BV(6);
      _delay_ms(1000);
    }
}

----
itoa() - convert integer to string.

Software :

For uploading hex data to avr :
eXtreme Burner - AVR => GUI alternative to avrdude - for uploading hex data to AVR
http://extremeelectronics.co.in/


For compiling code to hex :
WinAVR - Gnu C compiler and AVRLibC -  http://sourceforge.net/projects/winavr/
AVR Studio - IDE  - aStudio4b589.exe

Resurse :
Using LCD module with AVR - http://extremeelectronics.co.in/avr-tutorials/using-lcd-module-with-avrs/
AVR basic programming - SPI PROGRAMMING BASICS
Interfacing ps/2 - http://codelake9.wordpress.com/2011/12/10/interfacing-ps2-keyboard-to-atmega128atmega64/

ADC - analog to digital convertor

   //InitADC
   ADMUX=(1<<REFS0); // For Aref=AVcc;
   ADCSRA=(1<<ADEN)|(7<<ADPS0);

uint16_t ReadADC(uint8_t ch)
{
   ch = ch & 0b00000111;
   // clear previous channel selection
   ADMUX &= 0xF8;
   ADMUX |= ch; // add in the new selection bits (REFS0 untouched)

   //Start Single conversion
   ADCSRA|=(1<<ADSC);

   //Wait for conversion to complete
   while((ADCSRA & (1<<ADSC)));

   return(ADC);
}

     //ReadADC( channel )
     //ADC Channel ch must be 0-7 or what you micro has
      adc_value=ReadADC(7);

Avr - SPI (Serial Peripheral Interface)

Using USBASP :

CONECTIONS : 
MISO, MOSI, SCK, SS

CODE :

#define F_CPU 4000000UL


char spiData = 0;
SPCR = (1<<SPE);                   // Enable SPI

while(!(SPSR & (1 << SPIF)));   // Wait for transmission end
spiData = SPDR;                      // Read SPI Data Register - 1 byte

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