spi总线.c

AVR单片机SPI操作

#include <iom162v.h>
#include <macros.h>
#include <stdio.h>

 unsigned int i;
void port_init(void)
{
 PORTA = 0xFF;
 DDRA = 0x00;
 PORTB = 0xFF;
 DDRB = 0x00;
 PORTC = 0x00; 
 DDRC = 0xFF;
 PORTD = 0xFF;
 DDRD = 0x02; 
 PORTE = 0x00;
 DDRE = 0xFF;
}
void SpiInit(void )
{ 
  DDRB|=(1<<PB7)|(1<<PB5)|(1<<PB4);// Set SCK, MOSI & SS as outputs
  PORTB&=~(1<<PB7);
  PORTB&=~(1<<PB5);
 
  SPCR = 0x53;   
}
void SpiWriteByte(unsigned char c)
{
  SPDR = c;
  while (!(SPSR & 0x80));


}

unsigned char SpiReadByte(void)
{
  SPDR=0xFF;
  while (!(SPSR & 0x80));
  return SPDR;
  }
   

 void init_devices(void)
{
 //stop errant interrupts until set up
  CLI(); //disable all interrupts
  port_init();
  SpiInit();
  MCUCR=0x00; 
  EMCUCR=0x00;
  SFIOR=0x00; 
  TIMSK= 0x00;  
  ETIMSK=0x00;
  GICR= 0x00;
  PCMSK1=0x00;
  SEI(); //re-enable interrupts
 //all peripherals are now initialized
}
void main (void)
{ 
   init_devices();
   PORTB&=~(1<<PB4);    // Spi enable for write a spi command
   SpiWriteByte(0x55); 
   PORTB|=(1<<PB4);
   
  while(1)
  { if(PINA&(1<<PA1))
     {PORTB&=~(1<<PB4);
	  i=SpiReadByte();
	  PORTB|=(1<<PB4);
	  }
  }
 }