SPI-Kommunikation zwischen zwei ATTiny2313

/*

 * Communication_via_SPI_Master.c

 *

 * Created: 21.01.2014 15:02:29

 *  Author: Jens

 */ 

#include <avr/io.h>

#include <stdlib.h>

#include <util/delay.h>

#include <inttypes.h>

#define FCPU 1000000L

#define USART_BAUD 4800L

#define USART_UBBR_VALUE ((FCPU)/(USART_BAUD*16)-1)

// Initialization for the UART-Interface

void USART_vInit(void)

{

  // Set baudrate

  UBRRH = (uint8_t) (USART_UBBR_VALUE>>8);

  UBRRL = (uint8_t) USART_UBBR_VALUE;

  // Enable receiver and transmitter

  UCSRB = (1<<RXEN)|(1<<TXEN);

  // Set frame format to 8 data bits, no parity, 2 stop bits

  UCSRC = (1<<USBS)|(1<<UCSZ1)|(1<<UCSZ0);

}

// Initialization for the SPI-Interface

void SPI_init(void)

{

  //Output: PB7=USCK, PB6=DO, PB4=LED

  DDRB |= (1<<PB7)|(1<<PB6)|(1<<PB4);

  //Input: PB5=DI

  DDRB &= ~(1<<PB5);

  // Enable internal pull-up for PB5

  PORTB |= (1<<PB5);

  // Enable SPI in master mode

  USICR = (1<<USIWM0)|(1<<USICS1)|(1<<USICLK)|(1<<USITC);

}

// Function for receiving data via UART-Interface

unsigned char USART_ReceiveByte(void)

{

  // Wait until a byte has been received

  while(!(UCSRA&(1<<RXC)));

  // Return received data

  return UDR;

}

// Function for transmitting data via SPI-Interface

void SPI_Transfer(unsigned char data)

{

  // Load data into the data-register

  USIDR = data;

}

int main (void)

{

  unsigned char u8Data;

  DDRB = 0xFF;

  // Initialize USART and SPI

  USART_vInit();

  SPI_init();

  while(1)

  {

    // Receive data via UART

    u8Data = USART_ReceiveByte();

    while(!(UCSRA & (1<<UDRE)));

    UDR = u8Data;

    // Transmit the received data to the SPI-Slave

    SPI_Transfer(u8Data);

    // Led on

    PORTB |= (1<<PB4);

    _delay_ms(500);

    // Led off

    PORTB &= !(1<<PB4);

    _delay_ms(500);

  }

}