SPI.c

// Version 1.0
// 10/13/19

#include"SPI.h"

void SPI_MasterInit(void)
{
    //Set SS, MOSI and SCK output, all others as input
    DDRB = (1<<DDB2) | (1<<DDB3) | (1<<DDB5);
    PORTB |= (1<<PORTB2);
    //Enable SPI, set as Master, set clock rate fosc/16
    SPCR = (1<<SPE) | (1<<MSTR) | (1<<SPR0);
}

void SPI_MasterTransmit(char data)
{
    //Start transmission
    SPDR = data;
    //Pull Chip Select Low
    PORTB &= ~(1<<PORTB2);
    //Wait for transmission to complete
    while(!(SPSR & (1<<SPIF)))
    ;
    PORTB |= (1<<PORTB2);
}

void SPI_MasterTest(void)
{
    uint8_t x = 0;
    for(x = 0; x < 256; x++)
    {
        SPI_MasterTransmit(x);
    }
}

void SPI_SlaveInit(void)
{
    // Set MISO output, all others as input
    DDRB = (1<<DDB4);
    //Enable SPI
    SPCR = (1<<SPE);
}

char SPI_SlaveReceive(void)
{
    //Wait for reception to complete
    while(!(SPSR & (1<<SPIF)))
    ;
    //Return SPI Data Register
    return SPDR;
}