#include <avr/io.h>
#include <stdint.h>

#include "spi.h"

// Prevent Double Initialization
unsigned short SPI_flag = 0;

void SPI_MasterInit(void)
{
  // Check if already initialized
  if (!(SPI_flag & 1))
  {
    // Backup Status Register and disable Interrupts
    uint8_t sreg = SREG;
    cli();

    // Set MOSI, SCK and SS output
    DDRB |= (1 << PB5) | (1 << PB7) | (1 << PB4);

    // Enable SPI, Master
    SPCR = (1 << SPE) | (1 << MSTR);

    // Set Double SPI Speed Bit, SPI clock will be fck/2
    SPSR = (1 << SPI2X);

    // Restore Status Register
    SREG = sreg;

    // Set SPI Init Flag
    SPI_flag = 1;
  }
}

void SPI_MasterTransfer(unsigned char c)
{
  // Start transmission
  SPDR = c;

  // Wait for transmission complete
  while (!(SPSR & (1 << SPIF)))
    ;
}

unsigned char
SPI_MasterTransferRead(unsigned char c)
{
  // Start transmission
  SPDR = c;

  // Wait for transmission complete
  while (!(SPSR & (1 << SPIF)))
    ;

  // Return incoming character
  return SPDR;
}