spi.c


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#include <stdint.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include "spi.h"

void spi_init()
{
    DDR_SPI &= ~((1<<DD_MOSI)|(1<<DD_MISO)|(1<<DD_SS)|(1<<DD_SCK));
    DDR_SPI |= ((1<<DD_MOSI)|(1<<DD_SS)|(1<<DD_SCK));

    SPCR = ((1<<SPE)|               // SPI Enable
            (0<<SPIE)|              // SPI Interupt Enable
            (0<<DORD)|              // Data Order (0:MSB first / 1:LSB first)
            (1<<MSTR)|              // Master/Slave select
            (1<<SPR1)|(1<<SPR0)|    // SPI Clock Rate
            (0<<CPOL)|              // Clock Polarity (0:SCK low / 1:SCK hi when idle)
            (0<<CPHA));             // Clock Phase (0:leading / 1:trailing edge sampling)

    SPSR = (0<<SPIF)|(0<<WCOL)|(0<<SPI2X);              // Double Clock Rate
}

uint8_t spi_fast_shift(uint8_t data)
{
  SPDR = data;
  while((SPSR & (1<<SPIF))==0);
  return SPDR;
}

uint8_t spi_two_byte(uint8_t cmd, uint8_t arg)
{
  uint8_t data_buf;

  spi_cs_low();
  spi_fast_shift(cmd);
  data_buf = spi_fast_shift(arg);
  spi_cs_high();

  return data_buf;
}