source: firmware/FSC/usb_src/spi_master.c

//-----------------------------------------------------------------------------
#include "spi_master.h"

//-----------------------------------------------------------------------------
volatile U08 spi_clock_index;
volatile U08 spi_cpol;
volatile U08 spi_cpha;
volatile U08 spi_dord;
volatile BOOL spi_ss_active_high;
volatile U08 spi_read_buffer[SPI_READ_BUFFER_SIZE];
volatile U08 spi_write_buffer[SPI_WRITE_BUFFER_SIZE];

volatile U08 SPI_DEVICE_SS[4]={SPI_E_CS ,SPI_AD_CS ,SPI_M_CS ,SPI_A_CS };
volatile BOOL SPI_DEVICE_ACTIVE_HIGH[4]={false ,false ,false ,false };
//-----------------------------------------------------------------------------




void spi_init(void)
{
  // there are a total of 4 devices on the SPI bus:
        // 1.) Ethernet Modul WIZ812MJ 
        // 2.) AD7719 24bit ADC
        // 3.) LIS3LV accelerometer
        // 4.) MAX6662 temp sensor <---- not assembled!

        // We check if they all can live with the same SPI settings:
        // 1.) Ethernet modul:
        // supports spi mode=0 or mode=3 --> eighther cpol=cpha=0 or cpol=cpha=1
        //      THAT IS NOT TRUE!!!!
        // only mode 0 !!!!!!!!!!!!!!!!!!!!!!!!!!!1
        // MSB first
        // SCLK time 70ns minimum --> 14.2MHz maximum
        //
        // 2.) AD7719
        // supports mode=3 --> cpol=cpha=1
        // MSB first
        // SCLK time 200ns minimum --> 5MHz maximum
        //
        // 3.) LIS3LV
        // SPI CLK idles high                           --> cpol=1
        // data valid at rising edge. --> cpha=1 as well 
        // ==> mode 3 is supported only.
        // MSB first, but take take at multi byte transfers. LSbyte first
        // SCLK time - is not mentioned in the datasheet
        //
        // 4.) MAX6662 Tempsensor
        // since it is not assembled, this information is not necessary.

        // fastes SPI CLK frequency can be                                      --> F_CPU/2     = 4MHz
        // slowest can be                                                                                                       --> F_CPU/128   = 62.5KHz
        
        // Lets try with the fastest!
        spi_clock_index = 0;  // Set Clockindex for lowest clock speed (F_CPU / 128)

  spi_dord = 0;                                 // Data Order MSB first dord = 0  --> good for all devices
  spi_cpol = 1; spi_cpha = 1;                                   // SPI mode=3                   --> good for all devices
  spi_setup();                                  // Setup SPI bits and clock speed

}
//-----------------------------------------------------------------------------
void spi_setup(void)
{
  // Disable SPI, clear all flags
  SPCR = 0;

  // Set/Clear bits DORD, CPOL and CPHA in SPI Control Register
  spi_dord & 0x01 ? (SPCR |= (1 << DORD)) : (SPCR &= ~(1 << DORD));
  spi_cpol & 0x01 ? (SPCR |= (1 << CPOL)) : (SPCR &= ~(1 << CPOL));
  spi_cpha & 0x01 ? (SPCR |= (1 << CPHA)) : (SPCR &= ~(1 << CPHA));

  switch (spi_clock_index)
  {
    case 0:{ // F_CPU / 128
      SPCR |= (1 << SPR1) | (1 << SPR0);
      SPSR &= ~(1 <<SPI2X);
          }
    break;

    case 1:{ // F_CPU / 64
      SPCR |= (1 << SPR1);
      SPSR &= ~(1 << SPI2X);
          }
    break;

    case 2:{ // F_CPU / 32
      SPCR |= (1 << SPR1);
      SPSR |= (1 << SPI2X);
          }
    break;

    case 3:{ // F_CPU / 16
      SPCR |= (1 << SPR0);
      SPSR &= ~(1 << SPI2X);
          }
    break;

    case 4:{ // F_CPU / 8
      SPCR |= (1 << SPR0);
      SPSR |= (1 << SPI2X);
          }
    break;

    case 5: // F_CPU / 4
      SPSR &= ~(1 << SPI2X);
    break;

    case 6: // F_CPU / 2
      SPSR |= (1 << SPI2X);
    break;

    default:{ // F_CPU / 128
      SPCR |= (1 << SPR1) | (1 << SPR0);
      SPSR &= ~(1 << SPI2X);
          }
  }

  // Enable SPI in Master Mode
  SPCR |= (1 << SPE) | (1 << MSTR);
}

//-----------------------------------------------------------------------------

void spi_set_clock_index(U08 clock_index)
{
  if (clock_index > SPI_MAX_CLOCK_INDEX)
  {
    clock_index = SPI_MAX_CLOCK_INDEX;
  }

  spi_clock_index = clock_index;

  spi_setup(); // Setup SPI bits and clock speed
}
//-----------------------------------------------------------------------------

void spi_set_dord(U08 dord)
{
  if (dord > 1)
  {
    dord = 1;
  }

  spi_dord = dord;

  spi_setup(); // Setup SPI bits and clock speed
}
//-----------------------------------------------------------------------------

void spi_set_cpol(U08 cpol)
{
  if (cpol > 1)
  {
    cpol = 1;
  }

  spi_cpol = cpol;

  spi_setup(); // Setup SPI bits and clock speed
}
//-----------------------------------------------------------------------------

void spi_set_cpha(U08 cpha)
{
  if (cpha > 1)
  {
    cpha = 1;
  }

  spi_cpha = cpha;

  spi_setup(); // Setup SPI bits and clock speed
}

//-----------------------------------------------------------------------------

void spi_transfer(U08 bytes, U08 device)
{
/*
#define SPI_E_CS PB4            //device 0
#define SPI_AD_CS PD3           //device 1
#define SPI_M_CS PD4            //device 2
#define SPI_A_CS PD5            //device 3
*/
  U08 n;
  // Transfer requested bytes
  for (n = 0; n < bytes; n++)
  {
  // Check for active slave select level
  if (SPI_DEVICE_ACTIVE_HIGH[device])
  {
                if (device == 0) {
        PORTB |= (1 << SPI_DEVICE_SS[device]); // Set Slave Select high
                } else {
                        PORTD |= (1 << SPI_DEVICE_SS[device]); // Set Slave Select high
                }
  }
  else
  {
                if (device == 0) {
        PORTB &= ~(1 << SPI_DEVICE_SS[device]); // Set Slave Select low
                } else {
                        PORTD &= ~(1 << SPI_DEVICE_SS[device]); // Set Slave Select low
                }
  }

  
    spi_read_buffer[n] = spi_transfer_byte(spi_write_buffer[n]);
  

  // Check for inactive slave select level
  if (SPI_DEVICE_ACTIVE_HIGH[device])
  {
                if (device == 0) {
        PORTB &= ~(1 << SPI_DEVICE_SS[device]); // Set Slave Select low
                } else {
                        PORTD &= ~(1 << SPI_DEVICE_SS[device]); // Set Slave Select low
                }
  }
  else
  {
                if (device == 0) {
        PORTB |= (1 << SPI_DEVICE_SS[device]); // Set Slave Select high
                } else {
                        PORTD |= (1 << SPI_DEVICE_SS[device]); // Set Slave Select high
                }
  }
  
  }
}
//-----------------------------------------------------------------------------

U08 spi_transfer_byte(U08 data)
{
  // Start SPI Transfer
        if (!(SPCR & (1<<MSTR)) )
                SPCR |= 1<<MSTR;
  SPDR = data;

  // Wait for transfer completed
  while (!(SPSR & (1 << SPIF)))
  {
  }

  // Return result of transfer
  return SPDR;
}

//-----------------------------------------------------------------------------
void spi_transfer_string(U08 length, U08* addr, U08 device)
{
/*
#define SPI_E_CS PB4            //device 0
#define SPI_AD_CS PD3   //device 1
#define SPI_M_CS PD4            //device 2
#define SPI_A_CS PD5            //device 3
*/
  U08 n;
  
  // I assume the CS line is in "not enable"-state;
        if ( device == 0 ){
        TGL_BIT(PORTB, SPI_DEVICE_SS[device]);  // I toggle the line
        } else {
                TGL_BIT(PORTD, SPI_DEVICE_SS[device]);  // I toggle the line
        }
  // now the line is in "enable"-state
  

  // Transfer requested bytes
  for (n = 0; n < length; n++)
  {
    spi_transfer_byte(addr[n]);
  }
        
                if ( device == 0 ){
        TGL_BIT(PORTB, SPI_DEVICE_SS[device]);  // I toggle the line
        } else {
                TGL_BIT(PORTD, SPI_DEVICE_SS[device]);  // I toggle the line
        }

}
//-----------------------------------------------------------------------------