test.c

#include <avr/io.h>

#include <util/delay.h>

#define XCK      PB0

#define XCK_DDR  DDRB

#define XCK_PORT PORTB

#define XCK_HI   XCK_PORT |=  (1<<XCK);

#define XCK_LO   XCK_PORT &= ~(1<<XCK);

#define CLOCK    _delay_ms(1); \

                 XCK_HI        \

                 _delay_ms(1); \

                 XCK_LO

#define TXD      PD1

#define TXD_DDR  DDRD

#define TXD_PORT PORTD

#define TXD_HI   TXD_PORT |=  (1<<TXD);

#define TXD_LO   TXD_PORT &= ~(1<<TXD);

#define RXD      PD0

#define RXD_DDR  DDRD

#define RXD_PORT PORTD

#define LE       PD7

#define LE_DDR   DDRD

#define LE_PORT  PORTD

#define LE_HI    LE_PORT |=  (1<<LE);

#define LE_LO    LE_PORT &= ~(1<<LE);

#define LATCH    _delay_ms(1); LE_HI _delay_ms(1); LE_LO _delay_ms(1);

#define OE       PD6

#define OE_DDR   DDRD

#define OE_PORT  PORTD

#define OE_HI    OE_PORT |=  (1<<OE);

#define OE_LO    OE_PORT &= ~(1<<OE);

#define CONFIG_CODE(value) (((value) << 2) + 0x03)

void softSPI (uint8_t data) {

  uint8_t i;

  for (i = 7; i >= 0; i--) {

    if ((data & (1<<i)) > 0)

      TXD_HI

    else

      TXD_LO

    CLOCK

  }

}

#define SPECIAL 0

#define NORMAL 1

void mode (uint8_t newmode) {

  LE_LO

  OE_HI

  CLOCK

  OE_LO

  CLOCK

  OE_HI

  CLOCK

  if (newmode == SPECIAL) {

    LE_HI

    CLOCK

    LE_LO

    CLOCK

  } else {

    CLOCK

    CLOCK

  }

}

int main (void) {

  XCK_DDR |= (1<<XCK);

  TXD_DDR |= (1<<TXD);

  RXD_DDR &= ~(1<<RXD);

  LE_DDR  |= (1<<LE);

  OE_DDR  |= (1<<OE);

  OE_HI

  LE_LO

  XCK_LO

  _delay_ms(10);

  softSPI (0xFF);

  softSPI (0xFF);

  LATCH

  OE_LO

  /*

  _delay_ms(1000);

  mode (SPECIAL);

  softSPI (CONFIG_CODE(10));

  LATCH

  mode (NORMAL);

  OE_LO

  */

  while(1);

  return 0;

}