spi_soft.c

脱机ISP编程器

/*
  spi.c - part of USBasp

  Autor..........: Thomas Fischl <[e-mail]>
  Description....: Provides functions for communication/programming
                   over SPI interface
  Licence........: GNU GPL v2 (see Readme.txt)
  Creation Date..: 2005-02-23
  Last change....: 2007-07-23
  */
//---------------------------------------------------
/*--------------------------------------
  Modify.........: avenbbs([e-mail])
  Last change....: 2008-9-28
------------------------------------------*/
#include <avr/io.h>
#include "spi_soft.h"
//#include "clock.h"
//#include <util/delay.h>

#define	SPI_SW_OUT   PORTD
#define SPI_SW_IN    PIND
#define SPI_SW_DDR   DDRD
#define SPI_SW_SS    PD2
#define SPI_SW_MOSI  PD3
#define SPI_SW_MISO  PD4
#define SPI_SW_SCK   PD5


void spiSW_init(void)
{
	SPI_SW_OUT|=(1<<SPI_SW_SS);
	SPI_SW_DDR|=(1<<SPI_SW_MOSI)|(1<<SPI_SW_SCK)|(1<<SPI_SW_SS);
	SPI_SW_DDR&=~(1<<SPI_SW_MISO);
}

/*
void spiDelay()
{

	uint8_t starttime = TIMERVALUE;

	while ((uint8_t)(TIMERVALUE - starttime) < 12) { }
}
*/

unsigned char spiSWTransmit(unsigned char send_byte)
{

	unsigned char rec_byte = 0;
	unsigned char i;
	
	for (i = 0; i < 8; i++)
	{
	
		/* set MSB to MOSI-pin */
		if ((send_byte & 0x80) != 0)
		{
			SPI_SW_OUT |= (1 << SPI_SW_MOSI);  /* MOSI high */
		}
		
		else
		{
			SPI_SW_OUT &= ~(1 << SPI_SW_MOSI); /* MOSI low */
		}
		
		/* shift to next bit */
		send_byte  = send_byte << 1;
		
		/* receive data */
		rec_byte = rec_byte << 1;
		
		if ((SPI_SW_IN & (1 << SPI_SW_MISO)) != 0)
		{
			rec_byte++;
		}
		
		/* pulse SCK */
		SPI_SW_OUT |= (1 << SPI_SW_SCK);     /* SCK high */
		
		//spiDelay();
		//_delay_us(64);
		SPI_SW_OUT &= ~(1 << SPI_SW_SCK);    /* SCK low */
		
		//spiDelay();
		//_delay_us(64);
	}
	
	return rec_byte;
}