spi.c

通过车载终端采集GPS数据

/*****************************************************************
*SPI软件仿真程序
*SPI总线接口，高位先发送，数据在时钟的上升沿发送和接收。
*             正常情况下CLK为高电平。
******************************************************************/
#include "w77e532.h"
#include "spi.h"


void spi_init(void)
{
    SPI_CLK = 1;
    SPI_MOSI = 1;
    SPI_MISO = 1;
}

void spi_write(char value)//mode 3
{
    unsigned char bitCount;
    unsigned char bitTmp;

    bitTmp = value;
    for( bitCount=0; bitCount<8; bitCount++)
    {
        if( bitTmp & 0x80 )
            SPI_MOSI = 1;
        else
            SPI_MOSI = 0;

        SPI_CLK = 0;
        SPI_CLK = 1;

        bitTmp <<= 1;
    }    
    
}

code char SPIREAD_ARRAY[8] = {128, 64, 32, 16, 8, 4, 2, 1};
char spi_read(void)//mode 0
{
    data unsigned char bitCount;
    data unsigned char bitTmp;

    bitTmp = 0;
    for( bitCount=0; bitCount<8; bitCount++)
    {
        SPI_CLK = 1;//0;
        SPI_CLK = 0;//1;//cj mod

        SPI_MISO = 1;
        if( SPI_MISO )
            bitTmp += SPIREAD_ARRAY[bitCount];

//        if( bitCount != 7 )
//            bitTmp <<= 1;        
    }

    return(bitTmp);
}
/*
char spi_read(void)//mode 0
{
    unsigned char bitCount;
    unsigned char bitTmp;

    bitTmp = 0;
    for( bitCount=0; bitCount<8; bitCount++)
    {
        SPI_CLK = 1;//0;
        SPI_CLK = 0;//1;//cj mod

        SPI_MISO = 1;
        if( SPI_MISO )
            bitTmp |= 1;

        if( bitCount != 7 )
            bitTmp <<= 1;        
    }

    return(bitTmp);
}
*/