/**
 * \ingroup sd_raw
 * Sends a raw byte to the memory card.
 *
 * \param[in] b The byte to sent.
 * \see sd_raw_rec_byte
 */
void sd_raw_send_byte(uint8_t b)
{
#ifndef PIO_SPI
    SPDR = b;
    /* wait for byte to be shifted out */
    while(!(SPSR & (1 << SPIF)));
    SPSR &= ~(1 << SPIF);
#else
    int i;

    for(i=8; 0!=i; i--){
        clk_low();
        delayMicroseconds(3);
        if(b & 0x80)
            di_hi();
        else
            di_low();
        clk_hi();
        delayMicroseconds(3);
        b <<= 1;
    }
    clk_low();
    di_low();
#endif
}


/**
 * \ingroup sd_raw
 * Receives a raw byte from the memory card.
 *
 * \returns The byte which should be read.
 * \see sd_raw_send_byte
 */
uint8_t sd_raw_rec_byte()
{
#ifndef PIO_SPI
    /* send dummy data for receiving some */
    SPDR = 0xff;
    while(!(SPSR & (1 << SPIF)));
    SPSR &= ~(1 << SPIF);
    return SPDR;
#else
    uint8_t r = 0;
    int i;
    
    /* send dummy data for receiving some */
    di_hi();
    for(i=8; 0!=i; i--){
        clk_low();
        delayMicroseconds(3);
        clk_hi();
        r <<= 1;
        r |= do_read();
        delayMicroseconds(3);
    }
    clk_low();
    di_low();

    return r;
#endif
}