xyFC/src/spi.c

/*
 * Bit-Banged SPI routines
 */

//#define DEBUG_SLOW_SPI_TRAFFIC

#include "spi.h"

void spiInit(void) {
    MI_dir;
    MO_dir;
    SCK_dir;
    CS_dir;

    SCK_off;
    MO_off;
    CS_on;
}

uint8_t spiReadWrite(uint8_t command) {
    SCK_off;
    MO_off;

    uint8_t result = 0;
    for (uint8_t i = 0; i < 8; i++) {
        if (command & 0x80) {
            MO_on;
        } else {
            MO_off;
        }
        command = command << 1;

        if (MI_1) {
            result = (result << 1) | 0x01;
        } else {
            result = result << 1;
        }

        SCK_on;
        NOP();

#ifdef DEBUG_SLOW_SPI_TRAFFIC
        NOP();
        NOP();
        NOP();
        NOP();
#endif

        SCK_off;
        NOP();

#ifdef DEBUG_SLOW_SPI_TRAFFIC
        NOP();
        NOP();
        NOP();
        NOP();
#endif
    }

    return result;
}