spi.h

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#ifndef RASPI_SPI_H
#define RASPI_SPI_H

#include "raspi/hw.h"
#include <stdint.h>

#define raspi_SPI_FIFOSIZE 16


static inline void spi_init(uint32_t speed)
{
    int i;
    uint32_t div = CORE_CLOCK / speed;

    if (div >= 65536) div = 0;
    if (div < 2) div = 2;
    HW.SPI0.CLK.B.CDIV = div;
    HW.SPI0.CS.B.CPHA = 1;

    memory_barrier();
    for (i = 7; i <= 11; i++) gpio_configure(i, Alt0);
    memory_barrier();
}


static inline void spi_start(int destination)
{
    HW.SPI0.CS.B.CS = destination;
    HW.SPI0.CS.B.CLEAR = 2;
    HW.SPI0.CS.B.TA = 1;
}


static inline void spi_stop(void)
{
    while (!HW.SPI0.CS.B.DONE);
    HW.SPI0.CS.B.TA = 0;
}


static inline int spi_poll(int num)
{
    if (num <= 0) return 1;
    if (num < raspi_SPI_FIFOSIZE*3/4) return HW.SPI0.CS.B.RXD;
    if (num < raspi_SPI_FIFOSIZE) return HW.SPI0.CS.B.RXR;
    return HW.SPI0.CS.B.RXF;
}


static inline uint8_t spi_read(void)
{
    while (!HW.SPI0.CS.B.RXD);
    return HW.SPI0.FIFO;
}


static inline void spi_write(uint8_t data)
{
    while (!HW.SPI0.CS.B.TXD);
    HW.SPI0.FIFO = data;
}


static inline void spi_flush(void)
{
    while (HW.SPI0.CS.B.TA && !HW.SPI0.CS.B.DONE);
}

#endif