Raspberry Pi example for SPI operations

rpi_spi.c

#include "rpi_spi.h"

#define DEVICE "/dev/spidev0.0"

#define ARRAY_SIZE(a) ( sizeof(a) / sizeof( a[0] ) )

/* Init SPI */
uint8_t PI_SPI_Init(spi_t *spi)
{            
    spi->fd = open(DEVICE, O_RDWR);
    if (spi->fd < 0)
    {
        printf("Can't open device!\r\n\r");
        return (EXIT_FAILURE);
    }

    /*
     * spi mode
     */
    if (ioctl(spi->fd, SPI_IOC_WR_MODE, &spi->mode) == -1)
    {
        printf("Can't set spi mode!\r\n\r");
        return (EXIT_FAILURE);
    }
    
    if (ioctl(spi->fd, SPI_IOC_RD_MODE, &spi->mode) == -1)
    {
        printf("Can't get spi mode!\r\n\r");
        return (EXIT_FAILURE);
    }
    /*
     * bits per word
     */
    if (ioctl(spi->fd, SPI_IOC_WR_BITS_PER_WORD, &spi->bits) == -1)
    {
        printf("Can't set bits per word!\r\n\r");
        return (EXIT_FAILURE);
    }

    if (ioctl(spi->fd, SPI_IOC_RD_BITS_PER_WORD, &spi->bits) == -1)
    {
        printf("Can't get bits per word!\r\n\r");
        return (EXIT_FAILURE);
    }
    
    /*
     * max speed hz
     */
    if (ioctl(spi->fd, SPI_IOC_WR_MAX_SPEED_HZ, &spi->speed) == -1)
    {
        printf("Can't set max speed hz!\r\n\r");
        return (EXIT_FAILURE);
    }

    if (ioctl(spi->fd, SPI_IOC_RD_MAX_SPEED_HZ, &spi->speed) == -1)
    {
        printf("Can't get max speed hz!\r\n\r");
        return (EXIT_FAILURE);
    }

    printf("\r\n\rSPI mode: %d;\r\n\r", spi->mode);
    printf("Bits per word: %d;\r\n\r", spi->bits);
    printf("SPI prescaller: %d.\r\n\r", spi->speed);
    
    return (EXIT_SUCCESS);
}

/* Deinit SPI */
uint8_t PI_SPI_Deinit(spi_t *spi)
{
    if ( close(spi->fd) < 0 )
    {
        printf("Error close SPI!\r\n\r");
        return (EXIT_FAILURE);
    }
    else
    {
        printf("Close SPI.\r\n\r");
        return (EXIT_SUCCESS);
    }
}

/* Write n bytes */
uint8_t PI_SPI_Transmit(spi_t *spi, uint8_t *tx, int n)
{    
    struct spi_ioc_transfer transaction =
        {
            .tx_buf = (unsigned long)tx,
            .rx_buf = 0,
            .len = n,
            .delay_usecs = spi->delay,
            .speed_hz = spi->speed,
            .bits_per_word = spi->bits,
            .cs_change = 0,
        };
    if ( ioctl( spi->fd, SPI_IOC_MESSAGE(1), &transaction ) < 1 )
    {
        printf("Can't send spi message!\r\n\r");
        return (EXIT_FAILURE);
    }
    else
    {
#ifdef DEBUG
        printf("Transmitted in Hex:\r\n\r\t");
        for (int i = 0; i < n; i++)
        {
            printf("%.2X ", tx[i]);
        }
        printf("\r\n\rTransmitted in String:\r\n\r\t");
        for (int i = 0; i < n; i++)
        {
            printf("%c ", tx[i]);
        }
        printf("\r\n\r");
#endif
        return (EXIT_SUCCESS);
    }    
}

/* Read n bytes */
uint8_t PI_SPI_Receive(spi_t *spi, uint8_t *rx, int n)
{    
    struct spi_ioc_transfer transaction =
        {
            .tx_buf = 0,
            .rx_buf = (unsigned long)rx,
            .len = n,
            .delay_usecs = spi->delay,
            .speed_hz = spi->speed,
            .bits_per_word = spi->bits,
            .cs_change = 0,
        };
    if ( ioctl( spi->fd, SPI_IOC_MESSAGE(1), &transaction ) < 1 )
    {
        printf("Can't recived spi message!\r\n\r");
        return (EXIT_FAILURE);
    }
    else
    {
#ifdef DEBUG
        printf("Received in Hex:\r\n\r\t");
        for (int i = 0; i < n; i++)
        {
            printf("%.2X ", rx[i]);
        }
        printf("\r\n\rReceived in String:\r\n\r\t");
        for (int i = 0; i < n; i++)
        {
            printf("%c ", rx[i]);
        }
        printf("\r\n\r");
#endif
        return (EXIT_SUCCESS);
    }    
}

/* Write/Read n bytes */
uint8_t PI_SPI_TransmitReceive(spi_t *spi, uint8_t *tx, uint8_t *rx, int n)
{    
    struct spi_ioc_transfer transaction =
        {
            .tx_buf = (unsigned long)tx,
            .rx_buf = (unsigned long)rx,
            .len = n,
            .delay_usecs = spi->delay,
            .speed_hz = spi->speed,
            .bits_per_word = spi->bits,
            .cs_change = 0,
        };
    if ( ioctl( spi->fd, SPI_IOC_MESSAGE(1), &transaction ) < 1 )
    {
        printf("Can't recived spi message!\r\n\r");
        return (EXIT_FAILURE);
    }
    else
    {
#ifdef DEBUG
        printf("Transmitted in Hex:\r\n\r\t");
        for (int i = 0; i < n; i++)
        {
            printf("%.2X ", tx[i]);
        }
        printf("\r\n\r");
        
        printf("Received in Hex:\r\n\r\t");
        for (int i = 0; i < n; i++)
        {
            printf("%.2X ", rx[i]);
        }
        printf("\r\n\r");
#endif
        return (EXIT_SUCCESS);
    }
}

rpi_spi.h

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <linux/spi/spidev.h>

#ifndef RPI_SPI_H
#define RPI_SPI_H

#ifdef __cplusplus
extern "C" {
#endif

/* SPI options structure */
typedef struct
{
    int fd;
    uint8_t mode;
    uint8_t bits;
    uint32_t speed;
    uint16_t delay; /* uS */
} spi_t;

enum speeds {
    s125_0_MHz  = 2,
    s62_5_MHz   = 4,
    s31_2_MHz   = 8,
    s15_6_MHz   = 16,
    s7_8_MHz    = 32,
    s3_9_MHz    = 64,
    s1953_kHz   = 128,
    s976_kHz    = 256,
    s488_kHz    = 512,
    s244_kHz    = 1024,
    s122_kHz    = 2048,
    s61_kHz     = 4096,
    s30_5_kHz   = 8192,
    s15_2_kHz   = 16384,
    s7629_Hz    = 32768
};

/* Init SPI */
uint8_t PI_SPI_Init(spi_t *spi);

/* Deinit SPI */
uint8_t PI_SPI_Deinit(spi_t *spi);

/* Write n bytes */
uint8_t PI_SPI_Transmit(spi_t *spi, uint8_t *tx, int n);
        
/* Read n bytes */
uint8_t PI_SPI_Receive(spi_t *spi, uint8_t *rx, int n);

/* Write/Read n bytes */
uint8_t PI_SPI_TransmitReceive(spi_t *spi, uint8_t *tx, uint8_t *rx, int n);

#ifdef __cplusplus
}
#endif

#endif /* RPI_SPI_H */