/* 

Example SPI use on linux/raspberry pi

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

#include "spi.h"

#define SPI_DEVICE "/dev/spidev0.0"
#define SPI_SPEED 1000 * 1000 /* 1 MHz */

/*
 * Pinout config for this example
 *
 * MOSI - GPIO 10 (physical pin 19) => LIS3DH "SDA" or "SDI"
 * MISO - GPIO 9  (physical pin 21) => LIS3DH "SDO"
 * SCLK - GPIO 11 (physical pin 23) => LIS3DH "SCL"
 * CE0  - GPIO 8  (physical pin 24) => LIS3DH "!CS"
 *
 */

static int fd;

int spi_init(void) {
	uint8_t mode = SPI_MODE_0;
	uint8_t bits = 8;
	uint32_t speed = SPI_SPEED;

	if ((fd = open(SPI_DEVICE, O_RDWR)) < 0) {
		fprintf(stderr, "spi_init(): open(%s)\n", SPI_DEVICE);
		return 1;
	}

	if (ioctl(fd, SPI_IOC_RD_MODE, &mode) == -1) {
		fprintf(stderr, "spi_init(): SPI_IOC_RD_MODE\n");
		return 1;
	}

	if (ioctl(fd, SPI_IOC_WR_MODE, &mode) == -1) {
		fprintf(stderr, "spi_init(): SPI_IOC_WR_MODE\n");
		return 1;
	}

	if (ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits) == -1) {
		fprintf(stderr, "spi_init(): SPI_IOC_WR_BITS_PER_WORD\n");
		return 1;
	}

	if (ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits) == -1) {
		fprintf(stderr, "spi_init(): SPI_IOC_RD_BITS_PER_WORD\n");
		return 1;
	}

	if (ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed) == -1) {
		fprintf(stderr, "spi_init(): SPI_IOC_WR_MAX_SPEED_HZ\n");
		return 1;
	}

	if (ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) == -1) {
		fprintf(stderr, "spi_init(): SPI_IOC_RD_MAX_SPEED_HZ\n");
		return 1;
	}
	
	return 0;
}

int spi_read(uint8_t reg, uint8_t *dst, uint32_t size) {

	uint8_t send[2];
	struct spi_ioc_transfer tr[2] = {0};

	/* clear 2 MSbits */
	reg &= 0x3F;

	/* set READ bit */
    reg |= 0x80;
    
    if (size > 1) {
		/* set AUTO INC bit */
        reg |= 0x40;
    }

	send[0] = reg;
	send[1] = 0x00;

	tr[0].tx_buf = (unsigned long) send;
	tr[0].rx_buf = (unsigned long) 0;
	tr[0].len = 2;

	tr[1].tx_buf = (unsigned long) 0;
	tr[1].rx_buf = (unsigned long) dst;
	tr[1].len = size;

	if (ioctl(fd, SPI_IOC_MESSAGE(2), tr) < 0) {
		fprintf(stderr, "spi_read(): error ioctl()\n");
		return 1;
	}

	return 0;
}

int spi_write(uint8_t reg, uint8_t value) {
	struct spi_ioc_transfer tr[2] = {0};

	/* clear 2 MSbits */
	reg &= 0x3F;

	tr[0].tx_buf = (unsigned long) &reg;
	tr[0].rx_buf = (unsigned long) 0;
	tr[0].len = 1;

	tr[1].tx_buf = (unsigned long) &value;
	tr[1].rx_buf = (unsigned long) 0;
	tr[1].len = 1;

	if (ioctl(fd, SPI_IOC_MESSAGE(2), tr) < 0) {
		fprintf(stderr, "spi_write(): error ioctl()\n");
		return 1;
	}

	return 0;
}

int spi_deinit(void) {

	if (fd) {
		close(fd);
	}

	return 0;
}