/*********************************************************************************
 *      Copyright:  (C) 2022 Guo Wenxue <guowenxue@gmail.com>
 *                  All rights reserved.
 *
 *       Filename:  sht20.c
 *    Description:  This file is temperature and relative humidity sensor SHT20 code
 *
 *        Version:  1.0.0(2022/4/14)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "2022/04/14 12:13:26"
 *
 ********************************************************************************/

/*
 * Hardware connection:
 *
 *   Sht20 Module       RaspberryPi/IGKBoard
 *      VCC      <----->      3.3V
 *      SDA      <----->      SDA
 *      SCL      <----->      SCL
 *      GND      <----->      GND
 */

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <sys/stat.h>
#include <linux/i2c-dev.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <string.h>
#include <stdint.h>
#include <time.h>
#include <errno.h>
#include <string.h>


#define SOFTRESET                        0xFE
#define TRIGGER_TEMPERATURE_NO_HOLD      0xF3
#define TRIGGER_HUMIDITY_NO_HOLD         0xF5

static inline void msleep(unsigned long ms);
static inline void dump_buf(const char *prompt, uint8_t *buf, int size);
int sht2x_init(char *i2c_dev);
int sht2x_get_serialnumber(int fd, uint8_t *serialnumber, int size);
int sht2x_get_temp_humidity(int fd, float *temp, float *rh);

int main(int argc, char **argv)
{
    int         fd;
    float       temp;
    float       rh;
    uint8_t     serialnumber[8];

    if( argc != 2)
    {
        printf("This program used to do I2C test by sht20 temperature & humidity module.\n");
        printf("Usage: %s /dev/i2c-x\n", argv[0]);
        return 0;
    }

    fd = sht2x_init(argv[1]);
    if(fd < 0)
    {
        printf("SHT2x initialize failure\n");
        return 1;
    }

    if( sht2x_get_serialnumber(fd, serialnumber, 8) < 0)
    {
        printf("SHT2x get serial number failure\n");
        return 3;
    }

    if( sht2x_get_temp_humidity(fd, &temp, &rh) < 0 )
    {
        printf("SHT2x get get temperature and relative humidity failure\n");
        return 3;
    }

    printf("Temperature=%lf ℃ relative humidity=%lf.\n", temp, rh);

    close(fd);
}


static inline void msleep(unsigned long ms)
{
    struct timespec cSleep;
    unsigned long ulTmp;

    cSleep.tv_sec = ms / 1000;
    if (cSleep.tv_sec == 0)
    {
        ulTmp = ms * 10000;
        cSleep.tv_nsec = ulTmp * 100;
    }
    else
    {
        cSleep.tv_nsec = 0;
    }

    nanosleep(&cSleep, 0);
}

static inline void dump_buf(const char *prompt, uint8_t *buf, int size)
{
    int          i;

    if( !buf )
    {
        return ;
    }

    if( prompt )
    {
        printf("%s ", prompt);
    }

    for(i=0; i<size; i++)
    {
        printf("%02x ", buf[i]);
    }
    printf("\n");

    return ;
}


int sht2x_softreset(int fd)
{
    uint8_t           buf[4];

    if( fd<0 )
    {
        printf("%s line [%d] %s() get invalid input arguments\n", __FILE__, __LINE__, __func__ );
        return -1;
    }

    /* software reset SHT2x */
    memset(buf, 0, sizeof(buf));

    buf[0] = SOFTRESET;
    write(fd, buf, 1);

    msleep(50);

    return 0;
}

int sht2x_init(char *i2c_dev)
{
    int          fd;

    if( (fd=open(i2c_dev, O_RDWR)) < 0)
    {
        printf("i2c device open failed: %s\n", strerror(errno));
            return -1;
    }

    /* set I2C mode and SHT2x slave address */
    ioctl(fd, I2C_TENBIT, 0);    /* Not 10-bit but 7-bit mode */
    ioctl(fd, I2C_SLAVE, 0x40); /* set SHT2x slava address 0x40*/

    if( sht2x_softreset(fd) < 0 )
    {
        printf("SHT2x softreset failure\n");
        return -2;
    }

    return fd;
}

int sht2x_get_temp_humidity(int fd, float *temp, float *rh)
{
    uint8_t           buf[4];

    if( fd<0 || !temp || !rh )
    {
        printf("%s line [%d] %s() get invalid input arguments\n", __FILE__, __LINE__, __func__ );
        return -1;
    }

    /* send trigger temperature measure command and read the data */
    memset(buf, 0, sizeof(buf));
    buf[0]=TRIGGER_TEMPERATURE_NO_HOLD;
    write(fd, buf, 1);

    msleep(85); /* datasheet: typ=66, max=85 */

    memset(buf, 0, sizeof(buf));
    read(fd, buf, 3);
    dump_buf("Temperature sample data: ", buf, 3);
    *temp = 175.72 * (((((int) buf[0]) << 8) + buf[1]) / 65536.0) - 46.85;

    /* send trigger humidity measure command and read the data */
    memset(buf, 0, sizeof(buf));
    buf[0] = TRIGGER_HUMIDITY_NO_HOLD;
    write(fd, buf, 1);

    msleep(29); /* datasheet: typ=22, max=29 */
    memset(buf, 0, sizeof(buf));

    read(fd, buf, 3);
    dump_buf("Relative humidity sample data: ", buf, 3);
    *rh = 125 * (((((int) buf[0]) << 8) + buf[1]) / 65536.0) - 6;

    return 0;
}

int sht2x_get_serialnumber(int fd, uint8_t *serialnumber, int size)
{
    uint8_t           buf[4];

    if( fd<0 || !serialnumber || size!=8 )
    {
        printf("%s line [%d] %s() get invalid input arguments\n", __FILE__, __LINE__, __func__ );
        return -1;
    }

    /* Read SerialNumber from Location 1 */
    memset(buf, 0, sizeof(buf));
    buf[0] = 0xfa;  /* command for readout on-chip memory */
    buf[1] = 0x0f;  /* on-chip memory address */
    write(fd, buf, 2);

    memset(buf, 0, sizeof(buf));
    read(fd, buf, 4);

    serialnumber[5]=buf[0]; /* Read SNB_3 */
    serialnumber[4]=buf[1]; /* Read SNB_2 */
    serialnumber[3]=buf[2]; /* Read SNB_1 */
    serialnumber[2]=buf[3]; /* Read SNB_0 */

    /* Read SerialNumber from Location 2 */
    memset(buf, 0, sizeof(buf) );
    buf[0]=0xfc;  /* command for readout on-chip memory */
    buf[1]=0xc9;  /* on-chip memory address */
    write(fd, buf, 2);

    memset(buf, 0, sizeof(buf) );
    read(fd, buf, 4);

    serialnumber[1]=buf[0]; /* Read SNC_1 */
    serialnumber[0]=buf[1]; /* Read SNC_0 */
    serialnumber[7]=buf[2]; /* Read SNA_1 */
    serialnumber[6]=buf[3]; /* Read SNA_0 */

    dump_buf("SHT2x Serial number: ", serialnumber, 8);

    return 0;
}