reader.c

SHT11温度湿度传感器的详细资料包获C代码和使用方法

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <termio.h>
#include <errno.h>
#include <fcntl.h>
#include <time.h>

#define TEMP 0x01
#define HUMI 0x02
#define DEW  0x04
#define TIME 0x08

enum {LONG, SHORT};

calc_sht11(float *p_temp, float *p_hum) {
  const float C1 = -4.0;
  const float C2 = 0.0405;
  const float C3 = -0.0000028;
  const float T1 = 0.01;
  const float T2 = 0.0008;

  float rh = *p_hum;
  float t = *p_temp;
  float rh_lin, rh_true, t_C;

  t_C = t*0.01 - 40;
  rh_lin = C3*rh*rh + C2*rh + C1;
  rh_true =(t_C-25) * (T1+T2*rh) + rh_lin;
  if (rh_true > 100) rh_true = 100;
  if (rh_true < 0.1) rh_true = 0.1;

  *p_hum = rh_true;
  *p_temp = t_C;
}

float calc_dewpoint(float t, float h) {
  float logEx, dew_point;
  logEx=0.66077 + 7.5 * t / (237.3 + t) + (log10(h)-2);
  dew_point = (logEx - 0.66077) * 237.3 / (0.66077 + 7.5 - logEx);
  return dew_point;
}

void init_tty(char *s) {
  int fd;
  struct termio term;

  if ((fd = open(s, O_RDONLY)) == -1) {
    fprintf(stderr, "Can't open %s for reading\n",s);
    exit(errno);
  }
  if ( ioctl(fd, TCGETA, &term) == -1 ) {
    fprintf(stderr, "%s is not a tty\n",s);
    exit(errno);
  }
  term.c_cflag &= ~CBAUD;
  term.c_cflag |= B9600;
  ioctl(fd, TCSETAW, &term);
  close(fd);
}


int main(int argc, char **argv) {
  unsigned int hum,temp;
  float h,t;

  unsigned char displaymode = LONG;
  unsigned char output = 0;
  int  count = -1;
  
  int c;
  int digit_optind = 0;

  char device[20] = "/dev/ttyS0";
  FILE *f;

  time_t now;
  struct tm *tmstruct;
  char ts[20];

  while (1) {
    int this_option_optind = optind ? optind : 1;
    int option_index = 0;
    static struct option long_options[] = {
      {"timestamp", 0, 0, 'a'},
      {"count", 1, 0, 'c'},
      {"device", 1, 0, 'd'},
      {"help", 0, 0, 'h'},
      {"dewpoint", 0, 0, 'p'},
      {"short", 0, 0, 's'},
      {"temperature", 0, 0, 't'},
      {"humidity", 0, 0, 'u'},
      {0, 0, 0, 0}
    };

    c = getopt_long (argc, argv, "ac:d:hpstu", long_options, &option_index);
    if (c == -1)
      break;

    switch (c) {
      case 'a':
        output|=TIME;
        break;
      case 'c':
        count = atoi(optarg);
        break;
      case 'd':
        strncpy(device, optarg, 20);
        break;
      case 'h':
        printf ("Usage: %s [OPTION]...\n", argv[0]);
        printf ("\n");
        printf ("-a, --timestamp\t\tShow timestamp\n");
        printf ("-c, --count=COUNT\t\tDisplay COUNT lines and exit\n");
        printf ("-d, --device\t\tSet serial interface (default: /dev/ttyS0)\n");
        printf ("-h, --help\t\tDisplay this help and exit\n");
        printf ("-p, --dewpoint\t\tCalculate dew point\n");
        printf ("-s, --short\t\tShort output\n");
        printf ("-t, --temperature\tShow temperature\n");
        printf ("-u, --humidity\t\tShow humidity\n");
        printf ("\n");
        exit(0);
        break;
      case 'p':
        output|=DEW;
        break;
      case 's':
        displaymode = SHORT;
        break;
      case 't':
        output|=TEMP;
        break;
      case 'u':
        output|=HUMI;
        break;
    }
  }

  init_tty(device);
  if ((f = fopen(device, "r")) == NULL) {
    fprintf(stderr, "Can't open %s for reading\n",device);
    exit(errno);
  }

  while(count--) {
    if (count<0) count=-1;
    fscanf(f,"%x %x", &temp, &hum);
    h=(float)hum; t=(float)temp;
    calc_sht11(&t, &h);

    time(&now);
    tmstruct = localtime(&now);

    if (output == 0) output = TEMP|HUMI|DEW|TIME;

    if (displaymode == LONG) {
      strftime(ts, 20, "%x %X", tmstruct);
      if (output & TIME) printf("Time: %s\t", ts);
      if (output & TEMP) printf("Temp: %5.1fC\t", t);
      if (output & HUMI) printf("Hum: %5.1f%%\t", h);
      if (output & DEW)  printf("Dew point: %5.1fC\t", calc_dewpoint(t,h));
    } else {
      strftime(ts, 20, "%s", tmstruct);
      if (output & TIME) printf("%s\t", ts);
      if (output & TEMP) printf("%5.1f\t", t);
      if (output & HUMI) printf("%5.1f\t", h);
      if (output & DEW)  printf("%5.1f\t", calc_dewpoint(t,h));
    }
    printf("\n");
    fflush(stdout);
  }
}