raspberrypi/gpio/dht11.c

/*
 * DTH11 温度湿度传感器
 *
 */

#include <wiringPi.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#define MAX_TIME 85
#define MAX_TRIES 100

int dht11_val[5] = { 0, 0, 0, 0, 0 };

int dht11_read_val(int *h, int *t, int pin)
{
    uint8_t lststate = HIGH;
    uint8_t counter = 0;
    uint8_t j = 0, i;

    for (i = 0; i < 5; i++) {
        dht11_val[i] = 0;
    }

    pinMode(pin, OUTPUT);
    digitalWrite(pin, LOW);
    delay(18);
    digitalWrite(pin, HIGH);
    delayMicroseconds(40);
    pinMode(pin, INPUT);

    for (i = 0; i < MAX_TIME; i++) {
        counter = 0;
        while (digitalRead(pin) == lststate) {
            counter++;
            delayMicroseconds(1);
            if (counter == 255)
                break;
        }
        lststate = digitalRead(pin);
        if (counter == 255)
            break;
        // top 3 transitions are ignored
        if ((i >= 4) && (i % 2 == 0)) {
            dht11_val[j / 8] <<= 1;
            if (counter > 16)
                dht11_val[j / 8] |= 1;
            j++;
        }
    }

    // verify cheksum and print the verified data
    if ((j >= 40)
        && (dht11_val[4] ==
            ((dht11_val[0] + dht11_val[1] + dht11_val[2] +
              dht11_val[3]) & 0xFF))) {
        // Only return the integer part of humidity and temperature. The sensor
        // is not accurate enough for decimals anyway 
        *h = dht11_val[0];
        *t = dht11_val[2];
        return 0;
    } else {
        // invalid data
        return 1;
    }
}

static int is_num(char *str)
{
    int i, len;
    for (i = 0, len = strlen(str); i < len; i++) {
        if (isdigit(str[i]) == 0) {
            printf("不是数字\n");
           return 1;
        }
    }

    return 0;
}

int main(int argc, char *argv[])
{
    if (argc != 2) {
        printf("Parameter error.\n");
        exit(1);
    }
    if (is_num(argv[1]) == 1) {
        printf("Parameter error, parameter 1 is PIN pin value\n");
        exit(1);
    }

    int pin = atol(argv[1]);

    int h;                      //humidity
    int t;                      //temperature in degrees Celsius

    wiringPiSetup();

    // read the sensor until we get a pair of valid measurements
    // but bail out if we tried too many times
    int retval = 1;
    int tries = 0;
    while (retval != 0 && tries < MAX_TRIES) {
        retval = dht11_read_val(&h, &t, pin);
        if (retval == 0) {
            //printf("%d %d\n", h, t);
            printf("Humidity = %d Temperature = %d ℃  ( %f ℉ )\n", h, t, ((t*1.8)+32));
        } else {
            delay(3000);
        }
        tries += 1;
    }
    if (tries < MAX_TRIES)
        return 0;
    else
        return 1;

}