raspberrypi/gpio/dht12.c

116 lines
2.5 KiB
C

/*
* read temperature and humidity from DHT11 or DHT22 sensor
*
*/
#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#define MAX_TIMINGS 85
int data[5] = { 0, 0, 0, 0, 0 };
int read_dht_data(float *h, float *c, float *f, int PIN)
{
uint8_t laststate = HIGH;
uint8_t counter = 0;
uint8_t j = 0, i;
data[0] = data[1] = data[2] = data[3] = data[4] = 0;
/* pull pin down for 18 milliseconds */
pinMode(PIN, OUTPUT);
digitalWrite(PIN, LOW);
delay(18);
/* prepare to read the pin */
pinMode(PIN, INPUT);
/* detect change and read data */
for (i = 0; i < MAX_TIMINGS; i++) {
counter = 0;
while (digitalRead(PIN) == laststate) {
counter++;
delayMicroseconds(1);
if (counter == 255) {
break;
}
}
laststate = digitalRead(PIN);
if (counter == 255)
break;
/* ignore first 3 transitions */
if ((i >= 4) && (i % 2 == 0)) {
/* shove each bit into the storage bytes */
data[j / 8] <<= 1;
if (counter > 16)
data[j / 8] |= 1;
j++;
}
}
/*
* check we read 40 bits (8bit x 5 ) + verify checksum in the last byte
* print it out if data is good
*/
if ((j >= 40) &&
(data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF))) {
*h = (float)((data[0] << 8) + data[1]) / 10;
if (*h > 100) {
*h = data[0]; // for DHT11
}
*c = (float)(((data[2] & 0x7F) << 8) + data[3]) / 10;
if (*c > 125) {
*c = data[2]; // for DHT11
}
if (data[2] & 0x80) {
*c = -(*c);
}
*f = *c * 1.8f + 32;
return 0;
} else {
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);
}
if (wiringPiSetup() == -1)
exit(1);
int PIN = atol(argv[1]);
float h;
float c;
float f;
read_dht_data(&h, &c, &f, PIN);
printf("Humidity = %.1f Temperature = %.1f ℃ ( %.1f ℉ )\n", h, c, f);
return (0);
}