84 lines
2.1 KiB
C
84 lines
2.1 KiB
C
/**
|
|
* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
|
|
*
|
|
* SPDX-License-Identifier: BSD-3-Clause
|
|
**/
|
|
|
|
#include <stdio.h>
|
|
#include <math.h>
|
|
#include "pico/stdlib.h"
|
|
#include "hardware/gpio.h"
|
|
|
|
const uint LED_PIN = PICO_DEFAULT_LED_PIN;
|
|
const uint DHT_PIN = 15;
|
|
const uint MAX_TIMINGS = 85;
|
|
|
|
typedef struct {
|
|
float humidity;
|
|
float temp_celsius;
|
|
} dht_reading;
|
|
|
|
void read_from_dht(dht_reading *result);
|
|
|
|
int main() {
|
|
stdio_init_all();
|
|
gpio_init(LED_PIN);
|
|
gpio_init(DHT_PIN);
|
|
gpio_set_dir(LED_PIN, GPIO_OUT);
|
|
while (1) {
|
|
dht_reading reading;
|
|
read_from_dht(&reading);
|
|
float fahrenheit = (reading.temp_celsius * 9 / 5) + 32;
|
|
printf("Humidity = %.1f%%, Temperature = %.1fC (%.1fF)\n",
|
|
reading.humidity, reading.temp_celsius, fahrenheit);
|
|
|
|
sleep_ms(2000);
|
|
}
|
|
}
|
|
|
|
void read_from_dht(dht_reading *result) {
|
|
int data[5] = {0, 0, 0, 0, 0};
|
|
uint last = 1;
|
|
uint j = 0;
|
|
|
|
gpio_set_dir(DHT_PIN, GPIO_OUT);
|
|
gpio_put(DHT_PIN, 0);
|
|
sleep_ms(20);
|
|
gpio_set_dir(DHT_PIN, GPIO_IN);
|
|
|
|
gpio_put(LED_PIN, 1);
|
|
for (uint i = 0; i < MAX_TIMINGS; i++) {
|
|
uint count = 0;
|
|
while (gpio_get(DHT_PIN) == last) {
|
|
count++;
|
|
sleep_us(1);
|
|
if (count == 255) break;
|
|
}
|
|
last = gpio_get(DHT_PIN);
|
|
if (count == 255) break;
|
|
|
|
if ((i >= 4) && (i % 2 == 0)) {
|
|
data[j / 8] <<= 1;
|
|
if (count > 16) data[j / 8] |= 1;
|
|
j++;
|
|
}
|
|
}
|
|
gpio_put(LED_PIN, 0);
|
|
|
|
if ((j >= 40) && (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF))) {
|
|
result->humidity = (float) ((data[0] << 8) + data[1]) / 10;
|
|
if (result->humidity > 100) {
|
|
result->humidity = data[0];
|
|
}
|
|
result->temp_celsius = (float) (((data[2] & 0x7F) << 8) + data[3]) / 10;
|
|
if (result->temp_celsius > 125) {
|
|
result->temp_celsius = data[2];
|
|
}
|
|
if (data[2] & 0x80) {
|
|
result->temp_celsius = -result->temp_celsius;
|
|
}
|
|
} else {
|
|
printf("Bad data\n");
|
|
}
|
|
}
|