DHT11、DHT21系列的传感器小伙伴们一定很熟悉，单片机一接，写个小的APP，可以做个小型的室内温湿度监测系统。

材料清单：

元器件名称 数量
DHT11 1
Respberry Pi Pico 1
10k电阻 1
面包板 1

电气接线图：

pi-and-pico-uart-and-dht-sensor.png

Demo:

#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");
    }
}

CMakelist.txt:

add_executable(dht
        dht.c
        )

target_link_libraries(dht pico_stdlib)

pico_add_extra_outputs(dht)

# add url via pico_set_program_url
example_auto_set_url(dht)

终端的输出如下：

DHT1.jpg