libreria_dht22/main/main.c

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#include "esp_rom_sys.h"
#include "esp_log.h"

#define DHT_PIN GPIO_NUM_4
#define US_DELAY 3
#define DHT_DATA_BITS 40

static const char *TAG = "DHT22";

// Macro to check the return value of a function and log an error if it is not ESP_OK
#define CHECK_LOGE(x, msg, ...) do { \
        esp_err_t __; \
        if ((__ = x) != ESP_OK) { \
            portEXIT_CRITICAL(&mux); \
            ESP_LOGE(TAG, msg, ## __VA_ARGS__); \
            return __; \
        } \
    } while (0)

gpio_num_t dht_pin = DHT_PIN;

static portMUX_TYPE mux = portMUX_INITIALIZER_UNLOCKED;

static esp_err_t dht_attach_pin(gpio_num_t pin){
    if (pin < GPIO_NUM_0 || pin >= GPIO_NUM_MAX) {
        ESP_LOGE(TAG, "Invalid GPIO pin number: %d", pin);
        return ESP_ERR_INVALID_ARG;
    }
    gpio_set_direction(pin, GPIO_MODE_INPUT_OUTPUT_OD);
    gpio_set_level(pin, 1); // Set the pin high by default
    return ESP_OK;
}

static esp_err_t get_change_time(gpio_num_t pin, uint8_t timeout_us, bool expected_level, uint32_t *time_us){
    *time_us = 0;
    while (*time_us < timeout_us){
        if (gpio_get_level(pin) == expected_level) {
            return ESP_OK;
        }
        *time_us += US_DELAY;
        esp_rom_delay_us(US_DELAY);
    }
    return ESP_ERR_TIMEOUT;
}

static inline esp_err_t dht_communication(gpio_num_t pin, uint32_t *data){
    uint32_t high_time;
    uint32_t low_time;
    uint8_t checksum;

    // Send start signal
    gpio_set_direction(pin, GPIO_MODE_INPUT_OUTPUT_OD);
    gpio_set_level(pin, 0);
    esp_rom_delay_us(1500); // Pull low for at least 1ms
    gpio_set_level(pin, 1); // Release the line

    CHECK_LOGE(get_change_time(pin, 40, 1, &low_time), "Failed to get dht response"); // Wait for the sensor to pull low 20-40us
    CHECK_LOGE(get_change_time(pin, 80, 0, &high_time), "Failed to get dht response"); // Wait for the sensor to pull high 80us
    CHECK_LOGE(get_change_time(pin, 80, 1, &low_time), "Failed to get dht response"); // Wait for the sensor to pull low 80us

    for (uint8_t i = DHT_DATA_BITS; i > 0; i--){
        
        // Wait for the sensor to pull low 50us
        CHECK_LOGE(get_change_time(pin, 50, 0, &low_time), "Failed dht transmission"); 
        
        // Wait for the sensor to pull high 26-28us for 0 and 70us for 1
        CHECK_LOGE(get_change_time(pin, 70, 1, &high_time), "Failed dht transmission"); 

        if (i < 9){
            checksum |= (high_time > low_time) << (i - 1);
        }
        else {
            *data |= (high_time > low_time) << (i - 9);
        }

    }

    if (checksum != ((uint8_t)(*data >> 24) + (uint8_t)(*data >> 16) + (uint8_t)(*data >> 8) + (uint8_t)(*data))) {
        ESP_LOGE(TAG, "DHT22 checksum mismatch");
        return ESP_ERR_INVALID_CRC;
    }

    return ESP_OK;
}


esp_err_t dht_read(gpio_num_t pin, float *temperature, float *humidity){
    uint32_t data;

    gpio_set_direction(pin, GPIO_MODE_INPUT_OUTPUT_OD);
    gpio_set_level(pin, 1); 

    portENTER_CRITICAL(&mux);
    CHECK_LOGE(dht_communication(pin, &data), "Failed to read dht data");
    portEXIT_CRITICAL(&mux);

    gpio_set_direction(pin, GPIO_MODE_INPUT_OUTPUT_OD);
    gpio_set_level(pin, 1); 

    *humidity = ((int16_t)(data >> 16)) / 10.0;
    *temperature = ((int16_t)(data & 0xFFFF)) / 10.0;
    return ESP_OK;
}

void app_main(void)
{
    float temperature;
    float humidity;
    esp_err_t err = dht_attach_pin(dht_pin);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to attach DHT pin: %s", esp_err_to_name(err));
        vTaskDelay(pdMS_TO_TICKS(5000)); // Wait for 5 seconds before retrying
        return;
    }

    while (1) {
        if (dht_read(dht_pin, &temperature, &humidity) == ESP_OK) {
            ESP_LOGI(TAG, "Temperature: %.1f°C, Humidity: %.1f%%", temperature, humidity);
        } else {
            ESP_LOGE(TAG, "Failed to read from DHT22 sensor");
        }
        vTaskDelay(pdMS_TO_TICKS(5000)); // Wait for 5 seconds before the next reading
    }

}