libreria_dht22/dht22.c

#include <stdio.h>
#include "dht22.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 CONFIG_DHT_PIN
#define US_DELAY 3
#define DHT_DATA_BITS 40

static const char *TAG = "DHT22";

static portMUX_TYPE mux = portMUX_INITIALIZER_UNLOCKED;

// 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) { \
            ESP_LOGE(TAG, msg, ## __VA_ARGS__); \
            return __; \
        } \
    } while (0)

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

static esp_err_t get_change_time(uint8_t timeout_us, bool expected_level, uint32_t *time_us){
    *time_us = 0;
    while (*time_us < timeout_us){
        if (gpio_get_level(DHT_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(uint32_t *data){
    uint32_t high_time;
    uint32_t low_time;

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

    CHECK_LOGE(get_change_time(44, 0, &low_time), "Failed to get dht response"); // Wait for the sensor to pull low 20-40us
    CHECK_LOGE(get_change_time(88, 1, &high_time), "Failed to get dht response"); // Wait for the sensor to pull high 80us
    CHECK_LOGE(get_change_time(88, 0, &low_time), "Failed to get dht response"); // Wait for the sensor to pull low 80us
    
    uint8_t checksum = 0;

    for (uint8_t i = 0; i < DHT_DATA_BITS; i++){
        
        
        // Wait for the sensor to pull low 50us
        CHECK_LOGE(get_change_time(65, 1, &low_time), "Failed dht transmission %d h", i); 
        
        // Wait for the sensor to pull high 26-28us for 0 or 70us for 1
        CHECK_LOGE(get_change_time(80, 0, &high_time), "Failed dht transmission %d l", i); 

        if (i < 32){
            *data |= ((high_time > low_time) << (31 - i)); // Set the bit if high_time is greater than low_time
        }
        else checksum |= (high_time > low_time) << (39 - i); // Calculate checksum in the last 8 bits

    }
    
    if (checksum != (uint8_t)((*data >> 24) + (*data >> 16 & 0xFF) + (*data >> 8 & 0xFF) + (*data & 0xFF))) {
        ESP_LOGE(TAG, "DHT22 checksum mismatch: calculated %02X, received %02X", checksum, *data & 0xFF);
        return ESP_ERR_INVALID_CRC;
    }

    return ESP_OK;
}

static inline int16_t data_to_int16(uint8_t MSB, uint8_t LSB){
    return (int16_t)((MSB << 8) | LSB);
}


esp_err_t dht_read(float *temperature, float *humidity){
    uint32_t data = 0;

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

    portENTER_CRITICAL(&mux);
    esp_err_t err = dht_communication(&data);
    portEXIT_CRITICAL(&mux);

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

    if (err != ESP_OK) return err;


    *humidity = data_to_int16(data >> 24 & 0xFF, data >> 16 & 0xFF) / 10.0;
    *temperature = data_to_int16(data >> 8 & 0xFF, data & 0xFF) / 10.0;
    return ESP_OK;
}