dht22_sensor/dht22_sensor.c

#include "dht22_sensor.h"
#include "esp_log.h"
#include "esp_rom_sys.h"
#include "freertos/FreeRTOS.h"
#include "freertos/portmacro.h"
#include <string.h>

static const char *TAG = "DHT22_SENSOR";

// Default DHT22 timing constants (microseconds)
#define DHT22_DEFAULT_START_SIGNAL_US 18000   // 18ms start signal
#define DHT22_DEFAULT_RESPONSE_TIMEOUT_US 500 // 500us timeout for response
#define DHT22_DEFAULT_DATA_TIMEOUT_US 150     // 150us timeout for data bits
#define DHT22_DEFAULT_BIT_THRESHOLD_US 40     // Threshold for 0/1 detection

// Global configuration
static dht22_config_t current_config = {0};
static bool is_initialized = false;

// Internal function to read from DHT22
static dht22_result_t dht22_read_internal(int gpio_pin, float *temperature, float *humidity, const dht22_config_t *config);

esp_err_t dht22_init(int gpio_pin)
{
    dht22_config_t default_config = {
        .gpio_pin = gpio_pin,
        .start_signal_us = DHT22_DEFAULT_START_SIGNAL_US,
        .response_timeout_us = DHT22_DEFAULT_RESPONSE_TIMEOUT_US,
        .data_timeout_us = DHT22_DEFAULT_DATA_TIMEOUT_US,
        .bit_threshold_us = DHT22_DEFAULT_BIT_THRESHOLD_US};

    return dht22_init_with_config(&default_config);
}

esp_err_t dht22_init_with_config(const dht22_config_t *config)
{
    if (config == NULL)
    {
        ESP_LOGE(TAG, "DHT22 config cannot be NULL");
        return ESP_ERR_INVALID_ARG;
    }

    if (config->gpio_pin < 0)
    {
        ESP_LOGE(TAG, "Invalid GPIO pin: %d", config->gpio_pin);
        return ESP_ERR_INVALID_ARG;
    }

    ESP_LOGI(TAG, "Initializing DHT22 on GPIO %d", config->gpio_pin);

    // Store configuration
    memcpy(&current_config, config, sizeof(dht22_config_t));
    is_initialized = true;

    ESP_LOGI(TAG, "DHT22 initialized successfully");
    return ESP_OK;
}

dht22_result_t dht22_read(float *temperature, float *humidity)
{
    if (!is_initialized)
    {
        ESP_LOGE(TAG, "DHT22 not initialized");
        return DHT22_TIMEOUT_ERROR;
    }

    return dht22_read_internal(current_config.gpio_pin, temperature, humidity, &current_config);
}

dht22_result_t dht22_read_data(dht22_data_t *data)
{
    if (data == NULL)
    {
        ESP_LOGE(TAG, "DHT22 data pointer cannot be NULL");
        return DHT22_TIMEOUT_ERROR;
    }

    return dht22_read(&data->temperature, &data->humidity);
}

dht22_result_t dht22_read_from_pin(int gpio_pin, float *temperature, float *humidity)
{
    dht22_config_t temp_config = {
        .gpio_pin = gpio_pin,
        .start_signal_us = DHT22_DEFAULT_START_SIGNAL_US,
        .response_timeout_us = DHT22_DEFAULT_RESPONSE_TIMEOUT_US,
        .data_timeout_us = DHT22_DEFAULT_DATA_TIMEOUT_US,
        .bit_threshold_us = DHT22_DEFAULT_BIT_THRESHOLD_US};

    return dht22_read_internal(gpio_pin, temperature, humidity, &temp_config);
}

static dht22_result_t dht22_read_internal(int gpio_pin, float *temperature, float *humidity, const dht22_config_t *config)
{
    if (temperature == NULL || humidity == NULL)
    {
        ESP_LOGE(TAG, "Temperature and humidity pointers cannot be NULL");
        return DHT22_TIMEOUT_ERROR;
    }

    uint8_t data[5] = {0};
    int counter = 0;

    ESP_LOGD(TAG, "Reading DHT22 from GPIO %d", gpio_pin);

    // Disable interrupts during critical timing
    portDISABLE_INTERRUPTS();

    // Configure GPIO
    gpio_config_t io_conf = {
        .pin_bit_mask = (1ULL << gpio_pin),
        .mode = GPIO_MODE_OUTPUT_OD,
        .pull_up_en = GPIO_PULLUP_ENABLE,
        .pull_down_en = GPIO_PULLDOWN_DISABLE,
        .intr_type = GPIO_INTR_DISABLE,
    };
    gpio_config(&io_conf);

    // Send start signal
    gpio_set_level(gpio_pin, 0);
    esp_rom_delay_us(config->start_signal_us);
    gpio_set_level(gpio_pin, 1);
    esp_rom_delay_us(40);

    // Switch to input mode
    io_conf.mode = GPIO_MODE_INPUT;
    gpio_config(&io_conf);

    // Wait for DHT22 response (should go low then high)
    counter = 0;
    while (gpio_get_level(gpio_pin) == 1)
    {
        esp_rom_delay_us(1);
        if (++counter > config->response_timeout_us)
        {
            portENABLE_INTERRUPTS();
            ESP_LOGD(TAG, "DHT22 timeout waiting for initial response");
            return DHT22_TIMEOUT_ERROR;
        }
    }

    // Wait for response signal to go high
    counter = 0;
    while (gpio_get_level(gpio_pin) == 0)
    {
        esp_rom_delay_us(1);
        if (++counter > config->response_timeout_us)
        {
            portENABLE_INTERRUPTS();
            ESP_LOGD(TAG, "DHT22 timeout waiting for response high");
            return DHT22_TIMEOUT_ERROR;
        }
    }

    // Wait for response signal to go low (start of data)
    counter = 0;
    while (gpio_get_level(gpio_pin) == 1)
    {
        esp_rom_delay_us(1);
        if (++counter > config->response_timeout_us)
        {
            portENABLE_INTERRUPTS();
            ESP_LOGD(TAG, "DHT22 timeout waiting for data start");
            return DHT22_TIMEOUT_ERROR;
        }
    }

    // Read 40 bits of data
    for (int i = 0; i < 40; i++)
    {
        // Wait for signal to go high
        counter = 0;
        while (gpio_get_level(gpio_pin) == 0)
        {
            esp_rom_delay_us(1);
            if (++counter > config->data_timeout_us)
            {
                portENABLE_INTERRUPTS();
                ESP_LOGD(TAG, "DHT22 timeout waiting for bit %d high signal", i);
                return DHT22_TIMEOUT_ERROR;
            }
        }

        // Measure high pulse duration
        counter = 0;
        while (gpio_get_level(gpio_pin) == 1)
        {
            esp_rom_delay_us(1);
            if (++counter > config->data_timeout_us)
            {
                portENABLE_INTERRUPTS();
                ESP_LOGD(TAG, "DHT22 timeout during bit %d high pulse", i);
                return DHT22_TIMEOUT_ERROR;
            }
        }

        // DHT22 protocol: '0' = ~26-28us high, '1' = ~70us high
        data[i / 8] <<= 1;
        if (counter > config->bit_threshold_us)
        {
            data[i / 8] |= 1;
        }

        // Debug first few bits if we're getting all zeros
        if (i < 8)
        {
            ESP_LOGD(TAG, "Bit %d: pulse=%dus, value=%d", i, counter, (counter > config->bit_threshold_us) ? 1 : 0);
        }
    }

    // Re-enable interrupts
    portENABLE_INTERRUPTS();

    // Verify checksum
    uint8_t checksum = data[0] + data[1] + data[2] + data[3];

    // Debug output for problematic readings
    if ((data[0] == 0 && data[1] == 0 && data[2] == 0 && data[3] == 0) || checksum != data[4])
    {
        ESP_LOGD(TAG, "DHT22 raw data: %02X %02X %02X %02X %02X",
                 data[0], data[1], data[2], data[3], data[4]);
        ESP_LOGD(TAG, "Calculated checksum: %02X, Received: %02X", checksum, data[4]);
    }

    if (checksum != data[4])
    {
        ESP_LOGD(TAG, "DHT22 checksum mismatch");
        return DHT22_CHECKSUM_ERROR;
    }

    // Check for all-zero data (sensor not responding properly)
    if (data[0] == 0 && data[1] == 0 && data[2] == 0 && data[3] == 0)
    {
        ESP_LOGD(TAG, "DHT22 returned all zeros - sensor may not be connected");
        return DHT22_TIMEOUT_ERROR; // Treat as timeout to trigger retry
    }

    // Convert data to temperature and humidity
    *humidity = ((data[0] << 8) | data[1]) / 10.0f;

    int temp_raw = (data[2] << 8) | data[3];
    if (temp_raw & 0x8000)
    {
        *temperature = -(temp_raw & 0x7FFF) / 10.0f;
    }
    else
    {
        *temperature = temp_raw / 10.0f;
    }

    ESP_LOGD(TAG, "DHT22 read successful: T=%.2f°C, H=%.2f%%", *temperature, *humidity);
    return DHT22_OK;
}

const char *dht22_get_error_string(dht22_result_t result)
{
    switch (result)
    {
    case DHT22_OK:
        return "Success";
    case DHT22_TIMEOUT_ERROR:
        return "Timeout error";
    case DHT22_CHECKSUM_ERROR:
        return "Checksum error";
    default:
        return "Unknown error";
    }
}

bool dht22_test_connection(void)
{
    if (!is_initialized)
    {
        ESP_LOGW(TAG, "DHT22 not initialized for connection test");
        return false;
    }

    float temp, humid;
    dht22_result_t result = dht22_read(&temp, &humid);

    if (result == DHT22_OK)
    {
        ESP_LOGI(TAG, "DHT22 connection test successful: T=%.2f°C, H=%.2f%%", temp, humid);
        return true;
    }
    else
    {
        ESP_LOGW(TAG, "DHT22 connection test failed: %s", dht22_get_error_string(result));
        return false;
    }
}

esp_err_t dht22_deinit(void)
{
    if (!is_initialized)
    {
        ESP_LOGW(TAG, "DHT22 not initialized");
        return ESP_OK;
    }

    ESP_LOGI(TAG, "Deinitializing DHT22 sensor");
    is_initialized = false;
    memset(&current_config, 0, sizeof(dht22_config_t));

    ESP_LOGI(TAG, "DHT22 sensor deinitialized");
    return ESP_OK;
}