# zh_aht - AHT Humidity & Temperature Sensor Component for ESP-IDF

## Table of Contents

- [Overview](#overview)
- [Features](#features)
- [Installation](#installation)
- [API Reference](#api-reference)
- [Usage Examples](#usage-examples)
- [Technical Specifications](#technical-specifications)
- [Error Codes](#error-codes)
- [Contributing](#contributing)
- [License](#license)

---

## Overview

`zh_aht` is a lightweight ESP-IDF component for AHT10/AHT15/AHT20/AHT21/AHT25/AHT30/AHT40 humidity and temperature sensors. It provides a simple API to read humidity values from 0 to 100% and temperature values from -40 to +85°C. The component supports multiple sensors on a single I2C bus using the [zh_pca9548a](https://github.com/aZholtikov/zh_pca9548a) I2C multiplexer.

The component is designed specifically for ESP32 microcontrollers and uses ESP-IDF v5.0+ I2C driver API.

---

## Features

1. **Humidity and Temperature Measurement**: Reads humidity from 0 to 100% and temperature from -50 to +150°C
2. **I2C Interface**: Uses standard I2C protocol (400 kHz max frequency)
3. **Configurable I2C Address**: Supports 0x38, 0x39 and 0x44 addresses
4. **Multiple Model Support**: AHT10, AHT15, AHT20, AHT21, AHT25, AHT30, AHT40
5. **Error Statistics**: Built-in error counter for I2C driver errors
6. **Low Power**: Works with ESP-IDF power management
7. **Thread-Safe**: Uses ESP-IDF I2C driver (thread-safe)
8. **Minimal Overhead**: Low memory and CPU overhead
9. **Multiple Sensor Support**: Compatible with I2C multiplexer (zh_pca9548a)

---

## Installation

Navigate to your project's components directory:

```bash
cd ../your_project/components
```

Clone the repository:

```bash
git clone https://github.com/aZholtikov/zh_aht.git
```

In your application, include the header:

```c
#include "zh_aht.h"
```

The component will be automatically built with your project.

### Required menuconfig Settings

For correct operation, enable the following settings in menuconfig:

```text
I2C_ISR_IRAM_SAFE
I2C_MASTER_ISR_HANDLER_IN_IRAM
```

### Optional: Using with I2C Multiplexer (zh_pca9548a)

To use multiple AHT sensors on the same I2C bus, also install the [zh_pca9548a](https://github.com/aZholtikov/zh_pca9548a) component.

---

## API Reference

All functions in this library use double pointer (`zh_aht_handle_t **`) for the sensor handler to allow for proper memory management and thread-safe operations.

### zh_aht_init_config_t Structure

```c
typedef struct
{
    i2c_master_bus_handle_t i2c_handle; // Unique I2C bus handle
    uint8_t i2c_address;                // Sensor I2C address (0x38, 0x39, or 0x44)
    uint32_t i2c_frequency;             // Sensor I2C frequency (max 400000 Hz)
} zh_aht_init_config_t;
```

Use `ZH_AHT_INIT_CONFIG_DEFAULT()` macro to initialize with default values:

- `i2c_frequency`: 400000 Hz
- `i2c_address`: 0x38

---

### zh_aht_handle_t Structure

The structure is declared as `typedef struct _zh_aht_handle_t zh_aht_handle_t;` and encapsulates internal implementation details.

**Fields (internal):**

| Field | Type | Description |
|-------|------|-------------|
| `i2c_master_dev_handle_t` | `dev_handle` | Pointer to I2C device handle. |

---

### zh_aht_stats_t Structure

```c
typedef struct
{
    uint32_t i2c_driver_error; // Number of I2C driver errors
} zh_aht_stats_t;
```

---

### zh_aht_init()

Initializes the AHT sensor.

**Parameters:**

- `config` - Pointer to AHT initialization configuration structure
- `handle` - Double pointer to unique AHT handle (`zh_aht_handle_t **`). If the pointer is NULL, memory will be allocated.

**Returns:**

- `ESP_OK` - Success
- `ESP_ERR_INVALID_ARG` - Invalid argument (NULL config or handle)
- `ESP_ERR_INVALID_STATE` - Sensor is already initialized
- `ESP_ERR_NO_MEM` - Memory allocation failed
- `ESP_FAIL` - Initialization I2C device failed
- `ESP_ERR_NOT_FOUND` - Sensor did not respond

**Example:**

```c
zh_aht_handle_t *aht_handle = NULL;
zh_aht_init_config_t config = ZH_AHT_INIT_CONFIG_DEFAULT();
config.i2c_handle = i2c_bus_handle;
zh_aht_init(&config, &aht_handle);
```

---

### zh_aht_deinit()

Deinitializes the AHT sensor and removes it from the I2C bus. Memory for handle is automatically freed and the pointer is set to NULL.

**Parameters:**

- `handle` - Double pointer to unique AHT handle (`zh_aht_handle_t **`). Must not be NULL.

**Returns:**

- `ESP_OK` - Success
- `ESP_ERR_INVALID_ARG` - Invalid argument (NULL handle pointer)
- `ESP_FAIL` - I2C device removal failed

---

### zh_aht_read()

Reads humidity and temperature values from the sensor.

**Parameters:**

- `handle` - Double pointer to unique AHT handle (`zh_aht_handle_t **`). Must not be NULL.
- `humidity` - Pointer to store humidity value (in %)
- `temperature` - Pointer to store temperature value (in °C)

**Returns:**

- `ESP_OK` - Success
- `ESP_ERR_INVALID_ARG` - Invalid argument (NULL handle pointer or humidity pointer or temperature pointer)
- `ESP_FAIL` - I2C communication error
- `ESP_ERR_TIMEOUT` - Timeout waiting for data ready
- `ESP_ERR_INVALID_CRC` - Invalid CRC checksum

**Note:** The function performs measurement and waits ~80ms for data ready.

---

### zh_aht_reset()

Resets the AHT sensor.

**Parameters:**

- `handle` - Double pointer to unique AHT handle (`zh_aht_handle_t **`). Must not be NULL.

**Returns:**

- `ESP_OK` - Success
- `ESP_ERR_INVALID_ARG` - Invalid argument (NULL handle pointer)
- `ESP_FAIL` - I2C communication error

---

### zh_aht_get_stats()

Gets error statistics since last reset.

**Returns:**

- Pointer to the statistics structure

---

### zh_aht_reset_stats()

Resets error statistics counter.

---

## Usage Examples

### Basic Example: Single Sensor

```c
#include "zh_aht.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_aht_handle_t *aht_handle = NULL;

void app_main(void)
{
    esp_log_level_set("zh_aht", ESP_LOG_ERROR);
    i2c_master_bus_config_t i2c_bus_config = {
        .clk_source = I2C_CLK_SRC_DEFAULT,
        .i2c_port = I2C_PORT,
        .scl_io_num = GPIO_NUM_22,
        .sda_io_num = GPIO_NUM_21,
        .glitch_ignore_cnt = 7,
        .flags.enable_internal_pullup = true,
    };
    i2c_master_bus_handle_t i2c_bus_handle = NULL;
    i2c_new_master_bus(&i2c_bus_config, &i2c_bus_handle);
    zh_aht_init_config_t config = ZH_AHT_INIT_CONFIG_DEFAULT();
    config.i2c_handle = i2c_bus_handle;
    zh_aht_init(&config, &aht_handle);
    float humidity = 0.0;
    float temperature = 0.0;
    for (;;)
    {
        zh_aht_read(&aht_handle, &humidity, &temperature);
        printf("Humidity: %.2f%%\n", humidity);
        printf("Temperature: %.2f°C\n", temperature);
        const zh_aht_stats_t *stats = zh_aht_get_stats();
        printf("I2C errors: %ld\n", stats->i2c_driver_error);
        vTaskDelay(5000 / portTICK_PERIOD_MS);
    }
}
```

---

### Multiple Sensors: Using I2C Multiplexer (zh_pca9548a)

```c
#include "zh_pca9548a.h"
#include "zh_aht.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_pca9548a_handle_t pca9548a_handle = {0};
zh_aht_handle_t *aht_handle_chan_0 = NULL;
zh_aht_handle_t *aht_handle_chan_1 = NULL;
zh_aht_handle_t *aht_handle_chan_2 = NULL;

void app_main(void)
{
    esp_log_level_set("zh_pca9548a", ESP_LOG_ERROR);
    esp_log_level_set("zh_aht", ESP_LOG_ERROR);
    i2c_master_bus_config_t i2c_bus_config = {
        .clk_source = I2C_CLK_SRC_DEFAULT,
        .i2c_port = I2C_PORT,
        .scl_io_num = GPIO_NUM_22,
        .sda_io_num = GPIO_NUM_21,
        .glitch_ignore_cnt = 7,
        .flags.enable_internal_pullup = true,
    };
    i2c_master_bus_handle_t i2c_bus_handle = NULL;
    i2c_new_master_bus(&i2c_bus_config, &i2c_bus_handle);
    // Initialize I2C multiplexer
    zh_pca9548a_init_config_t pca_config = ZH_PCA9548A_INIT_CONFIG_DEFAULT();
    pca_config.i2c_handle = i2c_bus_handle;
    pca_config.i2c_address = 0x70;
    zh_pca9548a_init(&pca_config, &pca9548a_handle);
    // Initialize AHT sensors on different channels
    zh_aht_init_config_t aht_config = ZH_AHT_INIT_CONFIG_DEFAULT();
    aht_config.i2c_handle = i2c_bus_handle;
    zh_pca9548a_set(&pca9548a_handle, ZH_PCA9548A_CHAN_NUM_0);
    zh_aht_init(&aht_config, &aht_handle_chan_0);
    zh_pca9548a_set(&pca9548a_handle, ZH_PCA9548A_CHAN_NUM_1);
    zh_aht_init(&aht_config, &aht_handle_chan_1);
    zh_pca9548a_set(&pca9548a_handle, ZH_PCA9548A_CHAN_NUM_2);
    zh_aht_init(&aht_config, &aht_handle_chan_2);
    float humidity = 0.0;
    float temperature = 0.0;
    for (;;)
    {
        // Read sensor on channel 0
        zh_pca9548a_set(&pca9548a_handle, ZH_PCA9548A_CHAN_NUM_0);
        zh_aht_read(&aht_handle_chan_0, &humidity, &temperature);
        printf("Sensor 1. Humidity: %.2f%%\n", humidity);
        printf("Sensor 1. Temperature: %.2f°C\n", temperature);
        // Read sensor on channel 1
        zh_pca9548a_set(&pca9548a_handle, ZH_PCA9548A_CHAN_NUM_1);
        zh_aht_read(&aht_handle_chan_1, &humidity, &temperature);
        printf("Sensor 2. Humidity: %.2f%%\n", humidity);
        printf("Sensor 2. Temperature: %.2f°C\n", temperature);
        // Read sensor on channel 2
        zh_pca9548a_set(&pca9548a_handle, ZH_PCA9548A_CHAN_NUM_2);
        zh_aht_read(&aht_handle_chan_2, &humidity, &temperature);
        printf("Sensor 3. Humidity: %.2f%%\n", humidity);
        printf("Sensor 3. Temperature: %.2f°C\n", temperature);
        vTaskDelay(5000 / portTICK_PERIOD_MS);
    }
}
```

---

## Technical Specifications

| Parameter | Value |
| ----------- | ------- |
| **Humidity Range** | 0 - 100% |
| **Temperature Range** | -50 - +150°C |
| **Humidity Resolution** | 0.01% |
| **Temperature Resolution** | 0.01°C |
| **I2C Address** | 0x38, 0x39, 0x44 |
| **I2C Frequency** | Up to 400 kHz |
| **Measurement Time** | ~80 ms |
| **Supported Models** | AHT10, AHT15, AHT20, AHT21, AHT25, AHT30, AHT40 |
| **ESP-IDF Version** | >= 5.0 |
| **Platform** | ESP32 series |
| **Language** | C (C99) |

---

## Error Codes

| Error Code | Description |
| ------------ | ------------- |
| `ESP_OK` | Operation successful |
| `ESP_ERR_INVALID_ARG` | Invalid argument (NULL pointer or invalid configuration) |
| `ESP_ERR_INVALID_STATE` | Sensor is already initialized |
| `ESP_ERR_NO_MEM` | Memory allocation failed |
| `ESP_ERR_NOT_FOUND` | Sensor did not respond |
| `ESP_ERR_TIMEOUT` | Timeout waiting for data ready |
| `ESP_ERR_INVALID_CRC` | Invalid CRC checksum |
| `ESP_FAIL` | General failure (I2C communication error) |

---

## Contributing

Contributions are welcome! To contribute:

1. Fork the repository
2. Create a feature branch (`git checkout -b feature/AmazingFeature`)
3. Commit your changes (`git commit -m 'Add some AmazingFeature'`)
4. Push to the branch (`git push origin feature/AmazingFeature`)
5. Open a Pull Request

Please ensure your code follows the existing style and includes appropriate documentation.

---

## License

This project is licensed under the Apache License, Version 2.0 - see the [LICENSE](LICENSE) file for details.

### Apache License, Version 2.0

Copyright (c) 2026 Alexey Zholtikov

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

---

## Additional Notes

- **I2C Pull-up Resistors**: Ensure proper pull-up resistors are connected to SDA and SCL lines
- **Measurement Time**: The sensor requires ~80ms for each measurement
- **I2C_ISR_IRAM_SAFE**: For correct operation, enable `I2C_ISR_IRAM_SAFE` and `I2C_MASTER_ISR_HANDLER_IN_IRAM` in menuconfig
- **Thread Safety**: The component uses ESP-IDF I2C driver which is thread-safe
- **Memory Management**: All API functions now use double pointers for handle, which allows automatic memory management (freeing on deinitialization, setting to NULL)

---

*Generated for zh_aht v4.0.0*