aZholtikov/zh_aht

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

Overview
Features
Installation
API Reference
Usage Examples
Technical Specifications
Error Codes
Contributing
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 I2C multiplexer.

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

Features

Humidity and Temperature Measurement: Reads humidity from 0 to 100% and temperature from -40 to +85°C
I2C Interface: Uses standard I2C protocol (400 kHz max frequency)
Configurable I2C Address: Supports 0x38, 0x39 and 0x44 addresses
Multiple Model Support: AHT10, AHT15, AHT20, AHT21, AHT25, AHT30, AHT40
Error Statistics: Built-in error counter for I2C driver errors
Low Power: Works with ESP-IDF power management
Thread-Safe: Uses ESP-IDF I2C driver (thread-safe)
Minimal Overhead: Low memory and CPU overhead
Multiple Sensor Support: Compatible with I2C multiplexer (zh_pca9548a)

Installation

Navigate to your project's components directory:

cd ../your_project/components

Clone the repository:

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

In your application, include the header:

#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:

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 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

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

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:

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

#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)

#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	-40 - +85°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:

Fork the repository
Create a feature branch (git checkout -b feature/AmazingFeature)
Commit your changes (git commit -m 'Add some AmazingFeature')
Push to the branch (git push origin feature/AmazingFeature)
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 file for details.

Apache License, Version 2.0

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

12 KiB Raw Blame History

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

Table of Contents

Overview

Features

Installation

Required menuconfig Settings

Optional: Using with I2C Multiplexer (zh_pca9548a)

API Reference

zh_aht_init_config_t Structure

zh_aht_handle_t Structure

zh_aht_stats_t Structure

zh_aht_init()

zh_aht_deinit()

zh_aht_read()

zh_aht_reset()

zh_aht_get_stats()

zh_aht_reset_stats()

Usage Examples

Basic Example: Single Sensor

Multiple Sensors: Using I2C Multiplexer (zh_pca9548a)

Technical Specifications

Error Codes

Contributing

License

Apache License, Version 2.0

Additional Notes

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