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aZholtikov 95fca401de doc: updated readme
2026-10-17 20:15:16 +03:00

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ESP32 ESP-IDF component for PCF8574 8-bit I/O expander

Features

  1. I2C communication via the ESP-IDF I2C master driver.
  2. Configurable GPIO direction for each pin P0 through P7.
  3. Interrupt handling with GPIO level detection and event notification.
  4. Event-based architecture using the esp_event framework.
  5. Statistics tracking for debugging and monitoring.
  6. Multiple device instances on a single I2C bus.

Attention

  1. Requires ESP-IDF v5.0 or later with the I2C master driver.
  2. Interrupt handling runs in task context and is not IRAM-safe.
  3. A single interrupt GPIO pin is shared by all initialized devices.
  4. The internal task is deleted only when the last device instance is deinitialized.

Using

In an existing project, run the following command to install the component:

cd ../your_project/components
git clone https://github.com/aZholtikov/zh_pcf8574

In the application, add the component:

#include "zh_pcf8574.h"

Examples

Basic Example

#include "zh_pcf8574.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_pcf8574_handle_t *pcf8574_handle = NULL;

void app_main(void)
{
    esp_log_level_set("zh_pcf8574", ESP_LOG_ERROR);
    esp_log_level_set("zh_vector", 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_pcf8574_init_config_t config = ZH_PCF8574_INIT_CONFIG_DEFAULT();
    config.i2c_handle = i2c_bus_handle;
    config.i2c_address = 0x38;
    esp_err_t ret = zh_pcf8574_init(&config, &pcf8574_handle);
    if (ret != ESP_OK)
    {
        printf("PCF8574 initialization error: %s\n", esp_err_to_name(ret));
        return;
    }
    uint8_t reg = 0;
    ret = zh_pcf8574_read(&pcf8574_handle, &reg);
    if (ret == ESP_OK)
    {
        printf("GPIO status: 0x%02X\n", reg);
    }
    ret = zh_pcf8574_write(&pcf8574_handle, 0b10000010);
    if (ret == ESP_OK)
    {
        printf("Write OK\n");
    }
    ret = zh_pcf8574_read(&pcf8574_handle, &reg);
    if (ret == ESP_OK)
    {
        printf("GPIO status after write: 0x%02X\n", reg);
    }
    ret = zh_pcf8574_deinit(&pcf8574_handle);
    if (ret == ESP_OK)
    {
        printf("Deinit OK\n");
    }
}

GPIO Example

#include "zh_pcf8574.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_pcf8574_handle_t *pcf8574_handle = NULL;

void app_main(void)
{
    esp_log_level_set("zh_pcf8574", ESP_LOG_ERROR);
    esp_log_level_set("zh_vector", 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_pcf8574_init_config_t config = ZH_PCF8574_INIT_CONFIG_DEFAULT();
    config.i2c_handle = i2c_bus_handle;
    config.i2c_address = 0x38;
    esp_err_t ret = zh_pcf8574_init(&config, &pcf8574_handle);
    if (ret != ESP_OK)
    {
        printf("PCF8574 initialization error: %s\n", esp_err_to_name(ret));
        return;
    }
    ret = zh_pcf8574_write_gpio(&pcf8574_handle, ZH_PCF8574_GPIO_NUM_P4, ZH_PCF8574_GPIO_HIGH);
    if (ret == ESP_OK)
    {
        printf("P4 set high\n");
    }
    bool status = false;
    ret = zh_pcf8574_read_gpio(&pcf8574_handle, ZH_PCF8574_GPIO_NUM_P4, &status);
    if (ret == ESP_OK)
    {
        printf("P4 status: %d\n", status);
    }
    ret = zh_pcf8574_write_gpio(&pcf8574_handle, ZH_PCF8574_GPIO_NUM_P4, ZH_PCF8574_GPIO_LOW);
    if (ret == ESP_OK)
    {
        printf("P4 set low\n");
    }
    ret = zh_pcf8574_read_gpio(&pcf8574_handle, ZH_PCF8574_GPIO_NUM_P4, &status);
    if (ret == ESP_OK)
    {
        printf("P4 status: %d\n", status);
    }
    zh_pcf8574_deinit(&pcf8574_handle);
}

Reset Example

#include "zh_pcf8574.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_pcf8574_handle_t *pcf8574_handle = NULL;

void app_main(void)
{
    esp_log_level_set("zh_pcf8574", ESP_LOG_ERROR);
    esp_log_level_set("zh_vector", 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_pcf8574_init_config_t config = ZH_PCF8574_INIT_CONFIG_DEFAULT();
    config.i2c_handle = i2c_bus_handle;
    config.i2c_address = 0x38;
    esp_err_t ret = zh_pcf8574_init(&config, &pcf8574_handle);
    if (ret != ESP_OK)
    {
        printf("PCF8574 initialization error: %s\n", esp_err_to_name(ret));
        return;
    }
    zh_pcf8574_write(&pcf8574_handle, 0xFF);
    uint8_t reg = 0;
    ret = zh_pcf8574_read(&pcf8574_handle, &reg);
    if (ret == ESP_OK)
    {
        printf("GPIO before reset: 0x%02X\n", reg);
    }
    ret = zh_pcf8574_reset(&pcf8574_handle);
    if (ret == ESP_OK)
    {
        printf("Reset OK\n");
    }
    ret = zh_pcf8574_read(&pcf8574_handle, &reg);
    if (ret == ESP_OK)
    {
        printf("GPIO after reset: 0x%02X\n", reg);
    }
    zh_pcf8574_deinit(&pcf8574_handle);
}

Interrupt Example

#include "zh_pcf8574.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_pcf8574_handle_t *pcf8574_handle = NULL;

void zh_pcf8574_event_handler(void *arg, esp_event_base_t event_base, int32_t event_id, void *event_data)
{
    zh_pcf8574_event_on_isr_t *event = event_data;
    printf("Interrupt on address 0x%02X pin P%d level %d time %lld\n",
           event->i2c_address, event->gpio_number, event->gpio_level, event->interrupt_time);
}

void app_main(void)
{
    esp_log_level_set("zh_pcf8574", ESP_LOG_ERROR);
    esp_log_level_set("zh_vector", 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);
    esp_event_loop_create_default();
    esp_event_handler_instance_register(ZH_PCF8574, ESP_EVENT_ANY_ID, &zh_pcf8574_event_handler, NULL, NULL);
    zh_pcf8574_init_config_t config = ZH_PCF8574_INIT_CONFIG_DEFAULT();
    config.i2c_handle = i2c_bus_handle;
    config.i2c_address = 0x38;
    config.p0_gpio_work_mode = ZH_PCF8574_GPIO_INPUT;
    config.interrupt_gpio = GPIO_NUM_14;
    esp_err_t ret = zh_pcf8574_init(&config, &pcf8574_handle);
    if (ret != ESP_OK)
    {
        printf("PCF8574 initialization error: %s\n", esp_err_to_name(ret));
        return;
    }
    for (;;)
    {
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

Stats Example

#include "zh_pcf8574.h"

#define I2C_PORT (I2C_NUM_MAX - 1)

zh_pcf8574_handle_t *pcf8574_handle = NULL;

void app_main(void)
{
    esp_log_level_set("zh_pcf8574", ESP_LOG_ERROR);
    esp_log_level_set("zh_vector", 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_pcf8574_init_config_t config = ZH_PCF8574_INIT_CONFIG_DEFAULT();
    config.i2c_handle = i2c_bus_handle;
    config.i2c_address = 0x38;
    esp_err_t ret = zh_pcf8574_init(&config, &pcf8574_handle);
    if (ret != ESP_OK)
    {
        printf("PCF8574 initialization error: %s\n", esp_err_to_name(ret));
        return;
    }
    uint8_t reg = 0;
    zh_pcf8574_read(&pcf8574_handle, &reg);
    zh_pcf8574_write(&pcf8574_handle, 0xAA);
    zh_pcf8574_read(&pcf8574_handle, &reg);
    const zh_pcf8574_stats_t *stats = zh_pcf8574_get_stats();
    printf("I2C driver errors: %ld\n", stats->i2c_driver_error);
    printf("Event post errors: %ld\n", stats->event_post_error);
    printf("Vector errors: %ld\n", stats->vector_error);
    printf("Queue overflow errors: %ld\n", stats->queue_overflow_error);
    printf("Min free stack size: %ld\n", stats->min_stack_size);
    zh_pcf8574_reset_stats();
    stats = zh_pcf8574_get_stats();
    printf("After reset I2C driver errors: %ld\n", stats->i2c_driver_error);
    zh_pcf8574_deinit(&pcf8574_handle);
}
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