esp32 iic sht21 idf代码

以下是ESP32使用IIC接口读取SHT21温湿度传感器的IDF代码示例：

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/i2c.h"

#define I2C_MASTER_SCL_IO           22        /*!< GPIO number for I2C master clock */
#define I2C_MASTER_SDA_IO           21        /*!< GPIO number for I2C master data  */
#define I2C_MASTER_NUM              I2C_NUM_0 /*!< I2C port number for master dev */
#define I2C_MASTER_TX_BUF_DISABLE   0         /*!< I2C master do not need buffer */
#define I2C_MASTER_RX_BUF_DISABLE   0         /*!< I2C master do not need buffer */
#define I2C_MASTER_FREQ_HZ          100000    /*!< I2C master clock frequency */

#define SHT21_ADDR                  0x40      /*!< SHT21 I2C address */

esp_err_t i2c_master_init()
{
    i2c_config_t conf;
    conf.mode = I2C_MODE_MASTER;
    conf.sda_io_num = I2C_MASTER_SDA_IO;
    conf.sda_pullup_en = GPIO_PULLUP_ENABLE;
    conf.scl_io_num = I2C_MASTER_SCL_IO;
    conf.scl_pullup_en = GPIO_PULLUP_ENABLE;
    conf.master.clk_speed = I2C_MASTER_FREQ_HZ;
    i2c_param_config(I2C_MASTER_NUM, &conf);
    return i2c_driver_install(I2C_MASTER_NUM, conf.mode,
                              I2C_MASTER_RX_BUF_DISABLE,
                              I2C_MASTER_TX_BUF_DISABLE, 0);
}

void sht21_read_id()
{
    uint8_t cmd[1] = {0xEFC8}; // send command to read ID
    uint8_t data[8] = {0};
    i2c_cmd_handle_t cmd_handle = i2c_cmd_link_create();
    i2c_master_start(cmd_handle);
    i2c_master_write_byte(cmd_handle, (SHT21_ADDR << 1) | I2C_MASTER_WRITE, true);
    i2c_master_write(cmd_handle, cmd, 1, true);
    i2c_master_stop(cmd_handle);
    esp_err_t ret = i2c_master_cmd_begin(I2C_MASTER_NUM, cmd_handle, 1000 / portTICK_RATE_MS);
    i2c_cmd_link_delete(cmd_handle);
    if (ret != ESP_OK) {
        printf("Failed to send command\n");
        return;
    }
    // delay for conversion
    vTaskDelay(100 / portTICK_RATE_MS);
    // read ID
    cmd[0] = 0xFA0F; // send command to read ID
    cmd_handle = i2c_cmd_link_create();
    i2c_master_start(cmd_handle);
    i2c_master_write_byte(cmd_handle, (SHT21_ADDR << 1) | I2C_MASTER_WRITE, true);
    i2c_master_write(cmd_handle, cmd, 1, true);
    i2c_master_start(cmd_handle);
    i2c_master_write_byte(cmd_handle, (SHT21_ADDR << 1) | I2C_MASTER_READ, true);
    i2c_master_read(cmd_handle, data, 8, I2C_MASTER_LAST_NACK);
    i2c_master_stop(cmd_handle);
    ret = i2c_master_cmd_begin(I2C_MASTER_NUM, cmd_handle, 1000 / portTICK_RATE_MS);
    i2c_cmd_link_delete(cmd_handle);
    if (ret != ESP_OK) {
        printf("Failed to read ID\n");
        return;
    }
    uint16_t id = (data[0] << 8) | data[1];
    uint8_t crc = data[2];
    if (crc != (uint8_t)id * 5 / 256) {
        printf("CRC error\n");
        return;
    }
    printf("SHT21 ID: 0x%04X\n", id);
}

void app_main()
{
    i2c_master_init();
    sht21_read_id();
}

在示例中，使用ESP-IDF提供的I2C驱动程序，初始化I2C主机并发送命令读取SHT21传感器的ID。在读取ID之前需要等待一段时间，以便传感器完成转换。读取ID后，需要验证CRC以确保数据正确性。