static const size_t device_table_len = sizeof(device_table) / sizeof(device_table[0]);

这段代码定义了一个名为 `device_table_len` 的静态常量，该常量的值等于 `device_table` 数组的长度除以第一个元素的长度。具体来说，`sizeof(device_table)` 表示 `device_table` 数组占用的总字节数，`sizeof(device_table[0])` 表示 `device_table` 数组中第一个元素的字节数。将两者相除，就得到了 `device_table` 数组的长度，即存储设备的数量。这个常量的作用是在后续的代码中使用，以便能够遍历所有的存储设备。由于这是一个静态常量，其值在编译时就已经确定，因此不能在运行时修改。

相关问题

esp32 蓝牙启动流程_ESP32教你简单进行蓝牙串口调试

ESP32的蓝牙启动流程如下：

1. 初始化蓝牙协议栈

2. 配置蓝牙参数，如设备名称、服务UUID等

3. 注册蓝牙事件回调函数

4. 启动蓝牙广播

5. 开启蓝牙可见性

6. 等待连接

以下是一个简单的ESP32蓝牙串口调试的示例：

#include "esp_bt.h"
#include "esp_bt_main.h"
#include "esp_gap_ble_api.h"

#define GATTS_TAG "GATTS_DEMO"
#define TEST_DEVICE_NAME "ESP32_BLE_UART"
#define TEST_MANUFACTURER_DATA_LEN 17

/* The max length of characteristic value. When the gatt client write or prepare write,
*  the data length must be less than MAX_VALUE_LENGTH.
*/
#define MAX_VALUE_LENGTH 500

/* Declare global variable */
static uint8_t test_manufacturer[TEST_MANUFACTURER_DATA_LEN] = {0x4c, 0x00, 0x02, 0x15, 0xE2, 0x0A, 0x39, 0xF4, 0x73, 0xF5, 0x4B, 0xC4, 0xA1, 0x2F, 0x17, 0xD1, 0xAD};
static uint8_t test_service_uuid128[32] = {
    /* LSB <--------------------------------------------------------------------------------> MSB */
    //first uuid, 16bit, [12],[13] is the value
    0x13, 0x2B, 0x01, 0x00, 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5F, 0x9B, 0x34, 0xFB,
    //second uuid, 32bit, [12], [13], [14], [15] is the value
    0x14, 0x2B, 0x01, 0x00, 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5F, 0x9B, 0x34, 0xFB,
};

static uint8_t test_service_uuid[16] = {
    /* LSB <--------------------------------------------------------------------------------> MSB */
    //first uuid, 16bit, [12],[13] is the value
    0x01, 0x2B,
    //second uuid, 32bit, [12], [13], [14], [15] is the value
    0x01, 0x2B, 0x01, 0x00, 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5F, 0x9B, 0x34, 0xFB,
};

static uint8_t test_char_uuid[16] = {
    /* LSB <--------------------------------------------------------------------------------> MSB */
    //first uuid, 16bit, [12],[13] is the value
    0x02, 0x2B,
    //second uuid, 32bit, [12], [13], [14], [15] is the value
    0x02, 0x2B, 0x01, 0x00, 0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0x80, 0x5F, 0x9B, 0x34, 0xFB,
};

static esp_gatt_char_prop_t test_property = 0;

static uint8_t char1_str[] = {0x11,0x22,0x33};
static esp_attr_value_t gatts_demo_char1_val = {
    .attr_max_len = MAX_VALUE_LENGTH,
    .attr_len     = sizeof(char1_str),
    .attr_value   = char1_str,
};

static uint16_t gatts_demo_handle_table[3];

/* Full Database Description - Used to add attributes into the database */
static const esp_gatts_attr_db_t gatt_db[HRS_IDX_NB] =
{
    // Service Declaration
    [IDX_SVC]        =
    {
        {ESP_GATT_AUTO_RSP},
        {ESP_UUID_LEN_16, (uint8_t *)&primary_service_uuid, ESP_GATT_PERM_READ,
            sizeof(test_service_uuid), sizeof(test_service_uuid), (uint8_t *)&test_service_uuid},
        ESP_GATT_UUID_PRI_SERVICE,
        ESP_GATT_PERM_READ,
        sizeof(test_service_uuid),
        sizeof(test_service_uuid),
        (uint8_t *)&test_service_uuid,
        0
    },
    /* Characteristic Declaration */
    [IDX_CHAR_READ]  =
    {
        {ESP_GATT_AUTO_RSP},
        {ESP_UUID_LEN_16, (uint8_t *)&character_declaration_uuid, ESP_GATT_PERM_READ,
            CHAR_DECLARATION_SIZE, CHAR_DECLARATION_SIZE, (uint8_t *)&test_property},
        ESP_GATT_UUID_CHAR_DECLARE,
        ESP_GATT_PERM_READ,
        CHAR_DECLARATION_SIZE,
        CHAR_DECLARATION_SIZE,
        (uint8_t *)&test_property,
        0
    },
    /* Characteristic Value */
    [IDX_CHAR_VAL_READ] =
    {
        {ESP_GATT_AUTO_RSP},
        {ESP_UUID_LEN_128, (uint8_t *)&test_char_uuid, ESP_GATT_PERM_READ,
            MAX_VALUE_LENGTH, sizeof(gatts_demo_char1_val), gatts_demo_char1_val.attr_value},
        ESP_UUID_LEN_128,
        ESP_GATT_PERM_READ,
        MAX_VALUE_LENGTH,
        sizeof(gatts_demo_char1_val),
        gatts_demo_char1_val.attr_value,
        0
    },
};

static esp_ble_adv_data_t adv_data = {
    .set_scan_rsp        = false,
    .include_name        = true,
    .include_txpower     = true,
    .min_interval        = 0x20,
    .max_interval        = 0x40,
    .appearance          = 0x00,
    .manufacturer_len    = TEST_MANUFACTURER_DATA_LEN,
    .p_manufacturer_data = test_manufacturer,
    .service_data_len    = 0,
    .p_service_data      = NULL,
    .service_uuid_len    = sizeof(test_service_uuid),
    .p_service_uuid      = test_service_uuid,
    .flag = (ESP_BLE_ADV_FLAG_GEN_DISC | ESP_BLE_ADV_FLAG_BREDR_NOT_SPT),
};

static esp_ble_adv_params_t adv_params = {
    .adv_int_min         = 0x20,
    .adv_int_max         = 0x40,
    .adv_type            = ADV_TYPE_IND,
    .own_addr_type       = BLE_ADDR_TYPE_PUBLIC,
    .peer_addr           = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
    .peer_addr_type      = BLE_ADDR_TYPE_PUBLIC,
    .channel_map         = ADV_CHNL_ALL,
    .adv_filter_policy   = ADV_FILTER_ALLOW_SCAN_ANY_CON_ANY,
};

static void gap_event_handler(esp_gap_ble_cb_event_t event, esp_ble_gap_cb_param_t *param)
{
    switch (event) {
    case ESP_GAP_BLE_ADV_DATA_SET_COMPLETE_EVT:
        esp_ble_gap_start_advertising(&adv_params);
        break;
    case ESP_GAP_BLE_ADV_START_COMPLETE_EVT:
        if (param->adv_start_cmpl.status != ESP_BT_STATUS_SUCCESS) {
            ESP_LOGE(GATTS_TAG, "advertising start failed");
        }
        break;
    default:
        break;
    }
}

static void gatts_event_handler(esp_gatts_cb_event_t event, esp_gatt_if_t gatts_if, esp_ble_gatts_cb_param_t *param)
{
    switch (event) {
    case ESP_GATTS_REG_EVT:
        esp_ble_gap_set_device_name(TEST_DEVICE_NAME);
        esp_ble_gap_config_adv_data(&adv_data);
        break;
    case ESP_GATTS_CREAT_ATTR_TAB_EVT:
        if (param->add_attr_tab.status != ESP_GATT_OK){
            ESP_LOGE(GATTS_TAG, "create attribute table failed, error code=0x%x", param->add_attr_tab.status);
        }
        else if (param->add_attr_tab.num_handle != HRS_IDX_NB) {
            ESP_LOGE(GATTS_TAG, "create attribute table abnormally, num_handle (%d) \
                    doesn't equal to HRS_IDX_NB(%d)", param->add_attr_tab.num_handle, HRS_IDX_NB);
        }
        else {
            ESP_LOGI(GATTS_TAG, "create attribute table successfully, the number handle = %d\n",param->add_attr_tab.num_handle);
            memcpy(gatts_demo_handle_table, param->add_attr_tab.handles, sizeof(gatts_demo_handle_table));
            esp_ble_gatts_start_service(gatts_demo_handle_table[IDX_SVC]);
        }
        break;
    case ESP_GATTS_CONNECT_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_CONNECT_EVT");
        break;
    case ESP_GATTS_DISCONNECT_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_DISCONNECT_EVT");
        esp_ble_gap_start_advertising(&adv_params);
        break;
    case ESP_GATTS_WRITE_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_WRITE_EVT");
        break;
    case ESP_GATTS_MTU_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_MTU_EVT, MTU %d", param->mtu.mtu);
        break;
    case ESP_GATTS_CONF_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_CONF_EVT");
        break;
    case ESP_GATTS_EXEC_WRITE_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_EXEC_WRITE_EVT");
        break;
    case ESP_GATTS_START_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_START_EVT");
        break;
    case ESP_GATTS_STOP_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_STOP_EVT");
        break;
    case ESP_GATTS_OPEN_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_OPEN_EVT");
        break;
    case ESP_GATTS_CANCEL_OPEN_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_CANCEL_OPEN_EVT");
        break;
    case ESP_GATTS_CLOSE_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_CLOSE_EVT");
        break;
    case ESP_GATTS_LISTEN_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_LISTEN_EVT");
        break;
    case ESP_GATTS_CONGEST_EVT:
        ESP_LOGI(GATTS_TAG, "ESP_GATTS_CONGEST_EVT");
        break;
    case ESP_GATTS_UNREG_EVT:
    case ESP_GATTS_DELETE_EVT:
    default:
        break;
    }
}

void app_main()
{
    esp_err_t ret;

    ESP_LOGI(GATTS_TAG, "ESP_BLUETOOTH_BLE example started.");

    esp_bt_controller_config_t bt_cfg = BT_CONTROLLER_INIT_CONFIG_DEFAULT();
    ret = esp_bt_controller_init(&bt_cfg);
    if (ret) {
        ESP_LOGE(GATTS_TAG, "%s initialize controller failed\n", __func__);
        return;
    }

    ret = esp_bt_controller_enable(ESP_BT_MODE_BLE);
    if (ret) {
        ESP_LOGE(GATTS_TAG, "%s enable controller failed\n", __func__);
        return;
    }

    ret = esp_bluedroid_init();
    if (ret) {
        ESP_LOGE(GATTS_TAG, "%s init bluetooth failed\n", __func__);
        return;
    }

    ret = esp_bluedroid_enable();
    if (ret) {
        ESP_LOGE(GATTS_TAG, "%s enable bluetooth failed\n", __func__);
        return;
    }

    ret = esp_ble_gatts_register_callback(gatts_event_handler);
    if (ret){
        ESP_LOGE(GATTS_TAG, "gatts register error, error code = %x", ret);
        return;
    }

    ret = esp_ble_gap_register_callback(gap_event_handler);
    if (ret){
        ESP_LOGE(GATTS_TAG, "gap register error, error code = %x", ret);
        return;
    }

    ret = esp_ble_gatts_app_register(ESP_APP_ID);
    if (ret){
        ESP_LOGE(GATTS_TAG, "gatts app register error, error code = %x", ret);
        return;
    }

    esp_err_t local_mtu_ret = esp_ble_gatt_set_local_mtu(500);
    if (local_mtu_ret){
        ESP_LOGE(GATTS_TAG, "set local  MTU failed, error code = %x", local_mtu_ret);
    }

    ret = esp_ble_gatts_create_attr_tab(gatt_db, gatts_if, HRS_IDX_NB, ESP_APP_ID);
    if (ret){
        ESP_LOGE(GATTS_TAG, "create attr table failed, error code = %x", ret);
    }
}

在这个示例中，我们使用了ESP-IDF提供的蓝牙协议栈和GATT Server框架，实现了一个简单的GATT Server，并且开启了蓝牙广播和可见性，使得其他蓝牙设备可以扫描到并连接我们的设备。在连接建立后，我们可以向GATT Server中的特定Characteristic写入数据，也可以从特定Characteristic读取数据。

基于Linux4.19内核，写一个详细的lpc_master的驱动

LPC（Low Pin Count）总线是一种低速、低成本的系统总线，广泛应用于嵌入式系统中。在Linux内核中，LPC总线的驱动程序已经被实现，并且已经被集成到了内核中。但是，如果需要开发一个新的LPC设备的驱动程序，需要编写LPC Master控制器的驱动程序。下面是一个基于Linux4.19内核的LPC Master驱动程序的示例：

1. 定义驱动程序

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/interrupt.h>

#define DRIVER_NAME "lpc_master"

struct lpc_master_data {
    struct resource *res;
    void __iomem *io_base;
};

static struct platform_driver lpc_master_driver = {
    .probe      = lpc_master_probe,
    .remove     = lpc_master_remove,
    .driver     = {
        .name   = DRIVER_NAME,
        .of_match_table = of_match_ptr(lpc_master_of_match),
    },
};

static int __init lpc_master_init(void)
{
    return platform_driver_register(&lpc_master_driver);
}

static void __exit lpc_master_exit(void)
{
    platform_driver_unregister(&lpc_master_driver);
}

module_init(lpc_master_init);
module_exit(lpc_master_exit);

MODULE_DESCRIPTION("LPC Master Driver");
MODULE_AUTHOR("Your Name");
MODULE_LICENSE("GPL");

2. 定义设备树匹配表

static const struct of_device_id lpc_master_of_match[] = {
    { .compatible = "your,device,compatible", },
    { },
};
MODULE_DEVICE_TABLE(of, lpc_master_of_match);

3. 实现probe函数

static int lpc_master_probe(struct platform_device *pdev)
{
    struct resource *res;
    struct lpc_master_data *data;
    int ret;

    data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
    if (!data) {
        dev_err(&pdev->dev, "Failed to allocate driver data\n");
        return -ENOMEM;
    }

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!res) {
        dev_err(&pdev->dev, "Failed to get IORESOURCE_MEM\n");
        return -ENODEV;
    }

    data->io_base = devm_ioremap_resource(&pdev->dev, res);
    if (IS_ERR(data->io_base)) {
        dev_err(&pdev->dev, "Failed to ioremap IO resource\n");
        return PTR_ERR(data->io_base);
    }

    data->res = res;

    platform_set_drvdata(pdev, data);

    /* TODO: Initialize LPC master controller */

    return 0;
}

4. 实现remove函数

static int lpc_master_remove(struct platform_device *pdev)
{
    struct lpc_master_data *data = platform_get_drvdata(pdev);

    /* TODO: Release any resources allocated by the driver */

    return 0;
}

5. 初始化LPC Master控制器

在probe函数中，需要初始化LPC Master控制器。下面是一个示例函数：

static int lpc_master_init_controller(struct lpc_master_data *data)
{
    /* TODO: Initialize LPC controller registers */

    return 0;
}

6. 发送和接收数据

在LPC Master驱动程序中，需要实现发送和接收数据的功能。下面是一个示例函数：

static int lpc_master_send_recv(struct lpc_master_data *data, u8 *tx_buf, u8 *rx_buf, size_t len)
{
    /* TODO: Send and receive data using the LPC controller */

    return 0;
}

完成以上步骤后，就可以编译和安装LPC Master驱动程序了。在使用LPC设备时，只需要加载驱动程序，就可以通过/dev/lpc_master设备文件进行数据传输。