一、点亮LED业务代码

1.1.创建目录

编写业务时，务必先在./applications/BearPi/BearPi-HM_Micro/samples路径下新建一个目录（或一套目录结构），用于存放业务源码文件.

在samples文件夹下增加my_led_app文件夹，并新建BUILD.gn和my_led_app.c两个文件

1.2.编写业务代码

在my_led_app.c中添加以下业务代码

#include <fcntl.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <stdio.h>
#include "hdf_sbuf.h"
#include "hdf_io_service_if.h"

#define LED_WRITE_READ 1
#define LED_SERVICE "hdf_led"

static int SendEvent(struct HdfIoService *serv, uint8_t eventData)
{
    int ret = 0;
    struct HdfSBuf *data = HdfSBufObtainDefaultSize();
    if (data == NULL)
    {
        printf("fail to obtain sbuf data!\r\n");
        return 1;
    }

    struct HdfSBuf *reply = HdfSBufObtainDefaultSize();
    if (reply == NULL)
    {
        printf("fail to obtain sbuf reply!\r\n");
        ret = HDF_DEV_ERR_NO_MEMORY;
        goto out;
    }
    /* 写入数据 */
    if (!HdfSbufWriteUint8(data, eventData))
    {
        printf("fail to write sbuf!\r\n");
        ret = HDF_FAILURE;
        goto out;
    }
    /* 通过Dispatch发送到驱动 */
    ret = serv->dispatcher->Dispatch(&serv->object, LED_WRITE_READ, data, reply);
    if (ret != HDF_SUCCESS)
    {
        printf("fail to send service call!\r\n");
        goto out;
    }

    int replyData = 0;
    /* 读取驱动的回复数据 */
    if (!HdfSbufReadInt32(reply, &replyData))
    {
        printf("fail to get service call reply!\r\n");
        ret = HDF_ERR_INVALID_OBJECT;
        goto out;
    }
    printf("\r\nGet reply is: %d\r\n", replyData);
out:
    HdfSBufRecycle(data);
    HdfSBufRecycle(reply);
    return ret;
}

int main(int argc, char **argv)
{
    int i;
    
    /* 获取服务 */
    struct HdfIoService *serv = HdfIoServiceBind(LED_SERVICE);
    if (serv == NULL)
    {
        printf("fail to get service %s!\r\n", LED_SERVICE);
        return HDF_FAILURE;
    }

    for (i=0; i < argc; i++)
    {
        printf("\r\nArgument %d is %s.\r\n", i, argv[i]);
    }

    SendEvent(serv, atoi(argv[1]));

    HdfIoServiceRecycle(serv);
    printf("exit");

    return HDF_SUCCESS;
}

1.3.编写将构建业务代码的BUILD.gn文件

BUILD.gn文件由三部分内容（目标、源文件、头文件路径）构成，需由开发者完成填写。以my_led_app为例，需要创建./applications/BearPi/BearPi-HM_Micro/samples/my_led_app/BUILD.gn，并完如下配置

import("//build/lite/config/component/lite_component.gni")

HDF_FRAMEWORKS = "//drivers/framework"

executable("led_lib") {
    output_name = "my_led"
    sources = [
        "my_led_app.c",
    ]

    include_dirs = [
    "$HDF_FRAMEWORKS/ability/sbuf/include",
    "$HDF_FRAMEWORKS/core/shared/include",
    "$HDF_FRAMEWORKS/core/host/include",
    "$HDF_FRAMEWORKS/core/master/include",
    "$HDF_FRAMEWORKS/include/core",
    "$HDF_FRAMEWORKS/include/utils",
    "$HDF_FRAMEWORKS/utils/include",
    "$HDF_FRAMEWORKS/include/osal",
    "//drivers/adapter/uhdf/posix/include",
    "//third_party/bounds_checking_function/include",
    "//base/hiviewdfx/hilog_lite/interfaces/native/innerkits",
    ]

    deps = [
        "//base/hiviewdfx/hilog_lite/frameworks/featured:hilog_shared",
        "//drivers/adapter/uhdf/manager:hdf_core",
        "//drivers/adapter/uhdf/posix:hdf_posix_osal",
    ]
}

lite_component("my_led_app") {
    features = [
        ":led_lib",
    ]
}

首先导入 gni 组件，将源码my_led_app.c编译成led_lib库文件
输出的可执行文件名称由 output_name 定义为my_led
include_dirs 里面加入my_led_app.c里面需要用到的.h的头文件路径
deps 里面加入所依赖的库。
然后将led_lib打包成 lite_component，命名为my_led_app组件。

1.4.添加新组件

修改文件build/lite/components/applications.json，添加组件my_sample的配置

{
        "component": "my_sample",
        "description": "my samples",
        "optional": "true",
        "dirs": [
            "applications/BearPi/BearPi-HM_Micro/samples/my_first_app",
            "applications/BearPi/BearPi-HM_Micro/samples/my_led_app"
        ],
        "targets": [
            "//applications/BearPi/BearPi-HM_Micro/samples/my_first_app:my_app",
            "//applications/BearPi/BearPi-HM_Micro/samples/my_led_app:my_led_app"
        ],
        "rom": "",
        "ram": "",
        "output": [],
        "adapted_kernel": [ "liteos_a" ],
        "features": [],
        "deps": {
        "components": [],
        "third_party": [ ]
        }
    },

1.5.修改单板配置文件

修改文件vendor/bearpi/bearpi_hm_micro/config.json，新增my_sample组件的条目

{
      "subsystem": "applications",
      "components": [
         { "component": "my_sample", "features":[] },
         { "component": "bearpi_sample_app", "features":[] },
         { "component": "bearpi_screensaver_app", "features":[] }
      ]
},

二、编译

在项目根目录下执行hb set 设置开发板，只有一个，回车即可

执行编译命令

hb build -t notest --tee -f

等待编译完成后，屏幕出现：build success字样，说明编译成功。

当编译完后，可以直接查看到最终编译的固件，具体路径在： \project\bearpi-hm_micro_small\out\bearpi-hm_micro\bearpi-hm_micro

文件夹结构说明

OHOS_Image.stm32：系统镜像文件
rootfs_vfat.img：根文件系统
userfs_vfat.img：用户文件系统

执行以下三条指令将以上三个文件复制到applications/BearPi/BearPi-HM_Micro/tools/download_img/kernel/下，以便后续烧录系统使用

cp out/bearpi_hm_micro/bearpi_hm_micro/OHOS_Image.stm32 applications/BearPi/BearPi-HM_Micro/tools/download_img/kernel/
cp out/bearpi_hm_micro/bearpi_hm_micro/rootfs_vfat.img applications/BearPi/BearPi-HM_Micro/tools/download_img/kernel/
cp out/bearpi_hm_micro/bearpi_hm_micro/userfs_vfat.img applications/BearPi/BearPi-HM_Micro/tools/download_img/kernel/