C language application program of LED

introduction

In this article, an application program of LED lamp is written in C language, and the driver program of LED lamp developed in the article "HDF-based LED Driver Development" (1) and (2) is tested.

In addition, when writing applications for LED lights, we will use many APIs provided by the HDF framework. In order to facilitate the usage of these APIs, it is recommended that you open the article "API of HDF Driver Framework" (1) , (2) , (3) while reading this article . The APIs used in this article are collected in these articles. Of course, you can also directly read the source code and official documentation of these APIs.

This article refers to some tutorials of the BearPi-HM_Micro_Small development board.

https://gitee.com/bearpi/bearpi-hm_micro_small  

Before reading this article, make sure you have read "Hello_World of BearPi-HM_Micro_Small" .

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1. Write the source program

First, applications/BearPi/BearPi-HM_Micro/samples/dandelioncreate a new folder under the path: my_led_app.

Then, create a new file in the folder my_led_app: my_led_app.c, and then we write the source program in this file.

This application has no GUI, and can only be run in the form of command line: ./my_led 参数, the command parameter has three values: 0, 1, 2, which control LED off, on, and state switching respectively.

In the source program my_led_app.c, in addition to some header files and macro definitions, it mainly includes the following two functions:

function	describe
int main(int argc, char **argv)	application's main function
static int LedWriteRead(struct HdfIoService *serv, uint8_t sendData, uint8_t *recvData)	Send data to the driver, and receive the driver's response.

1.1 Header file, macro definition

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

#include "hdf_log.h"
#include "hdf_sbuf.h"
#include "hdf_io_service_if.h"

#define LED_WRITE_READ  1         //应用程序下发给LED驱动的命令字。1:写；0:读。
#define LED_SERVICE     "hdf_led" //LED驱动对外提供的服务的名称，与驱动配置中的名称一致。

1.2 Main function

int main(int argc, char **argv)
{
    int i;
    
    // 打印输出在终端中输入的命令行
    for (i=0; i < argc; i++)
    {
        printf("\r\nArgument %d is %s.\r\n", i, argv[i]);
    }

    // 获取驱动提供的服务 
    struct HdfIoService *serv = HdfIoServiceBind(LED_SERVICE);
    if (serv == NULL)
    {
        printf("fail to get service %s!\r\n", LED_SERVICE);
        return HDF_FAILURE;
    }
    
    // 向驱动发送LED的控制数据，从驱动接收LED当前的状态
    uint8_t replyData = 0;
    LedWriteRead(serv, atoi(argv[1]), &replyData);
    printf("\r\nGet reply is: %d\r\n", replyData);

    // 回收资源
    HdfIoServiceRecycle(serv);

	// 退出程序
    printf("exit");
    return HDF_SUCCESS;
}

In mainthe function, the interface functions provided by HDF are used: HdfIoServiceBind, HdfIoServiceRecycle, and structure HdfIoService.

1.3 LedWriteRead function

LedWriteReadmainThe function is called in the main function to exchange data with the driver in kernel mode. The first parameter serv: a pointer to the driver service object ( HdfIoServicestructure); the second parameter sendData: the data sent to the driver; the third parameter recvData: a pointer to a variable, which is used to store the data received from the driver function response data.

static int LedWriteRead(struct HdfIoService *serv, uint8_t sendData, uint8_t *recvData)
{
    int ret = HDF_SUCCESS;

    // 创建一个缓冲区，用于向驱动发送数据
    struct HdfSBuf *data = HdfSBufObtainDefaultSize();
    if (data == NULL)
    {
        printf("fail to obtain sbuf data!\r\n");
        return HDF_FAILURE;
    }

    // 创建一个缓冲区，用于从驱动接收响应
    struct HdfSBuf *reply = HdfSBufObtainDefaultSize();
    if (reply == NULL)
    {
        printf("fail to obtain sbuf reply!\r\n");
        ret = HDF_DEV_ERR_NO_MEMORY;
        goto out;
    }

    // 把要下发给驱动的数据写入缓冲区 
    if (!HdfSbufWriteUint8(data, sendData))
    {
        printf("fail to write sbuf!\r\n");
        ret = HDF_FAILURE;
        goto out;
    }

    // 调用应用态的Dispatch函数与驱动交互 
    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;
    }

    // 从缓冲区中读取驱动的响应数据
    if (!HdfSbufReadUint8(reply, recvData))
    {
        printf("fail to get service call reply!\r\n");
        ret = HDF_ERR_INVALID_OBJECT;
        goto out;
    }

out:
    // 回收缓冲区
    HdfSBufRecycle(data);
    HdfSBufRecycle(reply);
    
    return ret;
}

In mainthe function, the interface functions provided by HDF are used: HdfSBufObtainDefaultSize, HdfSbufWriteUint8, HdfSbufReadUint8, HdfSBufRecycle, and the structure HdfSBuf, HdfIoService.

​

2. Write/modify the compilation script

my_led_app1. Create a new file under the folder : BUILD.gn, and write the compilation script of the source program in this file my_led_app.c:

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

HDF_FRAMEWORKS = "//drivers/framework"

executable("my_led_exe") {
    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",
    ]
}

executable("my_led_exe")Used to declare a named my_led_exetarget of type executable, instructing the compile build subsystem to my_led_app.ccompile the source code into my_ledan executable file named .

output_nameUsed to specify the name of the compiled executable.

sourcesIn the list are the source code files required for compiling and building.

include_dirsIn the list are the paths to the header files referenced in the source files.

depsIn the list are other libraries that need to be relied upon when compiling and building.

2. Modify dandelionthe compilation script file under the folder: BUILD.gn.

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

lite_component("dandelion_app") {
    features = [
        "hello_world:hello_world_exe",
        "my_led_app:my_led_app",
    ]
}

lite_componentIt is build/lite/config/component/lite_component.gnia template defined in , which is used to my_led_exeincorporate the target named above into my_led_appthe compile and build target named.

​

3. Compile and burn

Refer to the fifth and sixth parts of "Hello_World of BearPi-HM_Micro_Small" .

​

4. Test

After the system starts up, execute the following commands in sequence on the serial port terminal:

./bin/my_led 1
./bin/my_led 0
./bin/my_led 2

The LEDs on the BearPi-HM_Micro_Small development board will be controlled to turn on, turn off, and switch states respectively. The output and output of the serial port terminal are shown in the figure below: