First, write a simple Hello World program
Write a Hello World program is relatively simple, you can refer to the official website:
https://device.harmonyos.com/cn/docs/start/introduce/oem_wifi_start-0000001050168544
This article is summarized here.
1.1, determine the directory structure
When developers write a business, be sure to create a directory (or a directory structure) in the ./applications/sample/wifi-iot/appl path, for the traffic source file file, for example: add business my_first_app under App, Among them, hello_world.c is a business code, build.gn's compilation script, the specific planning directory structure is as follows:
1.2, write business code
Newly create a new service entry function HelloWorld in Hello_World.c and implement business logic. And at the bottom of the code, use the HARMONYOS to start the recovery module interface SYS_RUN () to start the business. (Sys_RUN is defined in the ohos_init.h file)
1.3, writing build.gn files for building a static library
As described in step 1, the build.gn file consists of three parts content (target, source file, header file path), which is required to be fill in by the developer. Take my_first_app as an example, it is necessary to build ./applications/sample/wifi-ioot/app/my_first_app/build.gn, and configure it as follows.
Static_library specifies the compilation result of the service module, which is a static library file libmyapp.a, and the developer is completed according to the actual situation. The .c file and its path depends on the Sources .a dependent. If "//" is included in the path indicates the absolute path (here the code root path), if "//" is not included, the relative path is indicated. The .h file path required to specify the Source required in Include_DIRS.
1.4, write module build.gn files, specify the feature module that needs to participate in
Configure ./applications/sample/wifi-ioot/app/build.gn file, add an index in the Features field to enable the target module to participate in compilation. Features field Specifies the path and target of the service module, exemplified by my_first_app, the Features field is configured as follows.
My_first_app is a relative path, pointing ./applications/sample/wifi-ioot/App/my_first_app/build.gn.
MyApp is the target, pointing ./applications/sample/wifi-ioot/App/my_first_app/build.gn in static_library ("myApp").
Second, HI3861 related code structure
At present, the Hi3861 is used by the Liteos-M kernel, but the Liteos-M at the current Hi3681 is currently the chip ROM, cured inside the chip. So the HARMONYOS code is not found to find the kernel portion of the Hi3861. But this does not hinder the other code structure of the Hi3861. Hi3861 platform configuration file
BuildlitePlatformhi3861v100_liteos_riscvplatform.json
This file describes the code path associated with the Hi3681 platform, such as Application, Startup, etc.
Here I am listed in a few more important:
Subsystem: Applications
Path: Applications / Sample / WiFi-IoT / APP
Role: This path stores the application code written by Hi3681, for example, the Hello World code we just wrote is placed under this path.
Subsystem: IoT_hardware
Path: Base / IoT_hardware / frameworks / wiFiiot_lite
Role: The Hi3681 chip is stored, such as SPI, GPIO, UART, etc.
Subsystem: vendor
Path: vendor / hisi / hi3861 / hi3861
Role: The files such as the manufacturer SDK related to the Hi3681 are stored. The most important thing is
Vendorhisihi3861hi3861appwifiIOT_APPinitApp_io_init.c
VendorhisiHi3861hi3861AppwifiOT_APPSRCAPP_MAIN.C
Among them, App_IO_INIT.C is the IO-related setting of the Hi3681 kernel startup, and the user needs to reasonably select the IO multiplexing configuration of each peripheter according to the application scenario.
App_main.c is an application entry that the kernel starts entering.
Third, Hi3861 launch process
Since the Liteos-M of the Hi3681 is chemically in the chip, it is cured inside the chip. So we mainly look at the first inlet function after the kernel is started.
Code path:
App_main first prints the SDK version number, and the last line will call HOS_SYSTEMINIT (); functions for the initialization of the Hongmeng system. We will go in to see which movements do.
Path: Base / Startup / Services / Bootstrap_Lite / Source / System_init.c
We can see that some related modules are initialized, the system, including BSP, DEVICE. The ultimate is Module_init (RUN), which is responsible for calling all the code of all RUN segments, then which of the RUN segment is? In fact, we use the function name of the SYS_RUN () macro in front Application.
Remember the Hello World app written earlier?
That is to say, all functions with sys_run () macro will be used in using module_init (run); when it is called, in order to verify this, we can add some print information, as follows:
We recoiled and burned. Open the serial port to view print information, as follows:
You can see the information of the Hello World after 35 lines. In line with expectations.
Editor in charge: LQ, read full text, original title: As long as three steps! Even the teacher takes you to the Hi3861 code structure
Article Source: [Micro Signal: HARMONYOS_COMMUNITY, WeChat public number: Huawei Qilin] Welcome to add attention! Please indicate the source of the article.
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