OpenHarmony无人机MAVSDK开源库适配方案分享-编程知识

MAVSDK 是 PX4 开源团队贡献的基于 MavLink 通信协议的用于无人机应用开发的 SDK，支持多种语言如 C/C++、python、Java 等。通常用于无人机间、地面站与通信设备的消息传输。

MAVLink 是一种非常轻量级的消息传递协议，用于与无人机（以及机载无人机组件之间）进行通信。MAVLink 遵循现代混合发布-订阅和点对点设计模式，数据流作为主题发送/发布，而任务协议或参数协议等配置子协议是点对点的重传。其中 MAVLink 1 每个数据包只有 8 个字节的开销，包括开始标志和数据包丢弃检测。MAVLink 2 只有 14 字节的开销。由于 MAVLink 不需要任何额外的成帧，因此非常适合通信带宽非常有限的应用程序。

当我们想要在 OpenHarmony 上做无人机相关工作时，在通信方面需要面临 MAVLink 的移植适配工作。因此接下来我们将分享如何将 MAVSDK 移植至 OpenHarmony 系统当中。

MAVSDK Github 开源地址：GitHub - mavlink/MAVSDK: API and library for MAVLink compatible systems written in C++17

接下来讲解如何把 MAVSDK 开源库添加至 OpenHarmony 工程中进行编译。（此方法与其他开源库移植方法基本一致）

本次移植通过新建子系统 mavsdk，在子系统下添加名为 mavsdk 的组件，并在该组件下添加名为 MAVSDK 的模块，OpenHarmony 系统层级顺序如下：子系统-> 组件-> 模块，下文中将都以此为顺序进行叙述。

表 1：添加到工程后的目录结构

路径	描述
ohos/build/subsystem_config.json	子系统配置
ohos/productdefine/common/products/ohos-arm64.json	板级相关
ohos/third_party/MAVSDK/bundle.json	在子系统中添加组件配置
ohos/third_party/MAVSDK/BUILD.gn	三方库模块化，将其加入组件中的 gn 文件

subsystem_config.json

首先在 ohos/build/subsystem 中添加 subsystem 节点。

"mavsdk": {   "path": "third_party/MAVSDK", "name": "mavsdk"}

ohos-arm64.json 文件

在 ohos/productdefine/common/products/ohos-arm64.json 文件中添加板级相关的信息。

"mavsdk:MAVSDK":{}

如下图所示：

Bundle.json 文件

在 ohos/third 目录下添加 bundle.json 文件，以便系统可以添加名为 MAVSDK 的组件。

对于此文件要点如注释所见（编译时去除注释以保证配置文件整洁性）

{"name": "@ohos/MAVSDK","description": "","version": "","license": "","publishAs": "","segment": {"destPath": "third_party/MAVSDK"},"dirs": {},"scripts": {},"readmePath": {},"component": {"name": "MAVSDK","subsystem": "mavsdk","syscap": [],"features": [],"adapted_system_type": [],"rom": "","ram": "","deps": {"components": [ "jsoncpp","zlib"//此处添加了要用的三方库，后续的build.gn中还会有所体现。],"third_party": ["jsoncpp","zlib"]},"build": {"sub_component": [  "//third_party/mavsdk:MAVSDK","//third_party/mavsdk:mavsdk_test"],//此处添加了接下来要编译的组件，一个是代码主仓组件，一个是代码的测试文件组件"inner_kits": [],"test": ["//third_party/mavsdk:mavsdk_test"]}}}

BUILD.gn 文件

在完成上述步骤后，下面需要在 ohos/third 目录添加 BUILD.gn，根据不同的系统生成静态或者动态库，注意点如下：

文件	作用
build.make	生成目标的源文件
depend.make	需要依赖的其他 C 源文件
flags.make	cflags 相关的一些标志
link.txt	链接库相关信息

① 注意移植时的 cflags、cflags 应从原始的编译文件（例如 cmake 过程中 build 的生成文件：在 cmake 生成 makefile 的过程中分析 build.make、depend.make、flags.make、link.txt 等得出三方库对应的依赖关系）中获取相关的标志位

② 注意移植的源文件及头文件地址可以使用当前 build.gn 所在路径下相对位置，例如/src 与 build.gn 在同一路径下则路径可以直接应用 src/....

③ 注意 deps 若引用的是组件内的其他模块，例如其他 build.gn 文件中的组件或当前 build.gn 中位于此 deps 前的其他组件可以使用 ”:module 进行模块依赖，若是引用组件外的其他组件则需要使用 ”bundle

import("//build/ohos.gni")  
import("//build/test.gni")config("mavsdk_cflag_config") {#编译时的标志位cflags = [  "-fexceptions","-Wextra","-Wshadow","-Wno-strict-aliasing","-Wformat=2","-Wextra","-Wno-unused-lambda-capture","-Wno-pragmas","-Wno-unknown-warning-option","-Wduplicated-cond","-Wnull-dereference","-Wduplicated-branches","-Wlogical-op", "-Wno-old-style-cast","-pthread",]cflags_cc = [ "-frtti" ] #fix:[OHOS ERROR] ../../prebuilts/clang/ohos/linux-x86_64/llvm/bin/../include/libcxx-ohos/include/c++/v1/memory:3566:16: error: use of dynamic_cast requires -frttildflags = [ "-fPIC","-g","-shared","-Wl","-soname" ]
}ohos_source_set("libmavsdk_source") {configs = [":mavsdk_cflag_config"]deps = [ "//third_party/curl:curl"  ] #需要包含的源文件sources = ["src/mavsdk/core/call_every_handler.cpp" ,"src/mavsdk/core/connection.cpp" ,"src/mavsdk/core/connection_result.cpp" ,"src/mavsdk/core/curl_wrapper.cpp" ,"src/mavsdk/core/crc32.cpp" ,"src/mavsdk/core/system.cpp" ,"src/mavsdk/core/system_impl.cpp" ,"src/mavsdk/core/fs.cpp" ,"src/mavsdk/core/mavsdk.cpp" ,"src/mavsdk/core/mavsdk_impl.cpp" ,"src/mavsdk/core/http_loader.cpp" ,"src/mavsdk/core/mavlink_channels.cpp" ,"src/mavsdk/core/mavlink_command_receiver.cpp" ,"src/mavsdk/core/mavlink_command_sender.cpp" ,"src/mavsdk/core/mavlink_ftp.cpp" ,"src/mavsdk/core/mavlink_mission_transfer.cpp" ,"src/mavsdk/core/mavlink_parameters.cpp" ,"src/mavsdk/core/mavlink_receiver.cpp" ,"src/mavsdk/core/mavlink_request_message_handler.cpp" ,"src/mavsdk/core/mavlink_statustext_handler.cpp" ,"src/mavsdk/core/mavlink_message_handler.cpp" ,"src/mavsdk/core/ping.cpp" ,"src/mavsdk/core/plugin_impl_base.cpp" ,"src/mavsdk/core/serial_connection.cpp" ,"src/mavsdk/core/tcp_connection.cpp" ,"src/mavsdk/core/timeout_handler.cpp" ,"src/mavsdk/core/udp_connection.cpp" ,"src/mavsdk/core/log.cpp" ,"src/mavsdk/core/cli_arg.cpp" ,"src/mavsdk/core/geometry.cpp" ,"src/mavsdk/core/request_message.cpp" ,"src/mavsdk/core/mavsdk_time.cpp" ,"src/mavsdk/core/timesync.cpp" ,"src/mavsdk/plugins/action/action.cpp" ,"src/mavsdk/plugins/action/action_impl.cpp" ,"src/mavsdk/plugins/action_server/action_server.cpp" ,"src/mavsdk/plugins/action_server/action_server_impl.cpp" ,"src/mavsdk/plugins/calibration/calibration.cpp" ,"src/mavsdk/plugins/calibration/calibration_impl.cpp" ,"src/mavsdk/plugins/calibration/calibration_statustext_parser.cpp" ,"src/mavsdk/plugins/camera/camera.cpp" ,"src/mavsdk/plugins/camera/camera_impl.cpp" ,"src/mavsdk/plugins/camera/camera_definition.cpp" ,"src/mavsdk/plugins/camera/camera_definition_files/generated/camera_definition_files.cpp" ,"src/mavsdk/plugins/component_information/component_information.cpp" ,"src/mavsdk/plugins/component_information/component_information_impl.cpp" ,"src/mavsdk/plugins/component_information_server/component_information_server.cpp" ,"src/mavsdk/plugins/component_information_server/component_information_server_impl.cpp" ,"src/mavsdk/plugins/failure/failure.cpp" ,"src/mavsdk/plugins/failure/failure_impl.cpp" ,"src/mavsdk/plugins/follow_me/follow_me.cpp" ,"src/mavsdk/plugins/follow_me/follow_me_impl.cpp" ,"src/mavsdk/plugins/ftp/ftp.cpp" ,"src/mavsdk/plugins/ftp/ftp_impl.cpp" ,"src/mavsdk/plugins/geofence/geofence.cpp" ,"src/mavsdk/plugins/geofence/geofence_impl.cpp" ,"src/mavsdk/plugins/gimbal/gimbal.cpp" ,"src/mavsdk/plugins/gimbal/gimbal_impl.cpp" ,"src/mavsdk/plugins/gimbal/gimbal_protocol_v1.cpp" ,"src/mavsdk/plugins/gimbal/gimbal_protocol_v2.cpp" ,"src/mavsdk/plugins/info/info.cpp" ,"src/mavsdk/plugins/info/info_impl.cpp" ,"src/mavsdk/plugins/log_files/log_files.cpp" ,"src/mavsdk/plugins/log_files/log_files_impl.cpp" ,"src/mavsdk/plugins/manual_control/manual_control.cpp" ,"src/mavsdk/plugins/manual_control/manual_control_impl.cpp" ,"src/mavsdk/plugins/mavlink_passthrough/mavlink_passthrough.cpp" ,"src/mavsdk/plugins/mavlink_passthrough/mavlink_passthrough_impl.cpp" ,"src/mavsdk/plugins/mission/mission.cpp" ,"src/mavsdk/plugins/mission/mission_impl.cpp" ,"src/mavsdk/plugins/mission_raw/mission_raw.cpp" ,"src/mavsdk/plugins/mission_raw/mission_raw_impl.cpp" ,"src/mavsdk/plugins/mission_raw/mission_import.cpp" ,"src/mavsdk/plugins/mission_raw_server/mission_raw_server.cpp" ,"src/mavsdk/plugins/mission_raw_server/mission_raw_server_impl.cpp" ,"src/mavsdk/plugins/mocap/mocap.cpp" ,"src/mavsdk/plugins/mocap/mocap_impl.cpp" ,"src/mavsdk/plugins/offboard/offboard.cpp" ,"src/mavsdk/plugins/offboard/offboard_impl.cpp" ,"src/mavsdk/plugins/param/param.cpp" ,"src/mavsdk/plugins/param/param_impl.cpp" ,"src/mavsdk/plugins/param_server/param_server.cpp" ,"src/mavsdk/plugins/param_server/param_server_impl.cpp" ,"src/mavsdk/plugins/server_utility/server_utility.cpp" ,"src/mavsdk/plugins/server_utility/server_utility_impl.cpp" ,"src/mavsdk/plugins/shell/shell.cpp" ,"src/mavsdk/plugins/shell/shell_impl.cpp" ,"src/mavsdk/plugins/telemetry/telemetry.cpp" ,"src/mavsdk/plugins/telemetry/telemetry_impl.cpp" ,"src/mavsdk/plugins/telemetry/math_conversions.cpp" ,"src/mavsdk/plugins/telemetry_server/telemetry_server.cpp" ,"src/mavsdk/plugins/telemetry_server/telemetry_server_impl.cpp" ,"src/mavsdk/plugins/tracking_server/tracking_server.cpp" ,"src/mavsdk/plugins/tracking_server/tracking_server_impl.cpp" ,"src/mavsdk/plugins/transponder/transponder.cpp" ,"src/mavsdk/plugins/transponder/transponder_impl.cpp" ,"src/mavsdk/plugins/rtk/rtk.cpp" ,"src/mavsdk/plugins/rtk/rtk_impl.cpp" ,"src/mavsdk/plugins/tune/tune.cpp" ,"src/mavsdk/plugins/tune/tune_impl.cpp"]#需要包含的头文件include_dirs = ["src/mavsdk/core","src/mavsdk/core/include/mavsdk","src/mavsdk/plugins/action/include","src/mavsdk/plugins/action_server/include","src/mavsdk/plugins/calibration/include","src/mavsdk/plugins/camera/include","src/mavsdk/plugins/camera/camera_definition_files/generated","src/mavsdk/plugins/component_information/include","src/mavsdk/plugins/component_information_server/include","src/mavsdk/plugins/failure/include","src/mavsdk/plugins/follow_me/include","src/mavsdk/plugins/ftp/include","src/mavsdk/plugins/geofence/include","src/mavsdk/plugins/gimbal/include","src/mavsdk/plugins/info/include","src/mavsdk/plugins/log_files/include","src/mavsdk/plugins/manual_control/include","src/mavsdk/plugins/mavlink_passthrough/include","src/mavsdk/plugins/mission/include","src/mavsdk/plugins/mission_raw/include","src/mavsdk/plugins/mission_raw_server/include","src/mavsdk/plugins/mocap/include","src/mavsdk/plugins/offboard/include","src/mavsdk/plugins/param/include","src/mavsdk/plugins/param_server/include","src/mavsdk/plugins/rtk/include","src/mavsdk/plugins/server_utility/include","src/mavsdk/plugins/shell/include","src/mavsdk/plugins/telemetry/include","src/mavsdk/plugins/telemetry_server/include","src/mavsdk/plugins/tracking_server/include","src/mavsdk/plugins/transponder/include","src/mavsdk/plugins/tune/include","src/mavsdk/plugins/action","src/mavsdk/plugins/action_server","src/mavsdk/plugins/calibration","src/mavsdk/plugins/camera","src/mavsdk/plugins/component_information","src/mavsdk/plugins/component_information_server","src/mavsdk/plugins/failure","src/mavsdk/plugins/follow_me","src/mavsdk/plugins/ftp","src/mavsdk/plugins/geofence","src/mavsdk/plugins/gimbal","src/mavsdk/plugins/info","src/mavsdk/plugins/log_files","src/mavsdk/plugins/manual_control","src/mavsdk/plugins/mavlink_passthrough","src/mavsdk/plugins/mission","src/mavsdk/plugins/mission_raw","src/mavsdk/plugins/mission_raw_server","src/mavsdk/plugins/mocap","src/mavsdk/plugins/offboard","src/mavsdk/plugins/param","src/mavsdk/plugins/param_server","src/mavsdk/plugins/rtk","src/mavsdk/plugins/server_utility","src/mavsdk/plugins/shell","src/mavsdk/plugins/telemetry","src/mavsdk/plugins/telemetry_server","src/mavsdk/plugins/tracking_server","src/mavsdk/plugins/transponder","src/mavsdk/plugins/tune","src/third_party/mavlink","src/third_party/mavlink/mavlink/src/mavlink/include/mavlink/v2.0","src/third_party/mavlink/mavlink/src/mavlink/include/mavlink/v2.0/common","//third_party/jsoncpp/include","//third_party/curl/include","//third_party/tinyxml2","//third_party/zlib",]
}ohos_shared_library("MAVSDK") {deps = [    ":libmavsdk_source","//third_party/curl:curl_shared","//third_party/openssl:libssl_shared","//third_party/openssl:libcrypto_shared","//third_party/jsoncpp:jsoncpp","//third_party/tinyxml2:tinyxml2"]         #依赖的三方库part_name = "MAVSDK"subsystem_name = "mavsdk"output_name = "libmavsdk"}ohos_executable("takeoff_and_land") {use_exceptions = trueoutput_name = "takeoff_and_land" # 可选，模块输出名include_dirs = ["src/third_party/mavlink/mavlink/src/mavlink/include","src/mavsdk/core/include/mavsdk","src/mavsdk/plugins/action/include","src/mavsdk/plugins/telemetry/include"]sources = ["examples/takeoff_and_land/takeoff_and_land.cpp","examples/takeoff_and_land/autopilot_interface.cpp",]deps = ["//third_party/MAVSDK:MAVSDK"]part_name = "MAVSDK"subsystem_name = "MAVSDK"}
#演示编译部分
ohos_executable("offboard") {  use_exceptions = trueoutput_name = "offboard" # 可选，模块输出名include_dirs = ["src/third_party/mavlink/mavlink/src/mavlink/include","src/mavsdk/core/include/mavsdk","src/mavsdk/plugins/offboard/include","src/mavsdk/plugins/action/include","src/mavsdk/plugins/telemetry/include"]sources = ["examples/offboard/offboard.cpp",]deps= ["//third_party/MAVSDK:MAVSDK"]part_name = "MAVSDK"subsystem_name = "MAVSDK"}#编译测试文件
ohos_unittest("mavsdk_test") {module_out_path = "MAVSDK/mavsdk_test" testonly = trueuse_exceptions = trueinclude_dirs = [ "src/mavsdk/core/include/mavsdk","src/mavsdk/plugins/action/include","src/mavsdk/plugins/action_server/include","src/mavsdk/plugins/calibration/include","src/mavsdk/plugins/camera/include","src/mavsdk/plugins/camera/camera_definition_files/generated","src/mavsdk/plugins/component_information/include","src/mavsdk/plugins/component_information_server/include","src/mavsdk/plugins/failure/include","src/mavsdk/plugins/follow_me/include","src/mavsdk/plugins/ftp/include","src/mavsdk/plugins/geofence/include","src/mavsdk/plugins/gimbal/include","src/mavsdk/plugins/info/include","src/mavsdk/plugins/log_files/include","src/mavsdk/plugins/manual_control/include","src/mavsdk/plugins/mavlink_passthrough/include","src/mavsdk/plugins/mission/include","src/mavsdk/plugins/mission_raw/include","src/mavsdk/plugins/mission_raw_server/include","src/mavsdk/plugins/mocap/include","src/mavsdk/plugins/offboard/include","src/mavsdk/plugins/param/include","src/mavsdk/plugins/param_server/include","src/mavsdk/plugins/rtk/include","src/mavsdk/plugins/server_utility/include","src/mavsdk/plugins/shell/include","src/mavsdk/plugins/telemetry/include","src/mavsdk/plugins/telemetry_server/include","src/mavsdk/plugins/tracking_server/include","src/mavsdk/plugins/transponder/include","src/mavsdk/plugins/tune/include","src/mavsdk/core","src/mavsdk/plugins/action","src/mavsdk/plugins/action_server","src/mavsdk/plugins/calibration","src/mavsdk/plugins/camera","src/mavsdk/plugins/component_information","src/mavsdk/plugins/component_information_server","src/mavsdk/plugins/failure","src/mavsdk/plugins/follow_me","src/mavsdk/plugins/ftp","src/mavsdk/plugins/geofence","src/mavsdk/plugins/gimbal","src/mavsdk/plugins/info","src/mavsdk/plugins/log_files","src/mavsdk/plugins/manual_control","src/mavsdk/plugins/mavlink_passthrough","src/mavsdk/plugins/mission","src/mavsdk/plugins/mission_raw","src/mavsdk/plugins/mission_raw_server","src/mavsdk/plugins/mocap","src/mavsdk/plugins/offboard","src/mavsdk/plugins/param","src/mavsdk/plugins/param_server","src/mavsdk/plugins/rtk","src/mavsdk/plugins/server_utility","src/mavsdk/plugins/shell","src/mavsdk/plugins/telemetry","src/mavsdk/plugins/telemetry_server","src/mavsdk/plugins/tracking_server","src/mavsdk/plugins/transponder","src/mavsdk/plugins/tune","src/third_party/mavlink","src/third_party/curl/curl/src/curl/include","src/third_party/install/include","src/third_party/mavlink/mavlink/src/mavlink/include/mavlink/v2.0","src/third_party/mavlink/mavlink/src/mavlink/include/mavlink/v2.0/common",]sources = ["src/mavsdk/core/mavsdk_time_test.cpp" ,"src/mavsdk/core/mavsdk_math_test.cpp" ,"src/mavsdk/core/mavlink_channels_test.cpp" ,"src/mavsdk/core/unittests_main.cpp" ,"src/mavsdk/core/timeout_handler_test.cpp" ,"src/mavsdk/core/call_every_handler_test.cpp" ,"src/mavsdk/core/curl_test.cpp" ,"src/mavsdk/core/cli_arg_test.cpp" ,"src/mavsdk/core/locked_queue_test.cpp" ,"src/mavsdk/core/safe_queue_test.cpp" ,"src/mavsdk/core/mavsdk_test.cpp" ,"src/mavsdk/core/mavlink_mission_transfer_test.cpp" ,"src/mavsdk/core/mavlink_statustext_handler_test.cpp" ,"src/mavsdk/core/geometry_test.cpp" ,"src/mavsdk/core/ringbuffer_test.cpp" ,"src/mavsdk/plugins/calibration/calibration_statustext_parser_test.cpp" ,"src/mavsdk/plugins/camera/camera_definition_test.cpp" ,"src/mavsdk/plugins/mission_raw/mission_import_test.cpp" ,"src/mavsdk/plugins/telemetry/math_conversions_test.cpp"]deps = ["//third_party/MAVSDK:MAVSDK","//third_party/googletest:gmock_main","//third_party/googletest:gtest_main"]part_name = "MAVSDK"
}

通过以上操作以后，就可以在 OpenHarmony 编译源码了：

./build.sh --product-name rpi4 --build-target=MAVSDK --ccache

编译完成以后可以在 out/rpi4/mavsdk/MAVSDK 目录下看到编译生成的 libmavsdk.z.so 文件。

同时，还可以在 ohos/out/rpi4/tests/unittest/MAVSDK/mavsdk_test/mavsdk_test 目录下看到我们编译的测试文件，如下所示：

接下来把编译完成的 so 及测试文件到 RPI4 开发板中，运行测试文件验证整个库的移植情况。

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