OpenHarmony 串口服务访问-编程知识

项目介绍

本文档是在eTS项目hap包中实现串口访问的使用说明，通过JS接口开放给上层应用使用。

一、开发环境准备

安装OpenHarmony SDK

1. 在DevEco Studio菜单栏选择Tools->SDK Manager

2. OpenHarmony SDK选项中选择配备API版本进行安装

二、创建eTS项目

创建支持Native C++的eTS项目

三、NAPI库相关

生成串口NAPI库

1. 添加文件src/main/cpp/types/libserialhelper/serialhelper.d.ts

/** Copyright (C) 2021-2022 Huawei Device Co., Ltd.* Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**     http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/import {AsyncCallback, Callback} from "basic";
declare namespace serialHelper {/*** Open serial port.* @param dev Indicates the serial port dev.*/function openSerial(dev:string, callback: AsyncCallback<void>): void;function openSerial(dev:string): Promise<void>;/*** Close serial port.* @param dev Indicates the serial port dev.*/function closeSerial(dev:string, callback: AsyncCallback<void>): void;function closeSerial(dev:string): Promise<void>;
}
export default serialHelper;

2. 添加文件src/main/cpp/types/libserialhelper/package.json

{"name": "libserialhelper.so","types": "./serialhelper.d.ts"
}

3. 根据serialhelper.d.ts文件生成对应的c++源码

方式一：手动编写src/main/cpp/serial_helper.cpp

struct AsyncCallInfo{napi_env env = nullptr;napi_ref callbackRef = nullptr;napi_deferred deferred = nullptr;napi_async_work work = nullptr;void *data = nullptr;
};
static void AsyncCallFinish(AsyncCallInfo* asyncCallInfo, int32_t result, napi_value *asyncResult)
{if (asyncCallInfo->deferred) {if (result == 0) {napi_resolve_deferred(asyncCallInfo->env, asyncCallInfo->deferred,asyncResult[1]==nullptr?asyncResult[0]:asyncResult[1]);} else {napi_reject_deferred(asyncCallInfo->env, asyncCallInfo->deferred, asyncResult[0]);}} else {napi_value callback = nullptr;napi_get_reference_value(asyncCallInfo->env, asyncCallInfo->callbackRef, &callback);napi_call_function(asyncCallInfo->env, nullptr, callback, CALLBACK_ARGV_CNT, asyncResult, nullptr);napi_delete_reference(asyncCallInfo->env, asyncCallInfo->callbackRef);}
}

static napi_value Call_OpenSerial(napi_env env, napi_callback_info info)
{size_t argc = 0;napi_value args[DEFAULT_ARG_COUNT] = {0};napi_get_cb_info(env, info, &argc, args , nullptr, nullptr);...napi_value resourceName = nullptr;napi_create_string_utf8(env, "x_napi_tool", NAPI_AUTO_LENGTH, &resourceName);napi_create_async_work(env, nullptr, resourceName,[](napi_env env, void* data) {AsyncCallInfo* asyncCallInfo = (AsyncCallInfo*)data;OpenSerialValue* openValue = (OpenSerialValue*)asyncCallInfo->data;//openValue->out = SerialClient::GetInstance()->OpenSerial(openValue->dev);},[](napi_env env, napi_status status, void* data) {AsyncCallInfo* asyncCallInfo = (AsyncCallInfo*)data;OpenSerialValue* openValue = (OpenSerialValue*)asyncCallInfo->data;napi_value asyncResult[CALLBACK_ARGV_CNT]={nullptr, nullptr};napi_create_int32(env, openValue->out, &asyncResult[0]);AsyncCallFinish(asyncCallInfo, openValue->out,asyncResult);napi_delete_async_work(env, asyncCallInfo->work);delete openValue;delete asyncCallInfo;},(void*)asyncCallInfo, &asyncCallInfo->work);napi_queue_async_work(env, asyncCallInfo->work);return retValue;
}

方式二：使用NAPI框架生成工具生成工具链接

1）将serialhelper.d.ts、basic.d.ts复制到同一目录中，创建out目录

2）执行./napi_generator-linux -f serialhelper.d.ts -o out

3）将生成的源码文件复制到src/main/cpp

4. make文件：src/main/cpp/CMakeList.txt

# the minimum version of CMake.
cmake_minimum_required(VERSION 3.4.1)
project(XComponent)set(NATIVERENDER_ROOT_PATH ${CMAKE_CURRENT_SOURCE_DIR})include_directories(${NATIVERENDER_ROOT_PATH})
add_library(serialhelper SHARED serial_helper.cpp)
target_link_libraries(serialhelper PUBLIC libace_napi.z.so libc++.a)

5. 添加项目依赖

entry/package.json

"devDependencies": {"@types/libserialhelper.so": "file:./src/main/cpp/types/libserialhelper"
}

entry/package-lock.json

"dependencies": {"@types/libserialhelper.so": {"version": "file:src/main/cpp/types/libserialhelper","dev": true}
}

6. 编译生成

修改编译项entry/build-profile.json5：

"buildOption": {"externalNativeOptions": {"path": "./src/main/cpp/CMakeLists.txt","arguments": "-v -DOHOS_STL=c++_shared","abiFilters": ["armeabi-v7a",],"cppFlags": "",}
}

四、实现串口异步回调

添加串口IPC客户端libserialport_service_api.z.so库，并且实现具体的异步回调功能

将libserialport_service_api.z.so复制到entry/libs/armeabi-a7v目录
将库的头文件复制到entry/src/main/cpp/include目录

继承SerialCallbackBase类，实现串口数据异步回调SerialAsyncCallback

class SerialAsyncCallback: public SerialCallbackBase {
public:SerialAsyncCallback() = default;~SerialAsyncCallback();// 通知回调事件void OnCallBackEvent() override;// 接收到串口数据void OnRecvData(const uint8_t *buffer, uint32_t length) override;...
};

修改src/main/cpp/CMakeList.txt文件

# the minimum version of CMake.
cmake_minimum_required(VERSION 3.4.1)
project(XComponent)set(NATIVERENDER_ROOT_PATH ${CMAKE_CURRENT_SOURCE_DIR})include_directories(${NATIVERENDER_ROOT_PATH}${NATIVERENDER_ROOT_PATH}/include)link_directories(${NATIVERENDER_ROOT_PATH}/../../../libs/${CMAKE_OHOS_ARCH_ABI})
add_library(serialhelper SHARED serial_helper.cpp x_napi_tool.cpp serial_async_callback.cpp)
target_link_libraries(serialhelper PUBLIC libace_napi.z.so libc++.a libhilog_ndk.z.so libuv.so libserialport_service_api.z.so)

在napi函数中调用api函数，使用NAPI框架生成工具生成OpenSerial代码，如下：

struct OpenSerial_value_struct {std::string in0;int32_t out;
};void OpenSerial_execute(XNapiTool *pxt, void *data)
{OpenSerial_value_struct *vio = (OpenSerial_value_struct *)data;vio->out = get_serial_client()->OpenSerial(vio->in0);
}void OpenSerial_complete(XNapiTool *pxt, void *data)
{OpenSerial_value_struct *vio = (OpenSerial_value_struct *)data;napi_value result = nullptr;result = NUMBER_C_2_JS(pxt, Int32, vio->out);{napi_value args[XNapiTool::ARGV_CNT] = {result, nullptr};pxt->FinishAsync(vio->out, args);}delete vio;
}
napi_value OpenSerial_middle(napi_env env, napi_callback_info info)
{XNapiTool *pxt = std::make_unique<XNapiTool>(env, info).release();if (pxt->IsFailed()) {napi_value err = pxt->GetError();delete pxt;return err;}struct OpenSerial_value_struct *vio = new OpenSerial_value_struct();pxt->SwapJs2CUtf8(pxt->GetArgv(0), vio->in0);napi_value result = pxt->StartAsync(OpenSerial_execute, vio, OpenSerial_complete,pxt->GetArgc() == 2 ? pxt->GetArgv(1) : nullptr);if (pxt->IsFailed()) {result = pxt->GetError();}return result;
}

模块注册

static napi_value init(napi_env env, napi_value exports)
{std::shared_ptr<XNapiTool> pxt = std::make_shared<XNapiTool>(env, exports);//js函数与C++函数映射pxt->DefineFunction("setOptions", OHOS::SerialPort::SetOptions_middle);pxt->DefineFunction("openSerial", OHOS::SerialPort::OpenSerial_middle);pxt->DefineFunction("closeSerial", OHOS::SerialPort::CloseSerial_middle);pxt->DefineFunction("clearBuffer", OHOS::SerialPort::ClearBuffer_middle);pxt->DefineFunction("sendData", OHOS::SerialPort::SendData_middle);pxt->DefineFunction("recvData", OHOS::SerialPort::RecvData_middle);pxt->DefineFunction("transmit", OHOS::SerialPort::Transmit_middle);pxt->DefineFunction("on", OHOS::SerialPort::on_middle);pxt->DefineFunction("off", OHOS::SerialPort::off_middle);pxt->DefineFunction("setGPIODirection", OHOS::SerialPort::setGPIODirection_middle);pxt->DefineFunction("setGPIOValue", OHOS::SerialPort::setGPIOValue_middle);pxt->DefineFunction("getGPIOValue", OHOS::SerialPort::getGPIOValue_middle);return exports;
}static napi_module g_serialHelper_Module = {.nm_version = 1,.nm_flags = 0,.nm_filename = nullptr,.nm_register_func = init,.nm_modname = "serialhelper",.nm_priv = ((void *)0),.reserved = {(void *)0},
};extern "C" __attribute__((constructor)) void Register_serialHelper_Module(void)
{napi_module_register(&g_serialHelper_Module);
}

eTS调用接口验证

    import serialHelper from "libserialhelper.so"...//打开串口this.tty /dev/ttyXRUSB0serialHelper.openSerial(this.tty).then(()=>{HiLog.i(TAG, "serial openSerial " + this.tty + " success")this.status = '开'}).catch((error)=> {HiLog.i(TAG, "openSerial " + this.tty + " failed:" + error)});...//设置为异步serialHelper.on("/dev/ttyXRUSB0", (data) => {var dataString = "";for (var i = 0; i < data.length; i++) {dataString += String.fromCharCode(data[i]);}HiLog.i(TAG, "ttyXRUSB0 len:" + data.length + " data:" + dataString);})