Android系统中串口通信源码解析及实践

随着物联网技术的不断发展，Android设备在嵌入式领域的应用越来越广泛。串口通信作为一种常见的设备间通信方式，在Android系统中扮演着重要的角色。本文将深入解析Android系统中串口通信的源码，并介绍如何在实际项目中应用串口通信。

一、Android串口通信概述

Android系统中的串口通信主要依赖于Linux内核提供的串口驱动和Java层的串口API。通过这些API，开发者可以实现与串口设备的通信。Android系统中串口通信的基本流程如下：

1.通过串口API创建串口对象； 2.设置串口参数，如波特率、数据位、停止位、校验位等； 3.打开串口； 4.通过串口发送数据； 5.通过串口接收数据； 6.关闭串口。

二、Android串口通信源码解析

1.Linux内核串口驱动

Linux内核为串口通信提供了丰富的驱动程序，其中最常用的为cdcacm驱动。该驱动程序支持USB转串口设备，如CH340、FT232等。以下为cdcacm驱动的源码结构：

drivers/usb/serial/cdc-acm.c

在cdc_acm.c文件中，主要实现了以下功能：

• 初始化和卸载驱动程序；
• 处理USB设备连接和断开事件；
• 处理数据传输请求；
• 设置串口参数。

2.Java层串口API

Java层提供了SerialPort类，用于实现串口通信。以下为SerialPort类的源码结构：

frameworks/base/core/java/android/hardware/serialport/SerialPort.java

在SerialPort.java文件中，主要实现了以下功能：

• 创建串口对象；
• 设置串口参数；
• 打开和关闭串口；
• 发送和接收数据。

3.系统服务

Android系统提供了SystemServer服务，该服务负责启动各种系统服务，包括串口服务。以下为SystemServer启动串口服务的源码：

services/systemcore/java/com/android/server/SerialService.java

在SerialService.java文件中，主要实现了以下功能：

• 创建串口服务；
• 监听串口事件；
• 处理串口请求。

三、Android串口通信实践

以下为一个简单的Android串口通信示例，实现与串口设备的数据交互：

1.创建一个新的Android项目，并添加必要的权限：

`xml <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSELOCATION" /> <uses-permission android:name="android.permission.SYSTEMALERTWINDOW" /> <uses-permission android:name="android.permission.GETACCOUNTS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.AUTHENTICATEACCOUNTS" /> <uses-permission android:name="android.permission.CALLLOG" /> <uses-permission android:name="android.permission.WRITECALLLOG" /> <uses-permission android:name="android.permission.READCALLLOG" /> <uses-permission android:name="android.permission.BROADCASTSTICKY" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.GETTASKS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.RESTARTPACKAGES" /> <uses-permission android:name="android.permission.WAKELOCK" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSELOCATION" /> <uses-permission android:name="android.permission.SYSTEMALERTWINDOW" /> <uses-permission android:name="android.permission.GETACCOUNTS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.AUTHENTICATEACCOUNTS" /> <uses-permission android:name="android.permission.CALLLOG" /> <uses-permission android:name="android.permission.WRITECALLLOG" /> <uses-permission android:name="android.permission.READCALLLOG" /> <uses-permission android:name="android.permission.BROADCASTSTICKY" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.GETTASKS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.RESTARTPACKAGES" /> <uses-permission android:name="android.permission.WAKELOCK" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSELOCATION" /> <uses-permission android:name="android.permission.SYSTEMALERTWINDOW" /> <uses-permission android:name="android.permission.GETACCOUNTS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.AUTHENTICATEACCOUNTS" /> <uses-permission android:name="android.permission.CALLLOG" /> <uses-permission android:name="android.permission.WRITECALLLOG" /> <uses-permission android:name="android.permission.READCALLLOG" /> <uses-permission android:name="android.permission.BROADCASTSTICKY" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.GETTASKS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.RESTARTPACKAGES" /> <uses-permission android:name="android.permission.WAKELOCK" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSELOCATION" /> <uses-permission android:name="android.permission.SYSTEMALERTWINDOW" /> <uses-permission android:name="android.permission.GETACCOUNTS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.AUTHENTICATEACCOUNTS" /> <uses-permission android:name="android.permission.CALLLOG" /> <uses-permission android:name="android.permission.WRITECALLLOG" /> <uses-permission android:name="android.permission.READCALLLOG" /> <uses-permission android:name="android.permission.BROADCASTSTICKY" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.GETTASKS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.RESTARTPACKAGES" /> <uses-permission android:name="android.permission.WAKELOCK" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSELOCATION" /> <uses-permission android:name="android.permission.SYSTEMALERTWINDOW" /> <uses-permission android:name="android.permission.GETACCOUNTS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.AUTHENTICATEACCOUNTS" /> <uses-permission android:name="android.permission.CALLLOG" /> <uses-permission android:name="android.permission.WRITECALLLOG" /> <uses-permission android:name="android.permission.READCALLLOG" /> <uses-permission android:name="android.permission.BROADCASTSTICKY" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.GETTASKS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.RESTARTPACKAGES" /> <uses-permission android:name="android.permission.WAKELOCK" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSELOCATION" /> <uses-permission android:name="android.permission.SYSTEMALERTWINDOW" /> <uses-permission android:name="android.permission.GETACCOUNTS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.AUTHENTICATEACCOUNTS" /> <uses-permission android:name="android.permission.CALLLOG" /> <uses-permission android:name="android.permission.WRITECALLLOG" /> <uses-permission android:name="android.permission.READCALLLOG" /> <uses-permission android:name="android.permission.BROADCASTSTICKY" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.GETTASKS" /> <uses-permission android:name="android.permission.MANAGEACCOUNTS" /> <uses-permission android:name="android.permission.MOUNTUNMOUNTFILESYSTEMS" /> <uses-permission android:name="android.permission.READEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.WRITEEXTERNALSTORAGE" /> <uses-permission android:name="android.permission.RESTARTPACKAGES" /> <uses-permission android:name="android.permission.WAKELOCK" /> <uses-permission android:name="android.permission.WRITESECURESETTINGS" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.RECEIVEBOOTCOMPLETED" /> <uses-permission android:name="android.permission.CALLPHONE" /> <uses-permission android:name="android.permission.READPHONESTATE" /> <uses-permission android:name="android.permission.ACCESSWIFISTATE" /> <uses-permission android:name="android.permission.CHANGEWIFISTATE" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.FLASHLIGHT" /> <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.RECORDAUDIO" /> <uses-permission android:name="android.permission.MODIFYAUDIOSETTINGS" /> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTHADMIN" /> <uses-permission android:name="android.permission.ACCESSNETWORKSTATE" /> <uses-permission android:name="android.permission.CHANGENETWORKSTATE" /> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESSFINELOCATION" /> <uses-permission android:name="android.permission.ACCESSCOARSE_LOCATION