CubieBoard2串口

关于Linux串口的一些小知识

1. 串口名称使用 ls -l /dev/ttyS* 一般情况下串口的名称全部在dev下面，如果你没有外插串口卡的话默认是dev下的ttyS*,一般ttyS0对应com1，ttyS1对应com2，当然也不一定是必然的；

2. 记得看一下串口的权限，是不是rw-rw-rw-，不是的话请运行chmod 666 /dev/ttyS\*给予可读写权限。

3. 检查串口是否可用，可以对串口发送数据比如对com1口，echo Hello > /dev/ttyS0。

4. 串口驱动：cat /proc/tty/drivers/sw_serial。

5. 在PC上查看连接到CubieBoard2的串口设备：dmesg | grep ttyS*。
   
dmesg | grep ttyS*
[ 0.000000] console [tty0] enabled
[ 6.246827] systemd[1]: Created slice system-getty.slice.
[ 13.740764] usb 3-4: ch341-uart converter now attached to ttyUSB0


以下内容均在Android Studio中实现

配置环境

配置JAVA

下载并配置好JAVA（JAVA_HOME、CLASSPATH、PATH），CMD中要能使用javah命令。

配置gradle

1. 在gradle目录中找到gradle-wrapper.properties文件。
   修改其中配置为distributionUrl=https://services.gradle.org/distributions/gradle-2.10-all.zip。
   gradle必须高于一定的版本，好像网上说NDK支持是后面加进来的。

   在菜单中File->Project Structure->Project中修改Gradle version为2.10也可以，改完后OK。

2. 项目中的build.gradle

   // Top-level build file where you can add configuration options common to all sub-projects/modules.buildscript {    repositories {        jcenter()    }    dependencies {        classpath 'com.android.tools.build:gradle:2.1.2'        // NOTE: Do not place your application dependencies here; they belong        // in the individual module build.gradle files    }}allprojects {    repositories {        jcenter()    }}task clean(type: Delete) {    delete rootProject.buildDir}

3. NDK
   在项目中local.properties中配置ndk，ndk应该没什么要求。

   ndk.dir=D:\\Programs\\Androidsdk\\ndk-bundlesdk.dir=D:\\Programs\\Androidsdk

   我用的是AS自动下载配置的，版本为android-ndk-r12d。

工程

新建

1. 新建一个类，类名为SerialPort。代码如下：

   package com.bilibili.www.serialporttest;import java.io.File;import java.io.FileDescriptor;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import android.util.Log;public class SerialPort {    private static final String TAG = "SerialPort";    // JNI    static {        //指定库名，需要和build.gradle中一致        try {            System.loadLibrary("serial_port");        }        catch (UnsatisfiedLinkError e) {            Log.d(TAG, "Unsatisfied Link error: " + e.toString());        }    }    private static native FileDescriptor open(String path, int baudrate, int flags);    public native void close();    /*     * Do not remove or rename the field mFd: it is used by native method close();     */    private FileDescriptor mFd;    private FileInputStream mFileInputStream;    private FileOutputStream mFileOutputStream;    public SerialPort(File device, int baudrate, int flags) throws SecurityException, IOException {        /* Check access permission */        if (!device.canRead() || !device.canWrite()) {            try {                /* Missing read/write permission, trying to chmod the file */                Process su;                su = Runtime.getRuntime().exec("/system/bin/su");//获得root                String cmd = "chmod 666 " + device.getAbsolutePath() + "\n"                        + "exit\n";//全部用户权限为可读写                su.getOutputStream().write(cmd.getBytes());                if ((su.waitFor() != 0) || !device.canRead()                        || !device.canWrite()) {                    throw new SecurityException();                }            } catch (Exception e) {                e.printStackTrace();                throw new SecurityException();            }        }        Log.d(TAG, "Start！！！！！！！");        mFd = open(device.getAbsolutePath(), baudrate, flags);        if (mFd == null) {            Log.e(TAG, "native open returns null");            throw new IOException();        }else {            mFileInputStream = new FileInputStream(mFd);            mFileOutputStream = new FileOutputStream(mFd);        }    }    // Getters and setters    public InputStream getInputStream() {        return mFileInputStream;    }    public OutputStream getOutputStream() {        return mFileOutputStream;    }}

   1. 打开terminal，输入cd <你的工程位置>\app\src\main\java；输入javah -jni <你的包名>.<类名>。这里是如javah -jni com.bilibili.www.serialporttest.SerialPort
这样的命令，完成之后如果没有问题，会在java目录下出现一个com_bilibili_www_serialporttest_SerialPort.h的文件。

   2. 在<你的工程位置>\app\src\main目录下新建一个jni目录。

修改

1. 将com_bilibili_www_serialporttest_SerialPort.h文件放进jni目录。

2. 在jni目录下建立一个c文件，内容如下：

   /* * Copyright 2009-2011 Cedric Priscal * * 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. */#include "com_bilibili_www_serialporttest_SerialPort.h"#include <termios.h>#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <string.h>#include <jni.h>//#include "android/log.h"#include <android/log.h>#ifdef __cplusplusextern "C" {#endifstatic const char *TAG="serial_port";/* 这三个函数是为了打印信息而存在 */#define LOGI(fmt, args...) __android_log_print(ANDROID_LOG_INFO,  TAG, fmt, ##args)#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG, TAG, fmt, ##args)#define LOGE(fmt, args...) __android_log_print(ANDROID_LOG_ERROR, TAG, fmt, ##args)static speed_t getBaudrate(jint baudrate){    switch(baudrate) {    case 0: return B0;    case 50: return B50;    case 75: return B75;    case 110: return B110;    case 134: return B134;    case 150: return B150;    case 200: return B200;    case 300: return B300;    case 600: return B600;    case 1200: return B1200;    case 1800: return B1800;    case 2400: return B2400;    case 4800: return B4800;    case 9600: return B9600;    case 19200: return B19200;    case 38400: return B38400;    case 57600: return B57600;    case 115200: return B115200;    case 230400: return B230400;    case 460800: return B460800;    case 500000: return B500000;    case 576000: return B576000;    case 921600: return B921600;    case 1000000: return B1000000;    case 1152000: return B1152000;    case 1500000: return B1500000;    case 2000000: return B2000000;    case 2500000: return B2500000;    case 3000000: return B3000000;    case 3500000: return B3500000;    case 4000000: return B4000000;    default: return -1;    }}/* * Class:     com_bilibili_www_serialporttest_SerialPort * Method:    open * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor; */JNIEXPORT jobject JNICALL Java_com_bilibili_www_serialporttest_SerialPort_open        (JNIEnv *env, jclass thiz, jstring path, jint baudrate, jint flags){    int fd;    speed_t speed;    jobject mFileDescriptor;    /* Check arguments */    {        speed = getBaudrate(baudrate);        if (speed == -1) {            /* TODO: throw an exception */            LOGE("Invalid baudrate");            return NULL;        }    }    /* Opening device */    {        jboolean iscopy;        const char *path_utf = (*env)->GetStringUTFChars(env, path, &iscopy);        LOGD("Opening serial port %s with flags 0x%x", path_utf, O_RDWR | flags);        fd = open(path_utf, O_RDWR | flags);        LOGD("open() fd = %d", fd);        (*env)->ReleaseStringUTFChars(env, path, path_utf);        if (fd == -1)        {            /* Throw an exception */            LOGE("Cannot open port");            /* TODO: throw an exception */            return NULL;        }    }    /* Configure device */    {        struct termios cfg;        LOGD("Configuring serial port");        if (tcgetattr(fd, &cfg))        {            LOGE("tcgetattr() failed");            close(fd);            /* TODO: throw an exception */            return NULL;        }        cfmakeraw(&cfg);        cfsetispeed(&cfg, speed);        cfsetospeed(&cfg, speed);        if (tcsetattr(fd, TCSANOW, &cfg))        {            LOGE("tcsetattr() failed");            close(fd);            /* TODO: throw an exception */            return NULL;        }    }    /* Create a corresponding file descriptor */    {        jclass cFileDescriptor = (*env)->FindClass(env, "java/io/FileDescriptor");        jmethodID iFileDescriptor = (*env)->GetMethodID(env, cFileDescriptor, "<init>", "()V");        jfieldID descriptorID = (*env)->GetFieldID(env, cFileDescriptor, "descriptor", "I");        mFileDescriptor = (*env)->NewObject(env, cFileDescriptor, iFileDescriptor);        (*env)->SetIntField(env, mFileDescriptor, descriptorID, (jint)fd);    }    return mFileDescriptor;}/* * Class:     com_bilibili_www_serialporttest_SerialPort * Method:    close * Signature: ()V */JNIEXPORT void JNICALL Java_com_bilibili_www_serialporttest_SerialPort_close    (JNIEnv *env, jobject thiz){    jclass SerialPortClass = (*env)->GetObjectClass(env, thiz);    jclass FileDescriptorClass = (*env)->FindClass(env, "java/io/FileDescriptor");    jfieldID mFdID = (*env)->GetFieldID(env, SerialPortClass, "mFd", "Ljava/io/FileDescriptor;");    jfieldID descriptorID = (*env)->GetFieldID(env, FileDescriptorClass, "descriptor", "I");    jobject mFd = (*env)->GetObjectField(env, thiz, mFdID);    jint descriptor = (*env)->GetIntField(env, mFd,descriptorID);    LOGD("close(fd = %d)", descriptor);    close(descriptor);}#ifdef __cplusplus}#endif

3. module里面的build.gradle

   import com.android.build.gradle.api.AndroidSourceSetapply plugin: 'com.android.application'android {    compileSdkVersion 24    buildToolsVersion "24.0.0"    defaultConfig {        applicationId "com.bilibili.www.serialporttest"        minSdkVersion 16        targetSdkVersion 19        versionCode 1        versionName "1.0"        ndk {            moduleName = "serial_port"            ldLibs "log", "z", "m", "jnigraphics", "android"        }    }    buildTypes {        release {            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'            ndk {                moduleName = "serial_port"//模块名，要和类SerialPort中的System.loadLibrary();一致                ldLibs "log", "z", "m", "jnigraphics", "android"//所要链接的库                abiFilters "armeabi", "armeabi-v7a", "x86" //输出指定三种abi体系结构下的so库，目前可有可无。没有的话就生成NDK能生成的所有平台，比如mips            }        }        debug {            ndk {                moduleName = "serial_port"                ldLibs "log", "z", "m", "jnigraphics", "android"                abiFilters "armeabi", "armeabi-v7a", "x86"            }        }    }    productFlavors {    }}dependencies {    compile fileTree(include: ['*.jar'], dir: 'libs')    testCompile 'junit:junit:4.12'    compile 'com.android.support:appcompat-v7:24.0.0'}

4. MainActivity
   没有任何布局上的改变，要用控制台查看串口接受信息。这里我使用了接收，需要的话，可以自行添加发送代码。

   package com.bilibili.www.serialporttest;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.os.Handler;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.util.Arrays;import android.util.Log;import android.os.Message;public class MainActivity extends AppCompatActivity {    private static final String TAG = "MainActivity";    private static final int msgKey = 2;    private File mFile;    private FileInputStream mInputStream;    private SerialPort mSerialPort;    private ReadThread mThread;    //private StringBuffer mSb;    private String mSb;    private boolean flag = true;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        try {            mFile=new File("/dev/ttySAC0");            mSerialPort = new SerialPort(mFile, 115200, 0);        } catch (SecurityException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }        mInputStream = (FileInputStream) mSerialPort.getInputStream();        //启动线程        mThread = new ReadThread();        mThread.start();    }    public  static int searchByte(byte[] data, byte value) {        int size = data.length;        for (int i = 0; i < size; ++i) {            if (data[i] == value) {                return i;            }        }        return -1;    }    public class ReadThread extends Thread {        @Override        public void run() {            // TODO Auto-generated method stub            super.run();            while (!isInterrupted()) {                int size,couth = 128;                try {                    Log.d(TAG, "----ReadThread start----");                    if (mInputStream == null) {                        return;                    }                    /* 获取可以读取的数据长度 */                    /*for(int coutq1 = mInputStream.available();                        coutq1 != couth;                        coutq1 = mInputStream.available())                    {                        try {                            sleep(10L);                            couth = mInputStream.available();                            sleep(10L);                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                    }*/                    byte[] buffer = new byte[couth];                    Log.d(TAG, "----read(buffer)----");                    size = mInputStream.read(buffer);                    Log.d(TAG, "----size----" + String.valueOf(size));                    if (size > 0) {                        Log.d(TAG, "----ReadThread size>0----");                        /*mSb = new StringBuffer();                        for (int i = 0; i < buffer.length; i++) {                            mSb.append(buffer[i]);                        }                        Log.d(TAG, "Data=" + mSb.toString());*/                        mSb=new String(Arrays.copyOfRange(buffer,0,size));                        Log.d(TAG, "Data=" + mSb);                        Message msg = new Message();                        msg.what = msgKey;                        mHandler.sendMessage(msg);                    }                    else {                        Log.d(TAG, "----ReadThread DataisNull----");                    }                } catch (IOException e) {                    Log.d(TAG, "----ReadThread printStackTrace----");                    e.printStackTrace();                    return;                }            }        }    }    private Handler mHandler = new Handler() {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what) {                case msgKey:                    //Log.e(TAG, mSb.toString());                    Log.e(TAG, mSb);                    break;                default:                    break;            }        }    };}

编译

1. Make Project(Ctrl + F9)
2. 在<你的工程位置>\app\build\intermediates\ndk\debug\lib目录中，你会发现”armeabi”, “armeabi-v7a”, “x86”三个目录，将他们复制到<你的工程位置>\app\libs中。

运行

GLHF!

问题与经验

1. 编译没有问题，运行时提示tcgetaddr()函数出现错误，找不到该函数。
   没有把”armeabi”, “armeabi-v7a”, “x86”文件夹放进<你的工程位置>\app\libs中，所以apk不包含这几个文件夹中的so二进制文件，所以出现找不到函数的情况。
   另外一种情况是由于api 19 之后的 termios.h 里面的函数有调整，因此调试过程中，出现

   java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol “tcgetattr” referenced by libserialport.so

   解决方法：

   将api 19 的 termios.h 拷贝到 jni 目录下

   termios.h

    /* * Copyright (C) 2008 The Android Open Source Project * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: *  * Redistributions of source code must retain the above copyright *    notice, this list of conditions and the following disclaimer. *  * Redistributions in binary form must reproduce the above copyright *    notice, this list of conditions and the following disclaimer in *    the documentation and/or other materials provided with the *    distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */#ifndef _TERMIOS_H_#define _TERMIOS_H_#include <sys/cdefs.h>#include <sys/ioctl.h>#include <sys/types.h>#include <stdint.h>#include <linux/termios.h>__BEGIN_DECLS/* Redefine these to match their ioctl number */#undef  TCSANOW#define TCSANOW    TCSETS#undef  TCSADRAIN#define TCSADRAIN  TCSETSW#undef  TCSAFLUSH#define TCSAFLUSH  TCSETSFstatic __inline__ int tcgetattr(int fd, struct termios *s){    return ioctl(fd, TCGETS, s);}static __inline__ int tcsetattr(int fd, int __opt, const struct termios *s){    return ioctl(fd, __opt, (void *)s);}static __inline__ int tcflow(int fd, int action){    return ioctl(fd, TCXONC, (void *)(intptr_t)action);}static __inline__ int tcflush(int fd, int __queue){    return ioctl(fd, TCFLSH, (void *)(intptr_t)__queue);}static __inline__ pid_t tcgetsid(int fd){    pid_t _pid;    return ioctl(fd, TIOCGSID, &_pid) ? (pid_t)-1 : _pid;}static __inline__ int tcsendbreak(int fd, int __duration){    return ioctl(fd, TCSBRKP, (void *)(uintptr_t)__duration);}static __inline__ speed_t cfgetospeed(const struct termios *s){    return (speed_t)(s->c_cflag & CBAUD);}static __inline__ int cfsetospeed(struct termios *s, speed_t  speed){    s->c_cflag = (s->c_cflag & ~CBAUD) | (speed & CBAUD);    return 0;}static __inline__ speed_t cfgetispeed(const struct termios *s){    return (speed_t)(s->c_cflag & CBAUD);}static __inline__ int cfsetispeed(struct termios *s, speed_t  speed){    s->c_cflag = (s->c_cflag & ~CBAUD) | (speed & CBAUD);    return 0;}static __inline__ void cfmakeraw(struct termios *s){    s->c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL|IXON);    s->c_oflag &= ~OPOST;    s->c_lflag &= ~(ECHO|ECHONL|ICANON|ISIG|IEXTEN);    s->c_cflag &= ~(CSIZE|PARENB);    s->c_cflag |= CS8;}__END_DECLS#endif /* _TERMIOS_H_ */

   然后在c文件中，将#include <termios.h>改为#include "termios.h"。

2. 能运行，但是串口没有反应。
   请检查串口权限，要求other是可读可写的。