CubieBoard2串口

2022-09-16 15:23:55 浏览数 (1)

大家好，又见面了，我是你们的朋友全栈君。

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

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。

项目中的build.gradle

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// 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
}

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

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ndk.dir=D:\Programs\Androidsdk\ndk-bundle
sdk.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

新建一个类，类名为SerialPort。代码如下：

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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"
                          "exitn";//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>appsrcmainjava；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>appsrcmain目录下新建一个jni目录。

修改

将com_bilibili_www_serialporttest_SerialPort.h文件放进jni目录。

在jni目录下建立一个c文件，内容如下：

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/* * 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 __cplusplus

extern "C" {

#endif


static 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

module里面的build.gradle

代码语言：javascript复制
import com.android.build.gradle.api.AndroidSourceSet

apply 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'
}

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。

代码语言：javascript复制
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>appbuildintermediatesndkdebuglib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>applibs中。

运行

代码语言：javascript复制
GLHF!

问题与经验

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>applibs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

代码语言：javascript复制
 /* * 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 TCSETSF


static __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"。

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。

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