android串口通信实例分析

置顶] android串口通信实例分析

分类： android 2012-05-21 23:31 118人阅读 评论(4) 收藏 举报

android 串口通信实例分析，用的时开源的android-serialport-api

这个是用android ndk实现的串口通信，我把他做了一个简化，适合于一般的程序的串口通信移植，欢迎拍砖～～～～～～～～～

先说jni接口吧，原本文件太多，其实只需要SerialPort.c和Android.mk就可以实现

Serialport.c

#include     <stdio.h>
#include     <stdlib.h>
#include     <unistd.h>
#include     <sys/types.h>
#include     <sys/stat.h>
#include     <fcntl.h>
#include     <termios.h>
#include     <errno.h>
#include     <jni.h>
#include     <android/log.h>

#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "", __VA_ARGS__))//在logcat上打印信息用
//#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.huangcheng.serial.SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
 *
 * 用于打开串口，配置串口参数，包括的参数有path(需要打开的串口设备文件路径)，baudrate(波特率),flags(打开串口的参数，如O_NONBLOCK之类的，可以随不同情况设置)
 * 其串口数据的读取是用FileDescriptor来实现的
 *
 */
JNIEXPORT jobject JNICALL Java_com_huangcheng_serial_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 */
            LOGI("Invalid baudrate");
            return NULL;
        }
    }

    /* Opening device */
    {
        jboolean iscopy;
        const char *path_utf = (*env)->GetStringUTFChars(env, path, &iscopy);
        LOGI("Opening serial port %s with flags 0x%x", path_utf, O_RDWR | flags);
        fd = open(path_utf, O_RDWR | flags);
        LOGI("open() fd = %d", fd);
        (*env)->ReleaseStringUTFChars(env, path, path_utf);
        if (fd == -1)
        {
            /* Throw an exception */
            LOGI("Cannot open port");
            /* TODO: throw an exception */
            return NULL;
        }
    }

    /* Configure device */
    {
        struct termios cfg;
        LOGI("Configuring serial port");
        if (tcgetattr(fd, &cfg))
        {
            LOGI("tcgetattr() failed");
            close(fd);
            /* TODO: throw an exception */
            return NULL;
        }

        cfmakeraw(&cfg);
        cfsetispeed(&cfg, speed);
        cfsetospeed(&cfg, speed);

        if (tcsetattr(fd, TCSANOW, &cfg))
        {
            LOGI("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.huangcheng.serial.SerialPort
 * Method:    close
 * Signature: ()V
 *
 * 用于串口关闭
 */
JNIEXPORT void JNICALL Java_com_huangcheng_serial_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);

    LOGI("close(fd = %d)", descriptor);
    close(descriptor);
}

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := serial_port
LOCAL_SRC_FILES := SerialPort.c

LOCAL_LDLIBS    := -llog
include $(BUILD_SHARED_LIBRARY)

然后，直接在目录下ndk-build一下，便可得到我们需要的lib库文件。看看怎么调用吧，首先在SerialPort.java中实现打开和关闭串口，引用了lib 库

package com.huangcheng.serial;

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";

    /*
     * 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");
                String cmd = "chmod 666 " + device.getAbsolutePath() + "\n"
                        + "exit\n";
                su.getOutputStream().write(cmd.getBytes());
                if ((su.waitFor() != 0) || !device.canRead()
                        || !device.canWrite()) {
                    throw new SecurityException();
                }
            } catch (Exception e) {
                e.printStackTrace();
                throw new SecurityException();
            }
        }

        mFd = open(device.getAbsolutePath(), baudrate, flags);
        if (mFd == null) {
            Log.e(TAG, "native open returns null");
            throw new IOException();
        }
        mFileInputStream = new FileInputStream(mFd);
        mFileOutputStream = new FileOutputStream(mFd);
    }

    // Getters and setters
    public InputStream getInputStream() {
        return mFileInputStream;
    }

    public OutputStream getOutputStream() {
        return mFileOutputStream;
    }

    // JNI
    private native static FileDescriptor open(String path, int baudrate, int flags);
    public native void close();
    static {
        System.loadLibrary("serial_port");
    }
}

然后他做了一个很聪明的控制串口打开和关闭的类Application.java，继承自android.app.Application 这样，他便可以在所有的Activity类中调用实现串口打开和关闭。

/*
 * Copyright 2009 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./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.
 */

package com.huangcheng.serial;

import java.io.File;
import java.io.IOException;
import java.security.InvalidParameterException;

public class Application extends android.app.Application {

    private SerialPort mSerialPort = null;

    public SerialPort getSerialPort() throws SecurityException, IOException, InvalidParameterException {
        if (mSerialPort == null) {
            /* Open the serial port */
            mSerialPort = new SerialPort(new File("/dev/ttyUSB0"),19200, 0);
        }
        return mSerialPort;
    }

    public void closeSerialPort() {
        if (mSerialPort != null) {
            mSerialPort.close();
            mSerialPort = null;
        }
    }
}

最后写了一个类SerialPortActivity.java实现串口打开和关闭，串口数据通过Input/OutputStrean流来读取和发送，所有继承这个类的Activiy就可以实现串口读取或者发送。

/*
 * Copyright 2009 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./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.
 */

package com.huangcheng.serial;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.InvalidParameterException;

import com.huangcheng.zigbeeview.R;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.os.Bundle;
public abstract class SerialPortActivity extends Activity {

    protected Application mApplication;
    protected SerialPort mSerialPort;
    protected OutputStream mOutputStream;
    private InputStream mInputStream;
    private ReadThread mReadThread;

    private class ReadThread extends Thread {

        @Override
        public void run() {
            super.run();
            while(!isInterrupted()) {
                int size;
                try {
                    byte[] buffer = new byte[64];
                    if (mInputStream == null) return;
                    size = mInputStream.read(buffer);
                    if (size > 0) {
                        onDataReceived(buffer, size);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                    return;
                }
            }
        }
    }

    private void DisplayError(int resourceId) {
        AlertDialog.Builder b = new AlertDialog.Builder(this);
        b.setTitle("Error");
        b.setMessage(resourceId);
        b.setPositiveButton("OK", new OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                SerialPortActivity.this.finish();
            }
        });
        b.show();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mApplication = (Application) getApplication();
        try {
            mSerialPort = mApplication.getSerialPort();
            mOutputStream = mSerialPort.getOutputStream();
            mInputStream = mSerialPort.getInputStream();

            /* Create a receiving thread */
            mReadThread = new ReadThread();
            mReadThread.start();
        } catch (SecurityException e) {
            DisplayError(R.string.error_security);
        } catch (IOException e) {
            DisplayError(R.string.error_unknown);
        } catch (InvalidParameterException e) {
            DisplayError(R.string.error_configuration);
        }
    }

    protected abstract void onDataReceived(final byte[] buffer, final int size);

    @Override
    protected void onDestroy() {
        if (mReadThread != null)
            mReadThread.interrupt();
        mApplication.closeSerialPort();
        mSerialPort = null;
        super.onDestroy();
    }
}

最后，是一个测试Activity实现串口收发，ConsoleActivity.java

/*
 * Copyright 2009 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./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.
 */

package com.huangcheng.serial;

import java.io.IOException;

import com.huangcheng.zigbeeview.R;

import android.os.Bundle;
import android.view.KeyEvent;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.TextView.OnEditorActionListener;

public class ConsoleActivity extends SerialPortActivity {

    EditText mReception;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.console);

//      setTitle("Loopback test");
        mReception = (EditText) findViewById(R.id.EditTextReception);

        EditText Emission = (EditText) findViewById(R.id.EditTextEmission);
        Emission.setOnEditorActionListener(new OnEditorActionListener() {
            public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
                int i;
                CharSequence t = v.getText();
                char[] text = new char[t.length()];
                for (i=0; i<t.length(); i++) {
                    text[i] = t.charAt(i);
                }
                try {
                    mOutputStream.write(new String(text).getBytes());
                    mOutputStream.write('\n');
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return false;
            }
        });
    }

    @Override
    protected void onDataReceived(final byte[] buffer, final int size) {
        runOnUiThread(new Runnable() {
            public void run() {
                if (mReception != null) {
                    mReception.append(new String(buffer, 0, size));
                }
            }
        });
    }
}

我会把android-serialport-api源码上传，大家可以根据我的这个博客自己简化一下，就可以直接移植到需要到程序上去了，绝对可用！