Android串口操作,简化android-serialport-api的demo(附源码)

       最近在做android串口的开发,找到一个开源的串口类android-serialport-api。其主页在这里http://code.google.com/p/android-serialport-api/  ,这里可以下到APK及对源码。

    但是下载源码之后发现源码不能直接使用,而且源码结构较为复杂。关于串口的操作不外乎几步:

   1.打开串口(及配置串口);

   2.读串口;

   3.写串口;

   4.关闭串口。

android-serialport-api的代码使用了继承等复杂的行为,不容易使初学者很快掌握关于串口的上述4步,所以我特别自己写了一个demo,只有一个activity,其中包含了打开串口,写串口,读串口的操作,对于关闭串口,大家一开就会不明白怎么写了。

这篇文章主要参考http://blog.csdn.net/tangcheng_ok/article/details/7021470

还有http://blog.csdn.net/jerome_home/article/details/8452305


下面言归正传:


第一:

  说道android 串口,就不得不提JNI技术,它使得java中可以调用c语言写成的库。为可在android中使用串口,android-serialport-api的作者自己写了一个c语言的动态链接库serial_port.so(自动命名成libserial_port.so),并把它放在了libs/aemeabi 里,其c源文件在JNI中,大家在下载了android-serialport-api的源代码后,将这两个文件夹copy到自己新建的工程中即可。



第二:

然后将调用c语言写成的动态链接库的java类放入到src文件夹下的android.serialport包下,这里一定要将包名命名成这个,因为对JNI有一定了解的人就会知道,在写c语言链接库时候,函数的命名是和调用它的类所在的包名相关的,一旦包名与链接库中函数的命名不相符,就不能调用链接库的函数。这里可以打开jni中的.c文件(他就是动态链接库的源文件),可以看到源码:

/*
 * 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.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 
#include 
#include 
#include 
#include 
#include 
#include 

#include "android/log.h"
static const char *TAG="serial_port";
#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:     cedric_serial_SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;)V
 */
JNIEXPORT jobject JNICALL Java_android_serialport_SerialPort_open
  (JNIEnv *env, jobject thiz, jstring path, jint baudrate)
{
	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", path_utf);
		fd = open(path_utf, O_RDWR | O_DIRECT | O_SYNC);
		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, "", "()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:     cedric_serial_SerialPort
 * Method:    close
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_android_serialport_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);
}

可以看到,函数的命名规则直接和包名有关。


第三:

android.serialport包下,有两个类,分别是SerialPort.java 和SerialPortFinder.java。

其中,SerialPort.java,这个类主要用来加载SO文件,通过JNI的方式打开关闭串口。

/*
 * 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.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. 
 */

package android.serialport;

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) 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 777 " + device.getAbsolutePath() + "\n"
						+ "exit\n";
				/*String cmd = "chmod 777 /dev/s3c_serial0" + "\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);
		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);
	public native void close();
	static {
		System.loadLibrary("serial_port");
	}
}
可以看到System.loadLibrary("serial_port");一句,这一句就是用来加载动态链接库。我们的串口操作就是要给予这个类来实现。


含有一个类SerialPortFinder.java,这个类是用来找到系统中可以用的串口的,如果你知道的android设备有什么串口,就不必使用这个类来查找串口了,一次简化我们的demo。


第四:加入我们自己的Activity类

  为了方便我记在android.serialport包下加入了我自己的MyserialActivity.java,大家从上面的图中也可以看见。

代码如下:

package android.serialport;


import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

import android.app.Activity;

import android.os.Bundle;



//import android.serialport.sample.R;
import android.serialport.R;

import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MyserialActivity extends Activity {
    /** Called when the activity is first created. */
	
	
	 EditText mReception;
	 FileOutputStream mOutputStream;
	 FileInputStream mInputStream;
	 SerialPort sp;
	 
    @Override
   
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
  
    
    final Button buttonSetup = (Button)findViewById(R.id.ButtonSetup);
    buttonSetup.setOnClickListener(new View.OnClickListener() {
		public void onClick(View v) {
			mReception = (EditText) findViewById(R.id.EditTextRec);
			  
		      try {
			sp=new SerialPort(new File("/dev/ttyS2"),9600);
			} catch (SecurityException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}   
		      
		    
		      mOutputStream=(FileOutputStream) sp.getOutputStream();
		      mInputStream=(FileInputStream) sp.getInputStream();
			
		       Toast.makeText(getApplicationContext(), "open",
		    		    Toast.LENGTH_SHORT).show();
			
		}
	});
    
    
    
    final Button buttonsend= (Button)findViewById(R.id.ButtonSent1);
    buttonsend.setOnClickListener(new View.OnClickListener() {
		public void onClick(View v) {
			
			try {
				mOutputStream.write(new String("send").getBytes());
				mOutputStream.write('\n');
			} catch (IOException e) {
				e.printStackTrace();
			}
			  
		   
		      Toast.makeText(getApplicationContext(), "send",
		    		     Toast.LENGTH_SHORT).show();
			
		}
	});
    
    
    final Button buttonrec= (Button)findViewById(R.id.ButtonRec);
    buttonrec.setOnClickListener(new View.OnClickListener() {
		public void onClick(View v) {
			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;
		}
			
		}
	});
    }
    void onDataReceived(final byte[] buffer, final int size) {
		runOnUiThread(new Runnable() {
			public void run() {
				if (mReception != null) {
					mReception.append(new String(buffer, 0, size));
				}
			}
		});
	}
    
    
}

可以看见,功能比较简单,只有三个按钮,分别用来打开串口(buttonsetup),写串口(buttonsend),读串口(buttonrec),一个文本框用来显示串口接收到的信息。功能已经简化到了最简。


下面先说说在模拟器中使用串口的方法:

应先使用-serial选项打开你的模拟器,如图(修改你模拟器的名字)


然后进入adb shell 

  cd /dev

chmod 777 ttyS2

运行后结果:

相比大家都懂得,我们的串口就是ttyS2,使用chmod命令来获取对它的操作,否则之后你的应用可能没有串口的操作权限。

然后运行程序:

其中Console就是打开串口(原谅我偷懒,忘改名字了)。

你可以把你的电脑的COM1连接到另一台电脑的串口上,并在那台电脑上打开你的串口助手之类的软件,配置好串口(参数不难从源代码里看出来)。按下模拟器中的send键,就能在那台电脑的串口助手中看到:



同样,从那台电脑向这台电脑发送数据也可以显示


至此,这个小demo就完毕了。

  我的源码在这里:   http://download.csdn.net/detail/akunainiannian/5202173


你可能感兴趣的:(android)