【Android】串口通信

jni部分SerialPort.c

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);
		fd = open(path_utf, O_RDWR | 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, "<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:     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);
}

Java代码部分

SerialPort.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.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 {

		Log.i("chw", "SerialPort ---> SerialPort");
		/* 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() + "
"
						//+ "exit
";
				String cmd = "chmod 777 /dev/s3c_serial0" + "
"
				+ "exit
";
				su.getOutputStream().write(cmd.getBytes());
				if ((su.waitFor() != 0) || !device.canRead()
						|| !device.canWrite()) {
					throw new SecurityException();
				}
			} catch (Exception e) {
				e.printStackTrace();
				throw new SecurityException();
			}*/

			try {
	              String command = "chmod 777 " + device.getAbsolutePath();
	              Log.i("chw", "command = " + command  + "
device.getAbsolutePath = " + device.getAbsolutePath());
	              Runtime runtime = Runtime.getRuntime();  

	              Process proc = runtime.exec(command);
	             } catch (IOException e) {
         		 Log.i("chw","chmod fail!!  !!");
	              e.printStackTrace();
			 throw new SecurityException();
         		}
	        Log.i("chw", "Get serial port read/write   permission");
		}

		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() {
		Log.i("chw", "SerialPort ---> getInputStream");
		return mFileInputStream; 
	}

	public OutputStream getOutputStream() {
		Log.i("chw", "SerialPort ---> getOutputStream");
		return mFileOutputStream;  
	}

	// JNI
	private native static FileDescriptor open(String path, int baudrate);
	public native void close();
	static {
		Log.i("chw", "SerialPort ---> loadLibrary");
		System.loadLibrary("serial_port");
	}
}

SerialPortFinder.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.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.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
import java.util.Iterator;
import java.util.Vector;

import android.util.Log;

public class SerialPortFinder {

	public class Driver {
		public Driver(String name, String root) {
			Log.i("chw", "SerialPortFinder ---> Driver");
			mDriverName = name;
			mDeviceRoot = root;
		}
		
		private String mDriverName;
		private String mDeviceRoot;
		Vector<File> mDevices = null;
		public Vector<File> getDevices() {
			Log.i("chw", "SerialPortFinder ---> getDevices");
			
			if (mDevices == null) {
				mDevices = new Vector<File>();
				File dev = new File("/dev");
				File[] files = dev.listFiles();
				int i;
				for (i=0; i<files.length; i++) {
					if (files[i].getAbsolutePath().startsWith(mDeviceRoot)) {
						Log.d(TAG, "Found new device: " + files[i]);
						mDevices.add(files[i]);
					}
				}
			}
			return mDevices;
		}
		public String getName() {
			Log.i("chw", "SerialPortFinder ---> getName");
			return mDriverName;
		}
	}

	private static final String TAG = "SerialPort";

	private Vector<Driver> mDrivers = null;

	Vector<Driver> getDrivers() throws IOException {
		
		Log.i("chw", "SerialPortFinder ---> getDrivers");
		
		if (mDrivers == null) {
			mDrivers = new Vector<Driver>();
			LineNumberReader r = new LineNumberReader(new FileReader("/proc/tty/drivers"));
			String l;
			while((l = r.readLine()) != null) {
				String[] w = l.split(" +");
				if ((w.length == 5) && (w[4].equals("serial"))) {
					Log.d(TAG, "Found new driver: " + w[1]);
					mDrivers.add(new Driver(w[0], w[1]));
				}
			}
			r.close();
		}
		return mDrivers;
	}

	public String[] getAllDevices() {
		
		Log.i("chw", "SerialPortFinder ---> getAllDevices");
		
		Vector<String> devices = new Vector<String>();
		// Parse each driver
		Iterator<Driver> itdriv;
		try {
			itdriv = getDrivers().iterator();
			while(itdriv.hasNext()) {
				Driver driver = itdriv.next();
				Iterator<File> itdev = driver.getDevices().iterator();
				while(itdev.hasNext()) {
					String device = itdev.next().getName();
					String value = String.format("%s (%s)", device, driver.getName());
					devices.add(value);
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return devices.toArray(new String[devices.size()]);
	}

	public String[] getAllDevicesPath() {
		
		Log.i("chw", "SerialPortFinder ---> getAllDevicesPath");
		
		Vector<String> devices = new Vector<String>();
		// Parse each driver
		Iterator<Driver> itdriv;
		try {
			itdriv = getDrivers().iterator();
			while(itdriv.hasNext()) {
				Driver driver = itdriv.next();
				Iterator<File> itdev = driver.getDevices().iterator();
				while(itdev.hasNext()) {
					String device = itdev.next().getAbsolutePath();
					devices.add(device);
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return devices.toArray(new String[devices.size()]);
	}
}