Android串口通信

目前物联网已慢慢普及，NDK开发也慢慢普及。

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今天结合自己在项目中的串口的使用说明一下Android串口通信的使用和常见问题

1 、SerialPort.c

/*
 * 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 <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <jni.h>

#include "SerialPort.h"

#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:     android_serialport_SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
 */
JNIEXPORT jobject JNICALL Java_android_1serialport_1api_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:     cedric_serial_SerialPort
 * Method:    close
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_android_1serialport_1api_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);
}

注意 ： const char kClassName = "com/jerome/serialport/SerialPort";为你Java层与jni对应得包名；

2、SerialPort.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class android_serialport_api_SerialPort */

#ifndef _Included_android_serialport_api_SerialPort
#define _Included_android_serialport_api_SerialPort
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     android_serialport_api_SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
 */
JNIEXPORT jobject JNICALL Java_android_1serialport_1api_SerialPort_open
  (JNIEnv *, jclass, jstring, jint, jint);

/*
 * Class:     android_serialport_api_SerialPort
 * Method:    close
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_android_1serialport_1api_SerialPort_close
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

3、Android.mk

#
# 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. 
#

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

TARGET_PLATFORM := android-3
LOCAL_MODULE    := serial_port
LOCAL_SRC_FILES := SerialPort.c
LOCAL_LDLIBS    := -llog

include $(BUILD_SHARED_LIBRARY)

如果要修改生成so文件的名称，请修改LOCAL_MODULE := serial_port

4、SerialPort.java

package android_serialport_api;


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_serialport_api.scanType.utils.LogUtils;

/**
 * Created by v1ncent on 2017/10/23.
 */

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);//打开串口

        if (mFd == null) {
            LogUtils.e("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");
    }
}

5.SerialPortUtil

package android_serialport_api.scanType.base;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android_serialport_api.SerialPort;
import android_serialport_api.scanType.utils.LogUtils;

/**
 * ================================================
 * 作    者：v1ncent
 * 版    本：1.0.0
 * 创建日期：2018/4/2
 * 描    述：串口工具类
 * 修订历史：
 * ================================================
 */
public class SerialPortUtil {
    private String TAG = SerialPortUtil.class.getSimpleName();
    private SerialPort mSerialPort;//串口基类
    private OutputStream mOutputStream;//输出流
    private InputStream mInputStream;//输入流
    private ReadThread mReadThread;//读取线程
    private String path = "/dev/ttyS2";//串口名
    private int baudrate = 115200;//波特率
    private static SerialPortUtil portUtil;
    private OnDataReceiveListener onDataReceiveListener = null;//接受回调
    private boolean isStop = false;//控制线程的开关

    public interface OnDataReceiveListener {
        void onDataReceive(byte[] buffer, int size);
    }

    public void setOnDataReceiveListener(
            OnDataReceiveListener dataReceiveListener) {
        onDataReceiveListener = dataReceiveListener;
    }

    public static SerialPortUtil getInstance() {
        if (null == portUtil) {
            portUtil = new SerialPortUtil();
        }
        portUtil.onCreate();
        return portUtil;
    }

    /**
     * 初始化串口信息
     */
    public void onCreate() {
        try {
            mSerialPort = new SerialPort(new File(path), baudrate, 0);
            mOutputStream = mSerialPort.getOutputStream();
            mInputStream = mSerialPort.getInputStream();
            mReadThread = new ReadThread();
            isStop = false;
            mReadThread.start();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 发送指令
     *
     * @param mBuffer
     */
    public void sendBuffers(byte[] mBuffer) {
        try {
            mOutputStream = mSerialPort.getOutputStream();
            if (mOutputStream != null) {
                mOutputStream.write(mBuffer);
                mOutputStream.close();
            } else {
                return;
            }
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
    }

    /**
     * 接受处理数据线程
     */
    private class ReadThread extends Thread {

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

    /**
     * 关闭串口
     */
    public void closeSerialPort() {
        LogUtils.i(TAG, "关闭串口");
        isStop = true;
        if (mReadThread != null) {
            mReadThread.interrupt();
        }
        if (mSerialPort != null) {
            mSerialPort.close();
        }
    }
}

具体使用方法
1.配置好相关的串口所需的jni,.so文件等
2.在你要使用的地方初始化SerialPortUtil，实现回调接口OnDataReceiveListener即可接受数据.
不懂的地方可以私信我。