[RK3399][Android7.1] 调试笔记 --- 串口JNI测试用例

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/kris_fei/article/details/82254979

Platform: RK3399
OS: Android 7.1
Kernel: v4.4.83

Android并没有包含串口的JNI， 需要我们自己实现。(Android Thing已经有实现)
串口JNI的参考范例见： https://github.com/cepr/android-serialport-api。

有将它修改做了实现，也分享给大家做参考。

JNI部分：
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_com_example_serialport_SerialPort_open
  (JNIEnv *env, jclass thiz, jstring path, jint baudrate, jint flags)
{
    int fd;
    int 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);
    }

    LOGE("Java_com_example_serialport_SerialPort_open");
    return mFileDescriptor;
}

/*
 * Class:     cedric_serial_SerialPort
 * Method:    close
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_example_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);
}

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_com_example_serialport_SerialPort_open
  (JNIEnv *, jclass, jstring, jint, jint);

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

#ifdef __cplusplus
}
#endif
#endif

编译成so
Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := libserialport
LOCAL_SRC_FILES := SerialPort.c
LOCAL_SHARED_LIBRARIES := liblog libcutils

include $(BUILD_SHARED_LIBRARY)

---

测试程序：
Java调用JNI部分：
SerialPort.java

package com.example.serialport;

import android.util.Log;

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;

/**
 * Created by kris on 8/16/18.
 */

public class SerialPort {
    private static final String TAG = "SerialPort";
    private FileDescriptor mFd;
    private FileInputStream mFileInputStream;
    private FileOutputStream mFileOutputStream;

    public void onDataReceived(final byte[] buffer, final int size) {
    //事件处理很多或者耗时的话可以开个线程
/*        new Thread(new Runnable() {
            @Override
            public void run() {
                //do sth.
            Log.i(TAG, "onDataReceived: ");
            }
        }).start();*/

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

    public SerialPort(File device, int baudrate, int flags) throws SecurityException, IOException {
        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);
        //开一个线程实时接收串口数据
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    int size;

                    try {
                        byte[] buffer = new byte[64];
                        if (mFileInputStream == null) return;
                        size = mFileInputStream.read(buffer);
                        //数据处理
                        onDataReceived(buffer, size);
                    } catch (IOException e) {
                        e.printStackTrace();
                        return;
                    }
                }
            }
        }).start();
    }

    public int Send(final byte[] buffer, final int size)
    {
        try {
            if (mFileOutputStream != null) {
                mFileOutputStream.write(buffer);
            } else {
                return 0;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return 1;
    }

    // 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("serialport");
    }
}

打开串口
ExternalDevices.java

package com.example.serialport;

import java.io.File;
import java.io.IOException;

/**
 * Created by kris on 8/20/18.
 */

public class ExternalDevices {
    private static final String TAG = "ExternalDevices";
    public SerialPort mSerialPort = null;

    public  ExternalDevices()
    {
        try {
            mSerialPort = new SerialPort(new File("/dev/ttyS4"), 115200, 0);
        }catch (IOException e){}
    }
}

完整的测试见： https://download.csdn.net/download/kris_fei/10637861