默认的 serial_port 只支持修改波特率和串口，不支持 数据位 奇偶校验 停止位因在网上找了很多代码，奇偶校验都不行，查了很多linux 下串口编程 才解决问题 还有就是 原来的.c 文件无法编译成功 倒是.cpp 很简单 因此做了以下修改 希望对大家有帮助

前言

1.代码参考来自大神
github: https://github.com/silencefun/ComTest/tree/master/Android_SetN81
jianshu: https://www.jianshu.com/p/0868e90303be
2.将原来的.c 修改为.cpp 因为.c 编译老是失败
3.完善了原代码的奇偶校验功能

SerialPort.java 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. 
 */

package android_serialport_api;

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;

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 dataBits, int stopBits, char parity) throws SecurityException, IOException {


       // mFd = open(device.getAbsolutePath(), baudrate, flags);

        mFd = open(device.getAbsolutePath(), baudrate,dataBits,stopBits,parity);
        if (mFd == null) {
            Log.e(TAG, "native open returns null");
            throw new IOException();
        }
        mFileInputStream = new FileInputStream(mFd);
        mFileOutputStream = new FileOutputStream(mFd);
    }
//    public SerialPort(File device, int baudrate, int flags) throws SecurityException, IOException {
//
//
//        // mFd = open(device.getAbsolutePath(), baudrate, flags);
//
//        mFd = open(device.getAbsolutePath(), baudrate,8,2,'E');
//        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);

    // 调用JNI中 打开方法的声明

    /**
     * @param dataBits 类型 int数据位 取值 位7或8
     * @param parity   char校验类型 取值N ,E, O,,S
     * @param stopBits 类型 int 停止位 取值1 或者 2
     * @return
     */
    private native static FileDescriptor open(String path, int baudrate, int dataBits, int stopBits, char parity);

    public native void close();

    static {
        System.loadLibrary("serial_port");
    }
}

serial_port.cpp 源码

#include <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <jni.h>
#include <strings.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)
int fd;
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;
    }
}

/**

* 设置串口数据，校验位,速率，停止位

* @param nBits 类型 int数据位 取值 位7或8

* @param nEvent 类型 char 校验类型 取值N ,E, O

* @param mStop 类型 int 停止位 取值1 或者 2

*/

// 新的设置方法
int set_serial(int fd,int nSpeed,int nBits,char nEvent,int nStop)
{
    struct termios newttys1,oldttys1;

    /*保存原有串口配置*/
    if(tcgetattr(fd,&oldttys1)!=0)
    {
        LOGE("Setupserial 1");
        return -1;
    }
    bzero(&newttys1,sizeof(newttys1));
    newttys1.c_cflag|=(CLOCAL|CREAD ); /*CREAD 开启串行数据接收，CLOCAL并打开本地连接模式*/

    newttys1.c_cflag &=~CSIZE;/*设置数据位*/
    /*数据位选择*/
    switch(nBits)
    {
        case 7:
            newttys1.c_cflag |=CS7;
            break;
        case 8:
            newttys1.c_cflag |=CS8;
            break;
    }
    /*设置奇偶校验位*/
    switch( nEvent )
    {
        case 'o':  /*奇校验*/
        case 'O':
            newttys1.c_cflag |= PARENB;/*开启奇偶校验*/
            newttys1.c_iflag |= (INPCK | ISTRIP);/*INPCK打开输入奇偶校验；ISTRIP去除字符的第八个比特  */
            newttys1.c_cflag |= PARODD;/*启用奇校验(默认为偶校验)*/
            break;
        case 'E':/*偶校验*/
        case 'e':
            newttys1.c_cflag |= PARENB; /*开启奇偶校验  */
            newttys1.c_iflag |= ( INPCK | ISTRIP);/*打开输入奇偶校验并去除字符第八个比特*/
            newttys1.c_cflag &= ~PARODD;/*启用偶校验*/

            newttys1.c_iflag |= (INPCK | ISTRIP);
            newttys1.c_cflag |= PARENB;
            newttys1.c_cflag &= ~PARODD;

            break;
        case 'N': /*无奇偶校验*/
        case 'n':
            newttys1.c_cflag &= ~PARENB;
            break;
    }
    /*设置波特率*/
    switch( nSpeed )
    {
        case 2400:
            cfsetispeed(&newttys1, B2400);
            cfsetospeed(&newttys1, B2400);
            break;
        case 4800:
            cfsetispeed(&newttys1, B4800);
            cfsetospeed(&newttys1, B4800);
            break;
        case 9600:
            cfsetispeed(&newttys1, B9600);
            cfsetospeed(&newttys1, B9600);
            break;
        case 115200:
            cfsetispeed(&newttys1, B115200);
            cfsetospeed(&newttys1, B115200);
            break;
        default:
            cfsetispeed(&newttys1, B9600);
            cfsetospeed(&newttys1, B9600);
            break;
    }
    /*设置停止位*/
    if( nStop == 1)/*设置停止位；若停止位为1，则清除CSTOPB，若停止位为2，则激活CSTOPB*/
    {
        newttys1.c_cflag &= ~CSTOPB;/*默认为一位停止位； */
    }
    else if( nStop == 2)
    {
        newttys1.c_cflag |= CSTOPB;/*CSTOPB表示送两位停止位*/
    }

    /*设置最少字符和等待时间，对于接收字符和等待时间没有特别的要求时*/
    newttys1.c_cc[VTIME] = 0;/*非规范模式读取时的超时时间；*/
    newttys1.c_cc[VMIN]  = 0; /*非规范模式读取时的最小字符数*/
    tcflush(fd ,TCIFLUSH);/*tcflush清空终端未完成的输入/输出请求及数据；TCIFLUSH表示清空正收到的数据，且不读取出来 */

    /*激活配置使其生效*/
    if((tcsetattr( fd, TCSANOW,&newttys1))!=0)
    {
        LOGE("com set error");
        return -1;
    }

    return 0;
}

//旧的设置方法，奇偶校验有问题
int set_opt(jint nBits, jchar nEvent, jint nStop)
{

    LOGE("set_opt:nBits=%d,nEvent=%c,nStop=%d", nBits, nEvent,nStop);
    LOGE("set_opt:nStop=%d",  nStop);

    struct termios newtio;

    if(tcgetattr(fd, & newtio) != 0)
    {

        LOGE("setup serial failure");

        return -1;

    }

    bzero( & newtio, sizeof(newtio));

    //c_cflag标志可以定义CLOCAL和CREAD，这将确保该程序不被其他端口控制和信号干扰，同时串口驱动将读取进入的数据。CLOCAL和CREAD通常总是被是能的

    newtio.c_cflag |= CLOCAL | CREAD;


    switch(nBits) //设置数据位数
    {

        case 7:
            LOGE("设置数据位数==7");
            newtio.c_cflag &= ~CSIZE;

            newtio.c_cflag |= CS7;

            break;

        case 8:
            LOGE("设置数据位数==8");
            newtio.c_cflag &= ~CSIZE;

            newtio.c_cflag |= CS8;

            break;

        default:
            newtio.c_cflag &= ~CSIZE;

            newtio.c_cflag |= CS8;
            LOGE("设置数据位数==默认=8");
            break;

    }



    switch(nEvent) //设置校验位
    {
        case 'o':
        case 'O':

            newtio.c_cflag |= (PARODD | PARENB);
            newtio.c_iflag |= INPCK;
            LOGE("设置校验位O奇校验位");

            break;
        case 'e':
        case 'E':

            newtio.c_cflag |= PARENB;
            newtio.c_cflag &= ~PARODD;
            newtio.c_iflag |= INPCK;



            LOGE("设置校验位E偶校验位");

            break;

        case 'N':
        case 'n':
            newtio.c_cflag &= ~PARENB; //清除校验位

            LOGE("设置校验位N");
            break;


        default:
            newtio.c_cflag &= ~PARENB; //清除校验位
            LOGE("设置校验位默认N");
            break;

    }
    switch(nStop) //设置停止位
    {

        case 1:

            newtio.c_cflag &= ~CSTOPB;

            break;

        case 2:

            newtio.c_cflag |= CSTOPB;

            break;

        default:
            newtio.c_cflag &= ~CSTOPB;
            // LOGW("nStop:%d,invalid param", nStop);

            break;

    }

    newtio.c_cc[VTIME] = 0;//设置等待时间

    newtio.c_cc[VMIN] = 0;//设置最小接收字符

    tcflush(fd, TCIFLUSH);

    if(tcsetattr(fd, TCSANOW, & newtio) != 0)
    {

        LOGE("options set error");

        return -1;

    }


    LOGE("options set success");
    return 1;

}


/*
 * Class:     android_serialport_SerialPort
 * Method:    open
 * Signature: (Ljava/lang/String;II)Ljava/io/FileDescriptor;
 */
extern "C" JNIEXPORT jobject JNICALL Java_android_1serialport_1api_SerialPort_open
        (JNIEnv *env, jclass thiz, jstring path, jint baudrate,
         jint databits, jint stopbits, jchar parity)
{

    speed_t speed;
    jobject mFileDescriptor;

    /*波特率 */
    {
        speed = getBaudrate(baudrate);
        if (speed == -1)
        {
            /* TODO: throw an exception */
            LOGE("Invalid baudrate");
            return NULL;
        }
    }

    /* Opening device */
    {
        jint flags = 0;
        jboolean iscopy;
        const char *path_utf = env->GetStringUTFChars( path, &iscopy);
        LOGD("Opening serial port %s with flags 0x%x", path_utf, O_RDWR | flags);
        fd = open(path_utf, O_RDWR | O_NONBLOCK);
        //fd=fd;
        LOGD("open() fd = %d", fd);
        env->ReleaseStringUTFChars( 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);
        //设置波特率
        cfsetispeed(&cfg, speed);
        cfsetospeed(&cfg, speed);

        if (tcsetattr(fd, TCSANOW, &cfg))
        {
            LOGE("tcsetattr() failed");
            close(fd);
            /* TODO: throw an exception */
            return NULL;
        }

        //配置校验位 停止位等等
//        set_opt(databits, parity, stopbits);
        set_serial(fd,speed,databits,parity,stopbits);

    }

    /* Create a corresponding file descriptor */
    {
        jclass cFileDescriptor = env->FindClass( "java/io/FileDescriptor");
        jmethodID iFileDescriptor = env->GetMethodID( cFileDescriptor, "<init>", "()V");
        jfieldID descriptorID = env->GetFieldID( cFileDescriptor, "descriptor", "I");
        mFileDescriptor = env->NewObject( cFileDescriptor, iFileDescriptor);
        env->SetIntField( mFileDescriptor, descriptorID, (jint)fd);
    }

    return mFileDescriptor;

}

/*
 * Class:     cedric_serial_SerialPort
 * Method:    close
 * Signature: ()V
 */
extern "C" JNIEXPORT void JNICALL Java_android_1serialport_1api_SerialPort_close
        (JNIEnv *env, jobject thiz)
{
    jclass SerialPortClass = env->GetObjectClass( thiz);
    jclass FileDescriptorClass = env->FindClass( "java/io/FileDescriptor");

    jfieldID mFdID = env->GetFieldID( SerialPortClass, "mFd", "Ljava/io/FileDescriptor;");
    jfieldID descriptorID = env->GetFieldID( FileDescriptorClass, "descriptor", "I");

    jobject mFd = env->GetObjectField(thiz, mFdID);
    jint descriptor = env->GetIntField(mFd, descriptorID);

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

结尾

经串口助手测试 完全ok
新的代码地址 https://github.com/1053452188/Android_Serialport_Custom_Set_N81
能力有限 欢迎指正