为什么“tcsetattr（fd，TCSANOW，＆cfg）”总是失败？

-1

我使用了Google的串口API，但是这个函数总是返回-1。我不知道该怎么办。为什么“tcsetattr（fd，TCSANOW，＆cfg）”总是失败？

该项目在我的mac中运行成功，但在我的Windows和Ubuntu中运行错误。在Windows和Ubuntu上，代码始终在tcsetattr()中停止，因为它返回-1。

这是 “SerialPort.c”：

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_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)) 
     { 
      //There's always a problem in this place 
      LOGE("tcsetattr() failed"); 
      close(fd); 
      /* TODO: throw an exception */ 
      return NULL; 
     } 
    } 

    /* 创建一个相应的文件描述符 */ 
    { 
     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); 
}

来源

2017-07-15 Nevermore

......“perror”说了些什么？ –

如果你写了一个“，”，空间应该在它之后而不是之前发生。 [英文begginer类似，有用的提示和技巧列表]（https://meta.stackoverflow.com/a/291370/1783163）。 – peterh

没有可怕的说法。只是这个函数返回-1。 – Nevermore

我有同样的问题，尝试用Android的NDK-r11c和Android.mk编译。

来源

2017-08-11 09:00:03 panda

我解决了这个问题，确实问题是ndk的版本。 – Nevermore

我用了15，现在是14 – Nevermore

为什么“tcsetattr（fd，TCSANOW，＆cfg）”总是失败？

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