我有一个运行嵌入式Linux的基于TI Cortex的Pengwyn板，我试图用来从USB-ftdi外设读取原始串行数据，因此我可以将其处理成数据包 .

为此，我编写了一个简单的程序(使用Qt)和termios框架 . 这在我的桌面(Ubuntu VM)机器上没有问题 - 它打开/ dev / ttyUSB0，配置串口，读取和处理数据没有问题 .

当我在pengwyn板上运行相同的程序(显然交叉编译)时遇到问题... read()函数调用不会填充缓冲区 - 尽管它返回一个非错误值，表示数量已读取的字节???

(我还必须为pengwyn板重建linux内核以包含USB-ftdi串行驱动程序 . )

我怀疑这是一个目标配置问题，但我已经比较了两个平台之间的文件权限和termios设置，看起来没问题 . 我是这个平台和串口/ termios的新手，所以我毫无疑问地看了一些东西，但我查看了“POSIX操作系统的串行编程指南”并搜索了有关arm和usb-ftdi读取问题的类似帖子，但是还没找到任何东西 .

有什么建议/意见吗？

测试程序的相关摘录：

void Test::startRx(void)

{

bool retval = false;

m_fd = open(m_port.toLocal8Bit(),O_RDONLY |O_NOCTTY | O_NDELAY);

if (m_fd == -1)

{

qDebug() << "Unable to open: " << m_port.toLocal8Bit() << strerror(errno);

}

else

{

m_isConnected = true;

qDebug() << m_port.toLocal8Bit() << "is open...";

fcntl(m_fd, F_SETFL, 0);

struct termios options;

if (tcgetattr(m_fd, &options)!=0)

{

qDebug() << "tcgetattr() failed";

}

//Set the baud rates to 9600

cfsetispeed(&options, B9600);

cfsetospeed(&options, B9600);

//Enable the receiver and set local mode

options.c_cflag |= (CLOCAL | CREAD);

//Set character size

options.c_cflag &= ~CSIZE; /* Mask the character size bits */

options.c_cflag |= CS8; /* Select 8 data bits */

//No parity 8N1:

options.c_cflag &= ~PARENB;

options.c_cflag &= ~CSTOPB;

options.c_cflag &= ~CSIZE;

options.c_cflag |= CS8;

//Disable hardware flow control

options.c_cflag &= ~CRTSCTS;

//Disable software flow control

options.c_iflag &= ~(IXON | IXOFF | IXANY);

//Raw output

options.c_oflag &= ~OPOST;

//Raw input

options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);

//Set the new options for the port...

tcsetattr(m_fd, TCSANOW, &options);

int status;

ioctl(m_fd, TIOCMGET, &status );

qDebug() << "current modem status:" << status;

QThread* m_reader_thread = new QThread;

m_serial_port_reader = new SerialPortReader(0, m_fd);

if (m_serial_port_reader)

{

qDebug() << "creating serial port reader thread...";

m_serial_port_reader->moveToThread(m_reader_thread);

connect(m_serial_port_reader, SIGNAL(notifyRxPacketData(QByteArray *)), this, SLOT(processRxPacketData(QByteArray*)));

//connect(m_serial_port_reader, SIGNAL(error(QString)), this, SLOT(errorString(QString)));

connect(m_reader_thread, SIGNAL(started()), m_serial_port_reader, SLOT(process()));

connect(m_serial_port_reader, SIGNAL(finished()), m_reader_thread, SLOT(quit()));

connect(m_serial_port_reader, SIGNAL(finished()), m_serial_port_reader, SLOT(quit()));

connect(m_reader_thread, SIGNAL(finished()), m_reader_thread, SLOT(deleteLater()));

m_reader_thread->start();

retval = true;

}

....

void SerialPortReader::readData(int i)

{

m_socket_notifier->setEnabled(false);

if (i == m_fd)

{

unsigned char buf[BUFSIZE] = {0};

int bytesRead = read(m_fd, buf, BUFSIZE);

//qDebug() << Q_FUNC_INFO << "file decriptor:" << m_fd << ", no. bytes read:" << bytesRead;

if (bytesRead < 0)

{

qDebug() << Q_FUNC_INFO << "serial port read error";

return;

}

// if the device "disappeared", e.g. from USB, we get a read event for 0 bytes

else if (bytesRead == 0)

{

//qDebug() << Q_FUNC_INFO << "finishing!!!";

return;

}

//process data...

}

m_socket_notifier->setEnabled(true);

}