Linux-串行端口读取返回EAGAIN [英] Linux - serial port read returning EAGAIN
问题描述
我从以下列方式打开的串行端口读取某些数据时遇到麻烦.我已经多次使用此代码实例，并且一切正常，但是现在，由于某种原因，我无法弄清楚，我完全无法从串行端口读取任何内容.
I am having some trouble reading some data from a serial port I opened the following way. I've used this instance of code plenty of times and all worked fine, but now, for some reason that I cant figure out, I am completely unable to read anything from the serial port.
我能够写信，并且在另一端正确接收了所有消息，但从未收到答复(正确发送)(不，电缆都还好；))
I am able to write and all is correctly received on the other end, but the replies (which are correctly sent) are never received (No, the cables are all ok ;) )
我用来打开串行端口的代码如下:
The code I used to open the serial port is the following:
fd = open("/dev/ttyUSB0", O_RDWR | O_NONBLOCK | O_NOCTTY);
if (fd == -1)
{
Aviso("Unable to open port");
return (fd);
}
else
{
//Get the current options for the port...
bzero(&options, sizeof(options)); /* clear struct for new port settings */
tcgetattr(fd, &options);
/*-- Set baud rate -------------------------------------------------------*/
if (cfsetispeed(&options, SerialBaudInterp(BaudRate))==-1)
perror("On cfsetispeed:");
if (cfsetospeed(&options, SerialBaudInterp(BaudRate))==-1)
perror("On cfsetospeed:");
//Enable the receiver and set local mode...
options.c_cflag |= (CLOCAL | CREAD);
options.c_cflag &= ~PARENB; /* Parity disabled */
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE; /* Mask the character size bits */
options.c_cflag |= SerialDataBitsInterp(8); /* CS8 - Selects 8 data bits */
options.c_cflag &= ~CRTSCTS; // disable hardware flow control
options.c_iflag &= ~(IXON | IXOFF | IXANY); // disable XON XOFF (for transmit and receive)
options.c_cflag |= CRTSCTS; /* enable hardware flow control */
options.c_cc[VMIN] = 0; //min carachters to be read
options.c_cc[VTIME] = 0; //Time to wait for data (tenths of seconds)
//Set the new options for the port...
tcflush(fd, TCIFLUSH);
if (tcsetattr(fd, TCSANOW, &options)==-1)
{
perror("On tcsetattr:");
}
PortOpen[ComPort] = fd;
}
return PortOpen[ComPort];
端口初始化后，我通过简单的写命令向其中写一些东西...
After the port is initializeed I write some stuff to it through simple write command...
int nc = write(hCom, txchar, n);
其中hCom是文件描述符(没关系)，并且(如我所说)可以工作.但是...当我稍后进行读取时，我从errno收到资源暂时不可用"错误.
where hCom is the file descriptor (and it's ok), and (as I said) this works. But... when I do a read afterwards, I get a "Resource Temporarily Unavailable" error from errno.
我测试了select以查看何时无法读取文件描述符...但是它总是超时！
I tested select to see when the file descriptor had something t read... but it always times out!
我这样读取数据:
ret = read(hCom, rxchar, n);
我总是得到一个EAGAIN，我也不知道为什么.
and I always get an EAGAIN and I have no idea why.
硬件运行正常！我可以看到串行端口上有入站数据，因为我已经制作了一条调试电缆来读取另一个终端上发生的事情.所以...
The HW is working fine! I can see that there is inbound data on the serial port because I've made a debug cable to read whats going on on another terminal. So...
我知道非阻塞应该做什么.我的问题是...为什么什么都没有读！相同的设置在Windows上可以正常工作，因此所有硬件都可以正常工作...
I know what nonblocking should do. My question is... why isn't anything getting read!. The same setup works fine on windows, so all hardware is working fine...
这真让我发疯！我敢肯定这很简单！我什至试着摆脱O_NONBLOCK来看看什么时候可以收到东西...但是什么都没有...
This is driving me nuts! I'm sure it's something simple as hell! I even tried getting rid of O_NONBLOCK to see when I would receive something... but nothing...
