如何使用C从Linux中的串口读取数据？

I am new to serial programming in Linux using C. I have found a small piece of code to write data on serial port which I am sharing here. After running this code I may assume that data has written on a specific port. Now I would like to open another terminal and using separate code want to read the data written on that specific port - how do I do that?

我是使用C在Linux中进行串行编程的新手。我找到了一小段代码来在串口上写数据，我在这里分享。运行此代码后，我可能会认为数据已写入特定端口。现在我想打开另一个终端并使用单独的代码想要读取写在该特定端口上的数据 - 我该怎么做？

#include <stdio.h>   /* Standard input/output definitions */
#include <string.h>  /* String function definitions */
#include <unistd.h>  /* UNIX standard function definitions */
#include <fcntl.h>   /* File control definitions */
#include <errno.h>   /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */

/*
 * 'open_port()' - Open serial port 1.
 *
 * Returns the file descriptor on success or -1 on error.
 */
int
open_port(void)
{
  int fd; /* File descriptor for the port */

  fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
  if (fd == -1)
  {
   /* Could not open the port. */
    perror("open_port: Unable to open /dev/ttyS0 - ");
  }
  else
    fcntl(fd, F_SETFL, 0);

  n = write(fd, "ATZ\r", 4);
  if (n < 0)
    fputs("write() of 4 bytes failed!\n", stderr);

  return (fd);
}

The code above will write the data on a specific port.

上面的代码将在特定端口上写入数据。

2 个解决方案

#1

In theory, all you have to do is open the relevant port for reading, and use read() to get the data.

理论上，您所要做的就是打开相关的读取端口，并使用read（）来获取数据。

int
read_port(void)
{
    int fd = open("/dev/ttyS0", O_RDONLY | O_NOCTTY);
    if (fd == -1)
    {
        /* Could not open the port. */
        perror("open_port: Unable to open /dev/ttyS0 - ");
    }

    char buffer[32];
    int n = read(fd, buffer, sizeof(buffer));
    if (n < 0)
        fputs("read failed!\n", stderr);
    return (fd);
}

There are differences; notably, the read needs a buffer to put the data in. The code shown discards the first message read. Note that a short read simply indicates that there was less data available than requested at the time when the read completed. It does not automatically indicate an error. Think of a command line; some commands might be one or two characters (ls) where others might be quite complex (find /some/where -name '*.pdf' -mtime -3 -print). The fact that the same buffer is used to read both isn't a problem; one read gives 3 characters (newline is included), the other 47 or so.

有差异;值得注意的是，读取需要一个缓冲区来放入数据。显示的代码丢弃了第一个读取的消息。请注意，简短读取只表示可用数据少于读取完成时所请求的数据。它不会自动指示错误。想一下命令行;一些命令可能是一个或两个字符（ls），其他命令可能非常复杂（find / some / where -name'* .pdf'-mtime -3 -print）。使用相同缓冲区来读取两者的事实不是问题;一个读取给出3个字符（包括换行符），另外47个左右。

#2

The program posted makes a lot of assumptions about the state of the port. In a real world application you should do all the important setup explicitly. I think the best source for learning serial port programming under POSIX is the

发布的程序对端口的状态做了很多假设。在现实世界的应用程序中，您应该明确地执行所有重要的设置。我认为在POSIX下学习串口编程的最佳来源是

Serial Programming Guide for POSIX Operating Systems

POSIX操作系统的串行编程指南

I'm mirroring it here: http://mirror.datenwolf.net/serial/

我在这里反映它：http：//mirror.datenwolf.net/serial/

#1