linux c/c++串口通信

主要分成

1. 打开串口
2. 关闭串口
3. 发送字符、字符串
4. 发送格式化字符串
5. 等待接收字符的数量
6. 接收一个字符
7. 释放缓冲区

一、模块代码

用到的头文件

#include <stdio.h>

#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <stdint.h>
#include <sys/ioctl.h>
#include <string.h>
#include <stdarg.h>

1、打开串口

int serialOpen (const char *device, const int baud)
{
  struct termios options ;
  speed_t myBaud ;
  int     status, fd ;

  switch (baud)
  {
    case     50:	myBaud =     B50 ; break ;
    case     75:	myBaud =     B75 ; break ;
    case    110:	myBaud =    B110 ; break ;
    case    134:	myBaud =    B134 ; break ;
    case    150:	myBaud =    B150 ; break ;
    case    200:	myBaud =    B200 ; break ;
    case    300:	myBaud =    B300 ; break ;
    case    600:	myBaud =    B600 ; break ;
    case   1200:	myBaud =   B1200 ; break ;
    case   1800:	myBaud =   B1800 ; break ;
    case   2400:	myBaud =   B2400 ; break ;
    case   4800:	myBaud =   B4800 ; break ;
    case   9600:	myBaud =   B9600 ; break ;
    case  19200:	myBaud =  B19200 ; break ;
    case  38400:	myBaud =  B38400 ; break ;
    case  57600:	myBaud =  B57600 ; break ;
    case 115200:	myBaud = B115200 ; break ;
    case 230400:	myBaud = B230400 ; break ;
    default:
      return -2 ;
  }

  if ((fd = open (device, O_RDWR | O_NOCTTY | O_NDELAY | O_NONBLOCK)) == -1)
    return -1 ;

  fcntl (fd, F_SETFL, O_RDWR) ;

// Get and modify current options:
  tcgetattr (fd, &options) ;

    cfmakeraw   (&options) ;
    cfsetispeed (&options, myBaud) ;
    cfsetospeed (&options, myBaud) ;

    options.c_cflag |= (CLOCAL | CREAD) ;
    options.c_cflag &= ~PARENB ;
    options.c_cflag &= ~CSTOPB ;
    options.c_cflag &= ~CSIZE ;
    options.c_cflag |= CS8 ;
    options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG) ;
    options.c_oflag &= ~OPOST ;

    options.c_cc [VMIN]  =   0 ;
    options.c_cc [VTIME] = 100 ;	// Ten seconds (100 deciseconds)

  tcsetattr (fd, TCSANOW | TCSAFLUSH, &options) ;

  ioctl (fd, TIOCMGET, &status);

  status |= TIOCM_DTR ;
  status |= TIOCM_RTS ;

  ioctl (fd, TIOCMSET, &status);

  usleep (10000) ;	// 10mS

  return fd ;
}

2、关闭串口

void serialClose (const int fd)
{
  close (fd) ;
}

3、发送字符、字符串

void serialPutchar (const int fd, const unsigned char c)
{
  write (fd, &c, 1) ;
}

void serialPuts (const int fd, const char *s)
{
  write (fd, s, strlen(s)) ;
}

4、发送格式化字符串

void serialPrintf (const int fd, const char *message, ...)
{
  va_list argp ;
  char buffer [1024] ;
  
  va_start (argp, message) ;
    vsnprintf (buffer, 1023, message, argp) ;
  va_end (argp) ;

  serialPuts (fd, buffer) ;
}

5、等待接收字符的数量

int serialDataAvail (const int fd)
{
  int result ;

  if (ioctl (fd, FIONREAD, &result) == -1)
    return -1 ;

  return result ;
}

6、接收一个字符

int serialGetchar (const int fd)
{
  uint8_t x ;

  if (read (fd, &x, 1) != 1)
    return -1 ;

  return ((int)x) & 0xFF ;
}

6、释放缓冲区

void serialFlush (const int fd)
{
  tcflush (fd, TCIOFLUSH) ;
}

二、模块测试

#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>

int running = 1;

void sig_handle(int sig)
{
   if(sig == SIGINT)  running = 0;
}

int main()
{    
    signal(SIGINT, sig_handle);    

    int fd;
    if(wiringPiSetup() < 0){
        printf("wiringPi setup failed.\n");
        return 1;
    }

    int baudrate = 115200;

	// 打开串口
    //if((fd = serialOpen("/dev/ttyS0", baudrate)) < 0){  
    if((fd = serialOpen("/dev/ttyAMA0",baudrate)) < 0){  
        printf("serial open failed.\n");
        return 1;
    }

    printf("serial test output ...\n");   
    serialPrintf(fd, "0123456789abcdef");  // 发送

    while(running)
    {
       int sz = serialDataAvail(fd);  // 待接收的字符数量
       
       if(sz > 0)
       {
         printf("size %d, ", sz);
         char *buff =(char*)malloc(sz);
         printf("recv: ");
         for(int i = 0; i < sz; i++){
            int c = serialGetchar(fd);
            //if(c != -1)
            buff[i] = c;  
         }
         printf("%s\n", buff);
         free(buff);

         serialPrintf(fd, buff);
       }
       else{
           usleep(50000); // 必要的延时
       }
    }

    serialClose(fd);
    printf("close serial.\n");

    return 0;
}