串口编程

串口编程：

#define DEV_GPS_NAME "/dev/ttyS1"
#define GPS_BAUD_RATE 9600
int speed_arr[] = {B115200,B38400, B19200, B9600, B4800, B2400, B1200, B300,
        B38400, B19200, B9600, B4800, B2400, B1200, B300};
int name_arr[] = {115200,38400,  19200,  9600,  4800,  2400,  1200,  300,
        38400,  19200,  9600, 4800, 2400, 1200,  300};

void set_speed(int fd, int speed)
{
  int   i;
  int   status;
  struct termios   Opt;
  tcgetattr(fd, &Opt);

  printf("ispeed  =%lu ospeed=%lu\r\n",cfgetispeed(&Opt),cfgetospeed(&Opt));
  for ( i= 0;  i < sizeof(speed_arr) / sizeof(int);  i++)
   {
        if  (speed == name_arr[i])
        {
            printf("set_speed i =%d\r\n",i);
            tcflush(fd, TCIOFLUSH);
            cfsetispeed(&Opt, speed_arr[i]);
            cfsetospeed(&Opt, speed_arr[i]);
            status = tcsetattr(fd, TCSANOW, &Opt);
            if  (status != 0)
                perror("tcsetattr fd1");


            tcgetattr(fd, &Opt);

            printf("after ispeed  =%lu ospeed=%lu\r\n",cfgetispeed(&Opt),cfgetospeed(&Opt));
            return;
        }
        tcflush(fd,TCIOFLUSH);
    }
}

/**
*  设置串口数据位，停止位和效验位
*@param  fd     类型  int  打开的串口文件句柄*
*@param  databits 类型  int 数据位   取值 为 7 或者8*
*@param  stopbits 类型  int 停止位   取值为 1 或者2*
*@param  parity  类型  int  效验类型 取值为N,E,O,,S
*/
int set_Parity(int fd,int databits,int stopbits,int parity)
{
    struct termios options;

    if  ( tcgetattr( fd,&options)  !=  0)
    {
        perror("SetupSerial 1");
        return -1;
    }



    printf("options flag %x\r\n", options.c_cflag);
    options.c_cflag &= ~CSIZE;
    switch (databits) /*设置数据位数*/
    {
        case 7:
            options.c_cflag |= CS7;
            break;
            
        case 8:
            options.c_cflag |= CS8;
            break;
            
        default:
            fprintf(stderr,"Unsupported data size\n");
            return -1;
    }
    switch (parity)
    {
        case 'n':
        case 'N':
            options.c_cflag &= ~PARENB;   /* Clear parity enable */
            options.c_iflag &= ~INPCK;     /* Enable parity checking */
            break;
            
        case 'o':
        case 'O':
            options.c_cflag |= (PARODD | PARENB);  /* 设置为奇效验*/
            options.c_iflag |= INPCK;             /* Disnable parity checking */
            break;
            
        case 'e':
        case 'E':
            options.c_cflag |= PARENB;     /* Enable parity */
            options.c_cflag &= ~PARODD;   /* 转换为偶效验*/
            options.c_iflag |= INPCK;       /* Disnable parity checking */
            break;
            
        case 'S':
        case 's':  /*as no parity*/
            options.c_cflag &= ~PARENB;
            options.c_cflag &= ~CSTOPB;
            break;
            
        default:
            fprintf(stderr,"Unsupported parity\n");
            return -1;
    }
    /* 设置停止位*/
    switch (stopbits)
    {
        case 1:
            options.c_cflag &= ~CSTOPB;
            break;
            
        case 2:
            options.c_cflag |= CSTOPB;
            break;
            
        default:
            fprintf(stderr,"Unsupported stop bits\n");
            return -1;
    }
    
    /* Set input parity option */
    if (parity != 'n')
      options.c_iflag |= INPCK;
      
    options.c_cc[VTIME] = 150; // 15 seconds
    options.c_cc[VMIN] = 0;

    tcflush(fd,TCIFLUSH); /* Update the options and do it NOW  TCIFLUSH*/
    if (tcsetattr(fd,TCSANOW,&options) != 0)
    {
        perror("SetupSerial 3");
        return -1;
    }

    printf("after options flag %x\r\n", options.c_cflag);
    return 0;
}


static int OpenAndSetGpsDev(void)
{
    g_GpsFp = fopen(DEV_GPS_NAME,"r+");
    if (NULL == g_GpsFp)
    {
        perror("Open ttyS1 failed!");
        return -1;
    }  

    g_GpsFd = fileno(g_GpsFp);
    
    if (g_GpsFd > 0)
    {
        set_speed(g_GpsFd,GPS_BAUD_RATE);
    }
    else
    {
        perror("Can't Open Serial Port!");
        fclose(g_GpsFp);
        return -1;
    }

    if (set_Parity(g_GpsFd,8,1,'N') == -1)
    {
        perror("Set Parity Error");
        fclose(g_GpsFp);
        g_GpsFd = 0;
        return -1;
    }
    
    return 0;
}