linux下的串口编程—函数收发

操作系统：ubuntu10.04


前言：
    在串口编程中，当通信的设备不需求并发，可以封装成函数形式。

一，源码
    (1) 头文件

/*
 * lower,下位机
 * {
 */
/* 串口的初始化 */
extern     int32_t        com_init_lower(void *param);

/* 串口的发送 */
extern    int32_t        com_send_lower(uint8_t *send_buffer,int32_t buffer_len);

/* 串口接收 */
extern    int32_t        com_recv_lower(uint8_t *buffer,const int32_t need_to_recv);

/* 串口关闭*/
extern    int32_t        com_close_lower(void *param);

/*
 * lower,下位机
 * }
 */

    (2) *.c 文件

#define    LOWER_DEVICE_COM            "/dev/ttySAC0"



static     int32_t     __com_set(int32_t com_fd,speed_t baud_rate)
{
    int32_t fd = com_fd;
    struct termios opt;
//    struct timeval start;

    tcgetattr(fd, &opt);
//    cfsetispeed(&opt, B115200);
//    cfsetospeed(&opt, B115200);
    cfsetispeed(&opt, baud_rate);
    cfsetospeed(&opt, baud_rate);

    // 8n1
    opt.c_cflag &= ~CSIZE;
    opt.c_cflag &= ~CSTOPB;
    opt.c_cflag &= ~PARENB;         // 无奇偶校验
    opt.c_cflag |= CS8;

    opt.c_cflag &= ~CRTSCTS;        // 没有使用硬件流控制

//    opt.c_cflag &= ~INPCK;
    opt.c_cflag |= (CLOCAL | CREAD);                // Enable the receiver and set local mode

    opt.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);    // 原始数据

    opt.c_oflag &= ~OPOST;
    opt.c_oflag &= ~(ONLCR | OCRNL);             // 添加的

    opt.c_iflag &= ~(ICRNL | INLCR);
    opt.c_iflag &= ~(IXON | IXOFF | IXANY);         // 没有软件流控制

    tcflush(fd, TCIOFLUSH);

    opt.c_cc[VTIME] = 1;    // 以 十分之一秒(1/10 s) 为单位
    opt.c_cc[VMIN] = 0;



    if(tcsetattr(fd, TCSANOW, &opt) != 0 )
    {
           perror("tcsetattr error");
           return -COM_CONFIG_ERROR;
    }

    return OPER_OK;
}

/*
 * lower,下位机
 * {
 */

static    int32_t        lower_device_comfd = 0;        /* 与下位机通信的串口的描述符(R2000模块)*/



static     int32_t     _com_set_lower()
{
    int32_t    ret = 0;

    ret = __com_set(lower_device_comfd,B115200);

    return ret;
}




/* 串口的初始化 */
int32_t        com_init_lower(void *param)
{
    int32_t    ret = 0;

    lower_device_comfd = open(LOWER_DEVICE_COM,O_RDWR | O_NOCTTY);    // 阻塞读
    if(lower_device_comfd< 0)
    {
        ret = -COM_OPEN_ERROR;
    }
    else
    {
        ret = _com_set_lower();
    }

    return ret;
}


/*
 * 串口的发送
 * 返回值:正常返回发送的字节数，异常返回负值
 */
int32_t        com_send_lower(uint8_t *send_buffer,int32_t buffer_len)
{
    int32_t    ret = 0;

    // 疑问1:发送数据的长度是否需要判断有效值，有效值是多少??

    ret = write(lower_device_comfd, send_buffer, buffer_len);


    return ret;
}


/* 串口接收 */
int32_t        com_recv_lower(uint8_t *buffer,const int32_t need_to_recv)
{
    int32_t    ret = 0;
    while( (ret = read(lower_device_comfd, (char*)buffer, need_to_recv)) > 0 )
    {
        break;
    }

    return ret;
}

/* 串口关闭*/
int32_t        com_close_lower(void *param)
{
    int32_t    ret = 0;

    if(lower_device_comfd > 0 )
    {
        close(lower_device_comfd);
        lower_device_comfd = 0;
    }

    return ret;
}

/*
 * lower,下位机
 * }
 */

    (3) 测试

static    void        com_oper()
{
    unsigned char read_buf[256]     = {0};
    unsigned char write_buf[256]     = {0};
    int     index             = 0;
    int     data_len         = 0;


    for(index = 0; index < 3; index++)
    {
        bzero(read_buf, sizeof(read_buf)); //类似于memset
        bzero(write_buf, sizeof(write_buf));
        write_buf[0] = 0xBB;

        data_len = com_send_lower(write_buf, strlen((char*)write_buf));
        printf("write : %d\n",data_len);

        while( (data_len = com_recv_lower(read_buf, sizeof(read_buf))) > 0 )
        {
            break;
        }

        printf("read  : %d ,", data_len);
        printf("%02X %02X %02X %02X %02X %02X %02X %02X\n", read_buf[0]
        ,read_buf[1],read_buf[2],read_buf[3]
        ,read_buf[4],read_buf[5],read_buf[6],read_buf[7]);

        sleep(2);
    }
}


void     test_com()
{
    printf("hello\n");


    com_init_lower(NULL);
    com_oper();
    com_close_lower(NULL);

}

二，测试结果