Question

我有一个带FPGA的设备，它通过简单的UART发送数据。数据是一个32字节的数据包，波特率是115200.我通过UART-TTL / USB适配器将它们连接到我的笔记本电脑，因此在系统（Ubuntu 14.04）中，我可以从ttyUSB读取数据。我在GTK / C中创建了一个简单的应用程序来接收数据，进行数学运算并将结果保存在文本文件中。一切都工作正常，直到我增加了从每秒5次发送32字节数据包到每秒100次的频率。问题是十几个或几十个中的一个包具有错误的字节顺序。我已经用逻辑分析仪检查过我的FPGA每次都能正确发送数据。

例如，FPGA发送数据包：

1 2 3 4 5 6 7 8 9

但我的申请有时会收到：

1 2 7 3 4 5 6 8 9

我正在使用此功能打开串口：

int rs232_open(char *com_name, int baudrate, int databits, char *parity, int stopbits)
{
    serial_fd = open(com_name, O_RDWR | O_NOCTTY | O_NDELAY); //open port
    if(serial_fd==-1)
    {
        perror("unable to open comport ");
        return 1;
    }
    error = tcgetattr(serial_fd, &old_settings); //save actual port settings
    if(error==-1)
    {
        close(serial_fd);
        perror("unable to read portsettings ");
        return 2;
    }
    memset(&new_settings, 0, sizeof(new_settings));
    new_settings.c_iflag = 0; //without in processing
    new_settings.c_oflag = 0; //without out processing
    new_settings.c_lflag = 0; //without line processing
    new_settings.c_cflag = CLOCAL | CREAD; //without flow control, receiver active
    switch(baudrate) //baudrate
    {
        case 9600:      new_settings.c_cflag |= B9600; break;
        case 19200:     new_settings.c_cflag |= B19200; break;
        case 38400:     new_settings.c_cflag |= B38400; break;
        case 115200:    new_settings.c_cflag |= B115200; break;
        default:        return 3; break;
    }
    switch(databits) //number of data bits
    {
        case 5: new_settings.c_cflag |= CS5; break;
        case 6: new_settings.c_cflag |= CS6; break;
        case 7: new_settings.c_cflag |= CS7; break;
        case 8: new_settings.c_cflag |= CS8; break;
        default: return 3;
    }
    switch(parity[0]) //parity
    {
        case 'N': new_settings.c_iflag |= IGNPAR;  break;
        case 'E': new_settings.c_cflag |= PARENB; break;
        case 'O': new_settings.c_cflag |= PARENB | PARODD; break;
        default: return 3;
    }
    switch (stopbits) //stop bits
    {
        case 1: break; //1 bit
        case 2: new_settings.c_cflag |= CSTOPB; break; //2 bits
        default: return 3;
    }
    new_settings.c_cc[VMIN] = 1; //1 received char allows to read
    new_settings.c_cc[VTIME] = 0;
    tcflush(serial_fd, TCIOFLUSH); //clear port buffers
    error = tcsetattr(serial_fd, TCSANOW, &new_settings); //save new settings
    if(error==-1)
    {
        close(serial_fd);
        perror("unable to set portsettings ");
        return 4;
    }
    return 0;
}

在我的GTK / C应用程序中，单击“OPEN”按钮调用上面的函数：

rs232_open("ttyUSB0",115200,8,"N",2);

然后，我为串口创建一个通道，设置其编码并为接收事件添加处理程序：

int serial_fd; //serial port file descriptor
GIOChannel *serial_ch; //serial port channel
serial_ch = g_io_channel_unix_new(serial_fd); //attach channel to serial port
g_io_add_watch(serial_ch, G_IO_IN, read_channel, NULL); //attach read_channel handler function

函数read_channel()看起来像这样（frame是一个带有chars buffer表和整数字段byte_number）的结构：

gboolean read_channel(GIOChannel *channel, GIOCondition condition, gpointer data)
{
    unsigned char i;
    gsize bytes_read;
    gchar chr;
    GString *recdata = g_string_new(NULL);
    if(g_io_channel_read_chars(channel, &chr, 1, &bytes_read, NULL) == G_IO_STATUS_NORMAL) //if reading a byte is successful
    {
        if(bytes_read) //1 byte received
        {
            //
            // here I search for 0x55 0x55 sequence (start tag of 32 bytes packet)
            // if start tag is received frame buffer is cleared and byte counter zeroed
            //
            frame.buffer[frame.byte_number++]=chr; //save received byte to buffer
            if(frame.byte_number > BUFFER_SIZE-1) //frame buffer full
            {
                if(frame.buffer[BUFFER_SIZE-1] == 0x0D) //end tag is correct (0x0D is end tag of my 32 bytes packet)
                {
                    //
                    // here I convert received data (some int16 numbers)
                    // and save them in readable form to text file
                    // also as a string of hex numbers for debugging
                    //
                }
                else //end tag not correct
                {
                    //
                    // here I increase error counter
                    //
                }
                for(i=0; i<BUFFER_SIZE; i++) frame.buffer[i]=0; //clear the buffer
                frame.byte_number=0; //reset byte counter
            }
        }
    }
    return TRUE;
}

从串行端口收到的字节顺序错误

0 个答案: