1

我有这个程序，它使用 winapi 函数从串行端口读取：

#include <string>
#include <Windows.h>
using std::cin;
using std::cout;

DCB       blank_dcb = {0};

int main()
{
    int ierr, jsu, jcs, jto, jrf, nt;
    unsigned char readfile_chars[80];
    DWORD nr;
    std::string s;
    HANDLE port_h;
    COMMTIMEOUTS port_timeouts;
    DCB dcb;
    
    port_h = CreateFile("COM6", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
    if(INVALID_HANDLE_VALUE == port_h)
    {
        cout << "Failed to open COM6.\n";
        cout << "Press ENTER to exit.\n";
        getline(cin, s);
        return -1;
    }
    
    //
    // Call SetupComm().
    //
    jsu = SetupComm(port_h, 1024, 1024);
    if(0 == jsu)
    {
        cout << "Error while calling SetupComm(): ";
        ierr = GetLastError();
        cout << ierr << "\n";
        cout << "Press ENTER to exit.\n";
        getline(cin, s);
        return -1;
    }
    
    //
    // Set the comm state.
    //
    dcb = blank_dcb;
    dcb.DCBlength = sizeof(DCB);
    dcb.BaudRate = CBR_9600;
    dcb.ByteSize = 8;
    dcb.StopBits = ONESTOPBIT;
    dcb.Parity = NOPARITY;
    dcb.fBinary = TRUE;
    
    jcs = (int) SetCommState(port_h,&dcb);
    if(0 == jcs)
    {
        cout << "Error while setting comm state.\n";
        cout << "Press ENTER to exit.\n";
        getline(cin, s);
        return -1;
    }
    
    //
    // Set the port's timeouts.
    //
    port_timeouts.ReadIntervalTimeout = MAXDWORD;
    port_timeouts.ReadTotalTimeoutConstant = 0;
    port_timeouts.ReadTotalTimeoutMultiplier = 0;
    port_timeouts.WriteTotalTimeoutConstant = 0;
    port_timeouts.WriteTotalTimeoutMultiplier = 0;
    
    jto = SetCommTimeouts(port_h, &port_timeouts);
    if(0 == jto)
    {
        cout << "Error setting comm timeouts.\n";
        cout << "Press ENTER to exit.\n";
        getline(cin, s);
        return -1;
    }
    
    Sleep(5000);
    nt = 9;
    jrf = ReadFile(port_h, (LPVOID) &readfile_chars[0], nt, &nr, NULL);
    if(0 == jrf)
    {
        cout << "ReadFile() failed.\n";
    }
    
    cout << "Read " << nr << " characters.\n";
    readfile_chars[nr] = '\0';
    cout << "Characters read: " << readfile_chars << "\n";
    
    cout << "Press ENTER to exit.\n";
    getline(cin, s);
    return 1;
}

而这个使用 Boost.Asio 的程序：

#include <iostream>
#include <string>

#define _WIN32_WINNT 0x0601

#include <boost/asio.hpp>
using std::cin;
using std::cout;

int main()
{
    char message[80];
    std::string s;
    boost::asio::io_service io_svc;
    
    boost::asio::serial_port com6(io_svc, "COM6");
    com6.set_option(boost::asio::serial_port_base::baud_rate(9600));
    com6.set_option(boost::asio::serial_port_base::character_size(8));
    com6.set_option(boost::asio::serial_port_base::stop_bits(boost::asio::serial_port_base::stop_bits::one));
    com6.set_option(boost::asio::serial_port_base::parity(boost::asio::serial_port_base::parity::none));
    com6.set_option(boost::asio::serial_port_base::flow_control(boost::asio::serial_port_base::flow_control::none));
    
    boost::asio::read(com6, boost::asio::buffer(&message[0],9));
    
    message[9] = '\0';
    cout << "Characters received: " << message << "\n";
    
    cout << "Press ENTER to exit.\n";
    getline(cin, s);
}

我有一个通过 RS232 端口传输 ASCII 字符的数字电平。

数字水平仪成功地将字符传输到 Putty 窗口。

升压程序成功地从通过串行电缆连接到 COM6 的外部 PC 上的超级终端窗口读取字符。

升压程序成功地从数字级别读取字符。

winapi 程序从外部 PC 上的超级终端窗口成功读取字符。

winapi 程序不会从数字级别读取字符。函数 ReadFile() 成功返回，接收的字符数设置为零，表明它认为数字级别处于文件末尾。

为什么boost程序从数字级别读取成功，而winapi程序却没有？

4

0 回答 0