程式設計者天堂

 

 

 

在進入嵌入式系統之前，必須要懂得如何將裝置與電腦連線，一般來說，大部分都會透過RS232來與裝置建立連線，透過RS232傳送資料並做程式碼的偵錯。利用C撰寫出從RS232讀取到資料並不是一件太困難的事，透過CreateFile()這個函數能讓我們很快的與裝置建立連線，下面列出簡單的程式碼供大家參考。

 

你可以利用微軟的visual c++來進行編譯，參考資料 (1)

 

#include <stdlib.h>

#include <stdio.h>

#include <Windows.h>

 

#define READ_BUF_SIZE 512

#define READ_TIMEOUT 500

 

int main()

{

    HANDLE hFile;

    DWORD dwRead;
    BOOL fWaitingOnRead = FALSE;
    OVERLAPPED osReader = {0};

    char lpBuf[READ_BUF_SIZE];

 

    hFile=CreateFile(TEXT(\\\\.\\com), GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);

    if (hFile == INVALID_HANDLE_VALUE)
    {
        printf("Could not open file (error %d)\n", GetLastError());
        return 0;
    }

 

    osReader.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    if (osReader.hEvent == NULL)
    {
        printf("event error");
        return 0;
    } 

 

    while(1)
    {
        Sleep(50);
        if (!fWaitingOnRead)
        {
           // Issue read operation.
           if (!ReadFile(hFile, lpBuf, READ_BUF_SIZE, &dwRead, &osReader)) {
               if (GetLastError() != ERROR_IO_PENDING)
               {
                   printf("error");
                   break;
               }   
               else
                   fWaitingOnRead = TRUE;
        }

 

        if (fWaitingOnRead) {
            DWORD dwRes = WaitForSingleObject(osReader.hEvent, READ_TIMEOUT);
            switch(dwRes)
           {
                // Read completed.
                case WAIT_OBJECT_0:
                    if (!GetOverlappedResult(hFile, &osReader, &dwRead, FALSE))
                        break;
                    else
                    { 
                       // Read completed successfully.
                       for(int i=0; i<dwRead;i++)
                           printf("%c",lpBuf[i]);

                    }

                    //  Reset flag so that another opertion can be issued.
                    fWaitingOnRead = FALSE;
                    break;

                 

                case WAIT_TIMEOUT:
                    break;                      

                default:
                    break;
            }
        }

    }

 

 

    CloseHandle(hFile);

    return 0;

}

 

另一個方法可以使用Python這個程式語言來達成目的，先去下在serial library並將該函式庫安裝在你的電腦中，然後打開python直譯器，參考下面的範例，你應該可以很快的與裝置搭上線。

 

>>> import serial

>>> device=serial.Serial()

>>> device.timeout=500

>>> device.baudrate=115200

>>> device.port=1

>>> device.open()

>>>

>>> while(1):

>>>     x=device.read(1)

>>>     print ord(x[0])

>>>

>>> device.close()