Thread: HELP with storing serial port data into txt file

  1. #1
    Registered User
    Join Date
    Jul 2007
    Posts
    20

    HELP with storing serial port data into txt file

    I have a programming which draws a graph for .txt data and other things.

    Im trying to make this code take single character inputs from the serial port and store them into a txt file as an integer along with the date and time. I think im ok with the date and time. but im not sure how to change what ive done to save data to a txt file. At the mo it just keeps taking inputs, displaying them and sends out _kbhit's.

    Previously i was just manually inputing the data as you can see from the commented code at the top.

    I have been tying to overcome this problem for days now so any help welcome. Here is my code, thanks.

    Code:
    int  GetReadings(int nReadings, int *pReadings)   
    {
       	/*int iReadings;
    
    	printf("Enter readings, one at a time.\n");
    	
    	for(iReadings = 0; iReadings < nReadings; iReadings++){
    		printf("Enter readins #%i: ", iReadings+1);
    		scanf("%i", pReadings++);
    	}
    	return nReadings;
    	*/
        unsigned char c;
        DCB dcb;
        HANDLE hCom;
        char *pcCommPort;
        int portno;
        int nErrNo;
    	DWORD nWritten, nRead;
        COMMTIMEOUTS CommTimeOuts;
    
    // Which port is to be used 1 or 2?
        printf("Which port (1/2)?: ");
        scanf("%d",&portno);
        if(portno == 1)pcCommPort = "COM1";
        else pcCommPort = "COM2";
    
    // "Open" the port and get a handle to it
        hCom = CreateFile( pcCommPort,
    					 GENERIC_READ | GENERIC_WRITE,
    					 0,    // exclusive-access
                         NULL, // no security attributes
                         OPEN_EXISTING, // comm devices must use OPEN_EXISTING
                         0,    // not overlapped I/O
                         NULL  // must be NULL for comm devices
                         );
    
        if (hCom == INVALID_HANDLE_VALUE) {
            printf ("CreateFile failed with error %d.\n", GetLastError());
            return 0;
        }
    
    // Get the device control block for the port, check it's OK...
        if (!GetCommState(hCom, &dcb)) {
            printf ("GetCommState failed with error %d.\n", GetLastError());
            return 0;
        }
    
    // ...and adjust the values to baud=9600 bps, 8 data bits, no parity, and 1 stop bit...
        dcb.BaudRate = CBR_9600;     // set the baud rate
        dcb.ByteSize = 8;             // data size, xmit, and rcv
        dcb.Parity = NOPARITY;        // no parity bit
        dcb.StopBits = ONESTOPBIT;    // one stop bit
    
    // ...and write the device control block back.
        if (!SetCommState(hCom, &dcb)) {
            printf ("SetCommState failed with error %d.\n", GetLastError());
            return 0;
        }
    
    // Set up the comm timeouts
        if(!GetCommTimeouts(hCom, &CommTimeOuts)) {
            printf ("GetCommTimeouts failed with error %d.\n", GetLastError());
            return 0;
        }
        CommTimeOuts.ReadIntervalTimeout = MAXDWORD; // This combination of values
        CommTimeOuts.ReadTotalTimeoutConstant = 0;  // ..causes ReadFile to return
        CommTimeOuts.ReadTotalTimeoutConstant = 0;  // ..immediately even if no chars rec'd
        if (!SetCommTimeouts(hCom, &CommTimeOuts)) {
            printf ("SetCommTimeouts failed with error %d.\n", GetLastError());
            return 0;
        }
    
        printf ("Serial port %s successfully reconfigured.\n", pcCommPort);
    
        printf("Starting TTY emulator.\n");
    
    // Loop around reading the keyboard and comm port
        while(c != 'X'){
            if(_kbhit()){
                c = _getch();
    		        if(WriteFile(hCom, &c, (DWORD)1, &nWritten, NULL) != 0)
                        if((nErrNo = GetLastError()) != ERROR_SUCCESS)
    			            printf("\nWriteFile error: %d", GetLastError());   
            }
    		if(ReadFile(hCom,&c,(DWORD)1,&nRead,NULL) == 0)
    			printf("ReadFile error\n");
            if(nRead > 0)
                putchar(c);
    			
        }
    	
    }

  2. #2
    Hurry Slowly vart's Avatar
    Join Date
    Oct 2006
    Location
    Rishon LeZion, Israel
    Posts
    6,794
    how these 2 functions
    Code:
           if(_kbhit()){
                c = _getch();
    are concerned with the reading from the com-port?
    you should use the correct API functions to read using hCom handle
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

  3. #3
    Kernel hacker
    Join Date
    Jul 2007
    Location
    Farncombe, Surrey, England
    Posts
    15,677
    Quote Originally Posted by vart View Post
    how these 2 functions
    Code:
           if(_kbhit()){
                c = _getch();
    are concerned with the reading from the com-port?
    you should use the correct API functions to read using hCom handle
    They are not related to reading the comport, but from what I understand of the code, it's a very simple terminal program that reads the console and echoes it to the serial port, reads the comport and echoes to the console.

    To trivially write to a file, just open a file using fopen() and then use fputc() next to your putchar(). If you want both input and output to appear in the same file, then use a fputc() next to the WriteFile(hCom, ....) too.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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