Serial Communication help for capturing data

Hi,

I need to capture data from a card reader using serial communication...
The card stripe data should be returned to the calling program .... The card data is going to be around 500 - 1000 characters max.
I want to write this in C , or VC++. I have .Net 2003 installed and eventually I need to convert this in to a DLL so that it can be called from anywhere.

Can anyone please provide me with some sample examples on how this can be done .

Thank you .

Typically each packet will be seperated with a character 13.

http://www.daniweb.com/techtalkforum...ead.php?t=8020

HTH,

ahoodin,

thanks for ur link .

I am looking to write a very simple program.

Open Com1 and read the card that is swiped from the reader.

The link that you gave me has too much detail and I am not able to get most of it since I a beginner.

Can you give me some simple program just like a basic client program in sockets ?.

Thanks

These functions will allow you to open a COM port and read data. I've copied them from my comport functions cpp that I use every day.

Code:

---


const int COM_SUCCESS = 0;
const int COM_FAILURE = 1;
const int COM_TIMEOUT = 2;
const int COM_CHAR_READY = 3;
const int COM_EMPTY = 4;

/////////////////////////////////////////////////
// OpenComPort()
// Returns 0 for fail, 1 for pass
//
int OpenComPort(HANDLE *hcom,        // handle to com port
                                char port_no[],        // "COM1" etc as string
                                int baud,                // 9600, etc
                                int parity,                // NONE, EVEN, ODD
                                int bitlength,        // number of bits
                                int stopbits)        //1 or 2
{
                DCB dcb;                        // device control block
                BOOL fSuccess;


                *hcom = CreateFile( port_no,
              GENERIC_READ | GENERIC_WRITE,
              0,    // comm devices must be opened w/exclusive-access
              NULL, // no security attributes
              OPEN_EXISTING, // comm devices must use OPEN_EXISTING
              0,    // not overlapped I/O
              NULL  // hTemplate must be NULL for comm devices
            );

        //check that comm port opened correctly
        if (*hcom == INVALID_HANDLE_VALUE)
        {
                return (0);
        }

        //get comm port state
        fSuccess = GetCommState(*hcom, &dcb);

        //check for error getting comm state
        if (!fSuccess)
        {
                return(0);
        }

        // Fill in the DCB:
        // baud = 9,600
        // 8 data bits, no parity, and 1 stop bit.
        dcb.BaudRate = baud;                // set the baud rate
        dcb.ByteSize = bitlength;        // data size, xmit, and rcv
        dcb.Parity = parity;                // no parity bit
        dcb.StopBits = stopbits;        // one stop bit

        //set comm state
        fSuccess = SetCommState(*hcom, &dcb);

        //check for error setting comm state
        if (!fSuccess)
        {
                DWORD err = GetLastError(); // debugging
                return (0);
        }

        return fSuccess;
}

//////////////////////////////////////////////////////////////////
// read string from comport
// bytecount contains bytes read
//
unsigned char read_comport_str(HANDLE hCom,
        char *str, int* bytecount)
{
        unsigned long bytesread = 0;
        int tries = 0;
        unsigned long dErrorFlags;        //error variable from ClearCommError
        COMSTAT ComStat;                        //ComStat structure

        do{
                //Get communication port status structure to see if data is available
                ClearCommError(hCom,&dErrorFlags, &ComStat);
                //Read data from the com port if it's there
                if (ComStat.cbInQue > 0)
                {
                        //read the characters in the input buffer
                        ReadFile(hCom, str, ComStat.cbInQue, &bytesread, NULL);
                }

                Sleep(20); // 20 msec X 1000 = 20 sec timeout
                tries++;

        }while((bytesread == 0) && (tries < 1000));

        if(tries == 1000)
                return COM_TIMEOUT;

        else if(bytesread == 0)
                return COM_FAILURE;
        else
        {
                *bytecount = (int)bytesread;
                return COM_SUCCESS;
        }
}

---

You create a HANDLE object when you open the port, and use the handle when calling the read function. Don't forget to close the handle when you're done, to free up the port.

Code:

---

HANDLE hcom;
int ret, count;
char buffer[255];

ret = OpenComPort(&hcom,"COM1",57600,EVENPARITY,8,2); // open the com port

if(ret)
{
  ret = read_comport_str(hcom, buffer, &count);
}
else
{
  // error
}

CloseHandle(hcom);

---

buffer contains your data.

Thanks for this, This has helped!
The Data that is coming in is all scrambled thought :(

I have a Teensy 2.0 that is Sending data to COM8 like this:
!ANG: 0.22, 0.33, 0.12
!ANG: 0.22, 0.33, 0.12
!ANG: 0.22, 0.33, 0.12
!ANG: 0.22, 0.33, 0.12

Etc... etc...

But What the buffer contains is weird ascii characters - please help!

Quote:

---

Originally Posted by ChadReitsma

I have a Teensy 2.0 that is Sending data to COM8 like this:
!ANG: 0.22, 0.33, 0.12
!ANG: 0.22, 0.33, 0.12
!ANG: 0.22, 0.33, 0.12
!ANG: 0.22, 0.33, 0.12
...
But What the buffer contains is weird ascii characters - please help!

---

Define "weird ascii characters".

The thread is nearly six years old. Perhaps related to ChadReitsma's recent thread at http://forums.codeguru.com/showthread.php?t=522597

Mike