Thread: Comm Port - Send Packets

Hi guys,

I am trying to write sotware in C to send text to an LCD screen from a Win XP machine through a Comm Port Does anyone know how to do this. I think I have set up the port I just have no idea how to send the packets.


Can anyone help??

To make it easier I should supply my code to set up the port:

Code:

#include <windows.h>

#define RECEIVEBUFFERSIZE         4096

typedef ubyte;

int main(int argc, char *argv[])
{
  DCB dcb;
  HANDLE hCom;
  BOOL fSuccess;
  char *pcCommPort = "COM1";
  ubyte SerialReceiveBuffer[RECEIVEBUFFERSIZE];
  DWORD ReceiveBufferHead;
  DWORD ReceiveBufferTail;
  DWORD ReceiveBufferTailPeek;

  //----------------------------------------------------------------------------
     
  int Serial_Init(char *port, int baud_rate)
  {
     hCom = CreateFile( pcCommPort,
                      GENERIC_READ | GENERIC_WRITE,
                      0,    // must be opened with exclusive-access
                      NULL, // no security attributes
                      OPEN_EXISTING, // must use OPEN_EXISTING
                      0,    // not overlapped I/O
                      NULL  // hTemplate must be NULL for comm devices
                      );

     if (hCom == INVALID_HANDLE_VALUE)
     {
         // Handle the error.
         printf ("CreateFile() failed with error %d.\n", GetLastError());
         return (1);
     }

     // Build on the current configuration, and skip setting the size
     // of the input and output buffers with SetupComm.

     fSuccess = GetCommState(hCom, &dcb);

     if (!fSuccess)
     {
        // Handle the error.
        printf ("GetCommState() failed with error %d.\n", GetLastError());
        hCom = 0;
        return (2);
     }

     // Fill in DCB: 57,600 bps, 8 data bits, no parity, and 1 stop bit.

     dcb.BaudRate = baud_rate;     // set the baud rate
     dcb.ByteSize = 8;             // data size, xmit, and rcv
     dcb.Parity = NOPARITY;        // no parity bit
     dcb.StopBits = ONESTOPBIT;    // one stop bit
     dcb.fRtsControl = RTS_CONTROL_ENABLE;
     dcb.fDtrControl = DTR_CONTROL_ENABLE;
     dcb.fAbortOnError = FALSE;
     fSuccess = SetCommState(hCom, &dcb);

     if (!fSuccess)
     {
        // Handle the error.
        printf ("SetCommState() failed with error %d.\n", GetLastError());
        return (3);
     }
     
     COMMTIMEOUTS
       our_timeouts;
       
     if(TRUE != GetCommTimeouts (
             hCom, &our_timeouts))
     {
             hCom = 0;
             printf("GetCommTimeouts() failed with error %d.\n", GetLastError());
             return(4);
             }
             
     our_timeouts.ReadIntervalTimeout = 2000;
     our_timeouts.ReadTotalTimeoutMultiplier = 2000;
     our_timeouts.ReadTotalTimeoutConstant = 2000;
     
     if(TRUE != SetCommTimeouts(
             hCom, &our_timeouts))
     {
             hCom = 0;
             printf("SetCommTimeouts() failed with error %d.\n", GetLastError());
             return(5);
             }
             
     void EmptyReceiveBuffer(void);
     
     printf ("Serial port %s successfully reconfigured.\n", pcCommPort);
     return (0);
  }
  
  //----------------------------------------------------------------------------
  
  void Uninit_Serial() {
       CloseHandle(hCom);
       hCom = NULL;
       }
       
  //----------------------------------------------------------------------------
  
  void Sync_Read_Buffer_Void(void) {
       ubyte Incoming[4096];
       DWORD BytesRead;
       COMSTAT status;
       DWORD errors;
       DWORD i = 0;
       int j = 10;
       
       if(!hCom)
         return;
         
       ClearCommError(
                      hCom,
                      &errors,
                      &status);
       
       if(status.cbInQue)
         {
         if(!ReadFile(hCom,
           (LPVOID *)Incoming,
           status.cbInQue,
           &BytesRead,
           NULL))
           printf("ReadFile() failed with error %d.\n", GetLastError());
         else
           if(i < BytesRead) {
             SerialReceiveBuffer[ReceiveBufferHead] = Incoming[i];
             ReceiveBufferHead++;
             if(RECEIVEBUFFERSIZE <=ReceiveBufferHead) {
               ReceiveBufferHead = 0;
             }
             i++;
           }
         }
       }
       
  //----------------------------------------------------------------------------
       
  DWORD BytesAvail(void) {
    register int LocalReceiveBufferHead;
    register int return_value;
      
    LocalReceiveBufferHead = ReceiveBufferHead;
    if((return_value=(LocalReceiveBufferHead) - (int)ReceiveBufferTail) < 0)
      return_value += RECEIVEBUFFERSIZE;
    return(return_value);
  }
  
  //----------------------------------------------------------------------------
  
  ubyte GetByte(void) {
        register DWORD LocalReceiveBufferTail;
        register DWORD LocalReceiveBufferHead;
        register ubyte return_byte;
        
        LocalReceiveBufferTail = ReceiveBufferTail;
        LocalReceiveBufferHead = ReceiveBufferHead;
        
        if(LocalReceiveBufferTail != LocalReceiveBufferHead) {
          return_byte=SerialReceiveBuffer[LocalReceiveBufferTail];
          LocalReceiveBufferTail++;
          if(RECEIVEBUFFERSIZE <= LocalReceiveBufferTail) {
            LocalReceiveBufferTail = 0;
          }
        ReceiveBufferTail = LocalReceiveBufferTail;
        return(return_byte);
        }
          
  }  
  
  //----------------------------------------------------------------------------
  
  DWORD PeekBytesAvail(void) {
    register int LocalReceiveBufferHead;
    register int return_value;
    
    LocalReceiveBufferHead = ReceiveBufferHead;
    if((return_value = (LocalReceiveBufferHead) - (int)ReceiveBufferTailPeek) < 0) {
      return_value += RECEIVEBUFFERSIZE;
    }
    return(return_value);
  }
  
  //----------------------------------------------------------------------------
  
  void Sync_Peek_Pointer(void) {
    ReceiveBufferTailPeek = ReceiveBufferTail;
  }
  
  //----------------------------------------------------------------------------
  
  ubyte PeekByte(void) {
    register int LocalReceiveBufferTailPeek;
    register int LocalReceiveBufferHead;
    register ubyte return_byte;
    
    LocalReceiveBufferTailPeek = ReceiveBufferTailPeek;
    LocalReceiveBufferHead = ReceiveBufferHead;
    
    if(LocalReceiveBufferTailPeek != LocalReceiveBufferHead) {
      return_byte = SerialReceiveBuffer[LocalReceiveBufferTailPeek];
      LocalReceiveBufferTailPeek++;
      if(RECEIVEBUFFERSIZE <= LocalReceiveBufferTailPeek) {
        LocalReceiveBufferTailPeek = 0;
      }
      ReceiveBufferTailPeek = LocalReceiveBufferTailPeek;
    }
    return(return_byte);
  }