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Serial COM example

Started by sapero, August 04, 2008, 04:45:55 AM

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sapero

August 04, 2008, 04:45:55 AM Last Edit: August 04, 2008, 11:48:26 AM by sapero
This is an example program for serial COM ports programmers. I have not tested it yet, because my laptop does not have such ports.
Hey, I have one, but this is a Motorola phone modem attached to COM3.
// get the latest windows.inc from
// http://www.ionicwind.com/forums/index.php/topic,633.msg21983.html#msg21983
#include "windows.inc"
#include "stdio.inc"

sub main()
{
dstring buf[32];
DWORD ErrorCode;
BOOL success;

// open the first COM port
string *PortName = "COM3";
HANDLE hPort = CreateFile(PortName, GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, 0);

if (hPort == INVALID_HANDLE_VALUE)
{
// failed, but why?
return ShowError("Failed to open %s: \n", PortName, 0);
}

// change port settings
DCB dcb;
dcb.DCBlength = sizeof(dcb);
// baud=b
// parity=p
// data=d
// stop=s
// to={on|off}
// xon={on|off}
// odsr={on|off}
// octs={on|off}
// dtr={on|off|hs}
// rts={on|off|hs|tg}
// idsr={on|off}
success = BuildCommDCB("baud=1200 parity=N data=8 stop=1", &dcb);

// check for error
if (!success)
{
return ShowError("BuildCommDCB failed: ", NULL, hPort);
}

// apply new transmission settings
success = SetCommState(hPort, &dcb);

// check for error
if (!success)
{
ShowError("Failed to configure %s: \n", PortName, 0);
ShowComConfigDialog(hPort, PortName, 0);
}

// configure time-out parameters
COMMTIMEOUTS ct;
ct.ReadIntervalTimeout         = 3000; // total time for reading data (3s)
ct.ReadTotalTimeoutMultiplier  =  100; // maximum time for receiving a byte (100ms)
ct.ReadTotalTimeoutConstant    =    1;
ct.WriteTotalTimeoutMultiplier =  100; // maximum time for sending a byte
ct.WriteTotalTimeoutConstant   =    1;

success = SetCommTimeouts(hPort, &ct);

// check for error
if (!success)
{
return ShowError("Failed to set new timeouts on %s: \n", PortName, hPort);
}

// write data to port
string *pData = "cq dx";

DWORD BytesWriten;
DWORD BytesToWrite = strlen(pData);

success = WriteFile(hPort, pData, BytesToWrite, &BytesWriten, 0);

// check for error
if (!success)
{
return ShowError("Failed to write data to %s: \n", PortName, hPort);
}

// read response
DWORD BytesRead;
DWORD BytesToRead = 31; // size of <buf> is 32; reserve one byte for NULL
string *ReadBuffer = &buf;

success = ReadFile(hPort, ReadBuffer, BytesToRead, &BytesRead, 0);

// check for error
if (!success)
{
return ShowError("Failed to read data from %s: \n", PortName, hPort);
}

// received BytesRead bytes
// If received data is a string, show it:
*ReadBuffer[BytesRead] = 0; // cut all after received data
MessageBox(0, *ReadBuffer, "Received data");

// close the port and quit
CloseHandle(hPort);
}


sub ShowError(string *format, string *arg1, HANDLE hPort),int
{
string buf;

DWORD ErrorCode = GetLastError();

if (hPort)
CloseHandle(hPort);

int i = sprintf(buf, format, arg1);

FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
0, ErrorCode, 0, &buf + i, 256 - i, 0);

return MessageBox(0, buf, "Error");
}


// instead calling BuildCommDCB and SetCommState (or when SetCommState fails),
// use this function to open a dialog with configuration
// hPort    - opened COM1
// PortName - "COM1"
// hwndParent - zero, or handle to your window
sub ShowComConfigDialog(HANDLE hPort, string *PortName, HWND hwndParent)
{
COMMCONFIG cc;

DWORD cch = sizeof(cc);
if (!GetCommConfig(hPort, &cc, &cch))
{
ShowError("Failed to read device configuration:", 0, 0);
}
else
{
if (CommConfigDialog(PortName, hwndParent, &cc))
{
SetCommConfig(hPort, &cc, sizeof(cc));
}
}
}