Mega Code Archive
How to writeread a string tofrom the serial port
<![CDATA[
Title: How to write/read a string to/from the serial port
function OpenCOMPort: Boolean;
var
DeviceName: array[0..80] of Char;
ComFile: THandle;
begin
{ First step is to open the communications device for read/write.
This is achieved using the Win32 'CreateFile' function.
If it fails, the function returns false.
}
StrPCopy(DeviceName, 'COM1:');
ComFile := CreateFile(DeviceName,
GENERIC_READ or GENERIC_WRITE,
0,
nil,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
if ComFile = INVALID_HANDLE_VALUE then
Result := False
else
Result := True;
end;
function SetupCOMPort: Boolean;
const
RxBufferSize = 256;
TxBufferSize = 256;
var
DCB: TDCB;
Config: string;
CommTimeouts: TCommTimeouts;
begin
{ We assume that the setup to configure the setup works fine.
Otherwise the function returns false.
}
Result := True;
if not SetupComm(ComFile, RxBufferSize, TxBufferSize) then
Result := False;
if not GetCommState(ComFile, DCB) then
Result := False;
// define the baudrate, parity,...
Config := 'baud=9600 parity=n data=8 stop=1';
if not BuildCommDCB(@Config[1], DCB) then
Result := False;
if not SetCommState(ComFile, DCB) then
Result := False;
with CommTimeouts do
begin
ReadIntervalTimeout := 0;
ReadTotalTimeoutMultiplier := 0;
ReadTotalTimeoutConstant := 1000;
WriteTotalTimeoutMultiplier := 0;
WriteTotalTimeoutConstant := 1000;
end;
if not SetCommTimeouts(ComFile, CommTimeouts) then
Result := False;
end;
{
The following is an example of using the 'WriteFile' function
to write data to the serial port.
}
procedure SendText(s: string);
var
BytesWritten: DWORD;
begin
{
Add a word-wrap (#13 + #10) to the string
}
s := s + #13 + #10;
WriteFile(ComFile, s[1], Length(s), BytesWritten, nil);
end;
{
The following is an example of using the 'ReadFile' function to read
data from the serial port.
}
procedure ReadText: string;
var
d: array[1..80] of Char;
s: string;
BytesRead, i: Integer;
begin
Result := '';
if not ReadFile(ComFile, d, SizeOf(d), BytesRead, nil) then
begin
{ Raise an exception }
end;
s := '';
for i := 1 to BytesRead do s := s + d[I];
Result := s;
end;
procedure CloseCOMPort;
begin
// finally close the COM Port!
CloseHandle(ComFile);
end;
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