Hello,
I am doing simple read/write program for serial port. I am faceing a error that i don´t understand. Error is:

"error C2664: 'CreateFileW' : cannot convert parameter 1 from 'const char [5]' to 'LPCWSTR' "

My whole program:

#include <windows.h>
#include <iostream>
#include <string>

using namespace std;

void set_com_pin(bool value);


int main(int argc, char* argv[])
{
if(argc != 2)
{
cerr<<"bad usage !"<<endl;
return -1;
}

bool onoff;
if(string(argv[1])==string("-on"))onoff=true;
else if(string(argv[1])==string("-off"))onoff=false;
else
{
cerr<<"bad parameters !"<<endl;
return -1;
}

set_com_pin(onoff);
return 0;
}

void set_com_pin(bool value)
{
// open port for I/O
HANDLE hPort = CreateFile("COM1", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);

if(hPort == INVALID_HANDLE_VALUE) {
cout<<"Failed to open port" <<endl;
} else {
// set timeouts
COMMTIMEOUTS cto = { 1, 100, 1000, 0, 0 };


if(!SetCommTimeouts(hPort,&cto))
cout<<"SetCommTimeouts failed" <<endl;


// set DCB
DCB dcb;
memset(&dcb,0,sizeof(dcb));
dcb.DCBlength = sizeof(dcb);
dcb.BaudRate = 19200;
dcb.fBinary = 1;
dcb.fDtrControl = DTR_CONTROL_ENABLE;
dcb.fRtsControl = RTS_CONTROL_ENABLE;
// dcb.fOutxCtsFlow = 1;
// dcb.fRtsControl = DTR_CONTROL_HANDSHAKE;

dcb.Parity = NOPARITY;
dcb.StopBits = ONESTOPBIT;
dcb.ByteSize = 8;

if(!SetCommState(hPort,&dcb))
cout<<"SetCommState failed" << endl;

char buf[7];
DWORD read=0;
DWORD write=1; // Number of bytes to write to serial port
buf[0] = 72; // Decmial value to write to serial port
WriteFile(hPort, buf, write, &write, NULL);

ReadFile(hPort, buf, sizeof(buf), &read, NULL);

DWORD i;
for(i=0; i<read; i++)
cout<<"%i", (unsigned char)buf[i];

CloseHandle(hPort);
}


}

Thanks in advance

As the error says, the first parameter must be LPCWSTR and not directly "COM1", so you can try writing the next(before the createfile call):
and rewrite the createfile to :

Thanks,
But it still have new error. That is
"error C2440: 'initializing' : cannot convert from 'const char [5]' to 'LPCWSTR' "
Please chack it again.

try the below one

Hope the above help, you didn't ask what is LPCWSTR ok . So I am providing the solution only .

Just a curiosity, what Visual Studio version are you using ?
Because i tryied both :
and
And both worked under Visual Studio 2008 Professional.

Thanks, Now it didn´t show error.
I want to read/write data through "COM1". Could you check my program, am i in correct way? This is my first program for serial port/Embedded programming.

Thanks for your help.

yes Its seems fine with a cursory look.

Good luck (Y).

Hello jan140,
I am using Microsoft Visual Studio 2008.

LPCWSTR abc = "COM1";
CreateFile(abc, GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);

This shows an error that i mentioned before, but

CreateFile(TEXT("COM1"), GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);

This is OK. I don´t know why!!!

Thanks for your help.

http://msdn.microsoft.com/en-us/libr...h6(VS.71).aspx
Visual Studio 6 for example defaults to ANSI
Visual Studio 2008 defaults to UNICODE

The Win32 API functions (like CreateFile) are already wrapped, but many standard functions in the CRT are not.

Also, you need to use the TEXT() or _T() macro for ALL your string constants.

Read the rest of the MSDN link.

Hi,
I'm trying simple programme to open the visual com port and send data on it. could someone help me to advice the source code or the way to start? I'm using VC++ Express edition.

Thanks in advance.