Some problem with serial programming in vc++ mfc - c++

Question

When I connect my embedded device to my system, I am running my program which will write to the port my embedded is connect and it prints the reply to console.
When I connect my device and run this program it is not giving any output.
But when I connect my device and use PUTTY to send some commands first and then run my program it is working.
Maybe there is a problem in the way I am starting communication?
My source code is:
#include "stdafx.h"
#include <iostream>
//#include <windows.h>
#include <afx.h>
int main()
{
using namespace std;
int i=0;
// cout << "Hello world!" << endl;
HANDLE hSerial;
hSerial = CreateFile("COM5",
GENERIC_READ | GENERIC_WRITE,
FILE_SHARE_WRITE | FILE_SHARE_READ,
0,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
if(hSerial==INVALID_HANDLE_VALUE)
{
if(GetLastError()==ERROR_FILE_NOT_FOUND)
{
// TRACE("serial port does not exist for reading\n");
//serial port does not exist. Inform user.
}
// TRACE("some other error,serial port does not exist for reading\n");
//some other error occurred. Inform user.
}
DCB dcbSerialParams = {0};
dcbSerialParams.DCBlength=sizeof(dcbSerialParams);
if (!GetCommState(hSerial, &dcbSerialParams))
{
// TRACE("error getting state for reading\n");
//error getting state
}
dcbSerialParams.BaudRate=9600;
dcbSerialParams.ByteSize=8;
dcbSerialParams.StopBits=ONESTOPBIT;
dcbSerialParams.Parity=NOPARITY;
if(!SetCommState(hSerial, &dcbSerialParams))
{
//TRACE("error setting state for reading\n");
//error setting serial port state
}
COMMTIMEOUTS timeouts={0};
timeouts.ReadIntervalTimeout=50;
timeouts.ReadTotalTimeoutConstant=50;
timeouts.ReadTotalTimeoutMultiplier=10;
timeouts.WriteTotalTimeoutConstant=50;
timeouts.WriteTotalTimeoutMultiplier=10;
if(!SetCommTimeouts(hSerial, &timeouts))
{
// TRACE("some error occured for reading\n");
//error occureed. Inform user
}
int n=100,n1=100;
char szBuff[100];
DWORD dwBytesRead = 0;
char szBuff1[100];
DWORD dwByteswrote = 0;
memset(szBuff1,0,100);
memcpy(szBuff1,"LIST\r",5);
if(!WriteFile(hSerial, szBuff1,5, &dwByteswrote, NULL))
{
cout << "error writing" ;
}
cout << szBuff1 << endl;
cout << dwByteswrote << endl;
while(1)
{
if(!ReadFile(hSerial, szBuff, n1, &dwBytesRead, NULL))
{
cout << "error reading";
break;
}
else
{
cout << dwBytesRead << endl;
szBuff[dwBytesRead]='\0';
if(dwBytesRead>0)
{
cout << (szBuff);
break;
}
}
}
cin >> i;
}

Answer 1

Try this... you will probably need to do the code for exceptions (ex: if the response is bigger than 2024)
bool SendModemATCommand(const string &strCommand, int iModemPort, string &strRetValue)
{
bool bRetValue = false;
strRetValue = "";
char cBuffer[2024];
HANDLE hCom = NULL;
char cComPort[64];
sprintf_s(cComPort,"\\\\.\\COM%d", iModemPort);
hCom = CreateFile( cComPort,
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)
{
COMMTIMEOUTS comTimeOuts;
comTimeOuts.ReadIntervalTimeout = MAXDWORD;
comTimeOuts.ReadTotalTimeoutMultiplier = MAXDWORD;
comTimeOuts.ReadTotalTimeoutConstant = 0;//MAXDWORD;
comTimeOuts.WriteTotalTimeoutMultiplier = 0;
comTimeOuts.WriteTotalTimeoutConstant = 0;
if(SetCommTimeouts(hCom, &comTimeOuts))
{
DCB dcb;
dcb.DCBlength = sizeof(DCB);
if(GetCommState(hCom, &dcb))
{
DWORD dwBytesWritten = 0;
DWORD dwBytesRead = 0;
DWORD dwBytesTotal = 0;
if( WriteFile(hCom, strCommand.c_str(), (int)strCommand.size(), &dwBytesWritten, NULL) )
{
if(dwBytesWritten == strCommand.size())
{
dwBytesRead = 0;
DWORD tickStart = GetTickCount();
bool bTimeOut = false;
while(true)
{
while(ReadFile(hCom, cBuffer + dwBytesTotal, 1, &dwBytesRead, NULL))
{
if(dwBytesRead == 0 && dwBytesTotal != dwBytesWritten)
break;
dwBytesTotal += dwBytesRead;
}
if ( dwBytesTotal == 0 )
{
// timeout
if ( GetTickCount() - tickStart > 10000) // 10 Seconds
{
bTimeOut = true;
break;
}
}
else
break;
}
cBuffer[dwBytesTotal] = '\0';
strRetValue = cBuffer;
if(bTimeOut)
strRetValue = "Timed out:" + strCommand;
else
bRetValue = true;
}
}
}
}
CloseHandle(hCom);
}
return bRetValue;
}

Answer 2

Most likely the problem is with your initialization.
I recall having this type of trouble before and Com Timeouts structure was particularly troublesome.
I suggest you get a null modem cable from COM5 to another port on the machine (if you have one), or to another computer. Then use a terminal program to open up the other port and see you can see the "List" command coming through when you run the program. If not then it's very likely to be related to the way you are initializing & opening the com port.
This link may prove useful. Just strip out the Afx stuff and look particularly at the initialization.
http://www.codeproject.com/KB/system/chaiyasit_t.aspx
One other suggestion, you only send List once. If the device is not already plugged in and ready, nothing will happen. Maybe it should keep sending the list command until it gets a
Response.
Also, do you need "List\r\n" or just "List\r"? What is the other ends expecting?