Simple RS232 Question

Hi, could someone please supply me with code for Visual C++ to read from an RS232 connection on Com port 1 with 9600 baud, even parity, 1 stop bit and 7 data bits. I don't care about writing information I just want to read the data.

I have a powder metering system controlled via my PC and want to stop it when the reading from the RS232 connected balance hits the level I require.

many many thanks

Rich

Win32 treats the serial port as a kind of file
Start by reading all about createfile

So would you use "COM1" as the file to open? I'm just guessing; I remember doing something like that back in days of QBasic

Here is some code for doing com port I/O.

gg

When I try to compile that I get

Compiling...
SFile.cpp
Linking...
LIBCD.lib(crt0.obj) : error LNK2019: unresolved external symbol _main referenced in function _mainCRTStartup
Debug/rs232.exe : fatal error LNK1120: 1 unresolved externals

If someone could supply me with code which would read from Com port 1, 9600 baud, even parity, 7 data bits and 1 stop bit I promise to thank them forever (and possibly financially if this project works!). Please help!

If you want to use 7 data bits and even parity then you need to make some changes in SFile.cpp:

Code:

// Change this line
static TCHAR MODESETTINGS[]= _T("baud=%d parity=N data=8 stop=1  ");
// to
static TCHAR MODESETTINGS[]= _T("baud=%d parity=E data=7 stop=1  ");

Here is some simple code that demonstrates how to use SFile.

Code:

#include <windows.h>
#include "SFile.h"
#include <iostream>
using namespace std;

int main()
{
    SFile sf;

    // open COM1 at 9600, 7E1
    if (!sf.Open(1, 9600))
    {
        cerr << "Failed to open COM1, ec = " << GetLastError() << endl;
        return 1;
    }//if

    // read a byte at a time and display it
    // (this should loop forever)
    BYTE b;
    while (sf.ReadByte(b))
    {
        cout << (int)b << endl;
    }//while

    return 0;
}//main

gg

Thanks so much!! Am now able to get the reading from the balance! However, I need to get the reading every 5 seconds or so, which requires sending the command 'S(carriage return)', could you explain simply how the writebyte command works since I cannot get it to work correctly.

Thanks again, you are a star!

...since I cannot get it to work correctly.

Show what you have tried.

Here is how to use SFile::Write()

Code:

    char cmd[] = "S\r";
    DWORD written;
    ....
    sf.Write(cmd, 2, written);

You can use Sleep(5000) to sleep for 5 seconds.

gg

I'm trying to send the command using writebyte since write did not seem to work. I just don't know the exact syntax to use :s

I've worked it out!

Thanks again for your help, if you are ever in Oxford then I owe you at least one pint!

Hello Codeplug

I am using this library thank you very much for providing it. I have tried the example above and it works perfectly. So i have serial data in the form of (40 45 FE 12 34) coming from the serial port and the BYTE b displays them in line (it is pre formatted from my microcontroler) The thing is i would like to store the icoming bytes into a const char* to send it to TCP socket (I allready have that part of code working) Ive tried different manners but it seems i need to convert them to a string or something similar.
I am sorry i am not very strong in C++ and i have searched a lot i can only ask u now if u can give me a lil clue or an idea of how to perform this im sure this is easy for u
I thank u very much in advance

Please dont open long closed threads, please start a new one.

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