Read after restart - RS232 Serial communication using Serial Library - C++

Question

I am trying to read from RS-232 with serial connections by using serial libraries for C++ and some samples found at: http://www.codeproject.com/Articles/992/Serial-library-for-C

Is there any signal detection method or an event which lets me know. I connected the Rx and Neutral ONLY to the board using a serial to USB connector, and using serial libraries in Visual studio 2013 and writing the code in C++.

I want to write the ASCII data transmitted from my board, when it is restarted manually, to a text file, so I can parsing the data from a text file will be easy for me.

My board transmits sends data only when it is restarted. I am new to serial connections, and I wasn't able to figure out how to let my program understand to read the data when the board is reset.

I am using the listener program:

#define STRICT
#include <tchar.h>
#include <windows.h>
#include <stdio.h>
#include <string.h>
#include "Serial.h"

//C++ headers
#include <iostream>
#include <fstream>
#include <string>

enum { EOF_Char = 27 };

int ShowError (LONG lError, LPCTSTR lptszMessage)
{
    // Generate a message text
    TCHAR tszMessage[256];
    wsprintf(tszMessage,_T("%s\n(error code %d)"), lptszMessage, lError);

    // Display message-box and return with an error-code
    ::MessageBox(0,tszMessage,_T("Listener"), MB_ICONSTOP|MB_OK);
    return 1;
}

//int __cdecl _tmain (int /*argc*/, char** /*argv*/)
int WINAPI _tWinMain(HINSTANCE /*hInst*/, HINSTANCE /*hInstPrev*/, LPTSTR /*lptszCmdLine*/, int /*nCmdShow*/)
{
    CSerial serial;
    LONG    lLastError = ERROR_SUCCESS;

    const char* Port_name = "COM3";

    // Attempt to open the serial port (COM1)
    lLastError = serial.Open(_T(Port_name),0,0,false);
    if (lLastError != ERROR_SUCCESS)
        return ::ShowError(serial.GetLastError(), _T("Unable to open COM-port"));

    // Setup the serial port (9600,8N1, which is the default setting)
    lLastError = serial.Setup(CSerial::EBaud9600,CSerial::EData8,CSerial::EParNone,CSerial::EStop1);
    if (lLastError != ERROR_SUCCESS)
        return ::ShowError(serial.GetLastError(), _T("Unable to set COM-port setting"));

    // Register only for the receive event
    lLastError = serial.SetMask(CSerial::EEventBreak |
                                CSerial::EEventCTS   |
                                CSerial::EEventDSR   |
                                CSerial::EEventError |
                                CSerial::EEventRing  |
                                CSerial::EEventRLSD  |
                                CSerial::EEventRecv);
    if (lLastError != ERROR_SUCCESS)
        return ::ShowError(serial.GetLastError(), _T("Unable to set COM-port event mask"));

    // Use 'non-blocking' reads, because we don't know how many bytes
    // will be received. This is normally the most convenient mode
    // (and also the default mode for reading data).
    lLastError = serial.SetupReadTimeouts(CSerial::EReadTimeoutNonblocking);
    if (lLastError != ERROR_SUCCESS)
        return ::ShowError(serial.GetLastError(), _T("Unable to set COM-port read timeout."));

    // Keep reading data, until an EOF (CTRL-Z) has been received
    bool fContinue = true;
    do
    {
        // Wait for an event
        lLastError = serial.WaitEvent();
        if (lLastError != ERROR_SUCCESS)
            return ::ShowError(serial.GetLastError(), _T("Unable to wait for a COM-port event."));
        else
            return ::ShowError(serial.GetLastError(), _T("Waiting for a COM-port event."));

        // Save event
        const CSerial::EEvent eEvent = serial.GetEventType();

        // Handle break event
        if (eEvent & CSerial::EEventBreak)
        {
            printf("\n### BREAK received ###\n");
        }

        // Handle CTS event
        if (eEvent & CSerial::EEventCTS)
        {
            printf("\n### Clear to send %s ###\n", serial.GetCTS()?"on":"off");
        }

        // Handle DSR event
        if (eEvent & CSerial::EEventDSR)
        {
            printf("\n### Data set ready %s ###\n", serial.GetDSR()?"on":"off");
        }

        // Handle error event
        if (eEvent & CSerial::EEventError)
        {
            printf("\n### ERROR: ");
            switch (serial.GetError())
            {
            case CSerial::EErrorBreak:      printf("Break condition");          break;
            case CSerial::EErrorFrame:      printf("Framing error");            break;
            case CSerial::EErrorIOE:        printf("IO device error");          break;
            case CSerial::EErrorMode:       printf("Unsupported mode");         break;
            case CSerial::EErrorOverrun:    printf("Buffer overrun");           break;
            case CSerial::EErrorRxOver:     printf("Input buffer overflow");    break;
            case CSerial::EErrorParity:     printf("Input parity error");       break;
            case CSerial::EErrorTxFull:     printf("Output buffer full");       break;
            default:                        printf("Unknown");                  break;
            }
            printf(" ###\n");
        }

        // Handle ring event
        if (eEvent & CSerial::EEventRing)
        {
            printf("\n### RING ###\n");
        }

        // Handle RLSD/CD event
        if (eEvent & CSerial::EEventRLSD)
        {
            printf("\n### RLSD/CD %s ###\n", serial.GetRLSD()?"on":"off");
        }

        // Handle data receive event
        if (eEvent & CSerial::EEventRecv)
        {
            // Read data, until there is nothing left
            DWORD dwBytesRead = 0;
            char szBuffer[101];
            do
            {
                // Read data from the COM-port
                lLastError = serial.Read(szBuffer,sizeof(szBuffer)-1,&dwBytesRead);
                if (lLastError != ERROR_SUCCESS)
                    return ::ShowError(serial.GetLastError(), _T("Unable to read from COM-port."));

                if (dwBytesRead > 0)
                {
                    // Finalize the data, so it is a valid string
                    szBuffer[dwBytesRead] = '\0';

                    //writing data to text file
                    std::ofstream o("save.txt");
                    o << "Data: " << szBuffer << std::endl << "BytesRead: " <<dwBytesRead <<std::endl;

                    // Display the data
                    printf("%s", szBuffer);

                    // Check if EOF (CTRL+'[') has been specified
                    if (strchr(szBuffer,EOF_Char))
                        fContinue = false;
                }
            }
            while (dwBytesRead == sizeof(szBuffer)-1);
        }
    }
    while (fContinue);

    // Close the port again
    serial.Close();
    return 0; 
}

I did setup some break points at my while statements and was trying to restart the board. Then I get data written into my text file like this.

Trail 1:

Data: "H¢˜A,B™žX
BytesRead: 100

Trail 2:

Data: x]Ãßÿ$¢œŒ2Y¶SIeó1ñ\@ó8¬!)þ
BytesRead: 30

I know this data is not correct, I should get ASCII data. Are there any libraries which support a solution for my problem?

I need to read data after the UART is restarted and once it stops receiving data, it should write all the data to a text file.

Please help me with this, thank you very much.

Answer 1

Setting up the wrong Baudrate in the setup function is giving wrong output.

 lLastError = serial.Setup(CSerial::EBaud115200,CSerial::EData8,CSerial::EParNone,CSerial::EStop1);

and also

std::ofstream output_file;
        //Creating a text file
        output_file.open("save_test.txt", std::ios_base::app);
            //writing data to text file
                output_file /*<< "Data: "*/ << szBuffer;

instead of this code below (which will overwrite the text file everytime and no data is seen)

  //writing data to text file
                    std::ofstream o("save.txt");
                    o << "Data: " << szBuffer << std::endl << "BytesRead: " <<dwBytesRead <<std::endl;

will append the data to the text file, which will give the complete data which is transmitted by RS232 can be seen in the text file.