CODEWITHSUNDEEP
c++windowswinapiserial-port
User987123
User987123

Reputation: 97

Serial port ReadFile receives repeated data

I am working on a multi threading program to read and write to a serial port. If I test my application with Putty everything is fine. But when I test it with the created .exe-file, it doesn't work. (I start the program in VS2017 and then the .exe file)

E.g.: My input: "Test", the output in the other window: "Teeeeeeeeeeeessssssssssttttttt".

My code to send the data:

void SendDataToPort()
{
for (size_t i = 0; i <= strlen(line); i++) // loop through the array until 
 every letter has been sent
{
    try
    {
        if (i == strlen(line))  // If ever letter has been sent                 
        {                       // end it with a new line
            c = '\n';           // a new line
        }
        else
        {
            c = line[i];
        }
        WriteFile(serialHandle, &c, 1, &dwBytesWrite, NULL); // Send letter to serial port
    }
    catch (const exception&)
    {
        cout << "Error while writing.";
    }
}
cout << endl << "Sent." << endl;
}

In the array "line" I have the input from the user.

My code to read the data:

int newLineCounter = 0;
unsigned char tmp;
while (!endCurrentRead)
{
    ReadFile(hSerial, &tmp, 1, &bytesRead, NULL); // Get new letter

    if (tmp != '\n')
    {
        newLineCounter = 0;
        if (tmp >= 32 && tmp <= 126)
        {
            output += tmp; // Add current letter to the output
        }
    }
    else
    {
        newLineCounter++;
        if (newLineCounter < 2) // If there are more than 2 '\n' it doesn't write it down
        {
            output += tmp;
        }
        else if (newLineCounter == 2)
        {
            Print(output);
            output = receiverName;
            endCurrentRead = true;
        }
    }
}

After that I write the data down with the Print(output) function:

cout << output << endl;

How I create the Handle File:

serialHandle = CreateFile(LcomPort, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

Why is this happening and why is this only happening when I test it with the .exe-file and not with Putty?

Upvotes: 1

Views: 1793

Answers (1)

User987123
User987123

Reputation: 97

Thanks to the help of @quetzalcoatl, I was able to solve the problem. I have to check if the bytesRead are bigger then 0.

Solution:

int newLineCounter = 0;
DWORD dwCommModemStatus;
unsigned char tmp;
while (!endCurrentRead)
{
    ReadFile(hSerial, &tmp, 1, &bytesRead, NULL); // Get new letter
    if (bytesRead > 0)
    {
        if (tmp != '\n')
        {
            newLineCounter = 0;
            if (tmp >= 32 && tmp <= 126)
            {
                output += tmp; // Add current letter to the output
            }
        }
        else
        {
            output += tmp;
            Print(output);
            output = receiverName;
            endCurrentRead = true;
        }
    }
}

Upvotes: 2

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