RS232 300 baud communication problem

So now you can investigate what the difference is between HyperTerminal and what you are doing. At least you know that the device and other hardware will work at 300 baud.

I assume you know that 9600,8,N,1 means 9600 baud and 8 bits and no parity (error checking) and one stop bit. I am not sure what a stop bit is. And 300,7,E,1 means 7 bits and even parity.

Are you also familiar with flow control? I think there are two types of flow control; hardware and software. It is used to keep the two ends synchronized, so that one end does not go too fast or slow. At 300 baud it is very easy for one end to go too fast. So be sure that the flow control is set properly.

I think that Handshake is the same as flow control. I see in your code above that you have Handshake.None; that could be a problem.

For my unlucky with HyperTerminal works!

Then it works with HyperTerminal too!

Unless it does not work with HyperTerminal, and then you have made a huge diagnostic leap.

Assuming that C# is the problem and ignoring other possibilities is the type of problem that is often impossible to solve.

The device with VB6 application works!
I have a problem only with C#!

Did you try Deepender's suggestion? I consider it to be a logical and methodical diagnostic. See HyperTerminal Alternatives for Windows 7 if you don't have Microsoft's HyperTerminal.

That rules out the possibility that the driver doesn't support 300 baud and I don't think it can be a limitation with the .NET SerialPort class either as I found two other threads where 300 baud is being used (albeit with some other problems):

http://stackoverflow.com/questions/7107407/communicate-with-kohler-meter-in-c

http://stackoverflow.com/questions/6992530/change-baud-rate-in-c-without-closing-connection

It's difficult to know what else to suggest but, if you could post the VB6 code, it might give us some clues.

Yes, the same serial port driver.

The VB6 works on the other machine, but with the same hardware.

Is the VB6 code working on the same machine or a different machine?

If it's the same machine, can you post it here so we can see if there's anything we're missing.

Nothing. From the serial I don't read 25 bytes.
I'm using the HDD free serial port monitor for the monitoring the serial communication.
Normally, I don't have any characters on the serial. Often I have two or three bad characters.

 

I have tried, nothing. :-(

This is the code.

 public void Seriale()
        {
            System.IO.Ports.SerialPort seriale = new SerialPort();
            byte[] messaggio = new byte[5], ricezione = new byte[25];
            seriale.BaudRate = 300;
            seriale.DataBits = 7;
            seriale.Handshake = Handshake.None;
            seriale.Parity = Parity.Even;
            seriale.StopBits = StopBits.One;
            seriale.PortName = "COM3";
            seriale.ReadTimeout = 1000;
            seriale.Open();
            seriale.Encoding = System.Text.Encoding.GetEncoding(1252);
            messaggio[0] = (byte)0x2F;
            messaggio[1] = (byte)0X3F;
            messaggio[2] = (byte)0x21;
            messaggio[3] = (byte)0x0D;
            messaggio[4] = (byte)0x0A;
            for (int i = 0; i < 5; i++)
            {
                seriale.Write(messaggio, i, 1);
            }

            for (int i = 0; i < 25; i++)
            {
                    ricezione[i] = (byte)seriale.ReadByte();
                    seriale.DiscardInBuffer();
            }
        }

I have tried the same code in VB6 and the device works!
Are there some troubles regarding to 300 baud communication in C# .NET 2010?

I must use 300 baud because the device works at this baud in one condition!