Question

I am interfacing a scale to a computer through a serial port. I check the value SerialPort.BytesToRead for when it reaches 0 inside a loop. However the loop exits even though BytesToRead is not equal to 0. I can’t post a screenshot as I am a new user but by going through debug I can see that BytesToRead is in fact not 0.

This results in my data not being read entirely. I have tried for different expressions such as _port.BytesToRead > 0 but the result is the same. Even assigning the value of BytesToRead to a variable gives a 0. Without the loop ReadExisting doesn’t return all the data sent from the scale so I don’t really have a choice. ReadLine doesn’t work either. So why is BytesToRead always 0?

private void PortDataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        {
            var input = string.Empty;
            // Reads the data one by one until it reaches the end
            do
            {
                input += _port.ReadExisting();
            } while (_port.BytesToRead != 0);

            _scaleConfig = GenerateConfig(input);

            if (ObjectReceived != null)
                ObjectReceived(this, _scaleConfig);
        }
    }

Answer 1

My boss figured it out. Here’s the code.

private void PortDataReceived2(object sender, SerialDataReceivedEventArgs e)
    {
        var bytesToRead = _port.BytesToRead;
        _portDataReceived.Append(_port.ReadExisting());

        // Buffer wasn't full. We are at the end of the transmission.
        if (bytesToRead < _port.DataBits)
        {
            //Console.WriteLine(string.Format("Final Data received: {0}", _portDataReceived));
            IScalePropertiesBuilder scaleReading = null;

            scaleReading = GenerateConfig(_portDataReceived.ToString());
            _portDataReceived.Clear();


            if (ObjectReceived != null)
            {
                ObjectReceived(this, scaleReading);
            }
        }
    }