Read back AT command response in a richtextbox

Question

I am trying to send a string of AT commands to a USB dongle. i have been successful in writing to the serial port. But i have not been successful in reading back. Basically what i want to do is to send lets say AT to the dongle and receive OK in a richtextbox. Next will be to send info from another device to the dongle and read it in the richtextbox.

Below is the code I am using:

namespace WindowsFormsApplication5
{
    public partial class Form1 : Form
    {
        SerialPort sp = null; //<---- serial port at form level

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

            // initialise port in form loadmyport.PortName = "COM3";
            sp = new SerialPort();
            sp.PortName = "COM8";
            sp.BaudRate = 115200;
            sp.Parity = Parity.None;
            sp.DataBits = 8;
            sp.StopBits = StopBits.One;
            sp.NewLine = System.Environment.NewLine;
            sp.ReadTimeout = 2000;
            sp.WriteTimeout = 2000;
            sp.DtrEnable = false;
            sp.RtsEnable = false;
            sp.WriteBufferSize = 4096;
            sp.ReadBufferSize = 4096;
            sp.Handshake = Handshake.None;
            sp.Encoding = System.Text.Encoding.ASCII;

            // also set up baud rate etc here.
            // attach event handler to capture data received 
            sp.DataReceived += new SerialDataReceivedEventHandler(sp_DataReceived);
        }

        private void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
        SerialPort sp = (SerialPort)sender;
        string indata = sp.ReadExisting();
        Console.WriteLine("Data Received:");
        Console.Write(indata);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            connect.Enabled = false;
            try
            {
                // open port if not already open
                // Note: exception occurs if Open when already open.
                if (!sp.IsOpen)
                {
                    sp.Open();
                }
                // send data to port
                sp.Write("ATXXX,XXXXXXX\r\n");
                disconnect.Enabled = true;
            }
            catch (Exception)
            {

               // report exception to user
                Console.WriteLine(e.ToString());
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            connect.Enabled = true;

            try
            {
                // open port if not already open
                // Note: exception occurs if Open when already open.
                if (!sp.IsOpen)
                {
                    sp.Open();
                }
                // send data to port
                sp.Write("atXX,0\r\n");
            }
            catch (Exception)
            {

                Console.WriteLine(e.ToString());
            }
            finally
            {
                disconnect.Enabled = false;
            }
        }


        public void OnApplicationExit(object sender, EventArgs e)
        {
            sp.Close();
        }
    }
}

Answer 1

Don't read data from the serial port directly in your main code. You have an event handler in place for the data received event, and it currently writes the response to the debugging console. All you need to do is change the event handler to write the text into your rich text box instead. (The code you have in place to read the data and display it in the text box will never display anything because (a) port_DataRecieved looks like it is never subscribed to any events, so it won't be called, and (b) your sp_DataReceived event handler is reading the data and logging it to the debug output, so any other code that tries to read the port will find it "empty")

Note that the sp_DataReceived event will be raised on a different thread, not your UI thread, so you will need to Invoke or BeginInvoke to pass control back to the UI thread to add the text to your text box.

Note also that you may not get the response as a single"packet" of data. It may be split into several pieces, so you will need to add each incoming message to the end of the text in your text box in order to stitch together the entire response from all the pieces you received.