How to delay in DataReceivedHandler from Arduino to WPF - c#

I have the Arduino who send the data continuously without caring the delay and i want to put the delay on my display in C#, so i can print all the value without missing a thing but in every line i want to put a delay for (let say) two seconds. I did with Thread.Sleepsomehow it blocked and delayed my UI and Task.Delay won't help. Does anyone knows how to fix this?
My code :
private SerialPort mySerialPort;
private readonly StreamWriter sw = new(#"D:\MAAT\readcoba.csv");
public MainWindow()
{
InitializeComponent();
Configure();
}
private void Configure()
{
mySerialPort = new(Port())
{
BaudRate = 9600,
Parity = Parity.None,
StopBits = StopBits.One,
DataBits = 8,
};
mySerialPort.DataReceived += DataReceivedHandler;
mySerialPort.Open();
}
private string Port()
{
string port = "";
string[] ports = SerialPort.GetPortNames();
foreach (string x in ports)
{
port = x;
}
return port;
}
private async void DataReceivedHandler(
object sender,
SerialDataReceivedEventArgs e)
{
// It's still not work
await Task.Delay(2000);
string indata = mySerialPort.ReadExisting();
string[] arrData = indata.Split(',');
Application.Current.Dispatcher.Invoke(() =>
{
foreach (string item in arrData)
{
raw_data_label.Content = raw_data_label.Content.ToString().Contains("Nothing to Display") ?
$"{item}" : $"{raw_data_label.Content}" + $"{item}";
}
sw.WriteLine(indata);
});
}
private void WindowClosed(object sender, EventArgs e)
{
sw.Close();
mySerialPort.Close();
}
}


Instead of invoking the UI thread (which you don't have the control te limit). Put the data into a variable/field and use a DispatcherTimer to display it. This way you control the update speed on the screen.
Here's an example:
private SerialPort mySerialPort;
private readonly StreamWriter sw = new(#"D:\MAAT\readcoba.csv");
// create a dispatcher timer
private DispatcherTimer timer = new DispatcherTimer(TimeSpan.FromMilliseconds(200), DispatcherPriority.Normal, UpdateLabel, Dispatcher.CurrentDispatcher)
// a lock object to use threadsafe object access
private object lockObject = new Object();
private static void UpdateLabel(object sender, EventArgs e)
{
// never update UI within a lock (which is used on other threads)
// Create a copy or if the field is only written (on the other end) copy the reference.
string[] data;
lock(lockObject)
data = _arduinoData; // You don't need to create a copy, but that's only because the _arduinoData isn't used.
foreach (string item in data)
{
// ????? why write to the same label over and over? Rather use a StringBuilder
raw_data_label.Content = raw_data_label.Content.ToString().Contains("Nothing to Display") ?
$"{item}" : $"{raw_data_label.Content}" + $"{item}";
}
}
public MainWindow()
{
InitializeComponent();
Configure();
}
private void Configure()
{
mySerialPort = new(Port())
{
BaudRate = 9600,
Parity = Parity.None,
StopBits = StopBits.One,
DataBits = 8,
};
mySerialPort.DataReceived += DataReceivedHandler;
Thread.Sleep(2000);
mySerialPort.Open();
}
private string Port()
{
string port = "";
string[] ports = SerialPort.GetPortNames();
foreach (string x in ports)
{
port = x;
}
return port;
}
private string[] arduinoData;
private void DataReceivedHandler(
object sender,
SerialDataReceivedEventArgs e)
{
// It's still not work
// await Task.Delay(2000); <-- don't delay here!
string indata = mySerialPort.ReadExisting();
string[] arrData = indata.Split(',');
sw.WriteLine(indata);
// lock and assigny the reference to the field (this is only allowed when the reference isn't used anymore _(if the string array isn't yours, Use a ToArray to create a copy)_
// That's why the s.WriteLine(..) is move above this.
lock(lockObject)
arduinoData = arrData;
}
private void WindowClosed(object sender, EventArgs e)
{
sw.Close();
mySerialPort.Close();

Related

Read string from textbox

I have the below code in WPF application.
It reads the strings from the serial port and displays in textbox.
I want to execute an operation according to the serial input.
This I'm thinking to do either by reading the string variable (RData) or by reading the textbox.text.
I've tried with if statements in the functions but it doesn't work. Please help.
public partial class MainWindow : Window
{
SerialPort serial = new SerialPort();
string RData;
public MainWindow()
{
InitializeComponent();
getPorts();
}
void getPorts()
{
String[] ports = SerialPort.GetPortNames();
comboBoxPorts.ItemsSource = ports;
}
private void buttonConnect_Click(object sender, RoutedEventArgs e)
{
serial.PortName = comboBoxPorts.Text;
serial.BaudRate = 9600;
serial.DataBits = 8;
serial.Handshake = System.IO.Ports.Handshake.None;
serial.StopBits = StopBits.One;
serial.ReadTimeout = -1;
serial.WriteTimeout = -1;
serial.Open();
if (serial.IsOpen)
{
buttonConnect.IsEnabled = false;
labelConState.Content = "Connected";
labelConState.Foreground = System.Windows.Media.Brushes.Green;
serial.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(Recieve);
}
}
private delegate void UpdateUiTextDelegate(string text);
private void Recieve
(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
RData = serial.ReadExisting();
Dispatcher.Invoke(DispatcherPriority.Send, new UpdateUiTextDelegate(WriteData), RData);
}
private void WriteData(string text)
{
textBoxPrompt.Text += text;
}
}

You should set parity property of SerialPort.

Error reading serial port with C #

I have a system that makes a loop on all serial ports and send a command 'at' for them.
These ports return 'ok' in Putty, but in the C# the MessageBox is empty.
Why is this happening?
Putty: http://i.imgur.com/AZY7aRY.png /
C#: http://i.imgur.com/wgGyT2x.png
public partial class Form1 : Form
{
List<SerialPort> serialPort = new List<SerialPort>();
private delegate void SetTextDeleg(string text);
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
var portNames = SerialPort.GetPortNames();
foreach (var port in portNames)
{
SerialPort sp;
sp = new SerialPort(port, 9600, Parity.None, 8, StopBits.One);
sp.Handshake = Handshake.None;
sp.DataReceived += new SerialDataReceivedEventHandler(sp_DataReceived);
sp.ReadTimeout = 500;
sp.WriteTimeout = 500;
serialPort.Add(sp);
listPorts.Items.Add(port);
}
}
private void listPorts_SelectedIndexChanged(object sender, EventArgs e)
{
}
private void button1_Click_1(object sender, EventArgs e)
{
foreach (var sp in serialPort)
{
// Open port
try
{
if (!sp.IsOpen)
sp.Open();
sp.Write("at\r\n");
}
catch (Exception ex)
{
MessageBox.Show("Error opening/writing to serial port :: " + ex.Message, "Error!");
}
}
}
void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
Thread.Sleep(500);
SerialPort sp = (SerialPort)sender;
string data = sp.ReadLine();
this.BeginInvoke(new SetTextDeleg(si_DataReceived), new object[] { data });
}
private void si_DataReceived(string data)
{
String retorno = data.Trim();
MessageBox.Show(data);
}
}

Your modem response something like this: \n\rOK\n\r you should read all stream in the buffer or you should read 3 time the serial port buffer with ReadLine() method.

How to display weight from weighing scale into a textbox via serial port RS-232 or usb converter?

I've been assigned to display weight from weighing scale (CAS CI-201A) into a textbox using C#. The weight will be sent via serial port RS-232 or USB converter. The scale is with me but I don't know where to start. How can I achieve my goal?

Have you tried anything yet?
If you want to use the serial port it makes sense to first give the user a way to select which port to use. This can be done easily, by filling a combobox with all available ports.
private void Form1_Load(object sender, EventArgs e)
{
string[] portNames = SerialPort.GetPortNames();
foreach (var portName in portNames)
{
comboBox1.Items.Add(portName);
}
comboBox1.SelectedIndex = 0;
}
This code uses a form with a comboBox on it, called "comboBox1" (Default).
You will need to add:
using System.IO.Ports;
to the using directives.
Then add a button (button1) and a multiline textbox (textbox1) to the form and add this code:
private void button1_Click(object sender, EventArgs e)
{
_serialPort = new SerialPort(comboBox1.Text, BaudRate, Parity.None, 8, StopBits.One);
_serialPort.DataReceived += SerialPortOnDataReceived;
_serialPort.Open();
textBox1.Text = "Listening on " + comboBox1.Text + "...";
}
private void SerialPortOnDataReceived(object sender, SerialDataReceivedEventArgs serialDataReceivedEventArgs)
{
while(_serialPort.BytesToRead >0)
{
textBox1.Text += string.Format("{0:X2} ", _serialPort.ReadByte());
}
}
This also requires you to add:
private SerialPort _serialPort;
private const int BaudRate = 9600;
right below the opening brackets of
public partial class Form1 : Form
After clicking the button, all received data from the selected comPort will be displayed as hex values in the TextBox.
DISCLAIMER: The above code contains NO error-handling and will produce errors if button1 is clicked multiple times, due to the fact that the previous instance of "SerialPort" is not closed properly. Please remember this when using this example.
Regards Nico
Complete Code:
using System;
using System.IO.Ports; //<-- necessary to use "SerialPort"
using System.Windows.Forms;
namespace ComPortTests
{
public partial class Form1 : Form
{
private SerialPort _serialPort; //<-- declares a SerialPort Variable to be used throughout the form
private const int BaudRate = 9600; //<-- BaudRate Constant. 9600 seems to be the scale-units default value
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
string[] portNames = SerialPort.GetPortNames(); //<-- Reads all available comPorts
foreach (var portName in portNames)
{
comboBox1.Items.Add(portName); //<-- Adds Ports to combobox
}
comboBox1.SelectedIndex = 0; //<-- Selects first entry (convenience purposes)
}
private void button1_Click(object sender, EventArgs e)
{
//<-- This block ensures that no exceptions happen
if(_serialPort != null && _serialPort.IsOpen)
_serialPort.Close();
if (_serialPort != null)
_serialPort.Dispose();
//<-- End of Block
_serialPort = new SerialPort(comboBox1.Text, BaudRate, Parity.None, 8, StopBits.One); //<-- Creates new SerialPort using the name selected in the combobox
_serialPort.DataReceived += SerialPortOnDataReceived; //<-- this event happens everytime when new data is received by the ComPort
_serialPort.Open(); //<-- make the comport listen
textBox1.Text = "Listening on " + _serialPort.PortName + "...\r\n";
}
private delegate void Closure();
private void SerialPortOnDataReceived(object sender, SerialDataReceivedEventArgs serialDataReceivedEventArgs)
{
if (InvokeRequired) //<-- Makes sure the function is invoked to work properly in the UI-Thread
BeginInvoke(new Closure(() => { SerialPortOnDataReceived(sender, serialDataReceivedEventArgs); })); //<-- Function invokes itself
else
{
while (_serialPort.BytesToRead > 0) //<-- repeats until the In-Buffer is empty
{
textBox1.Text += string.Format("{0:X2} ", _serialPort.ReadByte());
//<-- bytewise adds inbuffer to textbox
}
}
}
}
}

Based on this:
Listening on COM1... 30 30 33 33 20 49 44 5F 30 30 3A 20 20 20 31 30
2E 36 20 6B 67 20 0D 0A 0D 0A
Being the ASCII for this:
0033 ID_00: 10.6 kg
You can get the result by trimming the received string. Assuming your listener puts the bytes into an array byte[] serialReceived :
string reading = System.Text.Encoding.UTF8.GetString(serialReceived);
textBox1.Text = reading.Substring(13);

Firstly, before you start to code anything, I would check whether you're using the right cable. Try open a serial terminal of your choice (HyperTerm, putty) and check whether there is any data at all.
Be sure to configure the same baudrate, stopbits and parity on both the weight scale and your terminal program.
If you receive data (the terminal program should at least display some garbage), then you can move on to coding. If not, check if you're using the right cable (nullmodem aka crossed-over).
When you're this far, then you may use the SerialPort class of C#
http://msdn.microsoft.com/en-us/library/system.io.ports.serialport.aspx

based on adam suggestion i converted the output to human readable format ( from ASCII to UTF8 )
i puts the bytes into an array byte[]
private void SerialPortOnDataReceived(object sender, SerialDataReceivedEventArgs serialDataReceivedEventArgs)
{
if (InvokeRequired) //<-- Makes sure the function is invoked to work properly in the UI-Thread
BeginInvoke(new Closure(() => { SerialPortOnDataReceived(sender, serialDataReceivedEventArgs); })); //<-- Function invokes itself
else
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
string str = System.Text.Encoding.UTF8.GetString(data);
textBox1.Text = str.ToString();
}
}
here is the full working code
using System;
using System.IO.Ports; //<-- necessary to use "SerialPort"
using System.Windows.Forms;
namespace ComPortTests
{
public partial class Form1 : Form
{
private SerialPort _serialPort; //<-- declares a SerialPort Variable to be used throughout the form
private const int BaudRate = 9600; //<-- BaudRate Constant. 9600 seems to be the scale-units default value
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
string[] portNames = SerialPort.GetPortNames(); //<-- Reads all available comPorts
foreach (var portName in portNames)
{
comboBox1.Items.Add(portName); //<-- Adds Ports to combobox
}
comboBox1.SelectedIndex = 0; //<-- Selects first entry (convenience purposes)
}
private void button1_Click(object sender, EventArgs e)
{
//<-- This block ensures that no exceptions happen
if(_serialPort != null && _serialPort.IsOpen)
_serialPort.Close();
if (_serialPort != null)
_serialPort.Dispose();
//<-- End of Block
_serialPort = new SerialPort(comboBox1.Text, BaudRate, Parity.None, 8, StopBits.One); //<-- Creates new SerialPort using the name selected in the combobox
_serialPort.DataReceived += SerialPortOnDataReceived; //<-- this event happens everytime when new data is received by the ComPort
_serialPort.Open(); //<-- make the comport listen
textBox1.Text = "Listening on " + _serialPort.PortName + "...\r\n";
}
private delegate void Closure();
private void SerialPortOnDataReceived(object sender, SerialDataReceivedEventArgs serialDataReceivedEventArgs)
{
if (InvokeRequired) //<-- Makes sure the function is invoked to work properly in the UI-Thread
BeginInvoke(new Closure(() => { SerialPortOnDataReceived(sender, serialDataReceivedEventArgs); })); //<-- Function invokes itself
else
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
string str = System.Text.Encoding.UTF8.GetString(data);
textBox1.Text = str.ToString();
}
}
}
if your are using A&D EK V Calibration Model : AND EK-610V. you have use BaudRate = 2400; and DataBits = 7
Note : if you get output like this
you have to check the BaudRate,DataBits (refer your weighing machine manual ) or check your cable

I was using Anto sujesh's Code, but I had the problem that some of the values I got from the scale were corrupted. I solved it by buffering the values in a cache file.
private void SerialPortOnDataReceived(object sender, SerialDataReceivedEventArgs serialDataReceivedEventArgs)
{
if (InvokeRequired) //<-- Makes sure the function is invoked to work properly in the UI-Thread
BeginInvoke(new Closure(() => { SerialPortOnDataReceived(sender, serialDataReceivedEventArgs); })); //<-- Function invokes itself
else
{
int dataLength = _serialPort.BytesToRead;
byte[] data = new byte[dataLength];
int nbrDataRead = _serialPort.Read(data, 0, dataLength);
if (nbrDataRead == 0)
return;
string str = Encoding.UTF8.GetString(data);
//Buffers values in a file
File.AppendAllText("buffer1", str);
//Read from buffer and write into "strnew" String
string strnew = File.ReadLines("buffer1").Last();
//Shows actual true value coming from scale
textBox5.Text = strnew;

using System;
using System.IO.Ports;
using System.Windows.Forms;
namespace ComPortTests
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private SerialPort _serialPort = null;
private void Form1_Load(object sender, EventArgs e)
{
_serialPort = new SerialPort("COM1", 9600, Parity.None, 8);
_serialPort.DataReceived += new SerialDataReceivedEventHandler(_serialPort_DataReceived);
_serialPort.Open();
}
void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
string data = _serialPort.ReadExisting();
textBox2.Text = data;
}
}
}

using System;
using System.IO;
using System.IO.Ports;
namespace comport
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private SerialPort _serialPort = null;
private void Form1_Load(object sender, EventArgs e)
{
AppConfiguration.sConfigType = "default";
_serialPort = new SerialPort("COM1", 9600, Parity.None, 8);
_serialPort.DataReceived += new SerialDataReceivedEventHandler(_serialPort_DataReceived);
_serialPort.Open();
}
void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
string data = _serialPort.ReadExisting();
textBox2.Text = data;
}
}
}

I am using
yaohua xk3190-a9
Weighing Scale indicator connected to my serial port. And after trying lots of codes, follwing code finally worked for me. I am pasting the code here so that if anybody is using the same device can get help.
private SerialPort _serialPort;
private const int BaudRate = 2400;
private void Form1_Load(object sender, EventArgs e)
{
string[] portNames = SerialPort.GetPortNames();
foreach (var portName in portNames)
{
comboBox1.Items.Add(portName);
}
comboBox1.SelectedIndex = 0;
//<-- This block ensures that no exceptions happen
if (_serialPort != null && _serialPort.IsOpen)
_serialPort.Close();
if (_serialPort != null)
_serialPort.Dispose();
//<-- End of Block
_serialPort = new SerialPort(comboBox1.Text, BaudRate, Parity.None, 7, StopBits.One); //<-- Creates new SerialPort using the name selected in the combobox
_serialPort.DataReceived += SerialPortOnDataReceived; //<-- this event happens everytime when new data is received by the ComPort
_serialPort.Open(); //<-- make the comport listen
}
private delegate void Closure();
private void SerialPortOnDataReceived(object sender, SerialDataReceivedEventArgs serialDataReceivedEventArgs)
{
if (InvokeRequired) //<-- Makes sure the function is invoked to work properly in the UI-Thread
BeginInvoke(new Closure(() => { SerialPortOnDataReceived(sender, serialDataReceivedEventArgs); })); //<-- Function invokes itself
else
{
string data = _serialPort.ReadExisting();
if (data != null)
{
if (data.ToString() != "")
{
if (data.Length > 6)
{
var result = data.Substring(data.Length - 5);
textBox1.Text = result.ToString().TrimStart(new Char[] { '0' });
}
}
}
}
}

SerialPort.BaseStream.BeginWrite & BeginRead questions

I'm having some issues trying to figure out Async communication on a serialport object and was hoping to get some help. I'm still learning Async stuff so be gentle:)
I basically need to make sure that the buffer isn't full prior to writing to the serial port and also all data has been read before any more data gets written to avoid packet collision. Unfortunately the microcontroller that I am writing to does not have any handshaking or CTSEnabled so I have to mimic it in code.
public partial class Form2 : Form
{
System.IO.Ports.SerialPort port = new System.IO.Ports.SerialPort();
System.Timers.Timer tmrPolling = new System.Timers.Timer(200);
static byte [] inputPacket = new byte[2] { (byte)255, (byte)0 }; // Byte to send to SerialPort when input polling timer is activated.
AsyncCallback callback;
IAsyncResult result;
Form2()
{
InitializeComponent();
port.PortName = "COM9";
port.BaudRate = 38400;
port.DataBits = 8;
port.StopBits = System.IO.Ports.StopBits.One;
port.Parity = System.IO.Ports.Parity.None;
port.ReadTimeout = 1;
port.ReceivedBytesThreshold = 5;
port.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(port_DataReceived);
callback = new AsyncCallback(ReadComplete);
port.ReadBufferSize = (byte)60;
port.WriteBufferSize = (byte)60;
port.Open();
tmrPolling.Elapsed += new System.Timers.ElapsedEventHandler(tmrPolling_Elapsed);
}
void WritePacket(byte[] packet)
{
result = port.BaseStream.BeginWrite(packet, 0, packet.Count(), callback, port); // writes the input packet to the SerialPort - needed to read the IO values
}
void ReadComplete(IAsyncResult result)
{
}
void tmrPolling_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
WritePacket(inputPacket); // writes the input packet to the SerialPort - needed to read the IO values
}
void port_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
port.BaseStream.EndWrite(result);
// Reads the data coming in from the serial port and calls the thread safe delegate to update the values on the form.
byte [] received = new byte[port.BytesToRead];
result = port.BaseStream.BeginRead(received, 0, received.Count(), callback, port);
port.BaseStream.EndRead(result);
}
private void UpdateValues()
{
byte[] b = new byte[] { (byte)255, (byte)6, (byte)hsbPan.Value, (byte)vsbTilt.Value, (byte)0,
(byte)0, (byte)0, (byte)0, (byte)13, (byte)10 };
WritePacket(b);
}
private void chkEnablePolling_CheckedChanged(object sender, EventArgs e)
{
tmrPolling.Enabled = chkEnablePolling.Checked;
test.Enabled = chkEnablePolling.Checked;
vsbInputInterval.Enabled = chkEnablePolling.Checked;
vsbInputInterval.Value = Convert.ToInt32(tmrPolling.Interval);
txtInputInterval.Enabled = chkEnablePolling.Checked;
txtInputInterval.Text = ((float)tmrPolling.Interval / ( float)1000).ToString() + " sec";
}
private void vsbInputInterval_Scroll(object sender, ScrollEventArgs e)
{
// adjusts the tick frequency of the Timer for input polling.
txtInputInterval.Text = ((float)tmrPolling.Interval / (float)1000).ToString() + " sec";
tmrPolling.Interval = vsbInputInterval.Value;
}
private void vsbTilt_Scroll(object sender, ScrollEventArgs e)
{
UpdateValues();
}
private void hsbPan_Scroll(object sender, ScrollEventArgs e)
{
UpdateValues();
}
}

Incoming serial data loop is causing my program to freeze

I am working on code that connects to a serial port of a stepper motor. I send a command to the stepper motor via textBox2 and am attempting to read in the return data from the command to textBox3. I am able to make a connection, send the command, and receive the data. But after my GUI populates textBox3 with the returned serial data it freezes.
I believe that the code is getting stuck in the try loop but I don't know how to break out of it. Here is my code:
private void button3_Click(object sender, EventArgs e)
{
if (isConnectedMotor)
{
string command = textBox2.Text;
portMotor.Write(command + "\r\n");
portMotor.DiscardInBuffer();
while (true)
{
try
{
string return_data = portMotor.ReadLine();
textBox3.AppendText(return_data);
textBox3.AppendText(Environment.NewLine);
}
catch(TimeoutException)
{
break;
}
}
}
}
DataReceived Code:
private void connectToMotor()
{
isConnectedMotor = true;
string selectedPort = comboBox2.GetItemText(comboBox2.SelectedItem);
portMotor = new SerialPort(selectedPort, 9600, Parity.None, 8, StopBits.One);
portMotor.RtsEnable = true;
portMotor.DtrEnable = true;
portMotor.Open();
portMotor.DiscardInBuffer();
portMotor.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);
button4.Text = "Disconnect";
enableControlsMotor();
}
private static void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort)sender;
string indata = sp.ReadExisting();
textBox3.AppendText(indata);
textBox3.AppendText(Environment.NewLine);
}
I am getting an error saying:
An object reference is required for the non-static field, method, or property 'Form1.textBox3'
Invoke code:
private void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
{
portMotor.DiscardInBuffer();
incoming_data = portMotor.ReadExisting();
this.Invoke(new EventHandler(displayText));
}
private void displayText(object o, EventArgs e)
{
textBox3.Text += incoming_data;
}

Instead of looping to read data, use a DataReceived event to get at the incoming bytes asynchronously.
See the documentation and example.
Also see this question for troubleshooting.
P.S. Here is a code sample to avoid locking up the UI.
private void ReceivedHandler(object sender, SerialDataReceivedEventArgs e) {
var incoming_data = portMotor.ReadExisting();
// this is executing on a separate thread - so throw it on the UI thread
Invoke(new Action(() => {
textBox3.Text += incoming_data;
}));
}

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