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Garbage Value Reading Serial Port Data

I am working on making GUI for a Smart Water flow meter whose communication protocol is RS485,
as per instructions from Communication Manual i am sending an inquiry packet and i am receiving proper response in serial port terminal. But when i am trying to do it on my C# app.
Things are happening oppositely.
string data = "[H201815000081]";
private void button1_Click(object sender, EventArgs e)
{
serialPort1.Write(data);
incoming_data = serialPort1.ReadExisting();
text_reciever.Text = incoming_data;
}
// text_reciver is the text box of my gui where i want to display the
// values from flow meter.Data Type of incoming_data is string
Here is the code, i am sending an inquiry code to the device and in return i am getting garbage values on my text box. Some times it is stream of Question mark symbol (?), some time it shows nothing.
But when i revert myself to serial port terminal (Real Term).
It is showing proper values as mentioned in communication manual.
Please assist in this regards.

After looking around i just found the answer to my question.
The point is previously i was communicating with serial port teminal, where everything was working fine, but when it comes to interacting with peripherals one need to make sure that Serialport.DTRProperty is enabled.
When opening the serial port one must enable the DTR property by:
serialPort1.DtrEnable = true;
Otherwise the windows form will read the garbage value.

the incoming data would be serial number of device (ASCII Format) and Water flow values

C# Serial Port Receive Only Ever Giving me a Single Character

Question Withdrawn. I found out that I was sending incorrect ASCII patterns and THIS was my problem versus any problems with the receiver. Receiving a single character was merely the echo back of my wrong command
Summary:
C# form app. Serial 38400:N81 no flow control. Talking to a custom device.
If I use Teraterm, everything's fine.
The device I attach to gives simple, immediate responses:
Type 'v' you get a version string "v1.34 02-18-16 17:22" where the v in that is the local echo of the typed command. There are other status commands which are similar, once a character is received by the device, it replies immediately.
In my C# application I have pretty much exactly what you see in this guide under the example:
https://msdn.microsoft.com/en-us/library/system.io.ports.serialport.datareceived%28v=vs.110%29.aspx
Differences are that I'm at 38400 versus 9600 and I also do not set up the Handshake or the RtsEnable.
I've done this before so feeling stupid as to some obvious problem here. And I did do a bit of searching/following similar question links too.
Instead of receiving the version string, I receive one character '6'.
For a different command I also receive one character '8'. The notable thing here is that while '6' is part of my version string, '8' is never in the response for that other command.
Any suggestions on how I'd debug the ReadExisting() call?
I fully understand that a received string may arrive in fragments. The issue is that I always only ever receive the one character and nothing else. The event handler never sees any additional data. When I re-issue my version command I get the same '6' back I get before.
My event handler where I'm trying to test the receiver:
private void ReceiveData(object sender, SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort)sender;
string indata = sp.ReadExisting();
Debug.WriteLine("Data Received: ");
Debug.Write(indata);
}
Under the debugger, indata.Length is 1.
Teraterm Port Settings:
I was suggested to look for errors and here's the code:
public event SerialErrorReceivedEventHandler ErrorReached;
protected virtual void OnReceiveError(SerialErrorReceivedEventArgs e)
{
SerialErrorReceivedEventHandler handler = ErrorReached;
if (handler != null)
{
handler(this, e);
}
Debug.WriteLine("Serial error");
}
I saw no errors.
Further comments were that the receiver needs to be run more than once. It is, when I issue a 'v' (just the v) I should see the version and 's' should give me status. Again, both work fine on Teraterm. I get 686868 if I issue vsvsvs or other matching patterns if I type like vvsss, I'll get 66888 in reply.
Other point is controlling this device if I issue r and s for run and stop, there is a LED on it which goes solid red (from intermittent flashing to indicate that it's running. I see it run and stop per my commands. So I know that I'm talking to the device in a proper/coherent fashion. Just still have troubles seeing valid receive data.

Some suggestions to try:
You're reading a string from the port, so if the data can't be readily interpreted as a string you may only get a fragment before it stops converting. Read into a byte array to be sure you are really seeing the data that you receive. Even if you think you should get a string, this lets you see what you are actually receiving.
Check your port settings. Symptoms of the wrong baud rate or encoding are frequently that you receive a reduced number of (possibly random, possibly repeatable) bytes of "garbage". This would be consistent with receiving characters that should not be in the response, and the string terminating early.
Remove all configuration options from your port, apart from setting the baud rate. Very few devices use anything other than 8n1 and attempting to set options can often screw the port up. If that doesn't work then start seeing additional options only if you have to.
Make sure you only open the port once and keep it open till you have finished talking to the device. (Repeatedly opening and closing the port I'd really five by accident, and would flush the data in it, interfering with your attempts to read)

Serial port read string

I have a serial port app that read weighing machine.
public void Read()
{
while (Puerto.BytesToRead > 0)
{
try
{
string inputData = Puerto.ReadExisting();
dataReceived = inputData;
}
catch (TimeoutException) { }
}
}
the return string is like this
It has other extrange chars in it, how can i do to parse or get a clean data from it? all I need is 0.52lb

I have no idea what weighing machine is it and what the serial port specs on it but, if it is black box to you too then, check the following:
- check if you have a technical spec that explains what comes out of RS232 port
- do several (10?) samples with one sample weight and see if the number of bytes are delivered each time
- if you see the number of bytes being constant (barring discrepancy in the 0.52lb text changing to 0.5lb once in a while), it is likely that garbage following the weight is additional binary data.
- if not, and you see the weight (text) with exact offset each time, you just can scrape the output
this is complete reverse engineering, I suggest going after technical spec and doing more insightful data handling though.

This could be anything - a bug in the weighing machine, some sort of hardware issue, or a problem in how the serial port is configured. I would suspect a configuration problem. Make sure all the settings are correct (BaudRate, Handshake, Parity, StopBits). Also, try connecting to the same serial port device using another program (e.g. see http://helpdeskgeek.com/windows-7/windows-7-hyperterminal/ ) and see if you see the same garbage data.

c# SerialPort PinChanged event handling

I have a null terminated serial port listener and I want it to pass on all data and pin events from the in port to the out port. The data is working well however I want to pass on all the pin events as well. I've added a listener using:
in_port.PinChanged += new SerialPinChangedEventHandler(port_PinChanged);
and then handle it with:
static void port_PinChanged(object sender, SerialPinChangedEventArgs e)
{
if (e.EventType == SerialPinChange.Break)
{
out_port.BreakState = in_port.BreakState;
}
else if (e.EventType == SerialPinChange.CDChanged)
{
}
else if (e.EventType == SerialPinChange.CtsChanged)
{
}
else if (e.EventType == SerialPinChange.DsrChanged)
{
}
else if (e.EventType == SerialPinChange.Ring)
{
}
}
How can I pass these changes in pin state to the out port?

This isn't going to work. CD and Ring are modem signals, they are wired as inputs on your PC. You don't have spare outputs that you could use to drive these signals. CTS and DSR are handshake signals that are wired to RTS and DTR on the other end. You need to use them yourself to implement handshaking, on both ports. Break cannot work well either, you don't know when it turns off, although you could simulate it with a timer. Don't bother, that signal dates from the stone age.
RS-232 just isn't made for this. Instead wire it directly and tap the signals. TxD+Gnd to one port, RxD+Gnd to another so you can snoop on the traffic. Not the greatest for noise, keep the cables short or baudrate low. Soldering iron required.

The CtsChanged and DsrChanged pin states are reactions to other things happening, you should not try to pass them on in this way. They relate to the dataflow.
I'm not sure about the other signals.

How to distinguish between multiple input devices in C#

I have a barcode scanner (which acts like a keyboard) and of course I have a keyboard too hooked up to a computer. The software is accepting input from both the scanner and the keyboard. I need to accept only the scanner's input. The code is written in C#. Is there a way to "disable" input from the keyboard and only accept input from the scanner?
Note:
Keyboard is part of a laptop...so it cannot be unplugged. Also, I tried putting the following code
protected override Boolean ProcessDialogKey(System.Windows.Forms.Keys keyData)
{
return true;
}
But then along with ignoring the keystrokes from the keyboard, the barcode scanner input is also ignored.
I cannot have the scanner send sentinal characters as, the scanner is being used by other applications and adding a sentinal character stream would mean modifying other code.
Also, I cannot use the timing method of determining if the input came from a barcode scanner (if its a bunch of characters followed by a pause) since the barcodes scanned could potentially be single character barcodes.
Yes, I am reading data from a stream.
I am trying to follow along with the article: Distinguishing Barcode Scanners from the Keyboard in WinForms. However I have the following questions:
I get an error NativeMethods is inaccessible due to its protection level. It seems as though I need to import a dll; is this correct? If so, how do I do it?
Which protected override void WndProc(ref Message m) definition should I use, there are two implementations in the article?
Am getting an error related to [SecurityPermission( SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)] error CS0246: The type or namespace name 'SecurityPermission' could not be found (are you missing a using directive or an assembly reference?). How do I resolve this error?
There is also an error on the line containing: if ((from hardwareId in hardwareIds where deviceName.Contains(hardwareId) select hardwareId).Count() > 0) Error is error CS1026: ) expected.
Should I be placing all the code in the article in one .cs file called BarcodeScannerListener.cs?
Followup questions about C# solution source code posted by Nicholas Piasecki on http://nicholas.piasecki.name/blog/2009/02/distinguishing-barcode-scanners-from-the-keyboard-in-winforms/:
I was not able to open the solution in VS 2005, so I downloaded Visual C# 2008 Express Edition, and the code ran. However, after hooking up my barcode scanner and scanning a barcode, the program did not recognize the scan. I put a break point in OnBarcodeScanned method but it never got hit. I did change the App.config with the id of my Barcode scanner obtained using Device Manager. There seems to be 2 deviceNames with HID#Vid_0536&Pid_01c1 (which is obtained from Device Manager when the scanner is hooked up). I don't know if this is causing the scanning not to work. When iterating over the deviceNames, here is the list of devices I found (using the debugger):
"\??\HID#Vid_0536&Pid_01c1&MI_01#9&25ca5370&0&0000#{4d1e55b2-f16f-11cf-88cb-001111000030}"
"\??\HID#Vid_0536&Pid_01c1&MI_00#9&38e10b9&0&0000#{884b96c3-56ef-11d1-bc8c-00a0c91405dd}"
"\??\HID#Vid_413c&Pid_2101&MI_00#8&1966e83d&0&0000#{884b96c3-56ef-11d1-bc8c-00a0c91405dd}"
"\??\HID#Vid_413c&Pid_3012#7&960fae0&0&0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd}"
"\??\Root#RDP_KBD#0000#{884b96c3-56ef-11d1-bc8c-00a0c91405dd}"
"\??\ACPI#PNP0303#4&2f94427b&0#{884b96c3-56ef-11d1-bc8c-00a0c91405dd}"
"\??\Root#RDP_MOU#0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd}"
"\??\ACPI#PNP0F13#4&2f94427b&0#{378de44c-56ef-11d1-bc8c-00a0c91405dd}"
So there are 2 entries for HID#Vid_0536&Pid_01c1; could that be causing the scanning not to work?
OK so it seems that I had to figure out a way to not depend on the ASCII 0x04 character being sent by the scanner...since my scanner does not send that character. After that, the barcode scanned event is fired and the popup with the barcode is shown. So thanks Nicholas for your help.

You could use the Raw Input API to distinguish between the keyboard and the scanner like I did recently. It doesn't matter how many keyboard or keyboard-like devices you have hooked up; you will see a WM_INPUT before the keystroke is mapped to a device-independent virtual key that you typically see in a KeyDown event.
Far easier is to do what others have recommended and configure the scanner to send sentinel characters before and after the barcode. (You usually do this by scanning special barcodes in the back of the scanner's user manual.) Then, your main form's KeyPreview event can watch those roll end and swallow the key events for any child control if it's in the middle of a barcode read. Or, if you wanted to be fancier, you could use a low-level keyboard hook with SetWindowsHookEx() to watch for those sentinels and swallow them there (advantage of this is you could still get the event even if your app didn't have focus).
I couldn't change the sentinel values on our barcode scanners among other things so I had to go the complicated route. Was definitely painful. Keep it simple if you can!
--
Your update, seven years later: If your use case is reading from a USB barcode scanner, Windows 10 has a nice, friendly API for this built-in in Windows.Devices.PointOfService.BarcodeScanner. It's a UWP/WinRT API, but you can use it from a regular desktop app as well; that's what I'm doing now. Here's some example code for it, straight from my app, to give you the gist:
{
using System;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
using Windows.Devices.Enumeration;
using Windows.Devices.PointOfService;
using Windows.Storage.Streams;
using PosBarcodeScanner = Windows.Devices.PointOfService.BarcodeScanner;
public class BarcodeScanner : IBarcodeScanner, IDisposable
{
private ClaimedBarcodeScanner scanner;
public event EventHandler<BarcodeScannedEventArgs> BarcodeScanned;
~BarcodeScanner()
{
this.Dispose(false);
}
public bool Exists
{
get
{
return this.scanner != null;
}
}
public void Dispose()
{
this.Dispose(true);
GC.SuppressFinalize(this);
}
public async Task StartAsync()
{
if (this.scanner == null)
{
var collection = await DeviceInformation.FindAllAsync(PosBarcodeScanner.GetDeviceSelector());
if (collection != null && collection.Count > 0)
{
var identity = collection.First().Id;
var device = await PosBarcodeScanner.FromIdAsync(identity);
if (device != null)
{
this.scanner = await device.ClaimScannerAsync();
if (this.scanner != null)
{
this.scanner.IsDecodeDataEnabled = true;
this.scanner.ReleaseDeviceRequested += WhenScannerReleaseDeviceRequested;
this.scanner.DataReceived += WhenScannerDataReceived;
await this.scanner.EnableAsync();
}
}
}
}
}
private void WhenScannerDataReceived(object sender, BarcodeScannerDataReceivedEventArgs args)
{
var data = args.Report.ScanDataLabel;
using (var reader = DataReader.FromBuffer(data))
{
var text = reader.ReadString(data.Length);
var bsea = new BarcodeScannedEventArgs(text);
this.BarcodeScanned?.Invoke(this, bsea);
}
}
private void WhenScannerReleaseDeviceRequested(object sender, ClaimedBarcodeScanner args)
{
args.RetainDevice();
}
private void Dispose(bool disposing)
{
if (disposing)
{
this.scanner = null;
}
}
}
}
Granted, you'll need a barcode scanner that supports the USB HID POS and isn't just a keyboard wedge. If your scanner is just a keyboard wedge, I recommend picking up something like a used Honeywell 4600G off eBay for like $25. Trust me, your sanity will be worth it.

What I did in a similar situation is distinguish between a scan and a user typing by looking at the speed of the input.
Lots of characters very close together then a pause is a scan. Anything else is keyboard input.
I don't know exactly your requirements, so maybe that won't do for you, but it's the best I've got :)

It depends on the way you are interacting with the device. Anyway it wont be a C# solution, it will be some other library. Are you reading data from a stream? If you are just taking keystrokes, there may be nothing you can do about it.

I know this is an old thread, found it by searching barcode scanning in WIN10.
Just a few notes in case someone needs it.
These scanners from Honeywell have several USB interfaces.
One is a keyboard + Hid Point of sales (composite device).
Also there are CDC-ACM (ComPort emulation) and Hid Point of sales (alone) + more.
By default the scanners expose a serial number, so the host can distinguish between many devices (I had once +20 connected). There is a command to disable the serial number though!
The newer models behave the same in this regard.
If you want to see it live, try my terminal program yat3 (free on my site).
It can open all the interfaces mentioned above and is tailored for such devices.
A word to use keyboard interfaces:
Only use them as a last resort. They are slow, less reliable when it comes to exotic characters. The only good use is if you want to enter data into existing applications. If you code anyway, then reading from ComPort/HidPos-Device is easier.

look at this: http://nate.dynalias.net/dev/keyboardredirector.rails (NOT AVAILABLE ANYMORE) works great!
Specify the keyboard and the keys you want to block, and it works like a charm!
Also take a look at this: http://www.oblita.com/interception.html
You can create a C# wrapper for it - it also works like a charm..

I think you might be able to distinguish multiple keyboards through DirectX API, or if that doesn't work, through raw input API.

I have successfully accomplished what you folks are looking for here. I have an application that receives all barcode character data from a Honeywell/Metrologic barcode scanner. No other application on the system receives the data from the scanner, and the keyboard continues to function normally.
My application uses a combination of raw input and the dreaded low-level keyboard hook system. Contrary to what is written here, I found that the wm_input message is received before the keyboard hook function is called. My code to process the wm_input message basically sets a boolean variable to specify whether or not the received character is from the scanner. The keyboard hook function, called immediately after the wm_input is processed, swallows the scanner’s pseudo-keyboard data, preventing the data from being received by other applications.
The keyboard hook function has to be placed in an dll since you want to intercept all system keyboard messages. Also, a memory mapped file has to be used for the wm_input processing code to communicate with the dll.