Led-Customer-Display-Emulator

Customer Display Emulator

Emulate a serial customer display on your PC — test your “customer total” code with no hardware.

Customer Display Emulator is a standalone WPF app that emulates a customer display (pole display) and listens on a COM port, so you can test your solution’s “customer total display” code without real hardware.

Note on naming: the repository, solution, assembly, and C# namespace use the name LedDisplayEmulator (historical), while the app is branded Customer Display Emulator. They refer to the same project.

Features

• Two display modes — Simple 8-Digit marquee and LED8 N-type with label indicators.
• No hardware required — pairs with your app over a virtual COM port (com0com).
• ESC/POS protocol support — standard commands used by real customer displays.
• Live hex log — inspect raw bytes received on the serial port.
• Bidirectional test — built-in Test button verifies the connection both ways.

Two Display Modes

Mode	Description
Simple 8-Digit	Basic 8-digit marquee display (ASCII characters shift right-to-left)
LED8 N-type	8-digit display + 4 label indicators (PRICE, TOTAL, COLLECT, CHANGE) with ESC/POS protocol

Switch between modes using the Display Type dropdown.

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Requirements

• Windows 10/11
• .NET 8 SDK (or Visual Studio 2022 with “.NET desktop development” workload)
• com0com (for virtual COM port pairing): https://sourceforge.net/projects/com0com/

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Build & Run

dotnet build
dotnet run

Or open LedDisplayEmulator.slnx in Visual Studio and press F5.

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How It Works

┌─────────────────────┐                ┌─────────────────────┐
│      Your App       │                │   Display Emulator  │
│                     │                │                     │
│  SerialPort("COM10")├────COM0COM─────► SerialPort("COM11") │
│                     │  virtual       │                     │
│  writes data ───────┼────────────────┼───► displays digits │
└─────────────────────┘                └─────────────────────┘

Your app writes bytes to one end of a virtual COM port pair (created with com0com). The emulator listens on the other end, parses the protocol (Simple or ESC/POS), and renders the data on a simulated 7-segment display. Anything written to COM10 appears on COM11, and vice versa.

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Complete Setup Guide: Testing with Your App

Step 1: Install com0com

1. Download com0com from: https://sourceforge.net/projects/com0com/
2. Run the installer (accept any Windows security prompts for unsigned drivers)
3. After installation, open Setup Command Prompt (Start Menu → com0com → Setup)
4. You’ll see a paired virtual port, for example:

   CNCB0 PortName=COM10
   CNCB1 PortName=COM11
   

5. If you need different port numbers, type:

   setupc CNCA0 PortName=COM10
   setupc CNCB0 PortName=COM11
   

6. Close the setup window when done

Step 2: Configure Your App

In your app code that sends data to the customer display, make sure it targets COM10 (or whichever port you configured above).

Example configuration in your app:

// In your app's display service or config
var displayPort = new SerialPort("COM10", 9600, Parity.None, 8, StopBits.One);

Or in appsettings.json:

{
  "CustomerDisplay": {
    "PortName": "COM10",
    "BaudRate": 9600
  }
}

Step 3: Start the Emulator

1. Run dotnet run or launch from Visual Studio
2. Select Display Type (Simple 8-Digit or LED8 N-type)
3. Select COM11 in the COM Port dropdown (the other end of the virtual pair)
4. Set Baud Rate to match your app (default: 9600)
5. Click Connect
6. You should see “Connected: COM11 @ 9600” in green

Step 4: Test from Your App

Trigger your “send total to customer display” code path in your app. You should see:

• The digits light up on the emulator
• Raw hex bytes logged at the bottom of the emulator window

Step 5: Use the Test Button

Click Test to send sample data from the emulator to your app (via the virtual COM port). This verifies the connection is working both ways.

Test button behavior:

• Simple mode: Sends CLR + "1234.56"
• LED8N mode: Sends CLR + ESC s 2 (TOTAL) + ESC Q A 2 + "99.95" + CR

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COM Port Settings for com0com

The emulator uses these serial settings (must match your app):

Setting	Value
Baud Rate	9600 (default) or 2400
Data Bits	8
Parity	None
Stop Bits	1
Handshake	None
DTR	Enabled
RTS	Enabled

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Display Modes Explained

Simple 8-Digit Mode

• Characters (0-9, -, space) shift in from the right like a marquee
• A . character sets the decimal point on the last digit shown
• Clear byte is configurable (default: 0x0C Form Feed)

Protocol:

[clear byte] [data...]  →  digits shift in from right

Example:

0C 31 32 2E 33 34     →  CLR + "12.34"  →  displays: [1][2][.][3][4][ ][ ][ ]

LED8 N-type Mode

Uses standard ESC/POS commands (same as real hardware).

Supported Commands:

Command	Hex	Description
CLR	0C	Clear all characters
CAN	18	Clear cursor line
ESC @	1B 40	Initialize display
ESC s n	1B 73 n	Set label (0=off, 1=PRICE, 2=TOTAL, 3=COLLECT, 4=CHANGE)
ESC Q A … CR	1B 51 41 ... 0D	Send display data

Sending a total with label:

1B 73 32              →  ESC s 2 (set label to TOTAL)
1B 51 41 32           →  ESC Q A + "2"
31 32 2E 33 34 0D     →  "12.34" + CR

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Sending Data from Your POS App (C# Code Examples)

Simple 8-Digit Mode

using System.IO.Ports;

// Connect to the emulator
using var port = new SerialPort("COM10", 9600, Parity.None, 8, StopBits.One);
port.Open();

// Clear and display a total
port.Write(new byte[] { 0x0C }, 0, 1);  // Clear
port.Write("12.34");                      // Display shifts in from right

LED8 N-type Mode

using System.IO.Ports;

using var port = new SerialPort("COM10", 9600, Parity.None, 8, StopBits.One);
port.Open();

// Set label to TOTAL and display 12.34
port.Write(new byte[] { 0x1B, 0x73, 0x32 }, 0, 3);  // ESC s 2 (TOTAL)
port.Write(new byte[] { 0x1B, 0x51, 0x41, 0x32 }, 0, 4);  // ESC Q A
port.Write("12.34");
port.Write(new byte[] { 0x0D }, 0, 1);  // CR

// Clear display
port.Write(new byte[] { 0x0C }, 0, 1);  // CLR

Reusable Display Service Class

public class CustomerDisplayService : IDisposable
{
    private SerialPort? _port;

    public void Connect(string portName, int baudRate = 9600)
    {
        _port = new SerialPort(portName, baudRate, Parity.None, 8, StopBits.One);
        _port.Open();
    }

    // For Simple 8-Digit mode
    public void ShowSimple(string text)
    {
        if (_port == null || !_port.IsOpen) return;
        _port.Write(new byte[] { 0x0C }, 0, 1);  // Clear
        _port.Write(text);
    }

    // For LED8 N-type mode
    public void ShowLed8N(string text, int label = 0)
    {
        if (_port == null || !_port.IsOpen) return;

        // Set label (0=none, 1=PRICE, 2=TOTAL, 3=COLLECT, 4=CHANGE)
        _port.Write(new byte[] { 0x1B, 0x73, (byte)(0x30 + label) }, 0, 3);

        // Send display data
        _port.Write(new byte[] { 0x1B, 0x51, 0x41 }, 0, 3);
        _port.Write(text);
        _port.Write(new byte[] { 0x0D }, 0, 1);  // CR
    }

    public void Clear()
    {
        _port?.Write(new byte[] { 0x0C }, 0, 1);
    }

    public void Dispose()
    {
        _port?.Close();
        _port?.Dispose();
    }
}

Usage:

var display = new CustomerDisplayService();
display.Connect("COM10");
display.ShowLed8N("12.34", label: 2);  // Show 12.34 with TOTAL label

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Project Structure

File	Description
MainWindow.xaml	UI layout: display area, labels, controls, log
MainWindow.xaml.cs	COM port handling, protocol parsers (Simple + LED8 N-type)
SevenSegmentDigit.xaml	Single 7-segment digit control
SevenSegmentDigit.xaml.cs	Procedural digit rendering
LedDisplayEmulator.csproj	Project file (.NET 8 / WPF, net8.0-windows)
LedDisplayEmulator.slnx	Solution file

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Troubleshooting

Problem	Solution
COM ports not appearing	Restart after com0com install, or run setupc to verify ports exist
“Access denied” on COM port	Close any other app using that port, or run as admin
Digits don’t light up	Check baud rate matches (both apps must use same speed)
Wrong characters displayed	Check you’re in the right display mode (Simple vs LED8 N-type)
Labels don’t appear	Make sure you’re in LED8 N-type mode and sending ESC s n command
Click Test button shows “Connect first!”	You must click Connect before testing
Test button shows “Send error”	Check the COM port isn’t held open by another app

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Contributing

Contributions are welcome! Please open an issue to discuss any significant change before submitting a pull request. Keep the code style consistent with the existing WPF/C# codebase.

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Acknowledgements

• com0com — virtual COM port driver used for testing.
• ESC/POS protocol reference for customer/pole displays.

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Disclaimer

This project is not affiliated with, endorsed by, or sponsored by any POS or display hardware vendor. It implements a subset of the ESC/POS command set for emulation and testing purposes only.

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License

Released under the MIT License.