eDNC Special Character Fix

Real-time file watcher that automatically removes invalid special characters from DNC (Direct Numerical Control) program files.

Problem

Some legacy DNC systems and communication protocols add padding or termination bytes that modern CNC controllers cannot process correctly. Common problematic characters include:

Byte	Hex	Name	Description
255	0xFF	Fill	Padding/fill character
0	0x00	NULL	Null character
26	0x1A	SUB	Ctrl+Z / EOF marker
127	0x7F	DEL	Delete character

Solution

This utility monitors a folder for DNC files and automatically strips specified characters as soon as files are created or modified.

Installation

1. Copy the project folder to your DNC workstation
2. Edit eDNC-SpecialCharFix.ps1 to set your watch folder (default: C:\Dnc_Files\Q)
3. Run Run-eDNCFix.bat - it will auto-elevate to Administrator

Note: The batch file automatically requests Administrator privileges via UAC prompt.

Run as Scheduled Task (Recommended)

For production use, install as a scheduled task that runs as SYSTEM with admin rights:

# Run as Administrator
.\Install-ScheduledTask.ps1

# With custom settings
.\Install-ScheduledTask.ps1 -WatchFolder "D:\DNC\Programs" -FileFilter "*.nc"

# To remove
.\Install-ScheduledTask.ps1 -Uninstall

This creates a task that:

• Starts at system boot (before any user logs in)
• Runs as SYSTEM with highest privileges
• Auto-restarts if it crashes
• Runs hidden (no console window)

Run at User Login (Alternative)

To run when a specific user logs in:

1. Press Win + R, type shell:startup, press Enter
2. Create a shortcut to Run-eDNCFix.bat in the Startup folder

Usage

Basic Usage

Double-click Run-eDNCFix.bat or run from PowerShell:

.\eDNC-SpecialCharFix.ps1

Custom Watch Folder

.\eDNC-SpecialCharFix.ps1 -WatchFolder "D:\DNC\Programs"

Different File Types

.\eDNC-SpecialCharFix.ps1 -FileFilter "*.nc"

Remove Additional Characters

# Remove 0xFF, NULL, and SUB characters
.\eDNC-SpecialCharFix.ps1 -CharactersToRemove @(255, 0, 26)

All Options

.\eDNC-SpecialCharFix.ps1 `
    -WatchFolder "C:\Dnc_Files\Q" `
    -FileFilter "*.pun" `
    -IncludeSubfolders $true `
    -CharactersToRemove @(255)

Parameters

Parameter	Type	Default	Description
WatchFolder	String	C:\Dnc_Files\Q	Folder to monitor
FileFilter	String	*.pun	File pattern to watch
IncludeSubfolders	Boolean	$true	Watch subdirectories
CharactersToRemove	Int[]	@(255)	Byte values to strip

Output

The script displays real-time activity:

========================================
 eDNC Special Character Fix v1.0.0
========================================

Configuration:
  Watch Folder:    C:\Dnc_Files\Q
  File Filter:     *.pun
  Subfolders:      True
  Removing bytes:  255 (0xFF)

Watching for files... Press Ctrl+C to stop

2025-12-12 08:30:15 | Created | PART001.pun
  [CLEANED] Removed 3 byte(s)
2025-12-12 08:30:22 | Changed | PART002.pun
  [OK] No special characters found

Requirements

• Windows PowerShell 5.1 or later
• Read/Write access to the watch folder

Troubleshooting

"Watch folder does not exist"

Create the folder or specify a different path with -WatchFolder.

"File locked" errors (v1.0.0)

If using v1.0.0, update to v1.1.0 for improved file locking handling with exponential backoff and stability checks.

Script doesn't detect files

• Verify the file extension matches -FileFilter
• Check that -IncludeSubfolders is set correctly
• Ensure the script has permissions to the folder

"[WAIT] File still being written..."

This is normal behavior. The script waits for the file size to stabilize before processing, which means eDNC is still transferring the file. The script will automatically process it once the transfer completes.

"[RETRY] File locked..."

The script uses exponential backoff (500ms → 1s → 2s → 4s → up to 16s) for up to 10 attempts. If you see [FAILED] messages, eDNC may be holding the file longer than expected.

Version History

Version	Date	Changes
1.3.1	2025-12-12	Added Install-ScheduledTask.ps1 for running as SYSTEM service
1.3.0	2025-12-12	Fixed header UI, live status/stats, auto-elevate to Administrator
1.2.1	2025-12-12	Added GE Aerospace ASCII banner
1.2.0	2025-12-12	Immediate processing: 50ms delay, aggressive retry (100ms+), 15 attempts
1.1.0	2025-12-12	Improved file locking: stability check, exponential backoff, debouncing
1.0.0	2025-12-12	Initial release

Author

GE Aerospace - Rutland