PWL Editor

A professional editor for Piecewise Linear Waveform (PWL) files compatible with LTSpice, Micro-Cap and more. Suitable for voltage, current, or any signal waveforms.

Key Features

• Table-first editing with inline cell edits and smart point insertion.
• Live plotting that mirrors table selections and highlights changes instantly.
• Waveform repair assistant to detect duplicate timestamps and time reversals.
• Signal generators for square, triangle, and saw profiles with guarded parameter entry.
• Menu-driven conversions for SI/scientific notation and ABS↔REL time formats.
• Export presets that enforce relative, absolute, or mixed timing during file export.
• Text editor mode with validation and undo support.
• Import/Export tooling compatible with LTSpice and MicroCap workflows.

Quick Look

Table View with Real-time Plotting

Edit points in the table while the plot highlights the same selection on the right.

Text Editor Mode

Switch to raw PWL text with live validation and instant round-tripping back to the table.

Waveform Tools

Waveform Repair

Inspect the dataset for duplicate timestamps or time reversals, preview the fix, and apply it in place.

• Max Slew Rate (V/s) – when spreading duplicates, ensure the local slope stays below this ceiling.
• Minimum Time Gap (s) – enforce at least this spacing between duplicate points after repairs.
• Duplicate strategy – choose to leave as-is, center duplicates, or nudge them forward/back.
• Time reversal strategy – keep, sort, or drop segments that run backward in time.
• Analyze / Preview / Apply – re-scan the data, test the repair, then commit it when happy.

Signal Generators

Each generator can append to the end of the waveform or replace the entire dataset. Previews update the plot before you apply changes.

Square Wave

• Low / High level – plateau values for the low and high states; swap them to invert the waveform.
• Period (s) – duration of one complete cycle.
• Duty cycle (%) – percentage of the period spent high.
• Cycles – number of cycles to generate.
• Start time (s) – timestamp where the generated segment begins when replacing the dataset; append mode always starts at the current end.
• Edge duration (ppm) – linear ramp length for each transition (rise/fall) expressed as parts per million of the period; automatically clamped so it never exceeds the available plateau.
• Start high – choose the initial state of the waveform.
• Prefer relative output – emit +Δt timestamps when enabled.
• Apply mode – choose whether to append to the end or replace the current waveform.

Triangle Wave

• Low / High level – minimum and peak amplitude (swap to flip the ramp direction).
• Period (s) – duration of one complete cycle.
• Symmetry (0.001–0.999) – fraction of the period spent rising; the remainder is the fall.
• Cycles – number of cycles to generate.
• Start time (s) – timestamp where the generated segment begins when replacing the dataset; append mode always starts at the current end.
• Prefer relative output – emit +Δt timestamps when enabled.
• Apply mode – choose whether to append to the end or replace the current waveform.

Saw Wave

• Low / High level – floor and ceiling of the ramp (swap to generate an inverted saw).
• Period (s) – duration of one complete cycle.
• Ramp fraction (0–1) – share of the period spent ramping up; the remainder is the reset interval (drop plus low hold).
• Cycles – number of cycles to generate.
• Start time (s) – timestamp where the generated segment begins when replacing the dataset; append mode always starts at the current end.
• Reset edge (ppm) – length of the linear drop back to the low level, in parts per million of the period; any remaining reset interval stays flat at the low level if the requested window is longer than available.
• Prefer relative output – emit +Δt timestamps when enabled.
• Apply mode – choose whether to append to the end or replace the current waveform.

Installation

Option 1: Pre-built Distribution (Recommended)

Download the latest release from: GitHub Releases

Option 2: Run from Source

If you prefer to run from source code:

1. Ensure Python 3.7+ is installed

2. Install required dependencies:

   pip install tkinter matplotlib numpy si-prefix
   

3. Run the application:

   python src/pwl_gui.py
   

For Developers

• Entry point: src/pwl_gui.py
• Build artifact: python scripts/build.py
• Core modules:
  • src/controllers/ – table/text/plot coordination
  • src/services/ – file IO, formatting, undo history, waveform repair
  • src/dialogs/ – generator and repair UIs
  • src/generators/ – waveform synthesis helpers

PWL Format

PWL files define piecewise linear waveforms using time-value pairs. Values are unitless and can represent voltage, current, or any signal:

Absolute Time Format

0 0
1m 1
2m 2

Time=0s Value=0, Time=1ms Value=1, Time=2ms Value=2

Relative Time Format (LTSpice Delta Format)

0 0
+1m 1
+1m 2

Time=0s Value=0, Time=previous+1ms Value=1, Time=previous+1ms Value=2

Note: Relative time format (+ prefix) is LTSpice-specific and may not be compatible with other SPICE simulators like Microcap.

Mixed Format

Both formats can be mixed in the same file. The editor provides smart conversion between formats while preserving the waveform shape.

Export Format Settings

Export presets live under Format → Export Format and are applied when you run File → Export...:

Export Format Options

• Preserve Mixed - Keeps the original mix of absolute and relative time formats as entered.
• Force Relative - Converts all time values to relative format (+ prefix) in the exported file.
• Force Absolute - Converts all time values to absolute format in the exported file (required for MicroCap compatibility).

Examples

The examples/ folder contains sample PWL files:

• simple_ramp.pwl - Basic linear ramp waveform
• mixed_format.pwl - Demonstrates mixing ABS and REL formats
• absolute_time.pwl - Pure absolute time format example
• digital_signal.pwl - Complex digital signal with nanosecond timing
• parser_testfile.txt - Simple test file for parser development
• repair_test_patterns.pwl - Crafted edge cases for waveform repair scenarios

Testing the Parser

You can test the PWL parser independently:

cd src
python pwl_parser.py

This will load and process the test file, demonstrating the parser's capabilities.

License

GPL-3.0-or-later

AI Tools Used

• Claude Sonnet 4 (Anthropic) - Code development and architecture
• GPT-5 (OpenAI) - Code development, bugfixes