Plotter

Web UI for controlling a 3D printer (Marlin firmware) as a pen plotter over serial.

Features

• Serial console with real-time output from the printer
• Pen up/down control with adjustable Z heights
• SVG file import with preview, scaling, and fit-to-bed
• Handles large/complex SVGs (100K+ paths) — server-side preprocessing, spatial-grid path optimization, batched command sending
• Circle drawing with G2 arc commands
• Real-time serial throughput stats (TX/RX bytes/sec, saturation, RTT, commands/sec)
• Emergency stop and serial reset
• Command queue with Marlin ok-based flow control
• Fill/shading support for closed paths (hatch, crosshatch, dots) with brightness-based density

Setup

python3 -m venv .venv
.venv/bin/pip install -r requirements.txt

Usage

.venv/bin/python server.py

This starts the server on port 8000 with auto-reload — any changes to .py, .html, .js, or .css files will restart the server automatically.

Open http://localhost:8000

Configuration

Edit server.py to change:

• SERIAL_PORT — defaults to /dev/ttyUSB0
• BAUD_RATE — defaults to 115200

Tests

.venv/bin/pytest
node tests/test_plotter.js

Tests cover:

• API endpoints (tests/test_api.py) — SVG preprocessing endpoint (parsing, transforms, simplification, bounding boxes, error handling), static file serving, and port listing API
• SVG processing (tests/test_svg_processing.py) — unit tests for parse_svg_path_to_subpaths (line/curve/arc commands, relative coordinates, implicit repeats, subpaths), apply_transform (translate, scale, matrix, combined), and douglas_peucker path simplification
• Client-side plotter logic (tests/test_plotter.js) — path optimization (simplify, sort, merge), coordinate transforms, bounds checking, G-code generation, and SVG element conversion

Tools

The tools/ directory contains standalone generators and utilities for creating plotter-ready SVG artwork (Perlin landscapes, typography posters, calibration grids, map conversion). See tools/README.md for details.

Hardware

Developed for a Creality CR-10S Pro (300x300mm bed) but should work with any Marlin-based printer. A 3D-printed pen holder replaces the hotend nozzle and holds standard pens or pencils.

Example Outputs