Marlin — Open-Source 3D Printer Firmware

Introduction

Marlin is the most widely used open-source firmware for FDM 3D printers and CNC machines. It runs on 8-bit AVR and 32-bit ARM boards, providing precise stepper motor control, thermal management, and G-code interpretation with extensive configuration options for virtually any RepRap-style machine.

What Marlin Does

• Interprets G-code commands to coordinate stepper motors, heaters, and fans
• Supports auto bed leveling with BLTouch, inductive, and capacitive probes
• Implements thermal runaway protection and safety features for unattended printing
• Provides an LCD/touchscreen UI for on-printer control and SD card printing
• Handles kinematics for Cartesian, Delta, CoreXY, SCARA, and polar machines

Architecture Overview

Marlin runs as a single firmware image on the printer control board. The motion planner converts G-code moves into a look-ahead buffer of trapezoidal velocity segments. Stepper ISRs generate precise step pulses using hardware timers. The temperature manager runs a PID loop for hotend and heated bed control. On 32-bit boards, Marlin uses a HAL layer to abstract hardware differences across STM32, LPC, and ESP32 platforms.

Self-Hosting & Configuration

• Clone the repository and copy the example configuration for your printer model
• Edit Configuration.h for board type, stepper drivers, bed size, and probe settings
• Edit Configuration_adv.h for linear advance, junction deviation, and input shaping
• Build with PlatformIO CLI or VS Code with the PlatformIO extension
• Flash via SD card, USB-DFU, or serial bootloader depending on the board

Key Features

• Linear Advance for pressure compensation and cleaner corners
• Input Shaping to reduce ringing artifacts at higher print speeds
• Unified Bed Leveling with mesh-based compensation across the build surface
• Multi-extruder support including mixing, switching, and IDEX configurations
• Host action commands for OctoPrint and Klipper integration

Comparison with Similar Tools

• Klipper — Offloads computation to a host Raspberry Pi for higher step rates; Marlin runs entirely on the printer MCU with no external dependency
• RepRapFirmware — Feature-rich with web interface and runtime configuration; Marlin has broader board support and a larger configuration database
• Smoothieware — Optimized for 32-bit LPC boards; Marlin supports both 8-bit and 32-bit with wider hardware coverage
• grbl — Focused on CNC milling; Marlin adds 3D printing features like temperature control, bed leveling, and filament sensors

FAQ

Q: Should I use Marlin or Klipper? A: Marlin works entirely on the printer board with no extra hardware needed. Klipper requires a Raspberry Pi but offers faster kinematics and runtime configuration changes. Both produce excellent print quality.

Q: How do I find the right configuration for my printer? A: Check the Configurations repository on GitHub, which contains pre-made configs for hundreds of printer models. Start from the closest match and adjust.

Q: Can Marlin run on 8-bit boards? A: Yes, though some features (input shaping, S-curve acceleration) require 32-bit boards due to processing constraints.

Q: How do I enable auto bed leveling? A: Define your probe type and pin in Configuration.h, set probe offsets, enable one of the leveling systems (bilinear, UBL, or mesh), and run G29 before printing.

Sources

• https://github.com/MarlinFirmware/Marlin
• https://marlinfw.org/docs/