This repository contains the K3NG Arduino CW Keyer, a highly configurable firmware for generating Morse code (CW) in amateur radio operations. The system runs on a wide range of Arduino-compatible microcontrollers (AVR, SAM, STM32, ESP32, Raspberry Pi Pico) and supports multiple input methods including paddles, straight keys, PS2 keyboards, USB keyboards (via MAX3421E USB host shield), and game controllers. It emulates the Winkey protocol for integration with logging software like N1MM+ and provides advanced features such as a CW decoder (using Goertzel algorithm), a built-in web server for remote control, beacon mode, practice/training modes, and SO2R (single operator two radio) support. The architecture is a monolithic Arduino sketch with extensive conditional compilation: over 20 hardware-specific configuration files (keyer_features_and_options_*.h, keyer_pin_settings_*.h, keyer_settings_*.h) allow tailoring the firmware to specific boards and feature sets. The main entry points are the standard Arduino setup() and loop() functions, with the web server module (k3ng_keyer_webserver.ino) providing HTTP-based control. External dependencies include the USB Host Shield library (for USB keyboard/controller input), Adafruit LiquidCrystal and TwiLiquidCrystal libraries (for LCD displays), and a PS2 keyboard library. The codebase is well-structured for its domain but carries significant complexity due to the sheer number of configuration combinations and bundled third-party libraries.