: A popular version that supports many features (LCD, rotary encoders, multiple TX ports) can be found in the K5BCQ K3NG Keyer Manual .

Elias sighed and pulled up the official GitHub repository for the K3NG Keyer on his laptop. He scrolled past the massive keyer.h file and opened the PDF schematic.

Connects to Digital Pin 5 (Internal pull-up resistor enabled).

For a full-featured keyer, the schematic includes a 16x2 LCD (using I2C to save pins) or a 128x64 OLED (I2C or SPI).

The paddle inputs connect directly to the Arduino’s digital pins.

This article provides a comprehensive breakdown of the K3NG keyer’s hardware architecture, explaining each critical section of the schematic, common variants, and how to customize the circuit for your specific needs.

: Used to enter the "command mode" for configuration via the paddle.

+-------------------+ | ARDUINO UNO | | / NANO | +-------------------+ Paddle Left ---->| D2 | Paddle Right ---->| D5 | | D13|----> Piezo Buzzer (+) | D11|----> Transmitter Keying Circuit +-------------------+ Use code with caution. 1. The Input Section (Paddles)

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The tip and ring connect to digital pins dedicated as paddle_left and paddle_right (e.g., D2 and D5), and the sleeve connects to Ground (GND). 3. Key Output (Transceiver Interface)

Arduino Nano +5V -----[10k]-----+----[Paddle Dah]---- GND | +----[Paddle Dit]----- GND

"Give it a tap," Silas whispered.

Open keyer_features_and_options.h and uncomment the lines corresponding to the hardware you plan to install. For example, to add a rotary encoder, uncomment #define FEATURE_ROTARY_ENCODER . For a basic keyer without an LCD, you may leave most options commented.

Design Note: The code activates the Arduino’s internal pull-up resistors on these pins. You do not need external resistors to keep the lines high; closing the paddle contact simply pulls the pin to GND. 3. The Transmitter Keying Circuit (Crucial Component)