This repository provides two Python-based Morse code (CW) keyer implementations that use RS-232 serial control lines as input paddles. Designed for amateur radio operators, these tools allow simple CW keying using either a straight key or an iambic paddle connected to a PC's serial port.
🔗 GitHub Repository: 7m4mon/CTSDSR-Keyer
A straight key implementation using the CTS line:
- Outputs a sine wave side-tone while the CTS line is held low.
- Designed for traditional "up/down" straight key operation.
- Uses real-time waveform synthesis with phase continuity for clean audio.
An Iambic A paddle keyer using:
- CTS for "dit" paddle (·)
- DSR for "dah" paddle (–)
- Supports squeeze keying (alternating dit/dah while both pressed).
- Smooth and precise timing of Morse elements.
- No audible clicks thanks to phase-preserving waveform generation.
Make sure Python 3.x is installed. Then install required packages:
pip install pyserial sounddevice numpyTested on both Windows and Linux.
Before running, edit each script to match your serial port name:
PORT = 'COM101' # Windows example
# PORT = '/dev/ttyUSB0' # Linux exampleOptional parameters you can modify:
TONE_FREQ: tone frequency in Hz (default: 600 Hz)SAMPLE_RATE: audio output rate (default: 48000 or 44100)WPM: words per minute (only in paddle keyer)
- Use a USB-to-Serial adapter with accessible CTS and DSR lines.
- Connect your straight key or paddle so that pressing closes the line to GND.
- No data is transmitted over the serial line—only control signals are read.
Pin Usage:
| Signal | Function |
|---|---|
| CTS | Straight key / Dit |
| DSR | Dah paddle (for iambic) |
- CW practice or training on your PC
- USB paddle interface for SDR
- Side-tone generator for code keying
- CW to SSB modulation gateway (when paired with audio input)
This project is licensed under the MIT License.
Developed by 7M4MON
Feel free to fork, modify, or integrate with your own amateur radio tools.
Pull requests are welcome!