CWSoftie

A Arduino-based CW sidetone generator and keyer.

The sidetone is generated in software and converted to a analog signal via PWM and a low-pass RC-filter.

Features

• Sine wave tone using PWM.
• Adjustable sidetone frequency 400-911Hz.
• Adjustable keyer speed 5-37wpm.
• Keyboard keyer.
• Serial keyer.
• Keyer output.
• Command mode (set speed and tone).

Backlog

• Iambic keyer.
• Gaussian wave envelope.
• Simple record and replay.

Schematic

Assembly

Characterisation

Pins assignment

Arduino pin	Attached to
A0	Tone pot slider
A1	Speed pot slider
D2	Paddle dit/key 3.5mm stereo plug tip
D2	10K ohm to GND
D3	PS/2 Keyboard CLK
D4	Keyer output circuit
D5	Paddle dah 3.5mm stereo plug ring
D5	10K ohm to GND
D7	PS/2 Keyboard DATA
D11	Low-pass filter

Potentiometer end terminals connected to GND and VCC.

VCC to paddle/key 3.5mm stereo plug sleeve.

Low pass filter (692 Hz):

• 5K resistor attached from D11 (PWM) to output
• 0.047uF cap from output to ground
• output to amplifier

Keyer output circuit:

• D4 to Logic level N-channel MOSFET gate pin
• MOSFET source pin to GND
• MOSFET drain pin to keyer output

Build

Requires the Arduino IDE installed in ARDUINODIR.

export ARDUINODIR=/Users/daijo/Code/Arduino/
export SERIALDEV=/dev/tty.usbserial-A6007ZuZ
export BOARD=atmega328
make
make upload

For the ATtiny custom board/kit you also need the arduino-tiny additions found at http://code.google.com/p/arduino-tiny/. You can also use my fork of Arduino with arduino-tiny https://github.com/daijo/Arduino.

export BOARD=at2313at1
export ARDUINOPORT=tiny

Reference

• http://www.atmel.com/Images/doc2542.pdf
• http://interface.khm.de/index.php/lab/experiments/arduino-dds-sinewave-generator/
• http://www.w8ji.com/cw_bandwidth_described.htm
• http://www.sm5bsz.com/txmod/rt0282eng.htm
• http://www.solorb.com/elect/hamcirc/sidetone/