ADX-MINI Open-Source Firmware for Digital HF QRP Transceiver

Overview

The ADX-MINI firmware is the open-source Arduino codebase that powers the ADX-MINI family of digital mode QRP transceivers designed by Scott Baker (KJ7NLA). The project includes firmware for three hardware revisions — the original ADX-MINI, the ADX-MI2 (with onboard USB sound card), and the ADX-MI3 (with OLED display and expanded CAT commands).

The firmware is a variation on the original ADX (Arduino Digital Transceiver) design by Barb WB2CBA, adapted for the MINI form factor with a CD2003 receiver chip and Class-E QRP transmitter. It is designed to work with WSJT-X software running on a host computer for FT8, FT4, JS8Call, and WSPR digital mode operations.

Key Features

• Support for FT8, FT4, JS8Call, and WSPR digital modes
• Coverage of HF bands from 160m to 6m using pluggable low-pass filter modules
• CAT control emulating Kenwood TS-2000 for seamless WSJT-X integration
• Si5351 programmable clock generator for frequency synthesis
• ADX-MI3 variant adds 128x32 OLED display with one-button UI and Tune Mode
• ADX-MI2/MI3 variants integrate USB hub, sound card, and serial adapter via single USB-C
• Approximately 5W RF output on 20m band
• Arduino IDE compatible for easy modification and flashing

Hardware Variants

• ADX-MINI: Base model with discrete USB connections
• ADX-MI2: Enhanced with onboard USB sound card, firmware-compatible with MINI
• ADX-MI3: Redesigned UI with OLED display and expanded CAT commands (not firmware-compatible with earlier versions)

Getting Started

1. Clone the repository from GitHub
2. Open the appropriate firmware file in Arduino IDE (MINI/MI2 or MI3)
3. Install required libraries (Etherkit SI5351, SSD1306 for MI3)
4. Flash to ATmega328P via USB or ISP programmer
5. Connect to computer running WSJT-X with Kenwood TS-2000 CAT profile