UDVBM-1 Universal Digital VFO/BFO

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I wanted to replace the drifty VFO in one of my rigs with a digital solution, but my hand-wired solution was messy, fiddly, and prone to ground loops and digital noise. So I designed a PCB and, well, I got carried away. The result is the UDVBM-1: a universal motherboard for an Arduino-compatible micro-controller (MCU) module and an Adafruit-compatible Si5351 PLL clock module.

The UDVBM-1 can be used in any rig for either the VFO or the BFO, or (usually) both. Additionally, the I2C, SPI, and 1-wire digital buses of the MCU are brought out to ports along the board edge to use for inputs (rotary encoders, buttons, and switches) and outputs (LCDs or other digital displays, panel idicators, buzzers, and cooling-fan control). To top it all off, the MCU’s analog-to-digital converter (ADC) inputs and pulse-width modulation (PWM) outputs are made available as well.

Currently, we have three versions of the UDVBM-1 available: one for the Arduino Pro-Mini, one for the Arduino Nano, and one for Seeed Studio’s (yes, three “e”s) family of Xiao (pronounced she-ow) MCU modules (based on the SAMD21, the RP2040, or the ESP32 MCU chips). In addition to Arduino’s C/C++ language, the Xiaos can be programmed in MicroPython or CircuitPython.

The UDVBM-1 offers these features:

• Board-edge connections (for use with or without headers) for I2C bus, SPI bus, 1-Wire bus, rotary encoder, ADC input, and PWM output.
• A manageable size, neither too big nor too small.
• Onboard linear regulator with back filter to keep digital noise out of the rig’s main supply.
• Available for Arduino ProMini or Nano, or for the family of Seeed Studio Xiao microcontroller modules.
• Free, open-source, and ready-to-use software included. Of course, you can also program the Arduino with your own software.
• The Xiao version can be programed in Arduino C/C++, MicroPython, and CircuitPython.
• Versions for the Arduino include a small breadboard area of isolated pads for additional user circuitry.
• Available as a bare board, as a kit of PCB and parts to use with your own Arduino (or Xiao) and Si5351 modules, or as a fully-populated and tested assembly.

Schematic Diagrams (PDF)

User manual (PDF)

Github Repository