Universal VFO Controller (ATMega328 & si5351)

This board is a universal radio project controller, with an ATMega328P(U) microcontroller and lots of options. The intention was for it to become a basic building block in transceivers, receivers, transmitters, signal generators, anywhere you need either a digital controller, one to three clocks, or both. The board has headers for the common si5351 breakout board, available from Adafruit or as a .CN clone, and a 16×2 HD7044 Liquid Crystal Display using the standard 14+2 parallel data header (+2 for backlight). It brings out all of the available digital IOs (D2..D13), analogue inputs (ADC) A0..A5), as well as headers for a 12V supply, and access to the regulated 7805 5v output, access to the LCD backlight in case you wish to take control of this in software, and an FTDI-compatible USB-to-serial programming board.

Yet another Arduino Nano and si5351 Digital VFO/BFO

January 2017, summer holiday season down-under, afforded time to build something I’ve been wanting to build for several years, my first Digital VFO. I’ve built a kit Digital VFO with pre-soldered surface mount parts and burned-in firmware, but this was to be a scratch build with Arduino Nano, C code with modifications, and a Silicon Labs si5351 PLL clock generator on a breakout board. I used the wiring map and script from Tom AK2B (modified from one by SQ9NJE ) and uses Jason NT7S si5351 library. The script is simple, supporting a single push-button to cycle frequency increments, and dealing with encoder interrupts, contact debouncing, refreshing the LCD display, IF offset and VFO/BFO outputs.  Jason’s si5351 library hides the gutsy device interfacing, giving you a handful of common-sense functions to call… for example, set_frequency() takes as its argument the frequency in centi-hertz (1/100th of a hertz) and the ‘clock 0/1/2’ flag. It couldn’t be simpler. The Adafruit board contains the si5351 and a 25MHz clock (from local IoT supplier Core Electronics).  Here’s a video demonstration of the VFO’s features.