Si5351A Synth VFO

What else is one to do on a lazy Sunday afternoon than to take a QRP Labs Si5351A Synth module and turn it into a VFO using an Arduino, LCD and Rotary encoder.I started out by ensuring that the Arduino was talking to the synth over I2C, with that accomplished I was then able to calibrate the frequency by adjusting in code the actual frequency the crystal was resonating at.


My freq counter only goes down to 100hz resolution, but I think for my needs that this is more than accurate enough. However when i can get my hands on a counter that goes to the Hz level, i will calibrate this a little further. Just because I can 🙂


With it all working, I then turned my attention to making it a VFO. Got the basics working with the rotary encoder. Next job will be to change to a 4 line LCD and start implementing features like USB, LSB, CW, band switching and the like.


2 thoughts on “Si5351A Synth VFO

    1. I have published both the code and board gerbers, but I think it was in a facebook group and not on here. I will dig them up and put them on here. No schematic, but i do have gerbers to have the boards made, which i have in the fab house now getting made. Check back in a few days and I will have the files up.

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