Sunday 5 October 2014


I've been wanting to get my hands on an Si5351 for months, excited by the prospect of three programmable oscillators in a tiny, inexpensive package. Well - today, it happened...

I got a couple of the nice little breakout boards from Her Ladyship, Limor Fried

As is usual for Adafruit products, this board is supported by an excellent tutorial and some software.

The tutorial support includes everything you need to know to get running with the Si5351 in an Arduino context (although the board can be used with other systems too) and the software is in the form of an Arduino sketch.

I had a MEGA lying on the bench - so I hooked my new Si5351 up to that (it needs just power and the two wires of an I2C interface)...

I downloaded the Adafruit library and example program and soon had the little chip squirting out square waves...

The Si5351A3 has three (independent) outputs and I only have a two channel 'scope here at the moment - so here are three channels captured on the ripoff logic analyser I purchased from Banggood the other day...

It works - but I have to say the Adafruit library is hardly "ready to use".

Fortunately, Jason, nt7s, has come to our rescue with a much smoother library which is also available for download from a GitHub repository.

I tried that code with the MEGA / Adafruit breakout combo and found it much easier to generate Ham-friendly RF.

Here's a 14 MHz signal...

which was set up very quickly and cleanly, as you can see below - all thanks to Jason's efficient library...

This is the way I'll be moving forward with the Si5351 - thanks Jason.

I wonder if I can drive it with the Arduino DUE.

...-.- de m0xpd


  1. How is the jitter / phase noise ? Is it usable for a decent receiver ?

  2. I also had trouble with Adafruit board and code so switched to the NT7S code with his breakout board(with 3 transformer coupled outputs) and everything then worked fine

  3. I have one of Jason's Si5351 breakout boards. Need to get it hooked up to an Arduino and working soon. Thanks for the inspiration Paul!


  4. I have one of these boards as well now. One thing I figured out from the datasheet and tested last night, is that you can produce I/Q outputs directly provided you stick with integer dividers. The big question is of course phase/jitter noise but it sounds clean at 144Mhz in another receiver.

    Andrew VK3JBL

  5. I'm using the Adafruit board with Raspberry and the Roseengineering software.
    I found that tuning above 118 MHz with a small stepsize the output jitter increased dramaticly. Only when the Multisync devider steps are 0,1 (7.5, 7.6 etc) there is no jitter. But when I enter 7.59 the jitter is back.
    Does anyone recognise this behavior and maybe has a tip?