Tuesday, February 24, 2015

Calibrating the Si5351

Jason's library has a very good calibration procedure found by clicking on 'File\Examples\Etherkit-si535\si5351_calibration'
You will need some way of measuring frequency. Once done you will end up with a number that will replace the 0 in this statement:

Initialization now takes two arguments in the new library. Instead of just the crystal load capacitance - it now takes the crystal frequency as well.

 si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0);

 A zero as the second parameter defaults to 25Mhz, as above.
 If you're using a 27Mhz crystal you could change it in the header file (si5351.h) or just put in 27000000.
Any and all comments are appreciated.


  1. hello Tom ...i m finished the lbs part II of my friend Pete N6qw but my arduino nano with adafruit si5351 dont working well .i am using Jason library si5351.h and si5351.cpp and Petes sketch http://www.jessystems.com/Images/Arduino/LBS%20Part%20II%20Si5351.txt .my english is not good but foe example my LSB frequency set to 4,9137 mhz for BFO but real frequency is 4,9462 also IF offset is not corect .maybe you can help me Tom.thanks in advance 73 de 9a3xz Mikele .

  2. Hi Mikele,
    In Pete's code:

    // Start serial and initialize the Si5351

    He has the line for setting the correction frequency commented out.
    Try making your line;
    The difference between 49462 and 49137. You should be doing this at 10MHz or so for better accuracy, but it won't hurt to try. After the correction works out to what you want, you can put comments before the line again.

    73 Tom

    1. ok Tom.....now is late but i will try tomorow .many thanks,

  3. Tom ...i wanna thank you .i always folow your projects ....


  4. Glad you got it to work, Mikele. Thanks for the video credit :).

  5. Hi Tom,

    It's such a pleasure reading your posts and following your endeavours. Keep on posting, you're doing a grea job! I have been inspired by the YouTube receiver video you posted and I ordered a si5351 breakout board from Jason NT7S and some cheap OLEDs from China in order to build a multiband CW rig for those summer fun times!

    73! de Adrian, YO6SSW

    P.S: what ever happened to Diz's forum? I noticed it's not available anymore.

  6. Hi Adrian,
    Good to hear from you again and thanks for the kind words.
    Diz upgraded his OS and it wouldn't take the forum software format of his previous version so he shut it down.
    Good luck with the multiband cw rig.
    73, Tom, ak2b