{"id":804,"date":"2015-11-11T12:16:56","date_gmt":"2015-11-11T11:16:56","guid":{"rendered":"http:\/\/pa0rwe.nl\/?page_id=804"},"modified":"2025-04-24T10:05:33","modified_gmt":"2025-04-24T08:05:33","slug":"universal-vfo-based-on-the-si5351","status":"publish","type":"page","link":"https:\/\/pa0rwe.nl\/?page_id=804","title":{"rendered":"Universal VFO based on the Si5351"},"content":{"rendered":"

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https:\/\/www.silabs.com\/Support%20Documents\/TechnicalDocs\/Si5351-B.pdf
\n<\/span><\/a><\/em> https:\/\/www.microchip.com\/wwwproducts\/Devices.aspx?product=PIC16F1825\u00a0<\/span><\/a><\/em>
\nhttps:\/\/ak2b.blogspot.nl\/2015\/04\/multi-featured-vfo.html<\/span><\/a><\/em><\/p>\n

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PIC version
\n<\/strong><\/span><\/h2>\n

Note: This version is obsolete and will no longer be maintained.
\n<\/em><\/strong>Please scroll down for the Arduino version.<\/strong><\/em><\/p>\n

Downloads:<\/span><\/em>\u00a0 Hex file for the 16F1825 click for 25MHz <\/span><\/em><\/a>version. For control board schematic click here<\/a><\/span><\/em> and for the Si5351 board click here<\/a><\/span><\/em> .
\nUpdate v.3.0 october 2023:<\/strong><\/span> Due to this version was not working properly, it has been updated.<\/p>\n

This VFO is based on the popular Si5351. It consists of two parts: the controller board and the Si5351 board.<\/p>\n

The control board is using a PIC16F1825 and the popular OLED SSD1306 display.
\nThe Adafruit board is using a 25 MHz x-tal and I2C address = 0xc0.<\/p>\n

There are 3 clock outputs available having the following outputs:
\nCLK0:<\/strong>\u00a0\u00a0 Tx Output frequency from 1 – 125 MHz (same frequency as on the display).
\nCLK1:<\/strong>\u00a0\u00a0\u00a0 First Rx LO calculated from CLK0<\/strong> + or – CLK2.
\nCLK2:<\/strong> \u00a0 Rx IF frequency.\u00a0 For instance 9 or 10.7 MHz. Every frequency is possible.<\/p>\n

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Si5351 board<\/p><\/div>\n

The two push buttons are for Calibration and selecting (and tune) the IF frequency.
\nThe toggle switch is for selecting RIT. With this function you can tune the Rx frequency separate from the Tx frequency.<\/p>\n

Below you see a test setup.<\/p>\n

\"Si5351<\/a>

Si5351 VFO test setup (PIC version)<\/p><\/div>\n

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Functions:<\/span>
\n– Output of 3 different frequencies (Tx, Rx, BFO\/LO) on CLK0-CLK2
\n– Select and tune BFO\/LO to any IF frequency
\n– Rx frequency based on Tx +\/- BFO\/LO
\n– Calibration function (see below)
\n– RIT function (only the Rx frequency is tuned with 100 Hz step size)<\/p>\n

Calibration:<\/span>
\n– Push the calibration button
\n– The frequency will be set to the X-tal frequency
\n– Measure the frequency at CLK0
\n– Tune to the measured<\/span> frequency and push again the calibration button
\n– Calibration is ready.<\/p>\n

Note:<\/strong>\u00a0 If calibration will not succeed: You can reset the calibration by pressing the Calibration button twice without<\/strong> tuning. Then try again to calibrate.<\/p>\n

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Arduino version<\/strong><\/span><\/h2>\n

Due to the popularity of the Arduino, I rewrite the PIC software for using an Arduino-Nano.
\nThe software has the same functionality as the PIC version. The Arduino version is partly based on the original MultiFeaturedVFO<\/em> software of Jason Mildrum, NT7S and Przemek Sadowski, SQ9NJE.
\nYou find the settings (x-tal frequency and I2C address) for the used Si5351 board in the RWE_si5351.h file.<\/p>\n

Notes:<\/strong><\/span><\/p>\n