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10kHz to 225MHz VFO/RF Generator with Si5351 - Version 2

10kHz to 225MHz VFO/RF Generator with Si5351 - Version 2 © GPL3+

For use in DIY homebrew radio equipment such superheterodyne single/double conversion receiver, SDR, HAM QRP transceivers or RF generator.

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Components and supplies

Apps and online services

About this project

This is a project of a VFO (variable frequency oscillator) for use in DIY homebrew radio equipement such as Superheterodyne Single / Double Conversion Receivers, DCR, SDR or Ham QRP Transceivers. It has a Bargraph indicator for Signal Strenght (S-Meter) and 20 Band presets. Can be used as RF/Clock generator too. This is the new version (V.2), I updated the previous project and it includes new features.

Features:

  • Operation range from 10kHz to 225MHz.
  • Tuning steps of 1Hz, 10Hz, 1kHz, 5kHz, 10kHz and 1MHz.
  • Intermediate Frequency (IF) offset (+ or -) adjustable.
  • 20 Band Presets (shortcuts) to the BCB and HAM frequencies.
  • Generator funcion mode.
  • RX / TX Mode Selector for use in Homebrew QRP Transceivers.
  • Bargraph for Signal Meter through the analog input (ADC).
  • For use as Local Oscillator on Homebrew radio receivers such as Superheterodyne, SDR, Direct Conversion and Homebrew QRP Transceivers.
  • For use in Double Conversion / Air Band Superhet Receivers in conjunction with Si4735 or Si4732 DSP radio chip.
  • For use as a simple RF/Clock generator for calibration reference or clock generation.
  • Works with Arduino Uno, Nano and Pro Mini.
  • Uses a common 128x64 I2C OLED SSD1306 display and Si5351 module.
  • I2C data transfer, only 2 wires to connect the display / Si5351 and arduino.
  • High stability and precision for frequency generation.
  • Simple yet very efficient and free.

Setup:

Schematics / wiring:

In operation video:

Instructions:

  • Open the scketch on Arduino IDE, install all the required libraries.
  • Choose the preferences (see note) and compile the sketch and then load it to the Arduino Nano, Uno or Pro Mini.
  • Follow the schematics to wire the Arduino, Display, Si5351 module, rotary encoder, etc.
  • Power up the Arduino.
  • Rotate the rotary encoder to tune up or down the frequency.
  • Push the push button 1 to change the frequency step tuning. The steps available are 1Hz, 10Hz, 1kHz, 5kHz, 10kHz and 1MHz.
  • Push the push button 2 to browse (select) the 20 band presets or enter the generator mode.
  • Turn on/off the switch SW 2 to change from RX to TX mode. RX mode = SW 2 Open and TX mode = SW 2 Closed to GND. When in TX mode, the IF value is not added/sub from the RF out. This is ideal for use in Homebrew QRP Transceivers.
  • Connect the S-Meter output signal from your radio to the X2 connector (S-Meter input). This input has adjustable sensitivity, the gain must be adjusted in Sketch, accepting signals from 500mV to 5V (max).
  • Known Issue: if it freezes in the initialization text, comment (put a //) at the line 77 statup_text ();

Note about User Preferences:

-It is possible to change the followings items on sketch:

#define IF 455 //Enter your IF frequency, ex: 455 = 455kHz, 10700 = 10.7MHz, 0 = to direct convert receiver or RF generator, + will add and - will subtract IF offfset.

#define BAND_INIT 7 //Enter your initial Band (1-21) at startup, ex: 1 = Freq Generator, 2 = 800kHz (MW), 7 = 7.2MHz (40m), 11 = 14.1MHz (20m).

#define XT_CAL_F 33000 //Si5351 calibration factor, adjust to get exatcly 10MHz. Increasing this value will decreases the frequency and vice versa.

#define S_GAIN 303 //Adjust the sensitivity of Signal Meter A/D input: 101 = 500mv; 202 = 1v; 303 = 1.5v; 404 = 2v; 505 = 2.5v; 1010 = 5v (max).

#define tunestep A0 //The pin used by tune step push button.

#define band A1 //The pin used by band selector push button.

#define rx_tx A2 //The pin used by RX / TX selector switch, RX = switch open, TX = switch closed to GND. When in TX, the IF is not considered.

#define adc A3 //The pin used by Signal Meter A/D input.

******************************************************************************

Julio Cesar - CesarSound - ver 2.0 - Feb/2021.

Code

Sketch SI5351_VFO_RF_GEN_OLED_JCR_V2C/C++
Load it to Arduino.
/**********************************************************************************************************
  10kHz to 225MHz VFO / RF Generator with Si5351 and Arduino Nano, with Intermediate Frequency (IF) offset
  (+ or -), RX/TX Selector for QRP Transceivers, Band Presets and Bargraph S-Meter. See the schematics for
  wiring and README.txt for details. By J. CesarSound - ver 2.0 - Feb/2021.
***********************************************************************************************************/

//Libraries
#include <Wire.h>                 //IDE Standard
#include <Rotary.h>               //Ben Buxton https://github.com/brianlow/Rotary
#include <si5351.h>               //Etherkit https://github.com/etherkit/Si5351Arduino
#include <Adafruit_GFX.h>         //Adafruit GFX https://github.com/adafruit/Adafruit-GFX-Library
#include <Adafruit_SSD1306.h>     //Adafruit SSD1306 https://github.com/adafruit/Adafruit_SSD1306

//User preferences
//------------------------------------------------------------------------------------------------------------
#define IF         455       //Enter your IF frequency, ex: 455 = 455kHz, 10700 = 10.7MHz, 0 = to direct convert receiver or RF generator, + will add and - will subtract IF offfset.
#define BAND_INIT  7         //Enter your initial Band (1-21) at startup, ex: 1 = Freq Generator, 2 = 800kHz (MW), 7 = 7.2MHz (40m), 11 = 14.1MHz (20m). 
#define XT_CAL_F   33000     //Si5351 calibration factor, adjust to get exatcly 10MHz. Increasing this value will decreases the frequency and vice versa.
#define S_GAIN     303       //Adjust the sensitivity of Signal Meter A/D input: 101 = 500mv; 202 = 1v; 303 = 1.5v; 404 = 2v; 505 = 2.5v; 1010 = 5v (max).
#define tunestep   A0        //The pin used by tune step push button.
#define band       A1        //The pin used by band selector push button.
#define rx_tx      A2        //The pin used by RX / TX selector switch, RX = switch open, TX = switch closed to GND. When in TX, the IF value is not considered.
#define adc        A3        //The pin used by Signal Meter A/D input.
//------------------------------------------------------------------------------------------------------------

Rotary r = Rotary(2, 3);
Adafruit_SSD1306 display = Adafruit_SSD1306(128, 64, &Wire);
Si5351 si5351(0x60); //Si5351 I2C Address 0x60

unsigned long freq, freqold, fstep;
long interfreq = IF, interfreqold = 0;
long cal = XT_CAL_F;
unsigned int smval;
byte encoder = 1;
byte stp, n = 1;
byte count, x, xo;
bool sts = 0;
unsigned int period = 100;
unsigned long time_now = 0;

ISR(PCINT2_vect) {
  char result = r.process();
  if (result == DIR_CW) set_frequency(1);
  else if (result == DIR_CCW) set_frequency(-1);
}

void set_frequency(short dir) {
  if (encoder == 1) {                         //Up/Down frequency
    if (dir == 1) freq = freq + fstep;
    if (freq >= 225000000) freq = 225000000;
    if (dir == -1) freq = freq - fstep;
    if (fstep == 1000000 && freq <= 1000000) freq = 1000000;
    else if (freq < 10000) freq = 10000;
  }
  if (encoder == 1) {                       //Up/Down graph tune pointer
    if (dir == 1) n = n + 1;
    if (n > 42) n = 1;
    if (dir == -1) n = n - 1;
    if (n < 1) n = 42;
  }
}

void setup() {
  Wire.begin();
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.display();

  pinMode(2, INPUT_PULLUP);
  pinMode(3, INPUT_PULLUP);
  pinMode(tunestep, INPUT_PULLUP);
  pinMode(band, INPUT_PULLUP);
  pinMode(rx_tx, INPUT_PULLUP);

  //statup_text();  //If you hang on startup, comment

  si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0, 0);
  si5351.set_correction(cal, SI5351_PLL_INPUT_XO);
  si5351.drive_strength(SI5351_CLK0, SI5351_DRIVE_8MA);
  si5351.output_enable(SI5351_CLK0, 1);                  //1 - Enable / 0 - Disable CLK
  si5351.output_enable(SI5351_CLK1, 0);
  si5351.output_enable(SI5351_CLK2, 0);

  PCICR |= (1 << PCIE2);
  PCMSK2 |= (1 << PCINT18) | (1 << PCINT19);
  sei();

  count = BAND_INIT;
  bandpresets();
  stp = 4;
  setstep();
}

void loop() {
  if (freqold != freq) {
    time_now = millis();
    tunegen();
    freqold = freq;
  }

  if (interfreqold != interfreq) {
    time_now = millis();
    tunegen();
    interfreqold = interfreq;
  }

  if (xo != x) {
    time_now = millis();
    xo = x;
  }

  if (digitalRead(tunestep) == LOW) {
    time_now = (millis() + 300);
    setstep();
    delay(300);
  }

  if (digitalRead(band) == LOW) {
    time_now = (millis() + 300);
    inc_preset();
    delay(300);
  }

  if (digitalRead(rx_tx) == LOW) {
    time_now = (millis() + 300);
    sts = 1;
  } else sts = 0;

  if ((time_now + period) > millis()) {
    displayfreq();
    layout();
  }
  sgnalread();
}

void tunegen() {
  si5351.set_freq((freq + (interfreq * 1000ULL)) * 100ULL, SI5351_CLK0);
}

void displayfreq() {
  unsigned int m = freq / 1000000;
  unsigned int k = (freq % 1000000) / 1000;
  unsigned int h = (freq % 1000) / 1;

  display.clearDisplay();
  display.setTextSize(2);

  char buffer[15] = "";
  if (m < 1) {
    display.setCursor(41, 1); sprintf(buffer, "%003d.%003d", k, h);
  }
  else if (m < 100) {
    display.setCursor(5, 1); sprintf(buffer, "%2d.%003d.%003d", m, k, h);
  }
  else if (m >= 100) {
    unsigned int h = (freq % 1000) / 10;
    display.setCursor(5, 1); sprintf(buffer, "%2d.%003d.%02d", m, k, h);
  }
  display.print(buffer);
}

void setstep() {
  switch (stp) {
    case 1: stp = 2; fstep = 1; break;
    case 2: stp = 3; fstep = 10; break;
    case 3: stp = 4; fstep = 1000; break;
    case 4: stp = 5; fstep = 5000; break;
    case 5: stp = 6; fstep = 10000; break;
    case 6: stp = 1; fstep = 1000000; break;
  }
}

void inc_preset() {
  count++;
  if (count > 21) count = 1;
  bandpresets();
  delay(50);
}

void bandpresets() {
  switch (count)  {
    case 1: freq = 100000; tunegen(); break;
    case 2: freq = 800000; break;
    case 3: freq = 1800000; break;
    case 4: freq = 3650000; break;
    case 5: freq = 4985000; break;
    case 6: freq = 6180000; break;
    case 7: freq = 7200000; break;
    case 8: freq = 10000000; break;
    case 9: freq = 11780000; break;
    case 10: freq = 13630000; break;
    case 11: freq = 14100000; break;
    case 12: freq = 15000000; break;
    case 13: freq = 17655000; break;
    case 14: freq = 21525000; break;
    case 15: freq = 27015000; break;
    case 16: freq = 28400000; break;
    case 17: freq = 50000000; break;
    case 18: freq = 100000000; break;
    case 19: freq = 130000000; break;
    case 20: freq = 144000000; break;
    case 21: freq = 220000000; break;
  }
  si5351.pll_reset(SI5351_PLLA);
  stp = 4; setstep();
}

void layout() {
  display.setTextColor(WHITE);
  display.drawLine(0, 20, 127, 20, WHITE);
  display.drawLine(0, 43, 127, 43, WHITE);
  display.drawLine(105, 24, 105, 39, WHITE);
  display.drawLine(87, 24, 87, 39, WHITE);
  display.drawLine(87, 48, 87, 63, WHITE);
  display.drawLine(15, 55, 82, 55, WHITE);
  display.setTextSize(1);
  display.setCursor(59, 23);
  display.print("STEP");
  display.setCursor(54, 33);
  if (stp == 2) display.print("  1Hz"); if (stp == 3) display.print(" 10Hz"); if (stp == 4) display.print(" 1kHz");
  if (stp == 5) display.print(" 5kHz"); if (stp == 6) display.print("10kHz"); if (stp == 1) display.print(" 1MHz");
  display.setTextSize(1);
  display.setCursor(92, 48);
  display.print("IF:");
  display.setCursor(92, 57);
  display.print(interfreq);
  display.print("k");
  display.setTextSize(1);
  display.setCursor(110, 23);
  if (freq < 1000000) display.print("kHz");
  if (freq >= 1000000) display.print("MHz");
  display.setCursor(110, 33);
  if (interfreq == 0) display.print("VFO");
  if (interfreq != 0) display.print("L O");
  display.setCursor(91, 28);
  if (!sts) display.print("RX"); if (!sts) interfreq = IF;
  if (sts) display.print("TX"); if (sts) interfreq = 0;
  bandlist(); drawbargraph();
  display.display();
}

void bandlist() {
  display.setTextSize(2);
  display.setCursor(0, 25);
  if (count == 1) display.print("GEN"); if (count == 2) display.print("MW"); if (count == 3) display.print("160m"); if (count == 4) display.print("80m");
  if (count == 5) display.print("60m"); if (count == 6) display.print("49m"); if (count == 7) display.print("40m"); if (count == 8) display.print("31m");
  if (count == 9) display.print("25m"); if (count == 10) display.print("22m"); if (count == 11) display.print("20m"); if (count == 12) display.print("19m");
  if (count == 13) display.print("16m"); if (count == 14) display.print("13m"); if (count == 15) display.print("11m"); if (count == 16) display.print("10m");
  if (count == 17) display.print("6m"); if (count == 18) display.print("WFM"); if (count == 19) display.print("AIR"); if (count == 20) display.print("2m");
  if (count == 21) display.print("1m");
  if (count == 1) interfreq = 0; else if (!sts) interfreq = IF;
}

void sgnalread() {
  smval = analogRead(adc); x = map(smval, 0, S_GAIN, 1, 14); if (x > 14) x = 14;
}

void drawbargraph() {
  byte y = map(n, 1, 42, 1, 14);
  display.setTextSize(1);

  //Pointer
  display.setCursor(0, 48); display.print("TU");
  switch (y) {
    case 1: display.fillRect(15, 48, 2, 6, WHITE); break;
    case 2: display.fillRect(20, 48, 2, 6, WHITE); break;
    case 3: display.fillRect(25, 48, 2, 6, WHITE); break;
    case 4: display.fillRect(30, 48, 2, 6, WHITE); break;
    case 5: display.fillRect(35, 48, 2, 6, WHITE); break;
    case 6: display.fillRect(40, 48, 2, 6, WHITE); break;
    case 7: display.fillRect(45, 48, 2, 6, WHITE); break;
    case 8: display.fillRect(50, 48, 2, 6, WHITE); break;
    case 9: display.fillRect(55, 48, 2, 6, WHITE); break;
    case 10: display.fillRect(60, 48, 2, 6, WHITE); break;
    case 11: display.fillRect(65, 48, 2, 6, WHITE); break;
    case 12: display.fillRect(70, 48, 2, 6, WHITE); break;
    case 13: display.fillRect(75, 48, 2, 6, WHITE); break;
    case 14: display.fillRect(80, 48, 2, 6, WHITE); break;
  }

  //Bargraph
  display.setCursor(0, 57); display.print("SM");
  switch (x) {
    case 14: display.fillRect(80, 58, 2, 6, WHITE);
    case 13: display.fillRect(75, 58, 2, 6, WHITE);
    case 12: display.fillRect(70, 58, 2, 6, WHITE);
    case 11: display.fillRect(65, 58, 2, 6, WHITE);
    case 10: display.fillRect(60, 58, 2, 6, WHITE);
    case 9: display.fillRect(55, 58, 2, 6, WHITE);
    case 8: display.fillRect(50, 58, 2, 6, WHITE);
    case 7: display.fillRect(45, 58, 2, 6, WHITE);
    case 6: display.fillRect(40, 58, 2, 6, WHITE);
    case 5: display.fillRect(35, 58, 2, 6, WHITE);
    case 4: display.fillRect(30, 58, 2, 6, WHITE);
    case 3: display.fillRect(25, 58, 2, 6, WHITE);
    case 2: display.fillRect(20, 58, 2, 6, WHITE);
    case 1: display.fillRect(15, 58, 2, 6, WHITE);
  }
}

void statup_text() {
  display.setTextSize(1); display.setCursor(13, 18);
  display.print("Si5351 VFO/RF GEN");
  display.setCursor(6, 40);
  display.print("JCR RADIO - Ver 2.0");
  display.display(); delay(2000);
}

Schematics

Schematics wiring
Wiring the circuit
V2 jqtbeiigrc

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