bitx20 v3 build – vfo

I’ve got the main bitx board built enough to test, so now I need the bfo and vfo. I put together an arduino nano, an si5351 breakout board, and a small oled display on a breadboard. I modified some of the vfo code I’ve used before and soldered clk0 and clk2 to the bitx with some rg174 coax.

/images/bitx20_vf0_web-1.jpg

/images/bitx20_vfo_full_web.jpg

/images/bitx20_vfo_waveform_web.jpg

I don’t have a 20 meter antenna up yet, so I can only test with a signal generator. The vfo (or the signal generator) is a little off, but the receiver seems to be working okay. I get a clear tone by holding the signal generator lead near the board.

Here is the code so far:

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#include <Rotary.h>
#include <si5351.h>
#include <Wire.h>
#include <Adafruit_SSD1306.h>


#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);

#define F_MIN        100000000UL               
#define F_MAX        5000000000UL

#define ENCODER_A    2                      
#define ENCODER_B    3                      
#define ENCODER_BTN  11

#define SWITCH_PIN 12
int switchstate = 0; 

Si5351 si5351;
Rotary r = Rotary(ENCODER_A, ENCODER_B);
volatile int32_t LSB = 999950000ULL;
volatile int32_t USB = 1000150000ULL;
volatile int32_t bfo = 1000150000ULL; //start in usb
//These USB/LSB frequencies are added to or subtracted from the vfo frequency in the "Loop()"
volatile int32_t vfo = 1404700000ULL / SI5351_FREQ_MULT; //start freq - change to suit
volatile uint32_t radix = 100;	//start step size - change to suit
boolean changed_f = 0;
String tbfo = "";


/**************************************/
/* Interrupt service routine for      */
/* encoder frequency change           */
/**************************************/
ISR(PCINT2_vect) {
  unsigned char result = r.process();
  if (result == DIR_CW)
    set_frequency(1);
  else if (result == DIR_CCW)
    set_frequency(-1);
}

/**************************************/
/* Change the frequency               */
/* dir = 1    Increment               */
/* dir = -1   Decrement               */
/**************************************/
void set_frequency(short dir)
{
  if (dir == 1)
    vfo += radix;
  if (dir == -1)
    vfo -= radix;

  changed_f = 1;
}

/**************************************/
/* Read the button with debouncing    */
/**************************************/
boolean get_button()
{
  if (!digitalRead(ENCODER_BTN))
  {
    delay(20);
    if (!digitalRead(ENCODER_BTN))
    {
      while (!digitalRead(ENCODER_BTN));
      return 1;
    }
  }
  return 0;
}

/**************************************/
/* Displays the frequency             */
/**************************************/
void display_frequency()
{
  uint16_t f, g;

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.print("BITX20            ");
  display.println(tbfo);
 
 
  switch (radix)
  {
    case 1:
      display.println("                  _");
      break;
    case 10:
      display.println("                _");
      break;
    case 100:
      display.println("              _");
      break;
    case 1000:
      display.println("          _");
      break;
    case 10000:
      display.println("        _");
      break;
    case 100000:
      display.println("      _");
      break;
  }

    display.setTextSize(2);
  
  f = vfo / 1000000;   //variable is now vfo instead of 'frequency'
  if (f < 10)
    display.print(' ');
  display.print(f);
  display.print('.');
  f = (vfo % 1000000) / 1000;
  if (f < 100)
    display.print('0');
  if (f < 10)
    display.print('0');
  display.print(f);
  display.print('.');
  f = vfo % 1000;
  if (f < 100)
    display.print('0');
  if (f < 10)
    display.print('0');
  display.print(f);

  
  display.display();
  display.clearDisplay();
}


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

  pinMode(SWITCH_PIN, INPUT_PULLUP);
  
  Serial.begin(19200);

  Wire.begin();

  si5351.set_correction(140); //**mine. There is a calibration sketch in File/Examples/si5351Arduino-Jason
  //where you can determine the correction by using the serial monitor.

  //initialize the Si5351
  si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0); //If you're using a 27Mhz crystal, put in 27000000 instead of 0
  // 0 is the default crystal frequency of 25Mhz.

  si5351.set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
  // Set CLK0 to output the starting "vfo" frequency as set above by vfo = ?

  //Serial.println((long)((vfo * SI5351_FREQ_MULT) + bfo) * -1);
  si5351.set_freq(((vfo * SI5351_FREQ_MULT) - bfo), SI5351_PLL_FIXED, SI5351_CLK0);
  volatile uint32_t vfoT = abs((vfo * SI5351_FREQ_MULT) - bfo);
  tbfo = "USB";
  // Set CLK2 to output bfo frequency
  si5351.set_freq( bfo, 0, SI5351_CLK2);
  //si5351.drive_strength(SI5351_CLK0,SI5351_DRIVE_2MA); //you can set this to 2MA, 4MA, 6MA or 8MA
  //si5351.drive_strength(SI5351_CLK1,SI5351_DRIVE_2MA); //be careful though - measure into 50ohms
  //si5351.drive_strength(SI5351_CLK2,SI5351_DRIVE_2MA); //

  Splash();

  pinMode(ENCODER_BTN, INPUT_PULLUP);
  PCICR |= (1 << PCIE2);           // Enable pin change interrupt for the encoder
  PCMSK2 |= (1 << PCINT18) | (1 << PCINT19);
  sei();
  display_frequency();  // Update the display
}


void loop()
{
  
  // Update the display if the frequency has been changed
  if (changed_f)
  {
    display_frequency();


    //Serial.println((long)((vfo * SI5351_FREQ_MULT) + bfo) * -1);
    si5351.set_freq(((vfo * SI5351_FREQ_MULT) - bfo), SI5351_PLL_FIXED, SI5351_CLK0);
    //you can also subtract the bfo to suit your needs
    //si5351.set_freq((vfo * SI5351_FREQ_MULT) - bfo  , SI5351_PLL_FIXED, SI5351_CLK0);

    switchstate = digitalRead(SWITCH_PIN);
    if (switchstate == HIGH) {
      //USB
      bfo = USB;
      tbfo = "USB";
      si5351.set_freq( bfo, 0, SI5351_CLK2);
      Serial.println("We've switched from LSB to USB");
    } else {
      // LSB
      bfo = LSB;
      tbfo = "LSB";
      si5351.set_freq( bfo, 0, SI5351_CLK2);
      Serial.println("We've switched from USB to LSB");
    
    }

    changed_f = 0;
  }

  // Button press changes the frequency change step for 1 Hz steps
  if (get_button())
  {
    switch (radix)
    {
      case 1:
        radix = 10;
        break;
      case 10:
        radix = 100;
        break;
      case 100:
        radix = 1000;
        break;
      case 1000:
        radix = 10000;
        break;
      case 10000:
        radix = 100000;
        break;
      case 100000:
        radix = 1;
        break;
    }
    display_frequency();
  }

}

void Splash()
{
  display.clearDisplay();
  display.setTextSize(4);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println("BITX");
  display.display();
  delay(4000);
  display.clearDisplay();
}
```