I added an arduino/SI5351 vfo that I had previously made for a dc receiver to my new bitx40 module. I tweaked the arduino code to add the offset, and added a low pass filter to the output of the SI5351. On the bitx board, I desoldered a leg of the L4 coil and plugged the output of the SI5351 to the DDS pins and it worked perfectly.
Here is the code that I used for the vfo. It still needs some cleanup and I plan to add a few more features, but it is enough to get the vfo working. It is based on code from Jason Mildrum, NT7S, Przemek Sadowski, SQ9NJE, and Tom Hall, AK2B.
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#include <Rotary.h>
#include <si5351.h>
#include <Wire.h>
#include <LiquidCrystal.h>
#define F_MIN 100000000UL // Lower frequency limit
#define F_MAX 5000000000UL
#define ENCODER_A 2 // Encoder pin A
#define ENCODER_B 3 // Encoder pin B
#define ENCODER_BTN 11
#define LCD_RS 5
#define LCD_E 6
#define LCD_D4 7
#define LCD_D5 8
#define LCD_D6 9
#define LCD_D7 10
LiquidCrystal lcd(LCD_RS, LCD_E, LCD_D4, LCD_D5, LCD_D6, LCD_D7); // LCD - pin assignement in
Si5351 si5351;
Rotary r = Rotary(ENCODER_A, ENCODER_B);
volatile int32_t LSB = -1199950000ULL;
volatile int32_t USB = -1200150000ULL;
volatile int32_t bfo = -1200150000ULL; //start in usb
//These USB/LSB frequencies are added to or subtracted from the vfo frequency in the "Loop()"
//In this example my start frequency will be 14.20000 plus 9.001500 or clk0 = 23.2015Mhz
volatile int32_t vfo = 700000000ULL / 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 = "";
//------------------------------- Set Optional Features here --------------------------------------
//Remove comment (//) from the option you want to use. Pick only one
#define IF_Offset //Output is the display plus or minus the bfo frequency
//#define Direct_conversion //What you see on display is what you get
//#define FreqX4 //output is four times the display frequency
//--------------------------------------------------------------------------------------------------
/**************************************/
/* 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;
lcd.setCursor(3, 0);
f = vfo / 1000000; //variable is now vfo instead of 'frequency'
if (f < 10)
lcd.print(' ');
lcd.print(f);
lcd.print('.');
f = (vfo % 1000000) / 1000;
if (f < 100)
lcd.print('0');
if (f < 10)
lcd.print('0');
lcd.print(f);
lcd.print('.');
f = vfo % 1000;
if (f < 100)
lcd.print('0');
if (f < 10)
lcd.print('0');
lcd.print(f);
lcd.print("Hz");
lcd.setCursor(0, 1);
lcd.print(tbfo);
//Serial.println(vfo + bfo);
//Serial.println(tbfo);
}
/**************************************/
/* Displays the frequency change step */
/**************************************/
void display_radix()
{
lcd.setCursor(9, 1);
switch (radix)
{
case 1:
lcd.print(" 1");
break;
case 10:
lcd.print(" 10");
break;
case 100:
lcd.print(" 100");
break;
case 1000:
lcd.print(" 1k");
break;
case 10000:
lcd.print(" 10k");
break;
case 100000:
//lcd.setCursor(10, 1);
lcd.print(" 100k");
break;
//case 1000000:
//lcd.setCursor(9, 1);
//lcd.print("1000k"); //1MHz increments
//break;
}
lcd.print("Hz");
}
void setup()
{
Serial.begin(19200);
lcd.begin(16, 2); // Initialize and clear the LCD
lcd.clear();
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 = ?
#ifdef IF_Offset
//Serial.println((long)((vfo * SI5351_FREQ_MULT) + bfo) * -1);
si5351.set_freq(((vfo * SI5351_FREQ_MULT) + bfo) * -1, 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); //
#endif
#ifdef Direct_conversion
si5351.set_freq((vfo * SI5351_FREQ_MULT), SI5351_PLL_FIXED, SI5351_CLK0);
#endif
#ifdef FreqX4
si5351.set_freq((vfo * SI5351_FREQ_MULT) * 4, SI5351_PLL_FIXED, SI5351_CLK0);
#endif
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
display_radix();
}
void loop()
{
// Update the display if the frequency has been changed
if (changed_f)
{
display_frequency();
#ifdef IF_Offset
//Serial.println((long)((vfo * SI5351_FREQ_MULT) + bfo) * -1);
si5351.set_freq(((vfo * SI5351_FREQ_MULT) + bfo) * -1, 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);
if (vfo >= 10000000ULL & tbfo != "USB")
{
bfo = USB;
tbfo = "USB";
si5351.set_freq( bfo, 0, SI5351_CLK2);
Serial.println("We've switched from LSB to USB");
}
else if (vfo < 10000000ULL & tbfo != "LSB")
{
bfo = LSB;
tbfo = "LSB";
si5351.set_freq( bfo, 0, SI5351_CLK2);
Serial.println("We've switched from USB to LSB");
}
#endif
#ifdef Direct_conversion
si5351.set_freq((vfo * SI5351_FREQ_MULT), SI5351_PLL_FIXED, SI5351_CLK0);
tbfo = "";
#endif
#ifdef FreqX4
si5351.set_freq((vfo * SI5351_FREQ_MULT) * 4, SI5351_PLL_FIXED, SI5351_CLK0);
tbfo = "";
#endif
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_radix();
}
}
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I found this circuit for an s meter and put it together on a small breadboard and used an old s/swr meter. It works okay, but it needs some work. I will probably add an swr bridge and use the same meter for both.
I still need to put it all together in a box. I looked at buying a bending brake and some sheet metal, but it was just too pricey for me at the moment. I did find an old rack mount firewall that has a built in 12v power supply that I may try to use if I can fit everything inside.
