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(); } } |
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.
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