Project tutorial
Arduino DDS VFO with AD9850 Module

Arduino DDS VFO with AD9850 Module © GPL3+

Inexpensive to build but a very useful tool for every electronics laboratory.

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  • 1 comment
  • 4 respects

Components and supplies

Necessary tools and machines

09507 01
Soldering iron (generic)

Apps and online services

About this project

Code

codeArduino
/*
Main code by Richard Visokey AD7C - www.ad7c.com
Revision 2.0 - November 6th, 2013
*/

// Include the library code
#include <LiquidCrystal.h>
#include <rotary.h>
#include <EEPROM.h>

//Setup some items
#define W_CLK 8   // Pin 8 - connect to AD9850 module word load clock pin (CLK)
#define FQ_UD 9   // Pin 9 - connect to freq update pin (FQ)
#define DATA 10   // Pin 10 - connect to serial data load pin (DATA)
#define RESET 11  // Pin 11 - connect to reset pin (RST) 
#define pulseHigh(pin) {digitalWrite(pin, HIGH); digitalWrite(pin, LOW); }
Rotary r = Rotary(2,3); // sets the pins the rotary encoder uses.  Must be interrupt pins.
LiquidCrystal lcd(12, 13, 7, 6, 5, 4); // I used an odd pin combination because I need pin 2 and 3 for the interrupts.
int_fast32_t rx=7150000; // Base (starting) frequency of VFO.  This only loads once.  To force load again see ForceFreq variable below.
int_fast32_t rx2=1; // variable to hold the updated frequency
int_fast32_t increment = 10; // starting VFO update increment in HZ.
int_fast32_t iffreq = 4192000; // Intermedite Frequency - Amount to subtract (-) from base frequency. ********************************************
int buttonstate = 0;
int buttonstate2 = 0;
int GoIF = 1;
String hertz = "10 Hz";
int  hertzPosition = 5;
byte ones,tens,hundreds,thousands,tenthousands,hundredthousands,millions ;  //Placeholders
String freq; // string to hold the frequency
int_fast32_t timepassed = millis(); // int to hold the arduino miilis since startup
int memstatus = 1;  // value to notify if memory is current or old. 0=old, 1=current.


int ForceFreq = 1;  // Change this to 0 after you upload and run a working sketch to activate the EEPROM memory.  YOU MUST PUT THIS BACK TO 0 AND UPLOAD THE SKETCH AGAIN AFTER STARTING FREQUENCY IS SET!



void setup() {
  pinMode(A0,INPUT); // Connect to a button that goes to GND on push
  pinMode(A5,INPUT); // IF sense **********************************************
  digitalWrite(A0,HIGH);
  digitalWrite(A5,HIGH);
  lcd.begin(16, 2);
  PCICR |= (1 << PCIE2);
  PCMSK2 |= (1 << PCINT18) | (1 << PCINT19);
  sei();
  pinMode(FQ_UD, OUTPUT);
  pinMode(W_CLK, OUTPUT);
  pinMode(DATA, OUTPUT);
  pinMode(RESET, OUTPUT); 
  pulseHigh(RESET);
  pulseHigh(W_CLK);
  pulseHigh(FQ_UD);  // this pulse enables serial mode on the AD9850 - Datasheet page 12.
  lcd.setCursor(hertzPosition,1);    
  lcd.print(hertz); 
 
  // Load the stored frequency  
  if (ForceFreq == 0) {
    freq = String(EEPROM.read(0))+String(EEPROM.read(1))+String(EEPROM.read(2))+String(EEPROM.read(3))+String(EEPROM.read(4))+String(EEPROM.read(5))+String(EEPROM.read(6));
    rx = freq.toInt();  
  }
}

void loop() {    
  // Update the display and frequency if the new Freq NEQ the old Freq  
  if (rx != rx2){   
        showFreq();
        sendFrequency(rx);
        rx2 = rx;        
      } 
        
  // Rotate through the rate of tuning as you hold down the button
  buttonstate = digitalRead(A0);
  if(buttonstate == LOW) {
        setincrement();        
    };
    
  // Check for PIN low to drive IF offset Freq
  buttonstate = digitalRead(A5);  
    if (buttonstate != buttonstate2){
        if(buttonstate == LOW) {       
              lcd.setCursor(15,1);
              lcd.print("."); 
              GoIF = 0; 
              buttonstate2 = buttonstate; 
              sendFrequency(rx);         
          }
        else{
            lcd.setCursor(15,1);
            lcd.print(" ");
            GoIF = 1;
            buttonstate2 = buttonstate;
            sendFrequency(rx);       
          };
    };
    
    // Write the frequency to memory if not stored and 2 seconds have passed since the last frequency change.
    if(memstatus == 0){   
      if(timepassed+2000 < millis()){
        storeMEM();
        }
      }  
    
 }
 
 
// Interrupt routine to catch the rotary encoder
ISR(PCINT2_vect) {
  unsigned char result = r.process();
  if (result) {    
    if (result == DIR_CW){rx=rx+increment;}
    else {rx=rx-increment;};       
      if (rx >=30000000){rx=rx2;}; // UPPER VFO LIMIT
      if (rx <=1000000){rx=rx2;}; // LOWER VFO LIMIT
  } 
}

// frequency calc from datasheet page 8 = <sys clock> * <frequency tuning word>/2^32
void sendFrequency(double frequency) {  
  if (GoIF == 1){frequency=frequency-iffreq;}; //If pin = low, subtract the IF frequency.
  int32_t freq = frequency * 4294967295/125000000;  // note 125 MHz clock on 9850.  You can make 'slight' tuning variations here by adjusting the clock frequency.
  for (int b=0; b<4; b++, freq>>=8) {
    tfr_byte(freq & 0xFF);
  }
  tfr_byte(0x000);   // Final control byte, all 0 for 9850 chip
  pulseHigh(FQ_UD);  // Done!  Should see output
}
// transfers a byte, a bit at a time, LSB first to the 9850 via serial DATA line
void tfr_byte(byte data)
{
  for (int i=0; i<8; i++, data>>=1) {
    digitalWrite(DATA, data & 0x01);
    pulseHigh(W_CLK);   //after each bit sent, CLK is pulsed high
  }
}

void setincrement(){
  if(increment == 10){increment = 50; hertz = "50 Hz"; hertzPosition=5;}
  else if (increment == 50){increment = 100;  hertz = "100 Hz"; hertzPosition=4;}
  else if (increment == 100){increment = 500; hertz="500 Hz"; hertzPosition=4;}
  else if (increment == 500){increment = 1000; hertz="1 Khz"; hertzPosition=6;}
  else if (increment == 1000){increment = 2500; hertz="2.5 Khz"; hertzPosition=4;}
  else if (increment == 2500){increment = 5000; hertz="5 Khz"; hertzPosition=6;}
  else if (increment == 5000){increment = 10000; hertz="10 Khz"; hertzPosition=5;}
  else if (increment == 10000){increment = 100000; hertz="100 Khz"; hertzPosition=4;}
  else if (increment == 100000){increment = 1000000; hertz="1 Mhz"; hertzPosition=6;}  
  else{increment = 10; hertz = "10 Hz"; hertzPosition=5;};  
   lcd.setCursor(0,1);
   lcd.print("                ");
   lcd.setCursor(hertzPosition,1); 
   lcd.print(hertz); 
   delay(250); // Adjust this delay to speed up/slow down the button menu scroll speed.
};

void showFreq(){
    millions = int(rx/1000000);
    hundredthousands = ((rx/100000)%10);
    tenthousands = ((rx/10000)%10);
    thousands = ((rx/1000)%10);
    hundreds = ((rx/100)%10);
    tens = ((rx/10)%10);
    ones = ((rx/1)%10);
    lcd.setCursor(0,0);
    lcd.print("                ");
   if (millions > 9){lcd.setCursor(1,0);}
   else{lcd.setCursor(2,0);}
    lcd.print(millions);
    lcd.print(".");
    lcd.print(hundredthousands);
    lcd.print(tenthousands);
    lcd.print(thousands);
    lcd.print(".");
    lcd.print(hundreds);
    lcd.print(tens);
    lcd.print(ones);
    lcd.print(" Mhz  ");
    timepassed = millis();
    memstatus = 0; // Trigger memory write
};

void storeMEM(){
  //Write each frequency section to a EPROM slot.  Yes, it's cheating but it works!
   EEPROM.write(0,millions);
   EEPROM.write(1,hundredthousands);
   EEPROM.write(2,tenthousands);
   EEPROM.write(3,thousands);
   EEPROM.write(4,hundreds);       
   EEPROM.write(5,tens);
   EEPROM.write(6,ones);   
   memstatus = 1;  // Let program know memory has been written
};

Schematics

ad980_dds_vfo_schematic_H5pNI85vTM.gif
Ad980 dds vfo schematic h5pni85vtm

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