Frequency generator AD9850

Thanks to various amateur radio enthusiasts for the code that makes this work.

I intend to expand it soon to include a tuning input (maybe push buttons, may be a knob...?) and a display of the frequency (that should be easy).

The module I used was just $3.5 on eBay!! And it is on sale from numerous suppliers in China - plus on in UK for £103!!! Clown.

Here's the setup



It is extremely easy to use the module, just four connections if in the serial communications mode set by pulsing FQ high.

This is the code

// DDS-9850 module programmer
 
#define W_CLK 8       // Pin 8  CLK
#define FQ_UD 9       // Pin 9  FQ
#define DATA 10       // Pin 10 DATA
#define RESET 11      // Pin 11 RST
 
#define pulseHigh(pin) {digitalWrite(pin, HIGH); digitalWrite(pin, LOW); }

void setup()
{
  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
}

void loop() 
{
  sendFrequency(14.23e6);  // freq MHz e6
  while(1);
}

 // transfers a byte, a bit at a time, LSB first 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
  }
}

 // frequency calc from datasheet page 8 =  * /2^32
void sendFrequency(double frequency) 
{
  int32_t freq = frequency * 4294967295/125000000;  // note 125 MHz clock on 9850
  
  for (int b=0; b<4; b++, freq>>=8) 
  {
    tfr_byte(freq & 0xFF);
  }
  tfr_byte(0x000);   // Final control byte, all 0
  pulseHigh(FQ_UD);
}

I have so far only tested it by generating the 14.230MHz signal you can see it is programmed for and listening on an experimental SSTV receiver that I have nearly completed - more news soon.