AD9850 DDS Signal Generator Module

// Canonical beginner example for the AD9850 DDS Signal Generator Module
// This sketch sends a serial programming word to set an output frequency.
// Wiring used:
//   D8  -> W_CLK
//   D9  -> FU_UD
//   D10 -> DATA
//   D11 -> RESET
//   5V  -> VCC
//   GND -> GND

const int PIN_W_CLK = 8;
const int PIN_FQ_UD = 9;   // Module label is FU_UD
const int PIN_DATA  = 10;
const int PIN_RESET = 11;

const unsigned long CLOCK_HZ = 125000000UL; // AD9850 reference clock on the module

void pulsePin(int pin) {
  digitalWrite(pin, HIGH);
  delayMicroseconds(1);
  digitalWrite(pin, LOW);
  delayMicroseconds(1);
}

void ad9850Reset() {
  digitalWrite(PIN_RESET, HIGH);
  delayMicroseconds(1);
  digitalWrite(PIN_RESET, LOW);
  delayMicroseconds(1);
  pulsePin(PIN_W_CLK);
  pulsePin(PIN_FQ_UD);
}

void ad9850SetFrequency(double frequencyHz) {
  // DDS tuning word = frequency * 2^32 / clock
  uint32_t tuningWord = (uint32_t)((frequencyHz * 4294967296.0) / (double)CLOCK_HZ);

  // Send 32-bit tuning word, LSB first
  for (int i = 0; i < 32; i++) {
    digitalWrite(PIN_DATA, (tuningWord >> i) & 0x01);
    pulsePin(PIN_W_CLK);
  }

  // Control byte: 0x00 for normal 28-bit frequency mode
  for (int i = 0; i < 8; i++) {
    digitalWrite(PIN_DATA, LOW);
    pulsePin(PIN_W_CLK);
  }

  // Latch the new frequency
  pulsePin(PIN_FQ_UD);
}

void setup() {
  pinMode(PIN_W_CLK, OUTPUT);
  pinMode(PIN_FQ_UD, OUTPUT);
  pinMode(PIN_DATA, OUTPUT);
  pinMode(PIN_RESET, OUTPUT);

  digitalWrite(PIN_W_CLK, LOW);
  digitalWrite(PIN_FQ_UD, LOW);
  digitalWrite(PIN_DATA, LOW);
  digitalWrite(PIN_RESET, LOW);

  Serial.begin(9600);
  while (!Serial) {
    ;
  }

  Serial.println(F("AD9850 DDS generator starting..."));
  ad9850Reset();

  // Set a beginner-friendly test frequency
  ad9850SetFrequency(1000000.0); // 1 MHz
  Serial.println(F("Output frequency set to 1 MHz"));
}

void loop() {
  // Nothing to do here for the canonical example.
  delay(1000);
}