​Complete Guide to MCP4725 DAC Module 12-bit DAC Development

				
					#include <Wire.h>
#include <Adafruit_MCP4725.h>

Adafruit_MCP4725 dac;

class NormalECG {
private:
  const float targetFreq;  // The frequency of an electrocardiogram (for example, heart rate)
  const int samples;       // Number of sampling points per cycle
  unsigned long startTime; // starting time
  int lastSample;          // The last sampling point
  float scaleFactor;       // The scaling factor of the waveform

public:
  NormalECG(float freq, int smp) : targetFreq(freq), samples(smp) {
    startTime = micros();
    lastSample = 0;
    scaleFactor = 2047.0;  // Used to adjust the amplitude of the waveform
  }

  void update() {
    unsigned long currentTime = micros();
    unsigned long period_us = 1000000 / targetFreq;  // Electrocardiogram cycle (microseconds)
    unsigned long elapsed = currentTime - startTime;
    
    // Precisely calculate the current sampling point
    int currentSample = (elapsed * samples / period_us) % samples;
    
    // Update only when necessary
    if (currentSample != lastSample) {
      // Generate simulated electrocardiogram waveforms by combining different sine waves
      float angle = 2.0 * PI * currentSample / samples;
      
      // P wave: Minor fluctuations
      float ecgValue = 0.4 * sin(angle);  
      
      // QRS complex wave: Rapid peak
      ecgValue += 1.0 * sin(3 * angle);
      
      // T wave: A relatively gentle fluctuation
      ecgValue += 0.5 * sin(5 * angle);

      // Scale the generated waveform to make it suitable for the output range of the DAC.
      int dacValue = (int)(ecgValue * scaleFactor + 2048);  // Adjust to the center at 2048
      dacValue = constrain(dacValue, 0, 4095); // Ensure that the output value is within the valid range.
      
      // Output to MCP4725 DAC
      dac.setVoltage(dacValue, false);
      lastSample = currentSample;
    }

    // Prevent overflow of micros()
    if (elapsed > 60000000) {  // Reset in 60 seconds
      startTime = currentTime;
    }
  }
};

// Create a simulation of an electrocardiogram waveform generator, assuming one heartbeat per second.
NormalECG ecgGen(1.0, 500);  // 1 Hz heart rate, 500 sampling points

void setup() {
  Serial.begin(9600);
  Wire.begin();

  if (!dac.begin(0x60)) {
    if (!dac.begin(0x62)) {
      Serial.println("MCP4725 not found!");
      while(1);
    }
  }
  
  Serial.println("The simulated electrocardiogram generator is ready.");
}

void loop() {
  ecgGen.update();  // Continuously update the simulated electrocardiogram waveform.
}