Creating a sine wave with a DAC and feeding it back

Question

I want to produce a digital sine wave, send it to DAC0, and then receive it back as input on A0 and plot the graph. I am using an Arduino Due. I wrote the following code:

#define maxSamplesNum 120
#define Sample 50000000/maxSamplesNum  // sample for the 50Hz signal expressed in microseconds

static int Table[maxSamplesNum] =                        // lookup table  for sine wave table
  {
    0x7ff, 0x86a, 0x8d5, 0x93f, 0x9a9, 0xa11, 0xa78, 0xadd, 0xb40, 0xba1,
    0xbff, 0xc5a, 0xcb2, 0xd08, 0xd59, 0xda7, 0xdf1, 0xe36, 0xe77, 0xeb4,
    0xeec, 0xf1f, 0xf4d, 0xf77, 0xf9a, 0xfb9, 0xfd2, 0xfe5, 0xff3, 0xffc,
    0xfff, 0xffc, 0xff3, 0xfe5, 0xfd2, 0xfb9, 0xf9a, 0xf77, 0xf4d, 0xf1f,
    0xeec, 0xeb4, 0xe77, 0xe36, 0xdf1, 0xda7, 0xd59, 0xd08, 0xcb2, 0xc5a,
    0xbff, 0xba1, 0xb40, 0xadd, 0xa78, 0xa11, 0x9a9, 0x93f, 0x8d5, 0x86a,
    0x7ff, 0x794, 0x729, 0x6bf, 0x655, 0x5ed, 0x586, 0x521, 0x4be, 0x45d,
    0x3ff, 0x3a4, 0x34c, 0x2f6, 0x2a5, 0x257, 0x20d, 0x1c8, 0x187, 0x14a,
    0x112, 0xdf, 0xb1, 0x87, 0x64, 0x45, 0x2c, 0x19, 0xb, 0x2,
    0x0, 0x2, 0xb, 0x19, 0x2c, 0x45, 0x64, 0x87, 0xb1, 0xdf,
    0x112, 0x14a, 0x187, 0x1c8, 0x20d, 0x257, 0x2a5, 0x2f6, 0x34c, 0x3a4,
    0x3ff, 0x45d, 0x4be, 0x521, 0x586, 0x5ed, 0x655, 0x6bf, 0x729, 0x794
  };

int i = 0;
int sample;
int sensorPin = A0;
int sensorValue = 0;

void setup() {
  Serial.begin(9600);
  analogWriteResolution(12); // set the analog output resolution to 12 bit (4096 levels)
  analogReadResolution(12); // set the analog input resolution to 12 bit
}

void loop() {
  sample = 50;

  analogWrite(DAC0, Table[i]); // write the selected waveform on DAC0

  i++;
  if (i == maxSamplesNum)  // Reset the counter to repeat the wave
    i = 0;
  delayMicroseconds(sample); // Hold the sample value for the sample time
  sensorValue = analogRead(sensorPin);
}

I want to create a 3.3 V (P-P) sine wave but I don't how to set the amplitude in this wave.

Also I would like to redirect the sine wave output from DAC0 to the A0 Pin and plot the graph to check if generating the sine wave was successful. How do I plot the graph ?

I uploaded the program but there was no result. I tried to read data from A0, but there wasn't any output. What am I doing wrong?

Answer 1

I ran your code unmodified and plugged in an oscilloscope to look at DAC0 (looks an OK sine wave) and A0 (looks flatline). Hope this helps.