Waveforms

waveforms/waveforms.ino

@@ -0,0 +1,83 @@
+//waveform generator
+
+// hacked from https://www.instructables.com/Arduino-Waveform-Generator-1/
+
+#include <Adafruit_MCP4728.h>
+#include <Wire.h>
+
+Adafruit_MCP4728 mcp;
+
+#define nsamp 256
+#define dacmax 256
+
+const byte nclk=42; //number of clock cycles of the loop
+long int freq; //frequency in mHz
+long unsigned int phase;
+long unsigned int phase_inc;
+
+void setup() {
+  //TIMSK0 &= ~_BV(TOIE0); // disable timer0 overflow interrupt
+ 
+  //Wire.setClock(1400000L); // wooooo
+  Serial.begin(115200);
+  while (!Serial)
+    delay(10); // will pause Zero, Leonardo, etc until serial console opens
+
+
+  // Try to initialize!
+  if (!mcp.begin(0x64)) {
+    Serial.println("Failed to find MCP4728 chip");
+    while (1) {
+      delay(10);
+    }
+  } else {
+    Serial.println("Adafruit MCP4728 initialised");
+  }
+
+
+  freq=660;
+  phase=0;
+  calc_phase_inc();
+  //phase_inc = 1;
+
+  setwave();
+}
+
+const float pi=3.14159265;
+byte waveform[nsamp];
+void setwave(){
+  for (int isamp=0; isamp<nsamp; ++isamp){
+    float phip=(isamp+0.5)/nsamp;
+    float phi=2*pi*phip;
+    int val=0;
+
+    //saw
+    val = dacmax * isamp / nsamp;
+    //val = ( isamp < nsamp / 2 ) ? 0 : dacmax - 1;
+        //sine
+    //val=(sin(phi)+1.0)*dacmax/2;
+    //val=((sin(phi)+0.333*sin(3*phi))/0.943+1)*dacmax/2;
+
+    val=max(val,0);
+    val=min(val,dacmax-1);
+    waveform[isamp]=val;
+  }
+}
+
+
+//calculate the phase increment. 2^32/16E6=268.435456
+void calc_phase_inc(){
+  phase_inc=0.268435456*nclk*freq;
+  Serial.println("phase inc");
+  Serial.println(phase_inc);
+}
+
+//regular running: generate waves
+void loop() {
+  //phase+=900;
+  //int redphase = phase >> 24;
+  phase += analogRead(A0);
+  int redphase = phase % nsamp;
+  mcp.fastWrite(waveform[redphase] << 4, 0, 0,   0);
+}
+