I am frustrated!

waveforms/waveforms.ino

@@ -10,21 +10,39 @@ 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
+const byte nclk = 200; // a guess
+long int freq; //frequency in Hz
 long unsigned int phase;
 long unsigned int phase_inc;
 
 void setup() {
-  //TIMSK0 &= ~_BV(TOIE0); // disable timer0 overflow interrupt
- 
-  //Wire.setClock(1400000L); // wooooo
+
+//   // Set a timer interrupt for the phase accumulation
+  cli();//stop interrupts
+
+
+//set timer1 interrupt at 44Hz
+  TCCR1A = 0;// set entire TCCR1A register to 0
+  TCCR1B = 0;// same for TCCR1B
+  TCNT1  = 0;//initialize counter value to 0
+  // set compare match register for 1hz increments
+  OCR1A = 500; // = (16 * 10**6) / (44000) - 1
+  // turn on CTC mode
+  TCCR1B |= (1 << WGM12);
+  // Set CS10 and CS12 bits for 1024 prescaler
+  TCCR1B |= (1 << CS12) | (1 << CS10);  
+  // enable timer compare interrupt
+  TIMSK1 |= (1 << OCIE1A);
+
+  sei();//allow interrupts
+
   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) {
@@ -34,11 +52,11 @@ void setup() {
     Serial.println("Adafruit MCP4728 initialised");
   }
 
+  Wire.setClock(3400000L);
 
-  freq=660;
+  freq=6600000;
   phase=0;
   calc_phase_inc();
-  //phase_inc = 1;
 
   setwave();
 }
@@ -52,10 +70,10 @@ void setwave(){
     int val=0;
 
     //saw
-    val = dacmax * isamp / nsamp;
+    //val = dacmax * isamp / nsamp;
     //val = ( isamp < nsamp / 2 ) ? 0 : dacmax - 1;
         //sine
-    //val=(sin(phi)+1.0)*dacmax/2;
+    val=(sin(phi)+1.0)*dacmax/2;
     //val=((sin(phi)+0.333*sin(3*phi))/0.943+1)*dacmax/2;
 
     val=max(val,0);
@@ -65,19 +83,21 @@ void setwave(){
 }
 
 
-//calculate the phase increment. 2^32/16E6=268.435456
+//calculate the phase increment. 
 void calc_phase_inc(){
   phase_inc=0.268435456*nclk*freq;
-  Serial.println("phase inc");
-  Serial.println(phase_inc);
 }
 
-//regular running: generate waves
+
+ISR(TIMER1_COMPA_vect){// timer1 interrupt
+   phase += phase_inc;
+}
+
+
+//regular running: 
 void loop() {
-  //phase+=900;
-  //int redphase = phase >> 24;
-  phase += analogRead(A0);
-  int redphase = phase % nsamp;
-  mcp.fastWrite(waveform[redphase] << 4, 0, 0,   0);
+  int redphase = phase >> 24;
+  mcp.fastWrite(waveform[redphase] << 4, 0, 0, 0);
+  //Serial.println(redphase);
 }