From 21521008734c807d69c3ab4eac4dc559d22c76fd Mon Sep 17 00:00:00 2001
From: Stephen Olesen <slepp@slepp.ca>
Date: Thu, 2 Jul 2015 18:04:12 -0600
Subject: [PATCH] Change amplitude scaling. Go back to refclk for ICR1. Added
 phase changes.

---
 DDS.cpp | 21 ++++++++++++++++++---
 DDS.h   | 12 +++++++++---
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/DDS.cpp b/DDS.cpp
index 8d0c02b..b4cf79e 100644
--- a/DDS.cpp
+++ b/DDS.cpp
@@ -42,8 +42,8 @@ void DDS::start() {
   // clock as the DDS.
   TCCR1B = _BV(CS11) | _BV(WGM13) | _BV(WGM12);
   TCCR1A = 0;
-  //ICR1 = ((F_CPU / 8) / refclk) - 1;
-  ICR1 = ((F_CPU / 8) / 9600) - 1;
+  ICR1 = ((F_CPU / 8) / refclk) - 1;
+  //ICR1 = ((F_CPU / 8) / 9600) - 1;
 
   // Configure the ADC here to automatically run and be triggered off Timer1
   ADMUX = _BV(REFS0) | _BV(ADLAR) | 0; // Channel 0, shift result left (ADCH used)
@@ -77,8 +77,21 @@ void DDS::setFrequency(unsigned short freq) {
   }
 }
 
+// Degrees should be between -360 and +360 (others don't make much sense)
+void DDS::setPhaseDeg(int16_t degrees) {
+  accumulator = degrees * (pow(2,ACCUMULATOR_BITS)/360.0);
+}
+void DDS::changePhaseDeg(int16_t degrees) {
+  accumulator += degrees * (pow(2,ACCUMULATOR_BITS)/360.0);
+}
+
 // TODO: Clean this up a bit..
 void DDS::clockTick() {
+/*  if(running) {
+    accumulator += stepRate;
+    OCR2A = getDutyCycle();
+  }
+  return;*/
   if(running) {
     accumulator += stepRate;
     if(timeLimited && tickDuration == 0) {
@@ -129,5 +142,7 @@ uint8_t DDS::getDutyCycle() {
   phAng = (accumulator >> ACCUMULATOR_BIT_SHIFT);
   uint8_t position = pgm_read_byte_near(ddsSineTable + phAng)>>(8-COMPARATOR_BITS);
   // Apply scaling and return
-  return position >> amplitude;
+  uint16_t scaled = position;
+  scaled *= amplitude;
+  return scaled>>8;
 }
diff --git a/DDS.h b/DDS.h
index 54199a4..e18f1e9 100644
--- a/DDS.h
+++ b/DDS.h
@@ -42,7 +42,7 @@
 // This is how often we'll perform a phase advance, as well as ADC sampling
 // rate. The higher this value, the smoother the output wave will be, at the
 // expense of CPU time. It maxes out around 62000 (TBD)
-#define DDS_REFCLK_DEFAULT     9600
+#define DDS_REFCLK_DEFAULT     38400
 // As each Arduino crystal is a little different, this can be fine tuned to
 // provide more accurate frequencies. Adjustments in the range of hundreds
 // is a good start.
@@ -193,10 +193,16 @@ public:
   // frequency supported will fit in a short.
   void setFrequency(unsigned short freq);
   
+  // Handle phase shifts
+  void setPhaseDeg(int16_t degrees);
+  void changePhaseDeg(int16_t degrees);
+  
   // Adjustable reference clock. This shoud be done before the timers are
   // started, or they will need to be restarted. Frequencies will need to
   // be set again to use the new clock.
-  void setReferenceClock(unsigned long ref);
+  void setReferenceClock(unsigned long ref) {
+    refclk = ref;
+  }
   unsigned long getReferenceClock() {
     return refclk;
   }
@@ -206,7 +212,7 @@ public:
   // Set a scaling factor. To keep things quick, this is a power of 2 value.
   // Set it with 0 for lowest (which will be off), 8 is highest.
   void setAmplitude(unsigned char amp) {
-    amplitude = 8 - amp;
+    amplitude = amp;
   }
   
   // This is the function called by the ADC_vect ISR to produce the tones