Added Crystal Calibration sketch with simple Serial UI. Fixed ddsAccumulator_t type.

AFSK.cpp

@@ -121,7 +121,7 @@ bool AFSK::Encoder::start() {
   lastZero = 0;
   bitPosition = 0;
   bitClock = 0;
-  preamble = 0b11000; // 6.7ms each, 23 = 153ms
+  preamble = 0b110000; // 6.7ms each, 23 = 153ms
   done = false;
   hdlc = true;
   packet = 0x0; // No initial packet, find in the ISR

DDS.cpp

@@ -40,10 +40,18 @@ void DDS::start() {
   // Second, setup Timer1 to trigger the ADC interrupt
   // This lets us use decoding functions that run at the same reference
   // clock as the DDS.
-  TCCR1B = _BV(CS11) | _BV(WGM13) | _BV(WGM12);
+  // We use ICR1 as TOP and prescale by 8
+  TCCR1B = _BV(CS10) | _BV(WGM13) | _BV(WGM12);
   TCCR1A = 0;
-  ICR1 = ((F_CPU / 8) / refclk) - 1;
+  ICR1 = ((F_CPU / 1) / refclk) - 1;
-  //ICR1 = ((F_CPU / 8) / 9600) - 1;
+#ifdef DDS_DEBUG_SERIAL
+  Serial.print(F("DDS SysClk: "));
+  Serial.println(F_CPU/8);
+  Serial.print(F("DDS RefClk: "));
+  Serial.println(refclk, DEC);
+  Serial.print(F("DDS ICR1: "));
+  Serial.println(ICR1, DEC);
+#endif
 
   // 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)
@@ -56,6 +64,10 @@ void DDS::start() {
 
 void DDS::stop() {
   // TODO: Stop the timers.
+#ifndef DDS_USE_ONLY_TIMER2
+  TCCR1B = 0;
+#endif
+  TCCR2B = 0;
 }
 
 // Set our current sine wave frequency in Hz

DDS.h

@@ -18,10 +18,10 @@
 
 #ifdef SHORT_ACCUMULATOR
 #define ACCUMULATOR_BITS      16
-typedef int16_t ddsAccumulator_t;
+typedef uint16_t ddsAccumulator_t;
 #else
 #define ACCUMULATOR_BITS      32
-typedef int32_t ddsAccumulator_t;
+typedef uint32_t ddsAccumulator_t;
 #endif
 
 // If defined, the timer will idle at 50% duty cycle
@@ -60,6 +60,9 @@ typedef int32_t ddsAccumulator_t;
 #define DDS_REFCLK_DEFAULT     (62500/4)
 #endif
 
+// Output some of the calculations and information about the DDS over serial
+#define DDS_DEBUG_SERIAL
+
 // When defined, use the 1024 element sine lookup table. This improves phase
 // accuracy, at the cost of more flash and CPU requirements.
 // #define DDS_TABLE_LARGE

examples/Crystal-Calibration/Crystal-Calibration.ino

@@ -0,0 +1,152 @@
+#define DDS_REFCLK_DEFAULT 19200
+#define DDS_REFCLK_OFFSET  0
+#define DDS_DEBUG_SERIAL
+
+#include <HamShield.h>
+#include <Wire.h>
+
+HamShield radio;
+DDS dds;
+
+void setup() {
+  Serial.begin(9600);
+  Wire.begin();
+  radio.initialize();
+  radio.setVHF();
+  radio.setRfPower(0);
+  radio.setFrequency(145050);
+  
+  pinMode(2, OUTPUT);
+  pinMode(3, OUTPUT);
+  pinMode(11, INPUT);
+  
+  dds.start();
+  dds.setFrequency(1200);
+  dds.on();
+  
+  radio.bypassPreDeEmph();
+}
+
+enum Sets {
+  SET_REF,
+  SET_TONE,
+  SET_AMPLITUDE
+} setting = SET_TONE;
+
+char freqBuffer[8];
+char *freqBufferPtr = freqBuffer;
+uint16_t lastFreq = 1200;
+
+void loop() {
+  while(Serial.available()) {
+    char c = Serial.read();
+    Serial.print(c);
+    switch(c) {
+      case 'h':
+        Serial.println(F("Commands:"));
+        Serial.println(F("RefClk: u = +10, U = +100, r XXXX = XXXX"));
+        Serial.println(F("        d = -10, D = -100"));
+        Serial.println(F("Radio:  T = transmit, R = receive"));
+        Serial.println(F("Tone:   t XXXX = XXXX Hz"));
+        Serial.println(F("Amp.:   a XXX  = XXX out of 255"));
+        Serial.println(F("DDS:    o = On, O = Off"));
+        Serial.println(F("ie. a 31 = 32/255 amplitude, r38400 sets 38400Hz refclk"));
+        Serial.println("> ");
+        break;
+      case 'u':
+        dds.setReferenceClock(dds.getReferenceClock()+10);
+        dds.setFrequency(lastFreq);
+        dds.start();
+        Serial.println(F("RefClk + 10 = "));
+        Serial.println(dds.getReferenceClock());
+        Serial.println("> ");
+        break;
+      case 'U':
+        dds.setReferenceClock(dds.getReferenceClock()+100);
+        dds.setFrequency(lastFreq);
+        dds.start();
+        Serial.println(F("RefClk + 100 = "));
+        Serial.println(dds.getReferenceClock());
+        Serial.println("> ");
+        break;
+      case 'd':
+        dds.setReferenceClock(dds.getReferenceClock()-10);
+        dds.setFrequency(lastFreq);
+        dds.start();
+        Serial.println(F("RefClk - 10 = "));
+        Serial.println(dds.getReferenceClock());
+        Serial.println("> ");
+        break;
+      case 'D':
+        dds.setReferenceClock(dds.getReferenceClock()-100);
+        dds.setFrequency(lastFreq);
+        dds.start();
+        Serial.println(F("RefClk - 100 = "));
+        Serial.println(dds.getReferenceClock());
+        Serial.println("> ");
+        break;
+      case 'T':
+        Serial.println(F("Radio transmit"));
+        radio.setModeTransmit();
+        Serial.println("> ");
+        break;
+      case 'R':
+        Serial.println(F("Radio receive"));
+        radio.setModeReceive();
+        Serial.println("> ");
+        break;
+      case 'r':
+        setting = SET_REF;
+        break;
+      case 't':
+        setting = SET_TONE;
+        break;
+      case 'a':
+        setting = SET_AMPLITUDE;
+        break;
+      case 'o':
+        dds.on();
+        Serial.println("> ");
+        break;
+      case 'O':
+        dds.off();
+        Serial.println("> ");
+        break;
+      default:
+        if(c >= '0' && c <= '9') {
+          *freqBufferPtr = c;
+          freqBufferPtr++;
+        }
+        if(c == '\n' && freqBufferPtr != freqBuffer) {
+          *freqBufferPtr = '\0';
+          freqBufferPtr = freqBuffer;
+          uint16_t freq = atoi(freqBuffer);
+          if(setting == SET_REF) {
+            dds.setReferenceClock(freq);
+            dds.setFrequency(lastFreq);
+            dds.start();
+            Serial.print(F("New Reference Clock: "));
+            Serial.println(dds.getReferenceClock());
+          } else if(setting == SET_TONE) {
+            dds.setFrequency(freq);
+            lastFreq = freq;
+            Serial.print(F("New Tone: "));
+            Serial.println(freq);
+          } else if(setting == SET_AMPLITUDE) {
+            dds.setAmplitude((uint8_t)(freq&0xFF));
+            Serial.print(F("New Amplitude: "));
+            Serial.println((uint8_t)(freq&0xFF));
+          }
+          Serial.println("> ");
+        }
+        break;
+    }
+  }
+}
+
+ISR(ADC_vect) {
+  TIFR1 = _BV(ICF1);
+  PORTD |= _BV(2);
+  dds.clockTick();
+  PORTD &= ~_BV(2);
+}