Added DDS sample. Fixed pin 11 PWM output, now default (3 works better).

examples/DDS/DDS.ino

@@ -0,0 +1,32 @@
+#include <HamShield.h>
+#include <Wire.h>
+
+DDS dds;
+
+void setup() {
+  pinMode(2, OUTPUT);
+  pinMode(3, OUTPUT);
+  pinMode(11, OUTPUT);
+  dds.start();
+  dds.setFrequency(440);
+  dds.on();
+  delay(5000);
+}
+
+void loop() {
+  dds.setFrequency(2200);
+  delay(5000);
+  dds.setFrequency(1200);
+  delay(5000);
+}
+
+#ifdef DDS_USE_ONLY_TIMER2
+ISR(TIMER2_OVF_vect) {
+  dds.clockTick();
+}
+#else // Use the ADC timer instead
+ISR(ADC_vect) {
+  TIFR1 = _BV(ICF1); // Clear the timer flag
+  dds.clockTick();
+}
+#endif