Modulation config added. Not great, but just enough for Dalek voice.

Author: PaintYourDragon

M4_Eyes/M4_Eyes.ino

@@ -420,12 +420,13 @@ void setup() {
 
 #if defined(ADAFRUIT_MONSTER_M4SK_EXPRESS)
   if(voiceOn) {
-    if(!voiceSetup(false)) {
+    if(!voiceSetup((waveform > 0))) {
       Serial.println("Voice init fail, continuing without");
       voiceOn = false;
     } else {
       voiceGain(gain);
       currentPitch = voicePitch(currentPitch);
+      if(waveform) voiceMod(modulate, waveform);
       digitalWrite(20, HIGH); // Speaker on
     }
   }
@@ -933,6 +934,7 @@ void loop() {
         }
         if(newlyPressed) {
           currentPitch = voicePitch(currentPitch);
+          if(waveform) voiceMod(modulate, waveform);
           Serial.print("Voice pitch: ");
           Serial.println(currentPitch);
         }

M4_Eyes/file.cpp

@@ -377,6 +377,15 @@ void loadConfig(char *filename) {
       if(v.is<bool>()) voiceOn = v.as<bool>();
       currentPitch = defaultPitch = doc["pitch"] | defaultPitch;
       gain = doc["gain"] | gain;
+      modulate = doc["modulate"] | modulate;
+      v = doc["waveform"];
+      if(v.is<char*>()) { // If string...
+        if(!strncasecmp(     v, "sq", 2)) waveform = 1;
+        else if(!strncasecmp(v, "si", 2)) waveform = 2;
+        else if(!strncasecmp(v, "t" , 1)) waveform = 3;
+        else if(!strncasecmp(v, "sa", 2)) waveform = 4;
+        else                              waveform = 0;
+      }
 #endif // ADAFRUIT_MONSTER_M4SK_EXPRESS
     }
     file.close();

M4_Eyes/globals.h

@@ -89,6 +89,8 @@ GLOBAL_VAR bool      voiceOn             GLOBAL_INIT(false);
 GLOBAL_VAR float     currentPitch        GLOBAL_INIT(1.0);
 GLOBAL_VAR float     defaultPitch        GLOBAL_INIT(1.0);
 GLOBAL_VAR float     gain                GLOBAL_INIT(1.0);
+GLOBAL_VAR uint8_t   waveform            GLOBAL_INIT(0);
+GLOBAL_VAR uint32_t  modulate            GLOBAL_INIT(30); // Dalek pitch
 #endif
 
 // EYE-RELATED STRUCTURES --------------------------------------------------

M4_Eyes/pdmvoice.cpp

@@ -76,7 +76,7 @@ static uint16_t       dcOffsetNext     = 32768; // between these two values
 
 static uint16_t       micGain          = 256;   // 1:1
 
-#define MOD_MIN 40 // Lowest supported modulation pitch (lower = more RAM use)
+#define MOD_MIN 20 // Lowest supported modulation frequency (lower = more RAM use)
 static uint8_t        modWave          = 0;     // Modulation wave type (none, sine, square, tri, saw)
 static uint8_t       *modBuf           = NULL;  // Modulation waveform buffer
 static uint32_t       modIndex         = 0;     // Current position in modBuf
@@ -217,20 +217,21 @@ void voiceGain(float g) {
 
 // SET MODULATION ----------------------------------------------------------
 
-// This is a work in progress and NOT FUNCTIONAL YET
+// This needs to be called after any call to voicePitch() -- the modulation
+// table is not currently auto-regenerated. Maybe that'll change.
 
 void voiceMod(uint32_t freq, uint8_t waveform) {
   if(modBuf) { // Ignore if no modulation buffer allocated
     if(freq < MOD_MIN) freq = MOD_MIN;
-    uint16_t period = TIMER->COUNT16.CC[0].reg + 1;
-    float    playbackRate = 48000000.0 / (float)period; // samples/sec
+    uint16_t period = TIMER->COUNT16.CC[0].reg + 1;     // Audio out timer ticks
+    float    playbackRate = 48000000.0 / (float)period; // Audio out samples/sec
     modLen = (int)(playbackRate / freq + 0.5);
     if(modLen < 2) modLen = 2;
     if(waveform > 4) waveform = 4;
     modWave = waveform;
-    switch(modWave) {
+    yield();
+    switch(waveform) {
      case 0: // None
-      memset(modBuf, 255, modLen);
       break;
      case 1: // Square
       memset(modBuf, 255, modLen / 2);
@@ -255,7 +256,6 @@ void voiceMod(uint32_t freq, uint8_t waveform) {
   }
 }
 
-
 // INTERRUPT HANDLERS ------------------------------------------------------
 
 static uint16_t const sincfilter[64] = { 0, 2, 9, 21, 39, 63, 94, 132, 179, 236, 302, 379, 467, 565, 674, 792, 920, 1055, 1196, 1341, 1487, 1633, 1776, 1913, 2042, 2159, 2263, 2352, 2422, 2474, 2506, 2516, 2506, 2474, 2422, 2352, 2263, 2159, 2042, 1913, 1776, 1633, 1487, 1341, 1196, 1055, 920, 792, 674, 565, 467, 379, 302, 236, 179, 132, 94, 63, 39, 21, 9, 2, 0, 0 };
@@ -401,6 +401,10 @@ void PDM_SERCOM_HANDLER(void) {
 void TIMER_IRQ_HANDLER(void) {
   TIMER->COUNT16.INTFLAG.reg = TC_INTFLAG_OVF;
 
+  // Modulation is done on the output (rather than the input) because
+  // pitch-shifting modulated input would cause weird waveform
+  // discontinuities. This does require recalculating the modulation table
+  // any time the pitch changes though.
   if(modWave) {
     nextOut = (((int32_t)nextOut - 2048) * (modBuf[modIndex] + 1) / 256) + 2048;
     if(++modIndex >= modLen) modIndex = 0;