First upload

Basic port complete - ESP32 specific features coming soon

sound.h

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+/*
+ *  This creates sound tones by outputting a square wave on a DAC pin. The
+ *  volume of the tone is the level of the DAC pin.
+ *  
+ *  The square wave is created by a timer. The timer runs at 2x the freq, because
+ *  it needs to transition high and then low.
+ * 
+ *   
+ */
+
+
+#include "esp32-hal-timer.h";
+
+#define ESP32_F_CPU         80000000  // the speed of the processor
+#define AUDIO_INTERRUPT_PRESCALER   80 
+#define SOUND_TIMER_NO 0
+//#define AUDIO_PIN 25
+#define MIN_FREQ 20
+#define MAX_FREQ 16000
+
+hw_timer_t * sndTimer = NULL;
+
+bool sound_on = true;
+bool sound_wave_high = true;  // this toggles to create the high/low transitions of the wave
+uint8_t sound_volume = 0;
+
+void sound_init(int pin);
+bool sound(uint16_t freq, uint8_t volume);
+void soundOff();
+
+int dac_pin;
+
+
+
+void IRAM_ATTR onSoundTimer() 
+{    
+  if (sound_on) {    
+			dacWrite(dac_pin, (sound_wave_high?sound_volume:0));
+      sound_wave_high = ! sound_wave_high;
+   
+  }
+  else
+    dacWrite(dac_pin, 0);
+}
+
+void sound_init(int pin){  // pin must be a DAC pin number !! (typically 25 or 26)
+  dac_pin = pin;
+	sound_on = false;
+	pinMode(dac_pin, OUTPUT);
+	sound_volume = 0;
+	
+	sndTimer = timerBegin(SOUND_TIMER_NO, AUDIO_INTERRUPT_PRESCALER, true);
+  timerAttachInterrupt(sndTimer, &onSoundTimer, true);          
+  timerAlarmWrite(sndTimer, ESP32_F_CPU/AUDIO_INTERRUPT_PRESCALER/MIN_FREQ, true); // lower timer freq
+  timerAlarmEnable(sndTimer);	
+}
+
+bool sound(uint16_t freq, uint8_t volume){
+	if (volume == 0) {
+		soundOff();
+		return false;
+	}
+	if (freq < MIN_FREQ || freq > MAX_FREQ) {
+		return false;
+	}
+	sound_on = true;
+	sound_volume = volume;
+  timerAlarmWrite(sndTimer, ESP32_F_CPU/AUDIO_INTERRUPT_PRESCALER/(freq * 2), true);
+	return true;	
+}
+
+void soundOff(){  
+ sound_on = false;
+ sound_volume = 0;
+ timerAlarmWrite(sndTimer, ESP32_F_CPU/AUDIO_INTERRUPT_PRESCALER/(MIN_FREQ), true);  // lower timer freq
+}
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