add modified Adafruit tone generator example

Author: sandeepmistry

libraries/I2S/examples/tone_generator/tone_generator.ino

@@ -0,0 +1,163 @@
+// Arduino Zero / Feather M0 I2S audio tone generation example.
+// Author: Tony DiCola
+//
+// Connect an I2S DAC or amp (like the MAX98357) to the Arduino Zero
+// and play back simple sine, sawtooth, triangle, and square waves.
+// Makes your Zero sound like a NES!
+//
+// NOTE: The I2S signal generated by the Zero does NOT have a MCLK /
+// master clock signal.  You must use an I2S receiver that can operate
+// without a MCLK signal (like the MAX98357).
+//
+// For an Arduino Zero / Feather M0 connect it to you I2S hardware as follows:
+// - Digital 0 -> I2S LRCLK / FS (left/right / frame select clock)
+// - Digital 1 -> I2S BCLK / SCLK (bit / serial clock)
+// - Digital 9 -> I2S DIN / SD (data output)
+// - Ground
+//
+// Depends on the Adafruit_ASFcore library from:
+//   https://github.com/adafruit/adafruit_asfcore
+//
+// Released under a MIT license: https://opensource.org/licenses/MIT
+#include <I2S.h>
+
+#define SAMPLERATE_HZ 44100  // The sample rate of the audio.  Higher sample rates have better fidelity,
+                             // but these tones are so simple it won't make a difference.  44.1khz is
+                             // standard CD quality sound.
+
+#define AMPLITUDE     5000   // Set the amplitude of generated waveforms.  This controls how loud
+                             // the signals are, and can be any value from 0 to 65535.  Start with
+                             // a low value like 5000 or less to prevent damaging speakers!
+
+#define WAV_SIZE      256    // The size of each generated waveform.  The larger the size the higher
+                             // quality the signal.  A size of 256 is more than enough for these simple
+                             // waveforms.
+
+
+// Define the frequency of music notes (from http://www.phy.mtu.edu/~suits/notefreqs.html):
+#define C4_HZ      261.63
+#define D4_HZ      293.66
+#define E4_HZ      329.63
+#define F4_HZ      349.23
+#define G4_HZ      392.00
+#define A4_HZ      440.00
+#define B4_HZ      493.88
+
+// Define a C-major scale to play all the notes up and down.
+float scale[] = { C4_HZ, D4_HZ, E4_HZ, F4_HZ, G4_HZ, A4_HZ, B4_HZ, A4_HZ, G4_HZ, F4_HZ, E4_HZ, D4_HZ, C4_HZ };
+
+// Store basic waveforms in memory.
+int16_t sine[WAV_SIZE]     = {0};
+int16_t sawtooth[WAV_SIZE] = {0};
+int16_t triangle[WAV_SIZE] = {0};
+int16_t square[WAV_SIZE]   = {0};
+
+void generateSine(uint16_t amplitude, int16_t* buffer, uint16_t length) {
+  // Generate a sine wave signal with the provided amplitude and store it in
+  // the provided buffer of size length.
+  for (int i=0; i<length; ++i) {
+    buffer[i] = uint16_t(float(amplitude)*sin(2.0*PI*(1.0/length)*i));
+  }
+}
+void generateSawtooth(uint16_t amplitude, int16_t* buffer, uint16_t length) {
+  // Generate a sawtooth signal that goes from -amplitude/2 to amplitude/2
+  // and store it in the provided buffer of size length.
+  float delta = float(amplitude)/float(length);
+  for (int i=0; i<length; ++i) {
+    buffer[i] = -(amplitude/2)+delta*i;
+  }
+}
+
+void generateTriangle(uint16_t amplitude, int16_t* buffer, uint16_t length) {
+  // Generate a triangle wave signal with the provided amplitude and store it in
+  // the provided buffer of size length.
+  float delta = float(amplitude)/float(length);
+  for (int i=0; i<length/2; ++i) {
+    buffer[i] = -(amplitude/2)+delta*i;
+  }
+    for (int i=length/2; i<length; ++i) {
+    buffer[i] = (amplitude/2)-delta*(i-length/2);
+  }
+}
+
+void generateSquare(uint16_t amplitude, int16_t* buffer, uint16_t length) {
+  // Generate a square wave signal with the provided amplitude and store it in
+  // the provided buffer of size length.
+  for (int i=0; i<length/2; ++i) {
+    buffer[i] = -(amplitude/2);
+  }
+    for (int i=length/2; i<length; ++i) {
+    buffer[i] = (amplitude/2);
+  }
+}
+
+void playWave(int16_t* buffer, uint16_t length, float frequency, float seconds) {
+  // Play back the provided waveform buffer for the specified
+  // amount of seconds.
+  // First calculate how many samples need to play back to run
+  // for the desired amount of seconds.
+  uint32_t iterations = seconds*SAMPLERATE_HZ;
+  // Then calculate the 'speed' at which we move through the wave
+  // buffer based on the frequency of the tone being played.
+  float delta = (frequency*length)/float(SAMPLERATE_HZ);
+  // Now loop through all the samples and play them, calculating the
+  // position within the wave buffer for each moment in time.
+  for (uint32_t i=0; i<iterations; ++i) {
+    uint16_t pos = uint32_t(i*delta) % length;
+    int16_t sample = buffer[pos];
+    // Duplicate the sample so it's sent to both the left and right channel.
+    // It appears the order is right channel, left channel if you want to write
+    // stereo sound.
+    I2S.write(sample);
+    I2S.write(sample);
+  }
+}
+
+void setup() {
+  // Configure serial port.
+  Serial.begin(9600);
+  Serial.println("I2S Audio Tone Generator");
+
+  // Initialize the I2S transmitter.
+  if (I2S.begin(I2S_PHILIPS_MODE, SAMPLERATE_HZ, 16)) {
+    Serial.println("Failed to initialize I2S!");
+    while (1);
+  }
+
+  // Generate waveforms.
+  generateSine(AMPLITUDE, sine, WAV_SIZE);
+  generateSawtooth(AMPLITUDE, sawtooth, WAV_SIZE);
+  generateTriangle(AMPLITUDE, triangle, WAV_SIZE);
+  generateSquare(AMPLITUDE, square, WAV_SIZE);
+}
+
+void loop() {
+  Serial.println("Sine wave");
+  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
+    // Play the note for a quarter of a second.
+    playWave(sine, WAV_SIZE, scale[i], 0.25);
+    // Pause for a tenth of a second between notes.
+    delay(100);
+  }
+  Serial.println("Sawtooth wave");
+  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
+    // Play the note for a quarter of a second.
+    playWave(sawtooth, WAV_SIZE, scale[i], 0.25);
+    // Pause for a tenth of a second between notes.
+    delay(100);
+  }
+  Serial.println("Triangle wave");
+  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
+    // Play the note for a quarter of a second.
+    playWave(triangle, WAV_SIZE, scale[i], 0.25);
+    // Pause for a tenth of a second between notes.
+    delay(100);
+  }
+  Serial.println("Square wave");
+  for (int i=0; i<sizeof(scale)/sizeof(float); ++i) {
+    // Play the note for a quarter of a second.
+    playWave(square, WAV_SIZE, scale[i], 0.25);
+    // Pause for a tenth of a second between notes.
+    delay(100);
+  }
+}

libraries/I2S/src/I2S.cpp

@@ -186,6 +186,31 @@ void I2SClass::flush()
 }
 
 size_t I2SClass::write(uint8_t data)
+{
+	return write((int)data);
+}
+
+size_t I2SClass::write(const uint8_t *buffer, size_t size)
+{
+	return 0;
+}
+
+size_t I2SClass::availableForWrite()
+{
+	return 0;
+}
+
+int I2SClass::read(int8_t data[], int size)
+{
+	return 0;
+}
+
+int I2SClass::write(short data)
+{
+	return write((int)data);
+}
+
+int I2SClass::write(int data)
 {
 	if (_uc_index == 0) {
 		while (!_i2s->INTFLAG.bit.TXRDY0);
@@ -203,22 +228,7 @@ size_t I2SClass::write(uint8_t data)
 		_i2s->INTFLAG.bit.TXRDY1 = 1;
 	}
 
-	return 0;
-}
-
-size_t I2SClass::write(const uint8_t *buffer, size_t size)
-{
-	return 0;
-}
-
-size_t I2SClass::availableForWrite()
-{
-	return 0;
-}
-
-int I2SClass::read(int8_t data[], int size)
-{
-	return 0;
+	return 1;
 }
 
 /*

libraries/I2S/src/I2S.h

@@ -29,6 +29,10 @@ class I2SClass : public Stream
 
   virtual size_t availableForWrite();
 
+
+  int write(short);
+  int write(int);
+
   int read(int8_t data[], int size);
   int read(int16_t data[], int size);
   int read(int32_t data[], int size);