1  // SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries
 2  //
 3  // SPDX-License-Identifier: MIT
 4  
 5  /*
 6   This example generates a sine wave based tone at a specified frequency
 7   and sample rate. Then outputs the data using the I2S interface.
 8  
 9   Public Domain
10  */
11  
12  #include <I2S.h>
13  
14  #define FREQUENCY    440  // frequency of sine wave in Hz
15  #define AMPLITUDE  10000  // amplitude of sine wave
16  #define SAMPLERATE 44100  // sample rate in Hz
17  
18  int16_t sinetable[SAMPLERATE / FREQUENCY];
19  uint32_t sample = 0;
20  
21  #define PI 3.14159265
22  
23  void setup() {
24    Serial.begin(115200);
25    Serial.println("I2S sine wave tone");
26  
27    // start I2S at the sample rate with 16-bits per sample
28    if (!I2S.begin(I2S_PHILIPS_MODE, SAMPLERATE, 16)) {
29      Serial.println("Failed to initialize I2S!");
30      while (1); // do nothing
31    }
32  
33    // fill in sine wave table
34    for (uint16_t s=0; s < (SAMPLERATE / FREQUENCY); s++) {
35      sinetable[s] = sin(2.0 * PI * s / (SAMPLERATE/FREQUENCY)) * AMPLITUDE;
36    }
37  }
38  
39  
40  void loop() {
41    if (sample == (SAMPLERATE / FREQUENCY)) {
42      sample = 0;
43    }
44  
45    // write the same sample twice, once for left and once for the right channel
46    I2S.write((int16_t) sinetable[sample]);  // We'll just have same tone on both!
47    I2S.write((int16_t) sinetable[sample]);
48  
49    // increment the counter for the next sample in the sine wave table
50    sample++;
51  }