nrf52840 (xiao) + PCM5102A

gistfile1.txt

class SimpleI2S {
private:
  uint32_t buffer[2];
public:
  void begin(uint32_t bck, uint32_t lrck, uint32_t din) {
    NRF_I2S->ENABLE = 0;
    NRF_I2S->PSEL.SCK = bck;
    NRF_I2S->PSEL.LRCK = lrck;
    NRF_I2S->PSEL.SDOUT = din;
    NRF_I2S->PSEL.MCK = 0xFFFFFFFF;
    NRF_I2S->PSEL.SDIN = 0xFFFFFFFF;
    NRF_I2S->CONFIG.MCKEN = 1;
    NRF_I2S->CONFIG.MCKFREQ = I2S_CONFIG_MCKFREQ_MCKFREQ_32MDIV11;
    NRF_I2S->CONFIG.RATIO = I2S_CONFIG_RATIO_RATIO_32X;
    NRF_I2S->CONFIG.MODE = I2S_CONFIG_MODE_MODE_MASTER;
    NRF_I2S->CONFIG.SWIDTH = I2S_CONFIG_SWIDTH_SWIDTH_16BIT;
    NRF_I2S->CONFIG.ALIGN = I2S_CONFIG_ALIGN_ALIGN_LEFT;
    NRF_I2S->CONFIG.FORMAT = I2S_CONFIG_FORMAT_FORMAT_I2S;
    NRF_I2S->CONFIG.CHANNELS = I2S_CONFIG_CHANNELS_CHANNELS_STEREO;
    NRF_I2S->ENABLE = 1;
    NRF_I2S->TASKS_START = 1;
  }
  
  void write(int16_t left, int16_t right) {
    while (!NRF_I2S->EVENTS_TXPTRUPD);
    buffer[0] = left;
    buffer[1] = right;
    NRF_I2S->TXD.PTR = (uint32_t)buffer;
    NRF_I2S->RXTXD.MAXCNT = 2;
    NRF_I2S->EVENTS_TXPTRUPD = 0;
  }
};

SimpleI2S i2s;
const float FREQ = 440.0;  // A440 concert pitch
const float SAMPLE_RATE = 44100.0;
const float ENVELOPE_FREQ = 2.0;  // 2Hz amplitude modulation

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);
  i2s.begin(3, 29, 4);
}

void loop() {
  static float phase = 0.0;
  static float envelope_phase = 0.0;
  
  // Generate sine wave with smooth amplitude modulation
  float envelope = (sin(envelope_phase) + 1.0) * 0.5;  // 0 to 1 smooth envelope
  float sample = sin(phase) * envelope * 16384.0;  // Reduced amplitude for less harshness
  
  i2s.write((int16_t)sample, (int16_t)sample);
  
  // Update phases
  phase += 2 * PI * FREQ / SAMPLE_RATE;
  if (phase >= 2 * PI) phase -= 2 * PI;
  
  envelope_phase += 2 * PI * ENVELOPE_FREQ / SAMPLE_RATE;
  if (envelope_phase >= 2 * PI) envelope_phase -= 2 * PI;
}