Synthesized sine streaming

Synthesize a 16 kHz mono PCM16 sine on the MCU and stream it to the Hapbeat. No stored audio, and frequency / intensity are live.

One-shot

hb.playSine(160.0f, 0.7f, 400);   // 160 Hz, intensity 0.7, 400 ms

playSine blocks for durationMs. Good for short haptic feedback.

Continuous (hold / live control)

To buzz while a button is held, or to drive frequency from a sensor, use beginSine / pumpSine / endSine. Call pumpSine() often from loop() to keep the device ring buffer filled.

void onPressDown() {
  hb.beginSine(160.0f, 0.8f);   // start a continuous sine
}

void loop() {
  // ... handle input ...
  if (hb.sineActive()) hb.pumpSine();   // call every loop (prevents dropouts)
}

void onPressUp() {
  hb.endSine();                 // stop
}

• pumpSine() sends a bounded number of chunks per call, so as long as you don’t block loop() for ~160 ms+, it self-paces.
• To change frequency / intensity mid-stream, call endSine() and then beginSine() again with the new values.

Reducing choppiness

Synthesized sine is sent over UDP, so Wi-Fi conditions can cause dropouts. To fix:

• Call WiFi.setSleep(false) after connecting (kills ESP32 modem-sleep jitter).
• Use unicast: broadcast UDP has no MAC-layer ACK / retry, so loss becomes audible gaps. discover() a single device and unicast to it, and the radio’s MAC ACK + retry makes it far smoother (see Discovery & targeting).
• Call pumpSine() frequently from loop(). If heavy work stalls loop(), the device ring (~256 ms) starves and you hear gaps.

Note

The sender keeps ~160 ms of audio buffered ahead, and combined with the device’s ~256 ms ring this absorbs Wi-Fi jitter. With unicast, a retransmit turns a would-be loss into a few ms of jitter the buffer absorbs; a broadcast “loss” is a true gap the buffer cannot fill.