Project_D/ultrasonic_driver.ino at main · Half-Silver/Project_D · GitHub

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/*
  ultrasonic_driver.ino

  Listens for ASCII serial commands 'buzz_on' and 'buzz_off' and drives a piezo ultrasonic
  transducer at 23 kHz using PWM.

  Supported boards:
  - Arduino Uno / Nano / Mega (uses tone())
  - ESP32 (uses LEDC hardware PWM)

  Wiring:
  - Connect piezo + to BUZZ_PIN (see defines below) and piezo - to GND.
  - For louder output, use a transistor/MOSFET driver and external power per the piezo datasheet.
  - Do NOT drive high-power transducers directly from the MCU pin.

  Serial:
  - 115200 baud by default. Commands end with a newline ('\n').
  - Commands:
      buzz_on  -> start 23 kHz tone
      buzz_off -> stop tone
*/

// ---------- Configuration ----------
#define ULTRASONIC_FREQ_HZ 23000  // 23 kHz target frequency

#if defined(ESP32)
  // ESP32 pin selection (GPIO 25 is DAC-capable and commonly free)
  #define BUZZ_PIN 25
  #define LEDC_CHANNEL 0
  #define LEDC_RES_BITS 8
#else
  // Arduino AVR boards (e.g., Uno): use a PWM-capable pin (tone() can use any digital pin)
  #define BUZZ_PIN 9
#endif

// ---------- Globals ----------
String inputLine;
bool buzzing = false;

void setup() {
  pinMode(BUZZ_PIN, OUTPUT);
  stopBuzz();

  Serial.begin(115200);
  while (!Serial) {
    ; // wait for serial port to connect (needed for native USB boards)
  }
  Serial.setTimeout(10);
  Serial.println(F("ultrasonic_driver ready. Send 'buzz_on' or 'buzz_off'."));
}

void loop() {
  // Read line-buffered commands
  while (Serial.available()) {
    char c = (char)Serial.read();
    if (c == '\r') continue;
    if (c == '\n') {
      processCommand(inputLine);
      inputLine = "";
    } else {
      inputLine += c;
      if (inputLine.length() > 64) {
        inputLine.remove(0); // prevent runaway
      }
    }
  }
}

void processCommand(const String &cmd) {
  if (cmd.equalsIgnoreCase("buzz_on")) {
    startBuzz();
    Serial.println(F("OK buzz_on"));
  } else if (cmd.equalsIgnoreCase("buzz_off")) {
    stopBuzz();
    Serial.println(F("OK buzz_off"));
  } else if (cmd.length() > 0) {
    Serial.print(F("ERR unknown: "));
    Serial.println(cmd);
  }
}

void startBuzz() {
  if (buzzing) return;
#if defined(ESP32)
  // Configure LEDC PWM at 23 kHz
  ledcSetup(LEDC_CHANNEL, ULTRASONIC_FREQ_HZ, LEDC_RES_BITS);
  ledcAttachPin(BUZZ_PIN, LEDC_CHANNEL);
  // 50% duty for square wave: for 8-bit resolution, 127 or 128
  ledcWrite(LEDC_CHANNEL, 128);
#else
  // Use Arduino tone() which uses a hardware timer
  tone(BUZZ_PIN, ULTRASONIC_FREQ_HZ);
#endif
  buzzing = true;
}

void stopBuzz() {
#if defined(ESP32)
  ledcWrite(LEDC_CHANNEL, 0);
  ledcDetachPin(BUZZ_PIN);
#else
  noTone(BUZZ_PIN);
#endif
  buzzing = false;
}