// Mutual-style capacitive sensor via charge transfer
// TX pin drives, RX pin senses — works through plastic/dielectric
// Pad 1 (TX) → GPIO 32
// Pad 2 (RX) → GPIO 33, also connected via 1MΩ resistor to GPIO 32

const int TX_PIN = 12;
const int RX_PIN = 13;
const int SAMPLES = 50;        // more = slower but more sensitive
const int PROX_THRESHOLD = 200;
const int TOUCH_THRESHOLD = 800;

long readCapacitance() {
  long total = 0;
  for (int i = 0; i < SAMPLES; i++) {
    // discharge RX
    pinMode(RX_PIN, OUTPUT);
    digitalWrite(RX_PIN, LOW);
    delayMicroseconds(10);

    // set TX low, float RX
    digitalWrite(TX_PIN, LOW);
    pinMode(RX_PIN, INPUT);

    // drive TX high — charge transfers through pad coupling & resistor
    digitalWrite(TX_PIN, HIGH);

    // count time until RX goes high
    long count = 0;
    while (digitalRead(RX_PIN) == LOW && count < 20000) {
      count++;
    }
    total += count;

    // reset
    digitalWrite(TX_PIN, LOW);
  }
  return total / SAMPLES;
}

void setup() {
  Serial.begin(115200);
  pinMode(TX_PIN, OUTPUT);
}

void loop() {
  long val = readCapacitance();
  Serial.println(val);

  if (val > TOUCH_THRESHOLD) {
    Serial.println("TOUCH");
  } else if (val > PROX_THRESHOLD) {
    Serial.println("PROXIMITY");
  }

  delay(50);
}