#define servoPin 12

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

void loop() {
  for (float pos = -90; pos <= 90; pos += 0.1) {
    float msec      = pos / 90.0 * 0.5 + 1.5;
    long  limitUSec = msec * 1000;

    digitalWrite(servoPin, HIGH);
    delayMicroseconds(limitUSec);
    digitalWrite(servoPin, LOW);
    delayMicroseconds(10000-limitUSec);

    delay(10);
  }
  delay(1000);
}