Servo limiter - limits servo signal to 25% (HW - Arduino Pro Mini)

servo_limiter.ino

/**
 * Program reads servo signal on "input", changes its aplitude by 25% and sends it to "output".
 * It is used for limiting RC car power - for kids.
 */

// input and output pin
const int input = 2;
const int output = 3;

const int led = LED_BUILTIN;

// servo signal timing
#define CENTER 750 // should be 1500, but my pro mini runs half clock
#define DIV 4 // 1/4 ~ 25%

void setup() {
  // put your setup code here, to run once:
  pinMode(led, OUTPUT);
  digitalWrite(led, 0);
  pinMode(input, INPUT);
  pinMode(output, OUTPUT);

  Serial.begin(115200); // its 57600 actually (half clock speed)
}

void loop() {
  while(digitalRead(input) == LOW);
  int32_t i = micros();
  while(digitalRead(input) == HIGH);
  i = micros()-i;

  int32_t o = (i - CENTER) / DIV + CENTER;
  uint32_t t = micros();
  digitalWrite(output, HIGH);
  while ((micros() - t) < o);
  digitalWrite(output, LOW);

  digitalWrite(led, !digitalRead(led));

  Serial.print(i);
  Serial.print(" ");
  Serial.println(o);
}