Arduino wait for Serial ready with timeout

waitForSerial.c

/**
 * Wait for serial connection, with timeout
 * @param timeout_milis The maximum time to wait for serial port, in milliseconds
 *
 * usage:
 * 
 * void setup() {
 *   Serial.begin(9600);
 *   // Wait up to 3 seconds for serial connection
 *   waitForSerial(3000);
 *   // Continue with sketch setup
 * }
 */
void waitForSerial(unsigned long timeout_millis) {
  unsigned long start = millis();
  while (!Serial) {
    if (millis() - start > timeout_millis)
      break;
  }
}