Brushless motor on an ESC, on an Arduino Uno

// A brushless motor on a 30 A ESC, its throttle on a thumb stick.
//
//   ESC SIG -> pin 9    ESC GND -> GND    (leave the ESC's red 5V wire off:
//                                          the Uno has its own supply)
//   ESC BAT+ / BAT- -> a 3S LiPo, 11.1 V
//   joystick VRY -> A0, VCC -> 5V, GND -> GND
//
// An ESC is driven like a servo: 1000 us is stopped and 2000 us is full. It
// will not spin until it has armed, and it arms only on low throttle after its
// start-up tones, so setup() holds 1000 us for three seconds. The stick at
// rest is low throttle; push it either way from the middle to open it up, as
// an RC transmitter's throttle stick does from the bottom.

#include <Servo.h>

Servo esc;
const int ESC_PIN = 9;

void setup() {
  Serial.begin(9600);
  esc.attach(ESC_PIN, 1000, 2000);
  esc.writeMicroseconds(1000);
  Serial.println("Mokxi Uno: arming the ESC at 1000 us");
  delay(3000);
  Serial.println("armed: push the stick");
}

void loop() {
  // How far the stick is from the middle, past a small dead band.
  int off = abs(analogRead(A0) - 512) - 20;
  int us = 1000 + (long)constrain(off, 0, 491) * 1000 / 491;
  esc.writeMicroseconds(us);
  static unsigned long last = 0;
  if (millis() - last > 500) {
    last = millis();
    Serial.print("throttle ");
    Serial.print(us);
    Serial.println(" us");
  }
  delay(20);
}