Control Brushless ESC From Arduino
I had a similar problem. I solved it by using an oscilloscope to measure the arming sequence of an out-of-the-box RC remote controller and receiver.

The arming sequence through the controller-receiver was like this:


Connect ESC to battery (arduino is connected to signal and ground prior to this)
Wait for 3 beeps
Set the throttle to the lowest possible
Wait for another beep


I then adjusted my arduino code to output the same(similar) sequence.

Here is the code:

#include &lt;Servo.h&gt;
#define POT A0

Servo m1;

void setup() {
  m1.attach(6);
  Serial.begin(9600);
  delay(50);
  Serial.println("Serial ready:");
  arm(m1);
}

void loop() {
  int potValue = analogRead(POT);
  int s = map(potValue,60,930,1200,1700); //Map the pot values to motor values

  m1.write(s);
  Serial.println(s);
}

void arm(Servo m){
  Serial.print("Arming.");
  m.write(0);
  delay(100);
  m.write(1224); //A value at which the motor starts turning
  delay(2000);
  m.write(1024); //A value at which the motor stands still
  delay(3000);
  Serial.println(" Armed!");
}


You can also see a video of the whole thing in action here: A2212/13T brushless motor on a pivoting arm

EDIT: Further testing shows, that it suffices to output a low non zero value to arm this ESC. Simply doing Servo.write(1024); until you hear the confirmation beep seems to work.