Once I started chatting with Gustavo Gonnet in the Particle Community boards, I began to improve my control of my balky servo. Things starting looking up for Detour Flag Guy. 

Gustavo enjoyed explaining how things worked. He added lavish comments to the code snippets he sent me. 

That's when the code started to make sense. 

Here's what we ended up with, and Gustavo's comments. The servo was now firmly in my control. 

​// create servo object to control a servo
//this is to move the detour flag
Servo myservo;
// variable to store the servo position
int pos = 0;

// NEW LINES HERE!   ******************************************************************
// DC: you can play with these values so the DETOUR panel shows correctly
//default parameters: 120, 140
const int servoInitialPosition = 90;
const int servoFinalPosition = 280;
//was 180
// GOAL: the servo will move from the initial position to the final position
// giving the ilussion that the worker is moving the detour sign

// this function gets executed once, when the photon boots up
void setup()
{
  // attaches the servo on the D0 pin to the servo object
  myservo.attach(D0);

  // original functions, I left them here just in case
  //Particle.function("setpos", setPosition);
  //Particle.variable("getpos", pos);

  // NEW LINES HERE!   ******************************************************************
  // new function to make the worker move the DETOUR sign
  Particle.function("moveit", moveit);

  // make the servo move to its initial position when the photon boots up
  myservo.write(servoInitialPosition);
}

// this function gets executed continuously, as long as the photon has power
void loop()
{
  // since there is nothing to execute, the photon will remain idle, looking at us 
  // until we decide to hit one of its cloud functions, like moveit()
}

int setPosition(String posValue)
{
  pos = posValue.toInt();
  myservo.write(pos);
  return 0;
}

// NEW LINES HERE!   ******************************************************************
// DC: you can play with this value so the DETOUR panel moves smoothly
const int bounceDelay = 1000;

int moveit(String dummy)
{

  Particle.publish("activated!", "booma", 60, PRIVATE);

  // the servo should be already at the initial position, but just in case
  myservo.write(servoInitialPosition);
  delay(bounceDelay);

  // this is the first DETOUR sign movement
  oneMovement();

  // this is the second DETOUR sign movement
  oneMovement();

  // this is third DETOUR sign movement
  oneMovement();

  // DC: are 3 movements fine? feel free to add/remove movements at will

  return 0;
}

// this function aims at making one DETOUR sign movement
// it assumes the servo is at its initial position!
void oneMovement()
{
  myservo.write(servoFinalPosition);
  delay(bounceDelay);
  myservo.write(servoInitialPosition);
  delay(bounceDelay);
}

Now I can send the servo a "coded signal" and it will:

• briskly move about 30 degrees
• and back 
• pause a second 
• then do it again more two times 
• then stop 

It looked like a future flag wave to me. 

Time to find a flagman, and a flag.