===== ITT Servo module =====
This laboratory is located in the office of ITT Group in Tallinn, Estonia.

==== Introduction  ====
This laboratory can be used to practice controlling the servo motor attached to the controller.

{{:en:iot:examples:servopicture2.jpg?300|}}

==== Prerequisites ====
For this laboratory, the student should understand basic MQTT concepts like topics, broker, subscribing and publishing.

==== Technical details ====
This laboratory consists of a servo with the add-on module attached to the ITT IoT controller module. 

=== Sensors ===
This laboratory does not have any sensors.

=== Specifications ===
<table Ref.Tab.1.1>
<caption>Servo specifications</caption>
^ Specification ^ Value ^
| Speed at 6V | 0,07 sec/60°|
| Stall torque at 6V | 0,042 N-m |
| Speed at 4,8V | 0,09 sec/60°|
| Stall torque at 4,8V | 0,028 N-m |
</table>

=== Electrical connection ===

The signal lead of the servo is connected to D3 pin of the controller.

=== Software, libraries and externals ===
  * ITTIoT libary - used to program the controller module.
  * Servo libary - used to control the servo.

=== Communication ===
The user can connect and program this controller using the Distancelab environment.

=== Limits ===
At the same time, only one user can program the controller. But all users connected to the Distancelab MQTT broker can subscribe and publish to topics specified.

==== Hands-on labs ====

=== Example code ===

<code c>
/*
 * IoT Servo example
 *
 * This example subscribe to the "servo" topic. When a message received, then it
 * change servo position
 *
 * Created 11 Sept 2017 by Heiko Pikner
 */

#include <Arduino.h>
#include <Servo.h>
#include <ittiot.h>

//Pin definition for the Servo (D3)
#define SERVO_PIN            D3

Servo myservo;  // create servo object to control a servo

// Change the servo position (value between 0 and 180)
// mosquitto_pub -u test -P test -t "RL/esp-{ESP-ID}/servo" -m "51" 
// = this calls servo motor to change position 

void iot_received(String topic, String msg)
{
  Serial.print("MSG FROM USER callback, topic: ");
  Serial.print(topic);
  Serial.print(" payload: ");
  Serial.println(msg);

  Serial.print("Servo: ");
  Serial.println(msg);

  myservo.write(msg.toInt());
}

// Function started after the connection to the server is established
void iot_connected()
{
  Serial.println("MQTT connected callback");
  // Subscribe to the topic "servo"
  iot.subscribe("servo");
  iot.log("IoT Servo example!");
}

void setup()
{
  Serial.begin(115200);
  Serial.println("Booting");

  // Print json config to serial
  iot.printConfig();
  // Initialize IoT library
  iot.setup();

  myservo.attach(SERVO_PIN);
}

void loop()
{
  // IoT behind the plan work, it should be periodically called
  iot.handle();
  delay(200);
}

</code>

==== Support ====
info@ittgroup.ee