Thermostat example demonstrate advantages of source/sink vs shared in certain applications.

Author: aentinger

examples/Threading_Basics/Thermostat/SharedVariables.h

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+/* Define a data sink named 'temperature' of type 'float'. */
+SINK(temperature, float, 10);
+
+static String living_room_message_prefix(String const & /* msg */)
+{
+  return String("[Living Room] ");
+}
+
+void setup()
+{
+  Serial.begin(9600);
+  Serial.prefix(living_room_message_prefix);
+  while (!Serial) { }
+}
+
+bool is_heating_on = false;
+
+void loop()
+{
+  float current_temperature_deg = temperature.pop();
+
+  /* Check if the temperature reported by the thermostat is above
+   * or below 22.0 °C. If the temperature is below 22.0 °C, turn
+   * on the heating.
+   */
+  bool turn_heating_on  = false,
+       turn_heating_off = false;
+
+  if (current_temperature_deg < 22.0f)
+    turn_heating_on = true;
+  else
+    turn_heating_off = true;
+
+  /* Only perform a simulated turning on of
+   * the heating if the heating is currently
+   * turned off.
+   */
+  if (is_heating_on && turn_heating_off)
+  {
+    is_heating_on = false;
+  
+    Serial.block();
+    Serial.print("Heating OFF (");
+    Serial.print(current_temperature_deg);
+    Serial.println(" °C)");
+    Serial.unblock();
+  }
+
+  if (!is_heating_on && turn_heating_on)
+  {
+    is_heating_on = true;
+    
+    Serial.block();
+    Serial.print("Heating ON (");
+    Serial.print(current_temperature_deg);
+    Serial.println(" °C)");
+    Serial.unblock();
+  }
+}

examples/Threading_Basics/Thermostat/TemperatureControl_LivingRoom.inot

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+/* Define a data sink named 'temperature' of type 'float'. */
+SINK(temperature, float, 10);
+
+static String sleeping_room_message_prefix(String const & /* msg */)
+{
+  return String("[Sleeping Room] ");
+}
+
+void setup()
+{
+  Serial.begin(9600);
+  Serial.prefix(sleeping_room_message_prefix);
+  while (!Serial) { }
+}
+
+bool is_ac_on = false;
+
+void loop()
+{
+  float current_temperature_deg = temperature.pop();
+
+  /* Check if the temperature reported by the thermostat is above
+   * or below 20.0 °C. If the temperature is above 20.0 °C, turn
+   * on the AC.
+   */
+  bool turn_ac_on  = false,
+       turn_ac_off = false;
+
+  if (current_temperature_deg > 20.0f)
+    turn_ac_on = true;
+  else
+    turn_ac_off = true;
+
+  /* Only perform a simulated turning on of
+   * the air conditioner if the heating is
+   * air conditioner is currently turned off.
+   */
+  if (is_ac_on && turn_ac_off)
+  {
+    is_ac_on = false;
+  
+    Serial.block();
+    Serial.print("AC OFF (");
+    Serial.print(current_temperature_deg);
+    Serial.println(" °C)");
+    Serial.unblock();
+  }
+
+  if (!is_ac_on && turn_ac_on)
+  {
+    is_ac_on = true;
+    
+    Serial.block();
+    Serial.print("AC ON  (");
+    Serial.print(current_temperature_deg);
+    Serial.println(" °C)");
+    Serial.unblock();
+  }
+}

examples/Threading_Basics/Thermostat/TemperatureControl_SleepingRoom.inot

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+/* Define a data source named 'temperature' of type 'float'. */
+SOURCE(temperature, float);
+
+void setup()
+{
+
+}
+
+void loop()
+{
+  /* Read temperature - since this is just a simulation
+   * so we take a random value between 15 and 25 °C.
+   */
+  float const temperature_deg = (rand() % 16) + 10;
+  /* Store in temperature source variable. */
+  temperature.push(temperature_deg);
+  /* Do only one temperature sensore measurement per second. */
+  delay(5000);
+}

examples/Threading_Basics/Thermostat/TemperatureSensor.inot

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+/* Define a data sink named 'temperature' of type 'float'. */
+SINK(temperature, float);
+
+void setup()
+{
+  Serial.begin(9600);
+  while (!Serial) { }
+}
+
+void loop()
+{
+  float const current_temperature_deg = temperature.pop();
+
+  Serial.block();
+  Serial.print("Temperature = ");
+  Serial.print(current_temperature_deg);
+  Serial.println(" °C");
+  Serial.unblock();
+}

examples/Threading_Basics/Thermostat/TemperatureSensorReporter.inot

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+/* This example emulates a thermostat system which consists of
+ * a single temperature sensore and multiple heating devices
+ * or air-conditioners. The temperature sensor provides periodic
+ * temperature sensor measurements and acts as a temperature source.
+ * This temperature is consumed by various TemperatureControl_ threads
+ * which perform the act of actual room temperature control.
+ * 
+ * Note: While there is only a single temperature "source" there are
+ * multiple temperature "sinks". The source/sink paradigm is constructed
+ * in such a way, that each sink is guaranteed to see every value provided
+ * by a source. This is something that can not be modeled using the shared
+ * variable abstraction.
+ */
+
+void setup()
+{
+  /* Connect the TemperatureSensor thread providing temperature readings
+   * with the various TemperatureControl_* threads.
+   */
+  TemperatureSensor.temperature.connectTo(TemperatureControl_LivingRoom.temperature);
+  TemperatureSensor.temperature.connectTo(TemperatureControl_SleepingRoom.temperature);
+  TemperatureSensor.temperature.connectTo(TemperatureSensorReporter.temperature);
+
+  /* Start the individual threads for sensing the temperature
+   * and controlling heating/air-conditioning based on the sensed
+   * temperature on a per-room basis.
+   */
+  TemperatureSensor.start();
+  TemperatureControl_LivingRoom.start();
+  TemperatureControl_SleepingRoom.start();
+  TemperatureSensorReporter.start();
+}
+
+void loop()
+{
+
+}