/*
  Light Control system for Lingnan University UV Disinfection lights
  For Arduino Nano 33 BLE, connected to 3 motion sensors, UV light detection sensor, 5v <-> 3.3v level shifter, and relay
  Interfaces with UVConnect App
  Version 1.0: Initial release for field testing
*/

#include <ArduinoBLE.h> //Include Arduino BLE library. Install using Arduino IDE Library Manager

// Here you can set the local name of the light. If you change this, ensure that you also change the searchTerm variable in the 
//MIT App Inventor project using the .aia file. Each light can have a unique name, but all lights' name should include the search term. For example, we set the searchTerm to
//"LU_Light" but create unique names by including a different number suffix for each light. 
char bleLocalName[] = "LU_Light 9"; 

/* Bluetooth Low Energy centers around 'Services' and 'Characteristics'. Services hold data organized in Characteristics. This sketch uses one service "lightServices", 
 *  organize in four characteristics(switch, motion, status, connection). Services and characteristics are uniquely defined by UUIDs (the long code of digits).
 */
BLEService lightService("722bd000-ca2d-4512-a50f-d706a6f3cdfa"); //create lightService

/* The switch characteristic holds the data byte that determines if the relay should be triggered on or off. 
This can be written to (BLEWrite) and a notification is sent to connected devices when it changes value
*/
BLEByteCharacteristic switchCharacteristic("722bd000-ca2d-4512-a50f-d706a6f3cdfb", BLEWrite | BLENotify); 

/* The switch characteristic holds the data byte that determines if motion has been detected. 
This can be written to (BLEWrite) and a notification is sent to connected devices when it changes value
*/
BLEByteCharacteristic motionCharacteristic("722bd000-ca2d-4512-a50f-d706a6f3cdfc", BLEWrite | BLENotify);

/* The switch characteristic holds the data byte that determines if the UV sensor determines the light to be on or off. 
This can be written to (BLEWrite) and a notification is sent to connected devices when it changes value
*/
BLEByteCharacteristic statusCharacteristic("722bd000-ca2d-4512-a50f-d706a6f3cdfd", BLEWrite | BLENotify);

/* The connection characteristic holds the data byte that determines if the light is connected to a Bluetooth device or not. 
This can be written to (BLEWrite) and a notification is sent to connected devices when it changes value
*/
BLEByteCharacteristic connectionCharacteristic("722bd000-ca2d-4512-a50f-d706a6f3cdfe", BLEWrite | BLENotify);



//Define pin numbers
const int ledPin = 3; // status indication LED pin
const int motionPin1 = 10; //motion sensor pin
const int motionPin2 = 9; //motion sensor pin
const int motionPin3 = 8; //motion sensor pin
const int uvPin = A0; //UV detector pin
const int relayPin = 7; //Light activitaion relay pin
const int oePin = 2; // Level shifter enable pin

//Define somme constants
const int uvThreshold = 30; //Threshold for UV sensor to determine if light is on or off
const int motionInterval = 3000; //(ms) Length of time to leave motion sensors disabled
const int uvInterval = 1000; //(ms) Length of time bewteen UV light samples for determining if light is on or off
const int ledDelay = 1000; //(ms) delay time for led blinking
const int numUvReadings = 10; //number of UV readings to average

//Initialize variables
long uvTime = 0; //timer variable for UV detector
long motionTime = 0; //timer variable for motion sensor
int ledTimer = millis(); //timer variable for status indication led

int uvReadings[numUvReadings]; //array to store UV radings from UV light sensor
int uvIndex = 0; //index of current UV reading
int uvTotal = 0; //running total of UV readings
int uvAverage = 0; //average of UV readings

//int a = 0; For light sensor debugging
boolean motionFlag = false; //Inidcate if any motion sensor has been triggered
boolean motionDisable = false; //Flag for enabling or disabling motion sensors
boolean ledState = false; //state of status indication led


void setup() {
  Serial.begin(9600);
  enableWDT(); //Enable Watchdog timer for detecting microcontroller freezing and resetting
  resetWDT(); // Reset watchdog timer - indicate that the microcontroller is still running
  
  // Set modes for pins
  pinMode(ledPin, OUTPUT);
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH); //initialize relay as off (HIGH = OFF, LOW = ON);
  pinMode(oePin, OUTPUT);
  digitalWrite(oePin, HIGH); //initialize level shifter as ON
  digitalWrite(ledPin, LOW); //initialize status indication LED as OFF
  pinMode(motionPin1, INPUT);
  pinMode(motionPin2, INPUT);
  pinMode(motionPin3, INPUT);

  // begin initialization
  //Start bluetooth, if bluetooth does not initialize print error message, blink LED rapidly, reset Watchdog timer to keep Arduino set
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");
    while (1) {
      resetWDT();
      digitalWrite(ledPin, HIGH);
      delay(250);
      digitalWrite(ledPin, LOW);
      delay(250);
    }

  }

  // set advertised local name and service UUID:
  BLE.setLocalName(bleLocalName);
  BLE.setAdvertisedService(lightService);

  // add the characteristic to the service
  lightService.addCharacteristic(switchCharacteristic);
  lightService.addCharacteristic(motionCharacteristic);
  lightService.addCharacteristic(statusCharacteristic);
  lightService.addCharacteristic(connectionCharacteristic);

  // add service
  BLE.addService(lightService);

  // set the initial value for the characeristics:
  switchCharacteristic.writeValue((byte)0x00);
  statusCharacteristic.writeValue((byte)0x00);
  connectionCharacteristic.writeValue((byte) 0x01);

  // start advertising
  BLE.advertise();

  //Attach hardware interrupts for motion sensors and connect to motionDetected interrupt service routine
  attachInterrupt(digitalPinToInterrupt(motionPin1), motionDetected, RISING);
  attachInterrupt(digitalPinToInterrupt(motionPin2), motionDetected, RISING);
  attachInterrupt(digitalPinToInterrupt(motionPin3), motionDetected, RISING);

  //initialize UV readings to 0:
  for (int i = 0; i < numUvReadings; i++) {
    uvReadings[i] = 0;
  }
  
  resetWDT(); //Reset Watchdog timer to prevent Arduino from resetting
  
}

void loop() {

  // listen for BLE centrals to connect:
  BLEDevice central = BLE.central();

  // If no BLE central is connected, blink LED
  if (!central) {
    if (millis() - ledTimer > ledDelay) {
      ledTimer = millis();
      if (ledState) {
        digitalWrite(ledPin, LOW);
      }
      else {
        digitalWrite(ledPin, HIGH);
      }
      ledState = !ledState;
    }
    resetWDT();
    
  }

  // if a central connects, print its address, and set the status indication LED to solid, and reset the motion sensor timer
  if (central) {
    Serial.print("Connected to central: ");
    // print the central's MAC address:
    Serial.println(central.address());
    digitalWrite(ledPin, HIGH);
    motionTime = millis();
    resetWDT();
    
    // while the central is still connected, reset the watchdog timer to ensure microcontroller is running, check if motion
    // detector has been tripped, check for 'On' or "Off' command, and report status of UV light ('On or Off')

    // On Arduino Nano 33 BLE, "central.connected()" has a bug such that in the case that the central BLE device goes outside
    // the range of the Arduino and disconnects, central.disconnect() will not be changed to false and the Arduino will not
    // adverstise that it is available and it will not be possible to reconnect. This is why the Watchdog timer has been enabled to reset
    // the Arduino in case of a poor disconnection

    while (central.connected()) {
      
      // Re-enable the motion sensor if it has been more than desired motionInterval since the UV lights were turned "On"
      if (motionDisable == true && millis() - motionTime > motionInterval) {
        motionDisable = false;
        Serial.println("Motion Re-enabled");
      }

      // If motion has been detected, send notification to central device, turn relay off and reset motion flag
      if (motionFlag == true) {
        motionCharacteristic.writeValue((byte) 0x00);
        Serial.println(F("Motion Detected"));
        digitalWrite(relayPin, HIGH);
        motionFlag = false;
      }

      if (connectionCharacteristic.written()) {
         if (connectionCharacteristic.value() == (byte) 0x00) {
         central.disconnect();
        }
       else if (connectionCharacteristic.value() == (byte) 0x01) {
          resetWDT(); //reset the Watchdog timer. If the central has disconnected by going out of range, the Arduino will hang and never reach this step
      // After 2 seconds it will reset the Arduino
        }
      }

      // If Central has sent an "On" or "Off" message, determine which one and turn UV light on or off accordingly
      if (switchCharacteristic.written()) {

        // If message is an "On" message, set motionDisable flag to disable motion sensors while the lights turn on so the sensors
        // are not accidently triggered. Start the motion sensor timer so they are re-enabled after 3 seconds
        if (switchCharacteristic.value() == (byte) 0x01) {
          Serial.println(F("LED on"));
          motionDisable = true;
          motionTime = millis();
          digitalWrite(relayPin, LOW);
          digitalWrite(LED_BUILTIN, HIGH); //Turn on internal LED for debugging
        }

        //If "off message", turn off relay
        else if (switchCharacteristic.value() == (byte) 0x00 ) {                  // a 0 value
          Serial.println(F("LED off"));
          digitalWrite(relayPin, HIGH);
          digitalWrite(LED_BUILTIN, LOW);

        }
      }

      // Poll UV sensor at desired interval set by uvInterval, calculate running average of last 10
      // readings. If UV light level is below threshold, indicate that light is off
      // Otherwise indicate that it is on
      long currentMillis = millis();
      if (currentMillis - uvTime >= uvInterval) { //if it is time to take another reading
        uvTime = currentMillis; //We are taking a reading now, record the time
        uvTotal = uvTotal - uvReadings[uvIndex]; //Subtract the 'old' reading with index uvIndex from the total
        uvReadings[uvIndex] = analogRead(uvPin); //Store a new reading with index uvIndex
        Serial.println(uvReadings[uvIndex]);
        uvTotal = uvTotal + uvReadings[uvIndex]; //Calculate new total using new reading with index uvIndex
        uvIndex = uvIndex + 1; // Increase uvIndex by one to prepare for next step

        if (uvIndex >= numUvReadings) { //If the Index has reached the maximum, return to index 0
          uvIndex = 0;
        }
        uvAverage = uvTotal / numUvReadings; //Calculate new average     

        //Serial.println(currentBright);
        if (uvAverage < uvThreshold) {
          statusCharacteristic.writeValue((byte) 0x00); //if UV level is below threshold, report light is off
        }
        else {
          statusCharacteristic.writeValue((byte) 0x01); //if UV level is above threshold, report light is on
        }
      }
    }

    // when the central disconnects, print it out, turn indicator LED off, turn UV light OFF
    Serial.print(F("Disconnected from central: "));
    Serial.println(central.address());
    digitalWrite(ledPin, LOW);
    digitalWrite(relayPin, HIGH);
  }
}


// Watchdog timer setup.
void enableWDT() {
  //Configure WDT on nRF52840.
  NRF_WDT->CONFIG         = 0x01;     // Configure WDT to run when CPU is asleep
  NRF_WDT->CRV            = 196609;  // Timeout set to 6 seconds, timeout[s] = (CRV-1)/32768
  NRF_WDT->RREN           = 0x01;     // Enable the RR[0] reload register
  NRF_WDT->TASKS_START    = 1;        // Start WDT
}

// Reset Watchdog timer
void resetWDT() {
  // Reload the WDTs RR[0] reload register
  NRF_WDT->RR[0] = WDT_RR_RR_Reload;
}
// Motion detect Interrupt Service Routine. If Motion is detected and the motion sensors have been disabled
// throw motion flag. Otherwise do nothing.
void motionDetected() {

  if (motionDisable == false) {
    motionFlag = true;
  }

  else {
  }
}