SLAVE

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

#define CE_PIN   7
#define CSN_PIN 8
#define RF_PWR_HIGH

const byte thisSlaveAddress[5] = {'R', 'x', 'A', 'B', 'A'};

RF24 radio(CE_PIN, CSN_PIN);

char dataReceived[10]; // this must match dataToSend in the TX
int ackData[2] = {0, 0}; // the two values to be sent to the master
bool newData = false;
bool blueLightState = 0;
const int ledPinA =  3;      // the number of the LED pin
int digitReceived = 0;
const int buttonPinA = 2;     // the number of the pushbutton pin A
int buttonStateA = 0;         // variable for reading the pushbutton status
bool buttonAActive = 0;
int slaveMode = 0;
unsigned int currentMillis = 0;
unsigned int lastCanx = 0;
int canxMS;
unsigned int lightOnTime;
unsigned int lightOffTime;
unsigned int prevSerial;

const int serialUpdateInterval = 500;
const int canxPersist = 1000;


//==============

void setup() {
  Serial.begin(9600);
  radio.begin();
  radio.setDataRate( RF24_250KBPS );
  radio.openReadingPipe(1, thisSlaveAddress);
  radio.enableAckPayload();
  radio.startListening();
  radio.writeAckPayload(1, &ackData, sizeof(ackData)); // pre-load data
  pinMode(ledPinA, OUTPUT);
}

//==========

void loop() {
  currentMillis = millis();
  getData();
  updateLight();
  checkButtonState();
  updateSerial();
}

void checkButtonState() {
  buttonStateA = digitalRead(buttonPinA);
  if (buttonStateA == HIGH) {
    doDeactivate();
  }
}

//==========

void updateLight() {
  if (currentMillis - lastCanx < canxPersist) {
    digitalWrite(ledPinA, LOW);
    digitalWrite(LED_BUILTIN, LOW);
  } else {
    if (slaveMode == 1) {
      digitalWrite(ledPinA, HIGH);
    } else {
      digitalWrite(ledPinA, LOW);
    }
  }
}

//============

void getData() {
  // Serial.println ("getData running");
  if ( radio.available() ) {
    radio.read( &dataReceived, sizeof(dataReceived) );
    updateAck();
    newData = true;
    digitReceived = dataReceived[0];

    switch (digitReceived) {
      case 48: // a '0' has been received - go into standby
        // Serial.println("Scenario 0 - Standby");
        doStandby();
        break;
      case 49: // turn your light on
        // Serial.println("Scenario 1 - Turn light on");
        doActivate();
        break;
    }
  }
}

//================

void doStandby() {
 // Serial.println("doStandby running");
  if (currentMillis - lastCanx < canxPersist) {
    slaveMode = 2;
  } else {
    slaveMode = 0;
  }
  blueLightState = 0;
  ackData[0] = 0;
}
//================

void doActivate() {
 //   Serial.println("doActivate running");
  if (slaveMode == 0) {
    lightOnTime = currentMillis;
  }
  if (currentMillis - lastCanx < canxPersist) {
    slaveMode = 2;
  } else {
    slaveMode = 1;
  }
  blueLightState = 1;
  ackData[0] = 1; // acknowledge that light is on
}
//================

void doDeactivate() {
  //  Serial.println("doDeactivate running");
  lightOffTime = currentMillis;
  //Serial.print("lightOffTime: ");
  //Serial.println(lightOffTime);
  canxMS = (lightOffTime - lightOnTime);
  slaveMode = 2;
  lastCanx = currentMillis;
}



//================

void updateAck() {
  if (slaveMode == 2) {
    ackData[0] = 2;
    ackData[1] = (canxMS);
  } else {
    ackData[0] = slaveMode;
    ackData[1] = 0;
  }
  // ackData[1] = millis();
  radio.writeAckPayload(1, &ackData, sizeof(ackData)); // load the payload for the next time
}

//================

void updateSerial() {
  if ((currentMillis - prevSerial) >= serialUpdateInterval) {
    Serial.print("Mode:  ");
    Serial.print(slaveMode);
    Serial.print(" canxMS: ");
    Serial.print(canxMS);
    Serial.print(" digitReceived: ");
    Serial.print(digitReceived);
    //Serial.print("lightOnTime: ");
    //Serial.print(lightOnTime);
    Serial.println();
    if (newData == true) {
      //Serial.print("Data received ");
      //Serial.println(dataReceived[8]);
      //Serial.print(" ackPayload sent ");
      //Serial.print(ackData[0]);
      //Serial.print(", ");
      // Serial.println(ackData[1]);
      newData = false;
    }
    prevSerial = currentMillis;
  }
}