Smart Voltage Unit for projects

//  Arduino, HM-10, App Inventor 2
//
//  Example Project Part 2: Turn an LED on and off 2 way control 01
//  By Martyn Currey. www.martyncurrey.com
//
//  Pins
//  BT VCC to Arduino 5V out. 
//  BT GND to GND
//  Arduino D8 (ASS RX) - BT TX no need voltage divider 
//  Arduino D9 (ASS TX) - BT RX through a voltage divider
//  Arduino D2 - Resistor + LED
//  Arduino D3 - 10K pull down resistor + button switch


// AltSoftSerial uses D9 for TX and D8 for RX. While using AltSoftSerial D10 cannot be used for PWM.
// Remember to use a voltage divider on the Arduino TX pin / Bluetooth RX pin
// Download from https://www.pjrc.com/teensy/td_libs_AltSoftSerial.html
#include <SoftwareSerial.h>
SoftwareSerial ASSserial(8,9);

// Constants for hardware
const byte Relay_Pin = 12;
const byte SwitchPin = 3;

// general variables
boolean Relay_State = false;
boolean switch_State = false;
boolean oldswitch_State = false;

bool first = true;

char c=' ';


void setup()  
{
    Serial.begin(9600);
    Serial.print("Sketch:   ");   Serial.println(__FILE__);
    Serial.print("Uploaded: ");   Serial.println(__DATE__);
    Serial.println(" ");
     
    ASSserial.begin(9600); 
    Serial.println("AltSoftSerial started at 9600"); 
    Serial.println(" ");

    pinMode(Relay_Pin, OUTPUT); 
    digitalWrite(Relay_Pin,LOW);

    pinMode(SwitchPin, INPUT); 
          
} // void setup()
 
 
void loop()  
{
  checkSwitch();
  checkRecievedData();
}


void checkSwitch()
{
     // Simple toggle switch function with even simpler debounce.
     boolean state1 = digitalRead(SwitchPin);
     delay(1);
     boolean state2 = digitalRead(SwitchPin);
     delay(1);
     boolean state3 = digitalRead(SwitchPin); 
     
     if ((state1 == state2) && (state1==state3)){ 
          switch_State = state1;  
         
          if ( (switch_State == HIGH) && (oldswitch_State == LOW) ){
               // toggle Relay_State.
               Relay_State = ! Relay_State;  
               // If Relay_State is HIGH then LED needs to be turned on.
               if ( Relay_State == HIGH) 
               {  
                    if(!first){
                      digitalWrite(Relay_Pin,HIGH);   // turn on the Relay
                      ASSserial.print("1");       // tell the app the Relay is now on
                      Serial.println("Sent - 1");
                    }else{
                      first=false;
                    }
               }
                                           
               else                     
               {  
                   digitalWrite(Relay_Pin,LOW);    // turn off the Relay
                   ASSserial.print("0");        // tell the app the Relay is now off
                   Serial.println("Sent - 0");    
               }    
          }          
          
          oldswitch_State = switch_State;
      }
}


void checkRecievedData()
{
     // Read from the Bluetooth module and turn the LED on and off
    if (ASSserial.available())
    {
        c = ASSserial.read();
        Serial.println(c);
 
        // The ascii code for 0 is dec 48
        // The ascii code for 1 is dec 49
        if ( c== '0') { digitalWrite(Relay_Pin, LOW);     Relay_State = LOW;}
        if ( c== '1') { digitalWrite(Relay_Pin, HIGH);    Relay_State = HIGH; first=false;}
    }
}