Я многократно повторяю одну и ту же ошибку - "не был объявлен в этой области, что мне делать?

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Вот этот код :

/*
  LiquidCrystal Library - Hello World

  The circuit:
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)


*/

// include the library code:
#include <LiquidCrystal.h>

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

//intialise all varibales being used in the program
float currentTemp = tempsensor();
int ledPin = 13; // choose the pin for the LED
int inPin = 7;   // choose the input pin (for a pushbutton)
int val = 0;     // variable for reading the pin status
digitalWrite(LED, HIGH);
 digitalWrite(LED, LOW);
void setup() {

  pinMode(ledPin, OUTPUT);  // declare LED as output
  pinMode(inPin, INPUT);    // declare pushbutton as input
  
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
}

void loop() {
  
  val = digitalRead(inPin);  // read input value
  if (val == HIGH) {         // check if the input is HIGH (button released)
  float currentTemp = tempsensor();
  if(currentTemp<maxTemp){
  //turn the heat up(LED )
   digitalWrite(LED, HIGH);
   }else if(currentTemp>maxTemp){
    //turn off heat(LED)
    digitalWrite(LED, LOW);
     }else{}
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(maxTemp);
}
}

Вот такие ошибки:

ArduinoLcdButtonFunctions:71: error: 'tempsensor' was not declared in this scope

   float currentTemp = tempsensor();

                                  ^

ArduinoLcdButtonFunctions:72: error: 'maxTemp' was not declared in this scope

   if(currentTemp<maxTemp){

                  ^

ArduinoLcdButtonFunctions:74: error: 'LED' was not declared in this scope

    digitalWrite(LED, HIGH);

                 ^

ArduinoLcdButtonFunctions:77: error: 'LED' was not declared in this scope

     digitalWrite(LED, LOW);

                  ^

ArduinoLcdButtonFunctions:83: error: 'maxTemp' was not declared in this scope

   lcd.print(maxTemp);

             ^

exit status 1
'tempsensor' was not declared in this scope

Что я могу сделать, чтобы исправить это ???

Что я уже пробовал:

Форумы Ardiuno, Youtube, StackOverFlow.

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