// Private Defintions
#define IR_pin A0
#define distance_1 20
#define distance_2 40

// Gloabal Variables
int adc_val;
int num_of_push_ups;
int state_1 = 0;
float distance = 0.0;

// Arduino Initialization
void setup()
{
  pinMode(IR_pin, INPUT);
  Serial.begin(9600);
}

// Infinite loop
void loop()
{
  /*
  Reads ADC value which is in range of 0-1023
  When ADC = 1023 -> Distance = 0
  When ADC = 0	  -> Distance = 50
  Construct straight line:
  y = -50/1023 x + 50
  y is distance
  x is ADC value
  This function will convert value from (0,1023)
  into distance from 50 to 0cm
  */
  adc_val = analogRead(IR_pin); //read ADC value
  distance = -(50.0/1023.0)*adc_val+50.0; //calculate distance from adc value
  
  /*
  Check completion of push-up
  When distance is less than 20 cm
  State 1 is enabled, so program is waiting for user to reach 40cm
  When distance is larger than 40 cm, number of push ups completed is increased
  Output is printed in the serial monitor
  */
  if (distance <= distance_1)
  {
    state_1 = 1;
  }
  if (distance >= distance_2 && state_1)
  {
    num_of_push_ups++;
    state_1 = 0;
    Serial.print("Number of push-ups:");
  	Serial.println(num_of_push_ups);
  } 
  
  delay(10);
}