Reversing Radar

/* Macro Define */
#define BUZZER_PIN               37            /* sig pin of the Grove Buzzer ,J16 on booster board*/

int length = 1;         /* the number of notes */
char notes[] = "c"; //notes in the song
int beats[] = {1}; //length of each note
int tempo = 200; 

 
#include "TM1637.h" 
#include "Ultrasonic.h"

/* Macro Define */
#define CLK               39              /* 4-Digit Display clock pin J14 on booster board */
#define DIO               38              /* 4-Digit Display data pin */
#define ULTRASONIC_PIN    24              /* pin of the Ultrasonic Ranger *,J6 on booster board*/

/* Global Variables */
TM1637 tm1637(CLK, DIO);                  /* 4-Digit Display object */
Ultrasonic ultrasonic(ULTRASONIC_PIN);    /* Ultrasonic Ranger object */
int distance = 0;                         /* variable to store the distance to obstacles in front */
int8_t bits[4] = {0};                     /* array to store the single bits of the value */
const int switchpin = 31;                 /* switch pin PF4 on board */
const int motorpin =23;                   /* motor  pin PD0 on board */

void setup() {
  /* set switch pin as input */
  pinMode(switchpin, INPUT);
  /* set buzzer pin and motor pin as output */
  pinMode(BUZZER_PIN, OUTPUT); 
  pinMode(motorpin, OUTPUT);
  /* Initialize 4-Digit Display */
    tm1637.init();
    tm1637.set(BRIGHT_TYPICAL);
}

void loop() {
  int switchval;
  switchval = digitalRead(switchpin);             /* read the value from switch pin (LOW ==0, HIGH ==1)*/
  distance = ultrasonic.MeasureInCentimeters();   /* read the value from the sensor */ 
  /*Turn off motor if switch is off*/
  if (switchval == LOW){
    analogWrite(motorpin, 0);
  }
  /*Turn on motor if switch is on and distance is greater than 20cm */
  if (switchval == HIGH && distance >= 20){
    analogWrite(motorpin, 200);
  }
  /*Turn off motor if switch is on and distance is smaller than 10cm */
  else if (distance <10){
    analogWrite(motorpin, 0);
  }
  /*If switch is on and distance is small than 10cm, play buzzer with an interval based on distance */
  if (distance < 20 && switchval ==HIGH){
    playNote(notes[0], beats[0] * tempo);
    delay(distance*20 );
  }
   for(int i = 3; i >= 0; i--) 
      {   
        /* Convert the value to individual decimal digits for display */
        bits[i] = distance % 10;
        distance = distance / 10;  
        tm1637.display(i, bits[i]);                 /* display on 4-Digit Display */
      }
  delay(20);
}
/* play tone */
void playTone(int tone, int duration) 
{
  for (long i = 0; i < duration * 1000L; i += tone * 2) 
  {
    digitalWrite(BUZZER_PIN, HIGH);
    delayMicroseconds(tone);
    digitalWrite(BUZZER_PIN, LOW);
    delayMicroseconds(tone);
  }
}

char names[] = { 'c', 'd', 'e', 'f', 'g', 'a', 'b', 'C' };
int tones[] = { 1915, 1700, 1519, 1432, 1275, 1136, 1014, 956 };

void playNote(char note, int duration) 
{
  
  
  // play the tone corresponding to the note name
  for (int i = 0; i < 8; i++) 
  {
    if (names[i] == note) 
    {
      playTone(tones[i], duration);
    }
  }
}