• Author: Sergiu Moga
• Email: sergiu.moga@protonmail.com
• Master: SAS
• Demo:

The “ESP32 Customizable Parking Sensor” project integrates an ESP32 microcontroller with a distance sensor, a buzzer, and an SDCard module to create a versatile parking assistance system. The core functionality involves storing music tracks on the SDCard and playing them through the buzzer. However, what sets this project apart is its user-friendly Web UI, which enables users to select their preferred music track. Additionally, a distance sensor enhances the functionality by adjusting the melody's playback speed based on the proximity of obstacles. As the distance to an obstacle decreases, the melody plays at a faster pace, providing real-time feedback to the user. This project not only offers practical assistance in parking situations but also showcases the capabilities of the ESP32 microcontroller in creating customizable and interactive solutions.

• SDCard stores music files
• Distance sensor reports obstacle proximity
• Buzzer outputs the music
• Buzzer frequency increases as obstacle gets closer
• Web interface allows user to choose the melody
• Web interface shows distance to obstacle

// Load Wi-Fi library
#include <WiFi.h>
#include "FS.h"
#include "SD.h"
#include "SPI.h"

char *current_durations;
short *current_melody;
int current_size, current_note;

const char *network_ssid = "TP-LINK_D5EA4C";
const char *network_password = "20401566";

WiFiServer web_server(80);
String http_header;

unsigned long current_time_ms = millis();
unsigned long previous_time_ms = 0;
const long timeout_ms = 2000;

const int trigger_pin = 33;
const int echo_pin = 32;
const int buzzer_pin = 17;

#define SOUND_SPEED_CM_PER_US 0.034
#define CM_TO_INCH_CONVERSION 0.393701

long pulse_duration_us;
float distance_cm;
float distance_inch;

char file_names[32][32];
short file_melody[32][32];
char file_duration[32][32];
char file_mdsize[32];
int file_count;

void setup() {
    Serial.begin(115200);
    if(!SD.begin(5)){
        Serial.println("Card Mount Failed");
        return;
    }
    
    File root = SD.open("/");
    if(!root){
      return;
    }
  
    if(!root.isDirectory()){
     return;
    }

    File file = root.openNextFile();
    while(file) {
        int idx = 0;
        while(file.available()){
          file_duration[file_count][idx] = file.read();
          idx++;
        }

        file_mdsize[file_count] = idx;

        strcpy(file_names[file_count++], file.name());
        char *dot = strchr(file_names[file_count], '.');
        *dot = '\0';

        file.close();
        file = root.openNextFile();
        idx = 0;
        while(file.available()){
          file_melody[file_count][idx] = file.read();
          idx++;
        }
        file_count++;

        file.close();
        file = root.openNextFile();
    }
    
    pinMode(buzzer_pin, OUTPUT);
    pinMode(trigger_pin, OUTPUT);
    pinMode(echo_pin, INPUT);
    WiFi.begin(network_ssid, network_password);
    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
    }
    web_server.begin();
    current_melody = file_melody[0];
    current_durations = file_duration[0];
    current_size = file_mdsize[0];
}

#define MIN_VALUE(a, b) (a > b ? b : a)

void play_note(int note) {
    long note_duration = 1000 / (int)current_durations[note] - (int)(50 - MIN_VALUE((int)distance_cm, 50));

    tone(buzzer_pin, (int)current_melody[note], note_duration);
    int pause_between_notes = note_duration * 1.30;
    Serial.println(pause_between_notes);
    delay(pause_between_notes);
    noTone(buzzer_pin);
}

unsigned long distance_probe_interval;

void update_distance(void) {
    digitalWrite(trigger_pin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigger_pin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigger_pin, LOW);
    pulse_duration_us = pulseIn(echo_pin, HIGH);
    distance_cm = pulse_duration_us * SOUND_SPEED_CM_PER_US / 2;
}

void loop() {
    WiFiClient client = web_server.available();
    int curr_file;

    if (client) {
        current_time_ms = millis();
        previous_time_ms = current_time_ms;
        String current_line = "";
        while (client.connected() && current_time_ms - previous_time_ms <= timeout_ms) {
            current_time_ms = millis();
            if (client.available()) {
                char c = client.read();
                http_header += c;
                if (c == '\n') {
                    if (current_line.length() == 0) {
                        client.println("HTTP/1.1 200 OK");
                        client.println("Content-type:text/html");
                        client.println("Connection: close");
                        client.println();

                        char req[100];
                        int i;
                        for (i = 0; i < file_count; i++) {
                            sprintf(req, "GET /%s/on", file_names[i]);
                            if (http_header.indexOf(req) >= 0) {
                                current_melody = file_melody[i];
                                current_durations = file_duration[i];
                                current_size = file_mdsize[i];
                                current_note = 0;
                                curr_file = i;
                                break;
                            }
                        }
                   
                        client.println("<!DOCTYPE html><html><head><meta name=\"viewport\" content=\"width=device-width,initial-scale=1\"><link rel=\"icon\" href=\"data:,\"><link href=\"https://fonts.googleapis.com/css2?family=Patrick+Hand&display=swap\" rel=\"stylesheet\"><style>html{font-family:'Patrick Hand',cursive;display:inline-block;margin:0px auto;text-align:center;background-color:#f0f8ff;color:#333;}h1{color:#4682b4;}ol{list-style-type:decimal;padding:0;margin:20px 0;}li{margin:10px 0;font-size:24px;transition:transform 0.3s ease,color 0.3s ease;transform-style:preserve-3d;}li:hover{transform:perspective(1000px) rotateX(10deg) scale(1.05);color:#4682b4;}.button{background-color:#1e90ff;border:none;color:white;padding:30px 70px;text-decoration:none;font-size:32px;cursor:pointer;border-radius:15px;transition:background-color 0.3s ease,transform 0.3s ease;display:block;width:90%;margin:0 auto;font-family:'Patrick Hand',cursive;transform-style:preserve-3d;}.button2{background-color:#555555;padding:24px 60px;font-size:28px;}.button:hover,.button2:hover{background-color:#4682b4;}</style></head><body><h1>ESP32 Alarm Music Player</h1>");
                        client.println(" <ol>");

                        for (i = 0; i < file_count; i++) {
                            if (i == curr_file) {
                                sprintf(req, "<li><a href=\"/%s/off\"><button class=\"button\">%s</button></a></li>", file_names[i], file_names[i]);
                            } else {
                                sprintf(req, "<li><a href=\"/%s/on\"><button class=\"button button2\">%s</button></a></li>", file_names[i], file_names[i]);
                            }
                            client.println(req);
                        }
                        
                        client.println(" </ol>");

                        client.println("</body></html>");

                        client.println();
                        break;
                    } else {
                        current_line = "";
                    }
                } else if (c != '\r') {
                    current_line += c;
                }

            } else {
                play_note(current_note++);
                if (current_note >= current_size)
                    current_note = 0;
                update_distance();
            }
        }
        http_header = "";
        client.stop();
    }

    play_note(current_note++);
    if (current_note >= current_size)
        current_note = 0;
    update_distance();
}