Skip to content
IoT - Students' Portfolio

System Requirements

To build the embedded device, the following requirements from DLO must be fulfilled:

Requirement ID# Requirement MoSCoW Compliant
EMBRQ#01 The embedded device acts as a client and sends measured sensor data to the application backend over http or https. MUST YES
EMBRQ#02 The embedded device also acts as a server and receives status messages from the application backend over http or https. MUST YES
EMBRQ#03 The embedded device contains at least two types of input sensors (e.g. LDR, buttons, joystick, capacitive touch, etc.). MUST YES
EMBRQ#04 The embedded device contains at least two types of visual and/or sensory outputs (e.g. LED, LED Matrix, 7-segment display, motor, servo, actuator, LCD-screen, buzzer, etc.). MUST YES
EMBRQ#05 The embedded device uses the WifiManager for configuration of SSID and password (PWD) for connecting to the network. MUST YES

EMBRQ#01 — Proof of HTTPS API Access from Devices

Both devices can access the API via https://yanisdeplazes.loca.lt using HTTPS requests. They can fetch data using GET and upload sensor readings using POST.

GET: Fetch Devices

File: Client.cpp — Line 165 Source

1
String raw = httpGET("/api/device");

GET: Latest Reading for Device

File: Client.cpp — Line 202 Source

1
String raw = httpGET("/api/views/LatestDeviceReadings?device_id=1");

POST: Register Device

File: Client.cpp — Line 208 Source

1
2
3
4
5
6
7
StaticJsonDocument<128> doc;
doc["key"] = mac;
doc["name"] = "Weather Station";

String payload;
serializeJson(doc, payload);
httpPOST("/api/device", payload, "application/json");

POST: Send Reading + Sensor Data

File: Client.cpp — Line 258 Source

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
StaticJsonDocument<1024> doc;
doc["device_id"] = deviceId;
JsonArray arr = doc.createNestedArray("sensor_data");

JsonObject obj = arr.createNestedObject();
obj["sensor_id"] = 1;
obj["value"] = 24.5;

String payload;
serializeJson(doc, payload);
httpPOST("/api/reading-with-sensordata", payload, "application/json");

Used Libraries

  • WiFiClientSecure for HTTPS
  • ArduinoJson for JSON handling

All traffic to and from the device is encrypted and uses HTTPS.

EMBRQ#02

The ESP32 device hosts a HTTPS server using a self-signed certificate. It exposes the /index route to get the current index of what device is currently displayed for a fallback.

GET: /index Endpoint

File: server.cpp — Line ~45 Source

1
2
3
4
5
6
7
esp_err_t handle_index(httpd_req_t *req) {
    char resp_str[32];
    snprintf(resp_str, sizeof(resp_str), "{\"index\": %d}", currentIndex);

    httpd_resp_set_type(req, "application/json");
    return httpd_resp_send(req, resp_str, HTTPD_RESP_USE_STRLEN);
}

HTTPS Server Setup

File: server.cpp — Line ~63 Source

1
2
3
4
5
6
7
httpd_ssl_config_t conf = HTTPD_SSL_CONFIG_DEFAULT();
conf.servercert = (const uint8_t *)server_cert;
conf.servercert_len = strlen(server_cert) + 1;
conf.prvtkey_pem = (const uint8_t *)server_key;
conf.prvtkey_len = strlen(server_key) + 1;

esp_err_t ret = httpd_ssl_start(&server, &conf);

Used Libraries

  • httpd_ssl from ESP-IDF for TLS web server
  • esp_tls for certificate handling
  • Custom cert.h and key.h headers for in-memory PEM cert and key

NGINX Settings

The system uses NGINX's Push Stream Module to broadcast the current index when it changes. The subscribed client (IPad or Browser) can receive real-time updates over the WebSocket-like connection.

File: nginx.conf — Line ~51 Source

1
2
3
4
5
6
7
8
9
    location ^~ /api/installation/ {
            rewrite ^/api/installation(/.*)$ $1 break;
            proxy_pass https://100.74.255.21; // Hardcoded: not optimal
            proxy_ssl_verify off;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
        }

EMBRQ#03

EMBRQ#03 — Sensor Data Collection

The reader device integrates 4 types of sensors (DHT11, BMP180, BH1750, analog water sensor) to measure environmental data and upload it to the backend API via HTTPS. Each sensor is initialized and polled in the main loop, with results printed to the serial monitor and sent as a single payload to the API.

Loop

File: sensors.ino — Lines ~119 Source

1
2
3
4
5
6
7
void loop() {
  readDht11();
  readBh1750();
  readWaterSensor();
  readBmp180();
  // ...
}

Reading Functions

File: sensors.ino — Lines ~134 Source

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
void readDht11() {
  float temp = dht.readTemperature();
  float hum = dht.readHumidity();
  if (!isnan(temp)) sensorData[0].value = temp;
  if (!isnan(hum)) sensorData[1].value = hum;
}

void readBh1750() {
  float lux = lightMeter.readLightLevel();
  if (lux >= MIN_VALID_LUX) {
    sensorData[IDX_BH1750_LUX].value = lux;
  }
}

void readWaterSensor() {
  sensorData[IDX_WATER_ANALOG].value = analogRead(WATERPIN);
}

void readBmp180() {
  if (!bmpReady) return;

  sensorData[IDX_BMP180_TEMP].value = bmp.readTemperature();
  sensorData[IDX_BMP180_PRESSURE].value = bmp.readPressure() / PA_TO_HPA_DIVISOR;
}

Used Libraries

  • DHT for temperature and humidity (DHT11)
  • Adafruit_BMP085 for temperature and pressure (BMP180)
  • BH1750 for ambient light (lux)
  • Wire (I2C) for communication

EMBRQ#04

Both devices have output components (3 in total). They allow the for visually or audibly feedback from weather data.

  • LED (Visualize when Setup is done)
  • WS2812B Ledstrip (Visualize Temperature)
  • Mini MP3 DFPlayer Player (Plays sound depending on weather)

LED

File: sensors.ino — Lines ~111 Source

1
  digitalWrite(WIFI_LED_PIN, HIGH);

WS2812B Ledstrip

File: LEDManager.cpp — Lines ~50 Source

1
2
3
4
void initLEDs() {
  FastLED.addLeds<LED_TYPE, LED_PIN, LED_COLOR_ORDER>(leds, NUM_LEDS);
  FastLED.setBrightness(LED_BRIGHTNESS);
}

File: LEDManager.cpp — Lines ~86 Source

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
void showColor(float temp) {
  CRGB color = (temp >= TEMP_COLOR_THRESHOLD)
                 ? interpolateColor(temp, TEMP_COLOR_THRESHOLD, TEMP_COLOR_MAX, COLOR_WARM_MIN, COLOR_WARM_MAX)
                 : interpolateColor(temp, TEMP_COLOR_MIN, TEMP_COLOR_THRESHOLD, COLOR_COLD_MIN, COLOR_COLD_MAX);

  for (int i = LOOP_START_INDEX; i < NUM_LEDS; i++) {
    leds[i] = color;
  }

  FastLED.show();

  Serial.printf("Static Temp Color → R: %d, G: %d, B: %d\n", color.r, color.g, color.b);
}

Mini MP3 DFPlayer Player

File: DFPlayerManager.cpp — Lines ~60 Source

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
void initDFPlayer(HardwareSerial* serial, int rx, int tx) {
  dfSerial = serial;
  rxPin = rx;
  txPin = tx;

  dfSerial->begin(DFPLAYER_BAUDRATE, SERIAL_8N1, rxPin, txPin);

  if (!player.begin(*dfSerial)) {
    Serial.println("DFPlayer init failed");
    while (true); // Halt if initialization fails
  }

  setVolume(currentVolume);
}

File: DFPlayerManager.cpp — Lines ~L117 Source

1
2
3
4
5
6
7
8
void playTrack(uint8_t track) {
  if (track != lastTrackPlayed) {
    Serial.println("Playing new Track");
    Serial.println(track);
    player.loop(track);
    lastTrackPlayed = track;
  }
}

Libraries Used

  • DFRobotDFPlayerMini
  • FastLED

EMBRQ#05

Both devices use the WiFiManager library for the network setup. If no credentials are stored, it launches a portal for configuration:

  • No hardcoded credentials
  • Portal fallback
  • Auto-reconnect to known networks
  • Reboots if config times out

File: installation: WiFiSetup.cpp — Lines ~21 Source

File: sensors: WiFiSetup.cpp — Lines ~21 Source

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
void connectToWiFi() {
  wifiManager.setConfigPortalTimeout(PORTAL_TIMEOUT_SEC);

  if (!wifiManager.autoConnect(WIFI_AP_NAME, WIFI_AP_PASSWORD)) {
    Serial.println("WiFi connection failed. Restarting...");
    delay(RESTART_DELAY_MS);
    ESP.restart();
  }

  Serial.println("WiFi connected.");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());
}

Libraries Used

  • WiFiManager