Unit 1: IoT hardware interfacing and cloud integration

• Safety: use a 220 Ω resistor with LEDs; Pi GPIO is 3.3 V — never feed it 5 V.

cppvoid setup() { pinMode(13, OUTPUT); pinMode(8, OUTPUT); }
void loop() {
  digitalWrite(13, HIGH); tone(8, 1000); delay(1000);   // on 1 s
  digitalWrite(13, LOW);  noTone(8);     delay(2000);   // off 2 s
}

cppvoid setup() { pinMode(2, INPUT_PULLUP); pinMode(7, INPUT); pinMode(13, OUTPUT); Serial.begin(9600); }
void loop() {
  bool pressed = digitalRead(2) == LOW;     // button to GND
  bool obstacle = digitalRead(7) == LOW;    // IR module output low when object near
  int light = analogRead(A0);               // LDR divider 0–1023
  digitalWrite(13, (pressed || obstacle || light < 300) ? HIGH : LOW);
  Serial.println(light); delay(200);
}

cpp#include <DHT.h>
DHT dht(2, DHT11);
void setup() { Serial.begin(9600); dht.begin(); }
void loop() {
  float h = dht.readHumidity(), t = dht.readTemperature();
  if (isnan(h) || isnan(t)) { Serial.println("Read failed"); return; }
  Serial.print(t); Serial.print(" C, "); Serial.print(h); Serial.println(" %");
  delay(2000);                                    // DHT11 needs ≥ 1 s between reads
}

cppvoid setup() { pinMode(4, OUTPUT); }
void loop() { digitalWrite(4, HIGH); delay(5000); digitalWrite(4, LOW); delay(5000); }   // motor 5 s on/off

• The relay isolates the low-voltage board from the motor supply; use a module with a flyback diode and opto-isolation.

cpp#include <Adafruit_SSD1306.h>
Adafruit_SSD1306 oled(128, 64, &Wire);
void setup() { oled.begin(SSD1306_SWITCHCAPVCC, 0x3C); oled.clearDisplay(); oled.setTextSize(2); oled.setTextColor(WHITE);
  oled.setCursor(0, 0); oled.println("SBS IoT"); oled.display(); }
void loop() {}

cpp#include <SoftwareSerial.h>
SoftwareSerial bt(10, 11);                     // HC-05 TX→10, RX←11 (via divider)
void setup() { bt.begin(9600); pinMode(13, OUTPUT); }
void loop() {
  if (bt.available()) { char c = bt.read(); digitalWrite(13, c == '1' ? HIGH : LOW); }   // LED on/off from app
  bt.print("T="); bt.println(analogRead(A0)); delay(1000);                              // send data to phone
}

• Pair the HC-05 (PIN 1234) and use a Bluetooth serial terminal app.

pythonimport requests, time, Adafruit_DHT
KEY_W, CH = "WRITE_KEY", "123456"
for _ in range(5):
    h, t = Adafruit_DHT.read_retry(Adafruit_DHT.DHT11, 4)
    requests.get("https://api.thingspeak.com/update", params={"api_key": KEY_W, "field1": t, "field2": h})
    time.sleep(16)                                   # free plan: one update per 15 s
r = requests.get(f"https://api.thingspeak.com/channels/{CH}/feeds.json", params={"results": 5})
print([f["field1"] for f in r.json()["feeds"]])

bashsudo apt install -y mariadb-server python3-pymysql
sudo mysql -e "CREATE DATABASE iot; CREATE USER 'pi'@'localhost' IDENTIFIED BY 'pi123'; GRANT ALL ON iot.* TO 'pi'@'localhost';"
sudo mysql iot -e "CREATE TABLE readings (id INT AUTO_INCREMENT PRIMARY KEY, temp FLOAT, ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP);"

pythonimport pymysql
db = pymysql.connect(host="localhost", user="pi", password="pi123", database="iot")
with db.cursor() as c:
    c.execute("INSERT INTO readings (temp) VALUES (%s)", (28.5,)); db.commit()
    c.execute("SELECT * FROM readings ORDER BY ts DESC LIMIT 5"); print(c.fetchall())

pythonimport paho.mqtt.client as mqtt, time, random
c = mqtt.Client(); c.connect("test.mosquitto.org", 1883)
for _ in range(5):
    c.publish("sbs/lab/temperature", f"{25 + random.random() * 5:.1f}", qos=1); time.sleep(2)

bashmosquitto_sub -h test.mosquitto.org -t "sbs/lab/#" -v     # subscriber to verify