Nano33IoT - Ultrasensor-System

A compact, interrupt-driven sensor system for the Arduino Nano 33 IoT.
It reads distance (HC-SR04), ambient light (BH1750) and a slide potentiometer threshold, and actuates LEDs + a buzzer.
Designed as a single-file, assessor-ready project with timer and external-interrupt logic.

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Overview

This project implements a Sense → Think → Act system on an Arduino Nano 33 IoT.

Sensors:

• HC-SR04 ultrasonic (distance)
• BH1750 light sensor (I²C)
• Slide potentiometer (threshold)

Actuators:

• Red LED
• Green LED
• Buzzer

Control:

• HC-SR04 echo via external interrupt (D2)
• Periodic sampling via hardware timer ISR (TC3, 500 ms)
  All logic is non-blocking and contained in one file TaskM1.cpp.

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Repository contents

• TaskM1.cpp — Final Arduino sketch (single file)
• Reflection_Report.md — 300–500 word reflection describing architecture, interrupts, and issues/resolutions
• circuit_diagram.png — Annotated breadboard/schematic image for wiring
• README.md — This file
• serial_sample.png — Screenshot of Serial Monitor showing sensor and timer events

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Key features

• External interrupt: HC-SR04 echo captured using attachInterrupt() on D2 (rising/falling edges)
• Hardware timer ISR: SAMD TC3 via SAMDTimerInterrupt library triggers sampling every 500 ms
• Separation of logic: ISRs only set flags; main loop performs sensor reads, processing and actuation
• Multiple sensors + actuators: HC-SR04, BH1750, potentiometer; red/green LEDs and buzzer
• Robustness: Distance values <3 cm or >400 cm are clamped/ignored; pot readings are smoothed; I²C sensor handled in continuous mode
• Single-file delivery: Everything required to run the system is in TaskM1.cpp

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Hardware (components)

• Arduino Nano 33 IoT (SAMD21)
• HC-SR04 ultrasonic distance sensor
• BH1750 light intensity sensor (I²C breakout)
• Keyestudio slide potentiometer module (use correct wiper OTA/OTB)
• LEDs: red, green (220 Ω resistors each)
• Active buzzer (or buzzer + transistor if high current)
• Breadboard, jumper wires, power from Nano 3.3 V rail

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Pin mapping

1. Power & Ground

• Nano 3.3V → breadboard + rail (use for sensors and pot)
• Nano GND → breadboard − rail

2. HC-SR04

• VCC → 3.3V
• GND → GND
• TRIG → D3
• ECHO → D2 (external interrupt)

3. BH1750 (I²C)

• VCC → 3.3V
• GND → GND
• SDA → A4
• SCL → A5
• AD0/ADDR → leave floating or tie to GND (default 0x23)

4. Potentiometer

• VCC → 3.3V
• GND → GND
• Wiper → A0 (confirm OTA/OTB; test with simple analogRead sketch)

5. Actuators

• Red LED anode → D8 → (220 Ω) → GND
• Green LED anode → D9 → (220 Ω) → GND
• Buzzer + → D10, − → GND (add resistor or transistor if needed)

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Software: install & upload

1. Install Arduino IDE (preferably v1.8+ or Arduino IDE 2.x)
2. In Library Manager, install:
   • BH1750 (Christopher Laws or equivalent)
   • SAMD TimerInterrupt (by Khoi Hoang) — ensure SAMD support (v1.10.1+)
3. Open TaskM1.cpp in the IDE.
4. Select Arduino Nano 33 IoT board and correct port.
5. Upload the sketch.
6. Open Serial Monitor at 115200 baud.

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Troubleshooting

• If potRaw stays small, confirm wiper pin (OTA vs OTB) and power rails. Test with a minimal analogRead(A0) sketch.
• HC-SR04 may need 3.3V on Nano 33 IoT; avoid relying on the 5V rail. If powering at 5V, use a level shifter or voltage divider on ECHO.
• BH1750 library may show warnings about SAMD metadata; the sensor works on Nano 33 IoT — verify wiring if readings are invalid.