exam-overview

Exam Overview — Connected Objects (420-6P3)

Exam Structure

Part 1: Practical (reTerminal)

• Bring your reTerminal (required)
• Open-book: course notes, your laptop, internet all allowed
• Teacher will ask you to connect 1–3 devices to your reTerminal
• Tasks: take measurements → record to file → upload
• Starter code will be provided on exam morning (generic sensor code for Digital/Analog/Serial + file recording)

Part 2: Theory (written on paper)

• Open-book
• Written answers on a sheet of paper provided
• Topics covered:
  • Bash / Linux
  • Python
  • Electronics (protocols + basic circuitry)
  • Web / IoT Protocols
• Questions will be relevant to the practical part

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Part 1 Workflow — Sensor Code Patterns

Digital sensor (GPIO Zero)

from gpiozero import Button
button = Button(2)
print(button.is_pressed)  # True/False

Analog sensor (Grove Hat ADC)

• Use AHT20 or similar I2C sensor via smbus2 or adafruit library
• Grove Hat provides 4 ADC channels (12-bit, 0–4095)
• See Serial Protocols for I2C Python code

Serial sensor (pySerial)

import serial
with serial.Serial('/dev/serial0', 9600) as ser:
    line = ser.readline()
    print(line)

Record measurements to a file

import json, time
 
with open('measurements.json', 'a') as f:
    record = {'timestamp': time.time(), 'value': reading}
    f.write(json.dumps(record) + '\n')

Upload (typical pattern)

# rsync to a remote host
rsync measurements.json user@host:/path/
 
# or copy to mounted Windows filesystem from WSL
cp measurements.json /mnt/c/Users/<you>/Desktop/

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Quick Navigation — Theory Topics

Area	Wiki page
Electronics (Ohm’s Law, resistors)	Electronics and Circuitry
Signals, ADC, sampling	Signals and ADC
Serial protocols (SPI/I2C/PWM/Serial)	Serial Protocols
MQTT, HTTP, pub/sub	MQTT and IoT Protocols
GPIO, reTerminal hardware, built-in sensors	GPIO and reTerminal
Python (argparse, venv, logging, pytest)	Python Essentials
Async Python (asyncio)	Async Python
Linux & Bash commands (5 fingers, pipes)	Linux and Bash Commands
Bash scripting (variables, if, chmod)	Bash Scripting
IoT system architecture (5 components)	IoT System Architecture
Azure D2C, Device Twins	Azure IoT Overview

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Key Formulas to Remember

Formula	Use
V = IR	Ohm’s Law — voltage, current, resistance
I = V / R	Find current given voltage and resistance
R = V / I	Find resistor value
Vr = Vsource − Vled	Kirchhoff’s Voltage Law (series circuit)
fs = 1 / T	Sampling frequency from sampling period
values = 2^n	Number of distinct values for n-bit ADC
bitrate = fs × bits	Bits per second for sampled signal

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Key GPIO Electrical Limits (reTerminal)

• Max current per GPIO pin: 16 mA
• GPIO voltage: 3.3 V (not 5 V tolerant!)
• Max current from 3.3 V / 5 V power pins: 2 A

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Sensor Types on the Exam

Type	Protocol	Python lib	Port
Digital	GPIO high/low	gpiozero	GPIO pin number
Analog	ADC via I2C (Grove Hat)	smbus2 / adafruit	I2C bus
Temperature/Humidity	I2C (AHT20)	adafruit-circuitpython-ahtx0	I2C
Serial	UART async	pySerial	/dev/serial0
Built-in light	Read file	open() / cat	/sys/bus/iio/devices/iio:device0/in_illuminance_input
Built-in LED	Write file	echo / tee	/sys/class/leds/usr_led0/brightness