Hardware &
Electronics
Halesowen College · T Level Data Analytics
Microcontroller vs Microprocessor
Microprocessor (CPU)
- Powerful general-purpose chip
- Needs external RAM, storage, peripherals
- Runs full operating systems (Linux, Windows)
- High power draw — needs cooling
- Examples: Intel i5, Apple M4, Raspberry Pi 4
Microcontroller (MCU)
- CPU + RAM + Flash + I/O all on one chip
- Designed to run a single dedicated program
- Very low power — can run on batteries
- Starts instantly, runs indefinitely
- Examples: Pico W, Arduino Uno, ESP32
For our project, a microcontroller is ideal — it boots in milliseconds, sips power from a USB socket, and runs our sensor loop 24/7 without any user intervention.
The Raspberry Pi Pico W
Core hardware
- RP2040 chip — designed by Raspberry Pi in the UK
- Dual-core ARM Cortex-M0+ @ 133 MHz
- 264 KB SRAM · 2 MB Flash memory
- 26 GPIO pins · 3 × SPI · 2 × I2C · 2 × UART
- 12-bit ADC for analogue sensors
The 'W' — Wi-Fi
- Infineon CYW43439 wireless chip
- 802.11n 2.4 GHz Wi-Fi (single-band)
- MicroPython's network module connects to WPA2
- Can act as a Wi-Fi access point too
Important: The college Wi-Fi uses enterprise authentication (802.1x). We will use a mobile hotspot during initial testing.
GPIO Pins — General Purpose I/O
What they are
- Physical pins on the Pico — programmable in software
- Input: read a button, a sensor signal, a switch
- Output: light an LED, trigger a relay, send a signal
- Digital: HIGH (3.3V) or LOW (0V)
- 3 pins can also do ADC — analogue voltage reading
In MicroPython
from machine import Pin
btn = Pin(15, Pin.IN)
print(btn.value())
led = Pin(25, Pin.OUT)
led.value(1) # HIGH → on
led.value(0) # LOW → off
I2C — The Sensor Protocol
Inter-Integrated Circuit — a 2-wire serial bus invented by Philips (1982)
How it works
- Just 2 wires carry all communication: SDA and SCL
- One controller (Pico) + one or more targets (sensors)
- Every device has a unique 7-bit address
- BME680 default address:
0x76or0x77 - Controller sends address, target responds with data
- Can chain up to 127 devices on one bus pair
Why I2C and not SPI? SPI is faster but needs 4 wires per device. I2C's 2-wire bus is perfect for slow sensors where we want clean wiring.
Connecting BME680 → Pico W
Only 4 jumper wires needed — power, ground, data, clock
| BME680 pin | Wire colour (convention) | Pico W pin | Why |
|---|---|---|---|
| VCC | Red | 3V3 (pin 36) | Powers the sensor — 3.3 V, not 5 V |
| GND | Black / Brown | GND (pin 38) | Completes the circuit |
| SDA | Yellow | GP4 (pin 6) | Serial data line (I2C bus 0) |
| SCL | Blue / White | GP5 (pin 7) | Serial clock line (I2C bus 0) |
Critical: Always use the 3V3 pin (3.3 V), never the VBUS pin (5V) — the BME680 is a 3.3 V device. 5 V will destroy the sensor permanently.
How a Breadboard Works
The rows and rails
- Each numbered row (1–30 etc.) connects horizontally
- Left and right halves are not connected to each other
- The coloured rails (+/−) run vertically — use for power & ground
- Components straddle the central gap to avoid short circuits
No soldering. No permanent connections. Perfect for prototyping — pull a wire and fix your mistake.
Our setup
- Pico W bridges the central gap — straddles both halves
- 3V3 → red rail, GND → blue rail
- BME680 module sits nearby on the same breadboard
- 4 jumper wires complete the I2C connection
Check before powering on: Ask a partner to verify your wiring against the table before connecting USB.
Activity: Assemble Your Sensor Node
⏱ 20 minutesFollow the wiring table and build your breadboard circuit.
(3 min) Orient the Pico W so it straddles the central gap. Confirm the USB port is accessible from the edge of the board.
(5 min) Connect 3V3 → red rail and GND → blue rail using jumpers. Verify polarity before going further.
(5 min) Place the BME680 module. Wire SDA → GP4 and SCL → GP5 using a yellow and blue jumper respectively.
(7 min) Peer review: Swap boards with your neighbour. Cross-check the 4 connections against the wiring table. Only connect USB once both reviewers agree.
💡 If the Pico's LED blinks when you connect USB, it has power. If MicroPython is already flashed, the REPL prompt will appear in Thonny.
Verify: Scan the I2C Bus
Quick check — does the Pico see the BME680?
from machine import I2C, Pin
i2c = I2C(0, sda=Pin(4), scl=Pin(5))
print(i2c.scan())
[118] — hex 0x76, the BME680 address ✓
What the numbers mean
[]— empty list → sensor not found → check wiring[118]— BME680 found at 0x76 → wiring correct ✓[119]— BME680 at 0x77 → also valid ✓[104, 118]— two devices found → normal if two sensors
Nothing shows? Power off → re-check VCC and GND → re-scan. Never wiggle wires while powered on.
Coming Up — Session 03
Date TBC · MicroPython Fundamentals
Writing your first sensor-reading loop in MicroPython — variables, while True, formatted output, and your first live readings from the BME680.
Before next session: Install Thonny IDE on your device — free at thonny.org. We'll use it to write and upload code.
Optional reading: MicroPython Quick Reference for RP2040 at micropython.org/rp2
Questions? Get in touch:
jwilliams.science · HalesAir Project