Microcontrollers & Code

workbench series · pamphlet no. 5

The brain of the whole series — the chip that reads the sensors and drives the actuators. A few dollars, a USB cable, and some code turns a pile of parts into something that decides. Here's where to start, and what to build toward.

Pick your board

Arduino

The friendly classic — easy, forgiving, huge community. The best first board.

start here

Pi Pico

Cheap, fast, dual-core (RP2040). MicroPython or C; great value.

cheap & capable

ESP32

WiFi and Bluetooth built in — the board for connected projects.

wireless

Raspberry Pi

Not an MCU — a full Linux computer. For cameras, AI, heavy lifting.

a computer

ATtiny

A tiny, cheap chip for a single job once you've outgrown the breadboard.

one job

micro:bit

Sensors, an LED grid, and radio already on board — instant projects.

batteries-included

First light

Blink

The first program — an LED on, off, on. Proof the board lives.

need a board · an LED + resistor

do set a pin high, wait, low, wait, repeat.

Fade (PWM)

Dim and brighten smoothly — the LED breathes.

need a board · an LED on a PWM pin

do ramp the duty cycle up and down in a loop.

Addressable LEDs

Set every pixel on a strip individually.

need a board · a WS2812/NeoPixel strip · a library

do color each pixel; run animations or ambient light.

Drive a display

Push text and graphics to a little screen.

need a board · an OLED/LCD · a library

do send it over I²C/SPI; show readings, menus, art.

Talk to the world

Read a button

The first input — and a lesson in debouncing.

need a board · a button · a pull resistor

do read the pin, debounce it, toggle something.

Sense & respond

Wire in any sensor and act on it — the core move.

need a board · a sensor (see no. 4) · an output

do read it, decide, drive the output.

Drive a motor or coil

Command the actuators from issues 2 & 3.

need a board · a driver (H-bridge / transistor + flyback) · the load

do never from the pin — through a driver, on its own supply.

Serial monitor

Print what the board sees, to your computer.

need a board · USB · the IDE's monitor

do print values live — the first debug tool you'll reach for.

Sense & decide

Reactive lighting

Sound or motion drives the LEDs.

need a board · a mic/PIR · addressable LEDs

do map the sensor to color and brightness.

Clock / timer

Keep time, show it, alarm.

need a board · a display · an RTC (for accuracy)

do count seconds; an RTC holds time through power loss.

Handheld game

Buttons + a small screen = a tiny console.

need a board · a screen · a few buttons

do code Pong or snake — the loop is the game.

Robot brain

Read sensors, run logic, drive motors — autonomous.

need a board · sensors · motors + driver

do sense → decide → move; the whole series in one build.

Go wireless

WiFi dashboard

An ESP32 serves a web page you open on your phone.

need an ESP32 · WiFi · a browser

do control outputs and read sensors from across the network.

Log to the cloud

Push readings online and get alerts.

need a connected board · a service endpoint

do post each reading; ping your phone above a threshold.

Bluetooth control

Drive a robot or read sensors from a phone.

need an ESP32/BLE board · a phone app

do send commands over BLE; stream data back.

Board-to-board

Two MCUs swap data over radio, serial, or I²C.

need two boards · a shared link

do one talks, one listens — the seed of a mesh.

Level up

Battery & sleep

Deep-sleep modes stretch a coin cell to months.

need a low-power board · sleep code

do wake on a timer or a pin; sleep between.

Interrupts & timing

Respond the instant something happens, not when you get around to polling.

need an interrupt-capable pin

do attach an interrupt; let the hardware catch the event.

State machines

Structure behavior so it doesn't become spaghetti.

need just a way of thinking

do name your states and the transitions between them.

Breadboard to PCB

Once it works, make it permanent.

need perfboard, or a PCB tool + a fab

do solder it down, or lay out a board and order it.

Core moves

GPIO — any pin is a digital output (drive it high/low: LED, transistor) or an input (read a switch). You pick the mode in code.
PWM — pins fake an analog level by switching fast: dim LEDs, set motor speed, position servos.
ADC — analog-input pins turn a voltage into a number; that's how you read most sensors. Not every pin is analog — and the full Raspberry Pi has none built in.
Buses — I²C (two wires, many chips), SPI (fast), UART/serial (to your PC): how the board talks to sensors and displays.
The loop — most sketches run setup() once, then loop() forever: read, decide, drive, repeat.
Current-hungry outputs — motors, coils, big LED strips — never hang off a pin. Use a driver (and a flyback diode for coils), give them their own supply, and tie grounds together.

Before it bites

It's low voltage, so you're safe — what's at risk is the board. Most magic smoke is a wiring mistake, not bad luck.
Match the logic voltage (3.3 V vs 5 V). Feeding 5 V into a 3.3 V pin can kill it — level-shift.
Common ground: every part of the circuit must share a ground, or nothing reads right.
A pin sources only a few milliamps — never run a motor, coil, or big strip straight off one.
Power hungry parts separately; their current spikes crash a board sharing the supply. Tie everything at ground.
Check + and − before powering up — reverse polarity kills boards instantly.
The honest one: the board does exactly what you wrote, not what you meant. When it misbehaves, print the values and check them against reality before blaming the hardware — the bug is almost always your assumption.

workbench series · read, decide, drive, repeat · it does what you wrote, not what you meant