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Microcontrollers Overview

Microcontrollers Overview

Introduction

A microcontroller (MCU) is a computer on one chip: CPU, RAM, flash, timers, ADC, UART, I²C, SPI — plus GPIO pins you can actually touch on a dev board. Your firmware runs here. Laptops use microprocessors with OS and gigabytes of RAM; your robot controller uses an MCU with kilobytes and no fan.

This article compares families you meet at HBO-ICT (AVR, ESP8266/ESP32, STM32), how to read a board as MCU + support circuits, and where to go deeper in the profile.

MCU vs microprocessor

Microcontroller (MCU) Microprocessor (MPU)
Memory On-chip flash + SRAM External DRAM, boot from storage
OS Often bare-metal or RTOS Linux, Windows
Power mW – W W – tens of W
Examples ATmega328, STM32F4, ESP32 Raspberry Pi CPU, PC CPU

A Raspberry Pi is an MPU running Linux — great for gateways, not the same as programming an STM32 directly. Many projects use both: MCU for real-time I/O, Pi for cloud and UI.

What is inside the chip

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┌─────────────────────────────────┐
│  CPU core (ARM, Xtensa, AVR…)   │
│  Flash (program)                │
│  SRAM (variables, stack)        │
│  Peripherals:                   │
│    GPIO, UART, I²C, SPI, ADC    │
│    Timers (PWM), DMA, RTC      │
└─────────────────────────────────┘

See Computer architecture and Memory systems for how this maps to theory.

Families you will meet

Family Example board Strengths Watch out for
AVR (8-bit) Arduino Uno (ATmega328) Simple, huge tutorial base 5 V logic, limited RAM
ESP8266 WeMos D1 Mini Wi-Fi, cheap Single core, limited pins
ESP32 DevKitC Wi-Fi + BLE, dual core, RTOS Power use, pin mux complex
STM32 (ARM) Nucleo, Blue Pill Professional HAL, many peripherals Steeper toolchain
RP2040 Raspberry Pi Pico Good docs, PIO Newer ecosystem

No family is "best" — match I/O count, connectivity, power, and course toolchain.

Dev board vs bare chip

Development board = MCU + USB-serial + regulator + LED + headers. You program the MCU; the extra chips handle power and upload.

Always find:

  1. MCU part number (e.g. ESP32-WROOM-32)
  2. Schematic PDF — which pin goes to which header
  3. Logic level — 3.3 V vs 5 V
  4. Boot strap pins — must be correct for flash mode

Use Reading datasheets for the chip; use board wiki for pinout.

Programming and flashing

Path Tools
Arduino-style USB cable, bootloader on board
STM32 / bare metal ST-Link, J-Link, openocd
ESP32 USB-UART or JTAG

Firmware lands in flash; RAM holds runtime data. See GCC toolchain in depth.

Videos — getting started

ESP32 introduction

Introduction to ESP32 - Getting Started

ESP8266 mini boards (shields ecosystem)

#106 Wemos ESP8266 Mini Shields — how dev boards stack and extend I/O.

Choosing an MCU for a project

Need Lean toward
Wi-Fi cloud telemetry ESP32, ESP8266
Low power battery STM32L, nRF52
Many motors/sensors, no Wi-Fi STM32F4, Teensy
Course requires Arduino Uno ATmega328 — learn, then migrate

Document choice in architecture — Hardware architecture.

Relevant topics

Starting points

  1. Identify MCU on your board — photo + part number.
  2. Open reference manual table of contents — find GPIO chapter.
  3. List three peripherals your project needs — match to datasheet.
  4. Draw block diagram: MCU, sensors, actuators, power.

Focus points

  • 3.3 V vs 5 V — ESP32/STM32 vs Uno.
  • Current budget — Wi-Fi transmit spikes; motor separate supply.
  • Debug header — know SWD/UART before board is soldered in enclosure.
  • Arduino is a layer — underneath is still C/C++ on an MCU.

Key points

  • MCU integrates CPU, memory, and peripherals for embedded control.
  • ESP8266/ESP32, STM32, and AVR are common in education and industry.
  • Dev board schematics bridge header labels to MCU pins.
  • Pick hardware for connectivity, I/O, power, and toolchain — not hype.