Microcontrollers

tags : Electronics, Computer Architecture, Robotics, Hardware stuff

FAQ §

STM32 vs ESP32 §

Feature	STM32	ESP32
Architecture	ARM Cortex-M (32-bit)	Tensilica Xtensa LX6 (dual-core 32-bit)
Manufacturer	STMicroelectronics	Espressif Systems
Primary Focus	Processing power, peripheral variety	Wireless connectivity (WiFi/BT)
Wireless Capabilities	Requires external modules	Built-in WiFi and Bluetooth
Price Range	$1-15+ depending on model	$3-10 depending on module
Power Efficiency	Generally better for non-wireless applications	Optimized for wireless with sleep modes
Development Environment	STM32CubeIDE, Keil, IAR	Arduino IDE, ESP-IDF, PlatformIO
Memory	Varies widely (8KB-2MB Flash, 2KB-640KB RAM)	Typically 4MB Flash, 520KB SRAM
Industrial Temperature Range	Most variants available	Limited options
Ecosystem Maturity	Mature, extensive documentation	Newer but rapidly growing
Use Case Sweet Spot	Industrial control, precise timing applications	IoT, wireless networking projects

What IDE to use? §

• https://arduino.github.io/arduino-cli/1.2/
• https://platformio.org/
• Your favorite text editor
• I don’t like arduino IDE that much

Terminologies/Jargons §

Microcontroller Architectures and Families §

Term	Full Name	Description
AVR	Alf and Vegard’s RISC processor	8-bit microcontroller architecture developed by Atmel (now Microchip)
PIC	Peripheral Interface Controller	Family of microcontrollers made by Microchip Technology
ARM	Advanced RISC Machines	Company and processor architecture widely used in embedded systems
STM32	ST Microelectronics 32-bit	Family of 32-bit ARM Cortex-M microcontrollers from ST Microelectronics
ESP32	Espressif Systems Platform 32	Dual-core microcontroller with integrated Wi-Fi and Bluetooth
ESP8266	Espressif Systems Platform 8266	Low-cost Wi-Fi microchip with TCP/IP stack
nRF52	Nordic RF 52 series	Bluetooth Low Energy SoCs from Nordic Semiconductor
RISC-V	Reduced Instruction Set Computer - V	Open-source instruction set architecture
ATmega328P	Atmel mega 328P	8-bit AVR microcontroller used in Arduino UNO
ATtiny	Atmel tiny	Smaller, simpler AVR microcontrollers with fewer features
RP2040	Raspberry Pi Microcontroller	Dual-core ARM Cortex-M0+ microcontroller developed by Raspberry Pi Foundation

Architecture Types §

See Computer Architecture

Term	Description
RISC	Reduced Instruction Set Computer - Simpler processor design with fewer instructions
CISC	Complex Instruction Set Computer - More complex processor with many specialized instructions
Harvard	Architecture where program and data memory are separate
Modified Harvard	Architecture that allows some controlled access between program and data memory
Von Neumann	Architecture where program and data share the same memory
SoC	System on Chip - Integrated circuit with all components of a computer or electronic system

Communication Protocols §

Term	Full Name	Description
UART	Universal Asynchronous Receiver/Transmitter	Serial communication protocol using TX/RX lines
USART	Universal Synchronous/Asynchronous Receiver/Transmitter	Enhanced UART with synchronous mode option
I2C	Inter-Integrated Circuit	Two-wire serial bus for connecting low-speed peripherals
TWI	Two Wire Interface	Another name for I2C, used primarily by Atmel
SPI	Serial Peripheral Interface	Synchronous serial communication for short-distance communication
CAN	Controller Area Network	Robust vehicle bus standard for connecting microcontrollers
USB	Universal Serial Bus	Standard for connecting computers and electronic devices
BLE	Bluetooth Low Energy	Wireless technology for short-range communication with low power requirements
WiFi	Wireless Fidelity	Wireless networking technology based on IEEE 802.11 standards
MQTT	Message Queuing Telemetry Transport	Lightweight messaging protocol for small sensors and mobile devices
LoRa	Long Range	Long-range, low-power wireless platform
RS-232/485	Recommended Standard 232/485	Standard for serial communication transmission of data

Peripherals and Hardware Features §

Term	Full Name	Description
GPIO	General Purpose Input/Output	Digital pins that can be configured as input or output
ADC	Analog-to-Digital Converter	Converts analog signals to digital values
DAC	Digital-to-Analog Converter	Converts digital values to analog signals
PWM	Pulse Width Modulation	Technique for getting analog results with digital means
JTAG	Joint Test Action Group	Standard interface for debugging and programming microcontrollers
SWD	Serial Wire Debug	Two-pin alternative to JTAG for debugging ARM processors
PIO	Programmable Input/Output	Flexible I/O system on the RP2040 (Raspberry Pi Pico)
Timer	Timer/Counter	Hardware module that counts clock cycles for timing operations
RTC	Real-Time Clock	Keeps track of current time
WDT	Watchdog Timer	Timer that resets the system if the program hangs
FPU	Floating Point Unit	Hardware that performs operations on floating point numbers
DSP	Digital Signal Processor	Specialized processor for digital signal processing operations
UART	Universal Asynchronous Receiver/Transmitter	Hardware for serial communication
PLL	Phase-Locked Loop	Circuit that generates an output signal whose phase is related to the phase of an input signal

Development Approaches and Environments §

Term	Full Name	Description
HAL	Hardware Abstraction Layer	Software layer that bridges hardware and operating system

Specific Development Boards §

Term	Description
Arduino UNO	Popular development board based on ATmega328P
Arduino Nano	Compact version of the Arduino UNO
Raspberry Pi Pico	Development board based on RP2040 microcontroller
ESP32-DevKit	Development board for the ESP32 microcontroller
NodeMCU	Development board based on ESP8266
STM32 Nucleo	Development board for STM32 microcontrollers
BBC micro:bit	Educational development board based on nRF51822
Teensy	Development board based on ARM Cortex-M4
Adafruit Feather	Family of development boards with standardized form factor
SparkFun RedBoard	Arduino-compatible development board

Tools and Equipment §

Term	Full Name	Description
Oscilloscope	-	Instrument that displays signal voltages as a function of time
Logic Analyzer	-	Device that captures and displays digital signals
Multimeter	-	Instrument that measures voltage, current, and resistance
Bus Pirate	-	Universal bus interface tool for debugging
UART-to-USB	-	Bridge for connecting UART interfaces to USB
ST-Link	-	Programming and debugging interface for STM32 microcontrollers
J-Link	-	Debug probe for ARM cores
OpenOCD	Open On-Chip Debugger	Open-source tool for on-chip debugging, in-system programming

History & Lineage of Microcontrollers §

Popular Microcontroller Families §

Family	Year Introduced	Architecture	Notable Examples	Bit Width	Key Features	Community/Support	Best For	Things to Be Aware Of
AVR	1996	Harvard	ATmega328P (Arduino UNO, 2005)	8-bit	- Simple architecture	Very large (Arduino)	Beginners	- Limited memory
			ATtiny Series (1999)		- Excellent documentation	Many tutorials	Battery-powered	- Lower processing power
					- Low power modes		Simple projects	- Slowly being phased out
					- Direct memory access
PIC	1976	Harvard	PIC16F (1993)	8-bit to 32-bit	- Wide variety	Strong but smaller than Arduino	Industrial applications	- Steeper learning curve
			PIC18F (2000)		- Industrial reliability		Long-term projects	- Less hobbyist-friendly IDE
			PIC32 (2007)		- Low power			- Often requires paid tools
					- Many peripherals
ARM Cortex-M	2004	Modified Harvard	STM32 (2007)	32-bit	- High performance	Growing rapidly	Complex projects	- More complex
			NXP LPC (2003)		- Rich peripheral set	Good documentation	Performance-critical applications	- Steeper learning curve
			SAM (2006)		- Advanced timers			- More difficult debugging
			RP2040 (Pi Pico, 2021)		- DMA controllers
nRF52	2015	Modified Harvard	nRF52832 (2015)	32-bit	- Built-in Bluetooth 5.x	Good Nordic support	Wearables, Bluetooth IoT	BLE complexity, More expensive than basic MCUs
			nRF52840 (2017), nRF52833 (2019)		- Ultra-low power
					- ARM Cortex-M4F
ESP	2014	Modified Harvard	ESP8266 (2014)	32-bit	- Built-in WiFi/BT	Large and active	IoT projects	- Higher power consumption
			ESP32 (2016)		- Dual-core (ESP32)	Many libraries	Wireless connectivity	- Documentation can be inconsistent
			ESP32-C3 (2020)		- Low cost			- Complex WiFi stack
					- Deep sleep modes
MSP430	2000	Von Neumann	MSP430G2 (2010)	16-bit	- Ultra-low power	Texas Instruments support	Battery/energy harvesting	- Smaller community
			MSP430FR (2014)		- FRAM options	Energia platform	Low-power sensing	- Fewer ready-made libraries
					- Analog peripherals			- Limited processing power
					- Simple instruction set
RISC-V	2010	Harvard/Von Neumann	GD32V (2019)	32-bit/64-bit	- Open architecture	Growing but still smaller	Future-proofing	- Still emerging ecosystem
			ESP32-C3 (2020)		- Growing ecosystem		Open-source projects	- Fewer off-the-shelf examples
			SiFive FE310 (2017)		- Modern design			- Some debugging challenges
					- Customizable
8051	1980	Harvard	AT89S52 (1995)	8-bit	- Simple architecture	Legacy resources	Learning computer architecture	- Outdated architecture
			STC microcontrollers (2005)		- Historical significance	Industrial support	Simple control systems	- Limited memory addressing
					- Still used in industry			- Fewer modern tools
					- Highly deterministic

Historical Timeline & Significance §

Era	Significant MCUs	Year	Impact	Legacy
1970s	Intel 8048	1976	First single-chip microcontroller	Set foundation for embedded computing
	Intel 8051	1980	First widely adopted MCU	8051 architecture still influences many modern designs
1980s	Motorola 68HC11	1984	Advanced integrated peripherals	Established MCU programming paradigms
	PIC16C	1985	RISC architecture for MCUs	Pioneered flash-based microcontrollers
1990s	AVR series	1996	Flash memory + RISC	AVR became foundation for Arduino
	PIC16F	1993	Low-cost flash MCUs	Brought MCUs to hobbyists
	8051 derivatives	1995+	Widespread adoption	Enabled early DIY electronics
2000s	ARM7TDMI	2001	32-bit becomes accessible	ARM dominance begins
	Arduino launch	2005	AVR-based development board	Hobbyist revolution
	ARM Cortex-M3	2004	Modern 32-bit architecture	Arduino ecosystem transformed accessibility
2010s	ARM Cortex-M4	2010	DSP + FPU capabilities	Advanced signal processing becomes accessible
	ESP8266	2014	$2 WiFi MCU	IoT revolution
	ESP32	2016	Dual-core WiFi+BT	WiFi integration becomes standard
	STM32F7/H7	2015-2016	High-performance MCUs	32-bit becomes affordable for all applications
2020s	RP2040 (Pi Pico)	2021	$4 dual-core with PIO	Open architectures gain traction
	ESP32-C3	2020	RISC-V based WiFi/BT	RISC-V enters mainstream
	ESP32-S3	2021	AI acceleration	AI capabilities in MCUs

How to study microcontrollers? §

Other notes §

8-bit vs 32-bit §

Pro 8-bit: Good for learning fundamentals (AVR/Arduino, PIC) Pro 32-bit: Not harder than 8-bit, more future-proof, competitive pricing Industry view: 8-bit primarily for high-volume cost-sensitive products

Application-Specific Options §

Bluetooth: Nordic (best documentation), alternatives: TI, STM32WB, Silabs WiFi: ESP32 (largest hobbyist community) General purpose: STM32 (industry standard) Recommendation: Choose based on project requirements, not preference

Development Methods §

Bare-metal: Best for fundamental understanding (no Arduino framework) Framework-based: Easier entry but may hide important concepts Best practice: Start with framework, progress to bare-metal

Skills Progression §

Basic peripherals: GPIO, Interrupts, Timers, ADC, PWM Communication protocols: UART, I2C, SPI Advanced topics: RTOS (only after mastering basics)

Learning Roadmap §

this is based on the hardware i currently have in lab.

Phase 1: Arduino Nano (8-bit AVR) - Fundamentals (1 month) §

• Week 1-2: AVR Basics

  • Setup development environment (Arduino IDE → PlatformIO → AVR-GCC)
  • Direct register manipulation (no Arduino framework)
  • GPIO control, timers, and interrupts

  • Project: Electronic Dice

    • Roll electronic dice using a button press
    • Display results on LEDs in binary pattern
    • Use timer interrupts for button debouncing
    • Implement true random number generation using analog noise

• Week 3-4: Communication & Peripherals

  • UART, SPI, and I²C implementation from scratch
  • ADC and sensor integration
  • Power management and sleep modes

  • Project: Weather Monitor

    • Connect temperature/humidity sensor via I²C
    • Implement custom low-level I²C driver (no Wire library)
    • Use sleep modes for power efficiency
    • Create serial protocol for data reporting

Phase 2: Raspberry Pi Pico (32-bit ARM) - Modern MCU (1-2 months) §

• Week 1-2: ARM Architecture

  • Setup Pico SDK environment (C/C++)
  • Understand ARM interrupt model
  • Multicore programming basics

  • Project: Digital Synthesizer

    • Generate waveforms using PWM and DMA
    • Use second core for effects processing
    • Implement MIDI input over USB
    • Create modular architecture for different sound modules

• Week 3-6: Advanced Peripherals

  • PIO (Programmable I/O) programming
  • DMA for efficient data transfers
  • USB interface implementation

  • Project: Logic Analyzer

    • Use PIO to capture digital signals at high speed
    • Implement circular buffer with DMA
    • Create USB interface for PC visualization
    • Add protocol decoder for common interfaces (I²C, SPI)

Phase 3: ESP32 (32-bit Xtensa) - Connectivity & RTOS (2 months) §

• Week 1-2: Wireless & ESP-IDF

  • Move from Arduino framework to ESP-IDF
  • Wi-Fi and BLE configuration
  • Web server and RESTful API development

  • Project: Home Environmental Controller

    • Monitor multiple environmental factors
    • Create elegant web interface
    • Implement secure API for remote control
    • Use BLE for local control from smartphone

• Week 3-4: Zephyr & Task Management

  • Zephyr tasks, queues, and semaphores
  • Memory management in multi-threaded environments
  • Power optimization for battery operation

  • Project: Wireless Sensor Network

    • Create mesh network of ESP32 devices
    • Implement efficient sleep/wake cycles
    • Use MQTT for cloud connectivity
    • Visualize data with dashboard

• Week 5-8: Advanced Integration

  • Capstone Project: Automated Garden System

    • Arduino Nano: Soil sensors and pump control (low-power sentinel)
    • Raspberry Pi Pico: Camera processing for plant health analysis
    • ESP32: Connectivity hub and user interface
    • Custom PCB design for permanent installation
    • Smartphone app for monitoring and control