Week 4: Embedded Programming

Course Overview

Welcome to the world of embedded programming! This course will lead you into a magical world of miniature computing. Imagine placing a chip the size of your fingernail on your fingertip, and within this tiny chip lies a complete computer system - this is the microcontroller we will explore.

This course forms the foundation of electronic design and manufacturing series, opening the door to embedded systems. Through this course, you will learn:

1. How to choose suitable microcontrollers
2. Understanding processor architecture and memory systems
3. Mastering basic programming skills
4. Learning debugging techniques
5. Hands-on project development

Why Learn Embedded Programming?

Embedded systems are everywhere in our daily lives:

• Processors controlling temperature and time in smart appliances
• Chips monitoring health data in wearable devices
• Automation controllers in industrial control systems
• Even simple LED light controllers

Through this course, you will be able to design and develop these fascinating systems.

Part One: Microcontroller Basics

Understanding Microcontrollers

What is a Microcontroller?

A microcontroller is a complete computer system integrating processor core, memory, and input/output interfaces. Taking the ATtiny412 microcontroller, which costs only 50 cents, as an example, it includes:

• 8-bit CPU core
• Program memory (Flash)
• Data memory (RAM)
• Multiple input/output interfaces
• Timers
• Analog-to-digital converter

This tiny chip functions like a miniature factory, capable of sensing the environment, processing data, and controlling other devices.

Processor Architecture

Von Neumann vs Harvard Architecture

These two architectures represent two fundamental design philosophies in computer systems:

Von Neumann Architecture:

• Programs and data stored in the same memory space
• Advantages: Simple structure, low hardware cost
• Disadvantages: Potential program and data access conflicts
• Applications: Mainly used in personal computers

Harvard Architecture:

• Programs and data use separate storage spaces and buses
• Advantages: Can access instructions and data simultaneously, higher efficiency
• Applications: Used in most microcontrollers
• History: Originated from early computer design at Harvard University

RISC vs CISC

The processor's instruction set architecture determines how it executes commands:

RISC (Reduced Instruction Set Computing):

• Few instructions, simple and direct
• Most instructions complete in one clock cycle
• Low power consumption, fast execution
• Representatives: ARM processors, RISC-V architecture

CISC (Complex Instruction Set Computing):

• Many instructions, single instructions can complete complex operations
• High code density, flexible programming
• Relatively high power consumption
• Representatives: x86 processors

Part Two: Major Processor Series

1. AVR Series - Best Choice for Beginners

Like choosing an entry-level car, the AVR series offers reliable and easy-to-use features:

Core Features:

• 8-bit processor, simple to use
• Affordable (about 50 cents)
• Wide operating voltage range (1.8-5.5V)
• Considerable running speed (20MHz)

Advantages:

• Single-pin programming, simple circuit design
• Rich resources, low entry barrier
• Low power consumption, suitable for battery power
• High reliability, industrial-grade quality

Common Models:

• ATtiny412: Compact and elegant, suitable for space-limited scenarios
• ATtiny44: More pins, richer functionality
• ATtiny1614: Enhanced analog capabilities

2. ARM Series - Performance Representative

If AVR is an entry-level car, ARM is like a performance vehicle, offering more powerful features:

Core Features:

• 32-bit processor architecture
• High clock frequency (48MHz+)
• Rich peripheral interfaces
• Supports more complex functions

Advantages:

• Powerful computing capability
• Supports advanced interfaces like USB
• Larger memory capacity
• Mature ecosystem

Common Models:

• SAMD11: Small but comprehensive
• SAMD21: More powerful, suitable for complex applications
• SAM51: High-end model, supports high-speed computing

3. RP2040 (Raspberry Pi) - Innovative Choice

This is a distinctive processor offering unique features:

Core Features:

• Dual-core 32-bit processor
• Base clock frequency 133MHz
• Can be overclocked to 250MHz+
• Innovative programmable IO system

Advantages:

• Affordable (about $1)
• Unique PIO functionality
• Strong development ecosystem
• Excellent price-performance ratio

4. ESP32/ESP8266 - Wireless Communication Expert

Suitable for projects requiring network connectivity:

Core Features:

• Integrated WiFi and Bluetooth functionality
• 32-bit processor
• Rich peripheral interfaces
• Multi-core design (ESP32)

Advantages:

• Strong wireless communication capabilities
• High integration
• Excellent price-performance ratio
• Rich development ecosystem

Part Three: Development Environment and Tools

Programming Language Selection

1. C/C++

The most basic and common embedded development language:

Advantages:

• High execution efficiency
• Small memory footprint
• Direct hardware control
• Comprehensive compiler support

Suitable Scenarios:

• High-performance projects
• Resource-constrained devices
• Scenarios requiring direct hardware control

2. Python (MicroPython/CircuitPython)

Suitable for rapid development and learning:

Advantages:

• Clean and readable code
• Fast development speed
• Easy debugging
• Rich library support

Considerations:

• Slower execution speed (about 1/100 of C)
• Requires more system resources
• Not suitable for real-time control

Recommended Development Environments

1. Arduino IDE

The most popular entry-level development environment:

Features:

• Simple installation
• Built-in common libraries
• One-click compile and upload
• Serial monitor

Advantages:

• Gentle learning curve
• Strong community support
• Rich examples
• Suitable for education

2. VS Code + PlatformIO

Professional-level development environment combination:

Features:

• Intelligent code completion
• Syntax checking
• Code refactoring
• Version control

Advantages:

• Comprehensive functionality
• Rich extensions
• Supports team collaboration
• Cross-platform

Part Four: Debugging Methods and Techniques

Basic Debugging Methods Arduino (C/C++)

LED Status Indication

The most basic and intuitive debugging method:

// Example code
void debugBlink(int times) {
    for(int i = 0; i < times; i++) {
        digitalWrite(LED_PIN, HIGH);
        delay(100);
        digitalWrite(LED_PIN, LOW);
        delay(100);
    }
}

Serial Print Debugging

Can output detailed debug information:

void debugPrint(const char* msg, int value) {
    Serial.print("Debug: ");
    Serial.print(msg);
    Serial.print(" = ");
    Serial.println(value);
}

Common Problems and Solutions

Program Upload Fails

Possible causes:

• Wiring errors
• Chip damage
• Incorrect fuse bit settings
• Power supply issues

Solution steps:

1. Check wiring
2. Verify power supply voltage
3. Try reducing programming speed
4. Check chip model

Practical Assignments

Group Assignment

1. Compare different embedded architectures
2. Test different processor development environments
3. Record and share comparison results

Individual Assignment

1. Choose a microcontroller and read its datasheet
2. Write simple programs to implement:
   • LED control
   • Button input
   • Serial communication
3. Verify program functionality using simulator
4. Optional: Test program on actual hardware

Learning Resources

Official Documentation

• Processor datasheets
• Programming guides
• Example code

Online Resources

• Course outline: Embedded Programming
• Arduino Official Documentation
• MicroPython Documentation
• ESP32 Documentation
• Raspberry Pi Pico Documentation

Important Notes

Safety Tips

1. Always match voltage and current correctly
2. LEDs must use current-limiting resistors
3. Avoid circuit shorts

Development Tips

1. Start with simple examples
2. Gradually add functionality
3. Save and backup code regularly
4. Establish good debugging habits

Documentation Organization

1. Record development process promptly
2. Save important code snippets
3. Document problems and solutions