All About AVR 🎛️

The ultimate bare-metal AVR reference hub. Learn AVR microcontroller programming from scratch — no Arduino libraries, no external dependencies. Pure AVR-GCC with direct register access.

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🎯 What Is This?

A complete, educational repository for mastering ATtiny85 and ATmega328P (Arduino Nano) at the register level. Every example uses raw AVR-GCC: <avr/io.h>, <avr/interrupt.h>, <util/delay.h> — nothing else.

📊 Chip Comparison

Feature	ATtiny85	ATmega328P (Nano)
Pins	8 (6 I/O)	32 (23 I/O)
Flash	8 KB	32 KB
SRAM	512 B	2 KB
EEPROM	512 B	1 KB
Timers	2 (8-bit)	3 (2×8-bit, 1×16-bit)
ADC	4 ch, 10-bit	8 ch, 10-bit
UART	USI (software)	1 hardware USART
SPI	USI	1 hardware SPI
I²C (TWI)	USI	1 hardware TWI
PWM	4 channels	6 channels
Clock	Up to 20 MHz	Up to 20 MHz
Voltage	2.7 – 5.5 V	1.8 – 5.5 V
Price	~$1	~$2–3
Package	DIP-8, SOIC-8	DIP-28, TQFP-32

🚀 Quickstart

1. Clone & Browse Docs

git clone https://github.com/yourusername/all-about-avr.git
cd all-about-avr
pip install mkdocs mkdocs-material pymdown-extensions
mkdocs serve
# → Open http://127.0.0.1:8000

2. Build & Flash an Example

cd examples
# ATtiny85 blink
make MCU=attiny85 TARGET=c/attiny85/gpio/blink_pb0

# ATmega328P blink
make MCU=atmega328p TARGET=c/atmega328p/gpio/blink_pb5

# Flash (adjust -P for your programmer)
make MCU=attiny85 TARGET=c/attiny85/gpio/blink_pb0 flash

📁 Repository Structure

all-about-avr/
├── docs/              # MkDocs documentation site (Material theme)
│   ├── common/        # Shared AVR basics: toolchain, fuses, debugging
│   ├── attiny85/      # ATtiny85 deep-dives: registers, peripherals
│   └── atmega328p/    # ATmega328P deep-dives: registers, peripherals
├── examples/
│   ├── c/             # Bare-metal C examples per chip
│   │   ├── common/    # Chip-agnostic examples (ifdef)
│   │   ├── attiny85/  # gpio/ timers/ uart/ adc/ sleep/ spi/ pwm/ ...
│   │   └── atmega328p/
│   └── assembly/      # AVR assembly examples
├── tools/             # Fuse calculator (HTML/JS), flash script
├── assets/            # Pinout SVGs, datasheet links
├── benchmarks/        # Performance data (cycles, power)
├── cheat-sheets/      # Quick-reference cards
└── .github/workflows/ # CI: MkDocs deploy + build checks

🔧 Prerequisites

Tool	Install Command (Debian/Ubuntu)
avr-gcc	sudo apt install gcc-avr
avr-libc	sudo apt install avr-libc
avrdude	sudo apt install avrdude
make	sudo apt install build-essential
mkdocs	pip install mkdocs mkdocs-material

macOS: brew install avr-gcc avrdude
Windows: Install WinAVR or use MSYS2.

📚 Topics Covered

• ⚡ GPIO: Digital I/O, pull-ups, port manipulation
• ⏱️ Timers: CTC, PWM (Fast/Phase-Correct), overflow interrupts
• 📡 UART/USART: TX/RX, printf redirect, baud calculation
• 🔌 SPI: Master/Slave, USI on Tiny85
• 🔗 I²C (TWI): Master/Slave, USI-based TWI
• 📈 ADC: Single conversion, free-running, noise reduction
• 💤 Sleep Modes: Idle, Power-Down, wake on interrupt
• 🐕 Watchdog Timer: System reset, wake from sleep
• 🔔 Interrupts: External (INT0/PCINT), timer, ADC complete
• 🔧 Fuses: Clock source, BOD, RSTDISBL, lock bits

🤝 Contributing

See CONTRIBUTING.md for guidelines. TL;DR:

1. Write bare-metal C (no Arduino libs)
2. Add docs in docs/ + code in examples/
3. Test on real hardware (or SimulAVR)
4. Submit a PR

📄 License

This project is licensed under the MIT License.

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