AVR-Core-Lib Collection

13 standalone, single-file C header libraries for bare-metal AVR programming — no Arduino, no abstraction layers, pure register-level control.

What Is This?

A production-ready collection of 13 single-file header libraries covering the complete ATmega AVR architecture — from GPIO fundamentals to advanced power management and software timers. Every library compiles with zero warnings under -Wall -Wextra -Werror and is validated on ATmega328P.

Each library is fully self-contained: just #include it, define the implementation guard in one .c file, and you're done. No build system dependencies, no linking headaches.

Libraries

^{¹ Flash usage includes the full example program + UART output. Library-only footprint is significantly smaller.}

Quick Start

Prerequisites

# Debian/Ubuntu
sudo apt install gcc-avr avr-libc

# Arch
sudo pacman -S avr-gcc avr-libc

# macOS (Homebrew)
brew tap osx-cross/avr && brew install avr-gcc avr-libc

Usage

Each library follows the single-file header pattern. In exactly one .c file, define the implementation macro before including:

#define F_CPU 16000000UL        // Your clock frequency

#define AVR_GPIO_IMPLEMENTATION // ← Enable implementation in THIS file
#include "avr_gpio.h"

#define AVR_UART_IMPLEMENTATION
#include "avr_uart.h"

int main(void) {
    gpio_set_mode(&DDRB, &PORTB, PB5, GPIO_OUTPUT);
    uart_init(9600);
    sei();

    uart_send_string("Hello, AVR!\r\n");

    while (1) {
        gpio_toggle_pin(&PINB, PB5);
        uart_send_string("Blink!\r\n");
        for (volatile uint32_t i = 0; i < 200000; i++);
    }
}

In other files that only need the API declarations, include without the #define:

#include "avr_gpio.h"   // declarations only — no duplicate symbols

Build

# Compile a single file
avr-gcc -std=c99 -Os -Wall -Wextra -Werror -mmcu=atmega328p -DF_CPU=16000000UL \
    -o main.elf main.c

# Generate hex for flashing
avr-objcopy -O ihex -R .eeprom main.elf main.hex

# Flash (e.g. with avrdude for Arduino Uno)
avrdude -p m328p -c arduino -P /dev/ttyUSB0 -b 115200 -U flash:w:main.hex:i

Build All Examples

make all     # Compile all 13 examples
make size    # Flash + SRAM usage report
make hex     # Generate .hex files for flashing
make clean   # Remove build artifacts

Examples

Every library has a matching example in examples/ that exercises every API function on ATmega328P @ 16 MHz:

Architecture

avr-libs/
├── avr_gpio.h            # Library 1  – GPIO
├── avr_timer.h           # Library 2  – Timer/Counter
├── avr_uart.h            # Library 3  – UART Serial
├── avr_adc.h             # Library 4  – ADC
├── avr_extint.h          # Library 5  – External Interrupts
├── avr_pwm.h             # Library 6  – PWM
├── avr_spi.h             # Library 7  – SPI
├── avr_i2c.h             # Library 8  – I2C/TWI
├── avr_eeprom.h          # Library 9  – EEPROM
├── avr_wdt.h             # Library 10 – Watchdog Timer
├── avr_bitops.h          # Library 11 – Bit Manipulation
├── avr_power.h           # Library 12 – Sleep & Power
├── avr_swtimer.h         # Library 13 – Software Timers
├── examples/             # ATmega328P examples (one per library)
├── Makefile              # Build system
├── doc.md                # Design document
├── LICENSE               # MIT
└── README.md

Design Principles

• Zero external dependencies — each library is standalone; no inter-library coupling
• No dynamic allocation — all buffers and pools are statically sized
• Atomic where it matters — SREG save/restore for multi-byte reads and R-M-W sequences
• Portable — #ifdef guards for ATmega328P / ATmega2560 / ATmega32U4
• Configurable — buffer sizes, pool counts, prescalers etc. via #ifndef macros

Supported MCUs

Toolchain

Compiler flags: -std=c99 -Os -Wall -Wextra -Werror -mmcu=<mcu> -DF_CPU=<freq>

License

MIT — use freely in personal, educational, and commercial projects.