The Atmega and Attiny series from Microchip (formerly Atmel) are 8-bit AVR microcontrollers widely used in embedded systems and the Arduino ecosystem. They are known for their simplicity, predictable behavior and strong community support.
This article provides a detailed technical overview of the most relevant AVR devices used in modern hobby and educational projects, including ATmega328P, ATmega2560, ATmega32U4, ATtiny85 and ATtiny88.
Architecture Overview
All devices in this family are based on the AVR 8-bit RISC architecture with a Harvard design (separate program and data memory).
8-bit CPU core
Single-cycle execution (most instructions)
Deterministic timing behavior
Very low architectural complexity
This makes AVR microcontrollers particularly suitable for timing-critical and low-level control applications.
Clock Speed and Operating Voltage
Clock frequency depends on supply voltage and must follow datasheet limits.
16 MHz typical at 5V (Arduino Uno, Nano)
8 MHz typical at 3.3V (Pro Mini 3.3V, low-power boards)
ATtiny devices often run at 1-8 MHz internal oscillator
External crystal recommended for precise timing
Important: Running 16 MHz at 3.3V is outside official specifications, even if commonly done in hobby projects.
Memory Overview
Flash: 4 KB to 256 KB
SRAM: 256 bytes to 8 KB
EEPROM: 256 bytes to 4 KB
Memory is limited compared to modern 32-bit MCUs and often the main constraint in larger projects.
GPIO and Electrical Characteristics
Typical GPIO count: 6 to 86 pins depending on device
Recommended current per pin: up to ~20 mA
Absolute maximum per pin: 40 mA
Total device current: typically up to ~200 mA (device/package dependent)
5V logic compatibility (major advantage)
Important: Absolute maximum ratings must not be used as operating values. For reliable designs, significantly lower currents should be used.
Analog Capabilities
ADC resolution: 10-bit
Channels: typically 4-16
Internal voltage reference available
No true DAC (PWM used instead)
Analog performance is suitable for sensors but not precision measurement.
Communication Interfaces
UART: 1-4 (depending on device)
I2C (TWI): 1 interface
SPI: 1 interface
USB: available on specific devices (ATmega32U4, ATmega16U2)
No native CAN controller
ATtiny devices often have reduced or software-based interface implementations.
Timers and PWM
Multiple 8-bit and 16-bit timers
PWM outputs available on many pins
Precise timing and signal generation possible
Toolchains and Ecosystem
Arduino IDE (primary ecosystem)
AVR-GCC
PlatformIO
Microchip Studio
Modern Arduino cores also support ATtiny devices, greatly expanding their usability.
