ATtiny85 Pinout

Overview

The ATtiny85 is a tiny 8-bit AVR chip from Microchip (formerly Atmel), designed for minimalistic projects where size, power efficiency and simplicity matter most. It has no onboard USB or voltage regulator, just the bare chip, so it’s programmed with an external ISP programmer rather than a USB cable.

Getting started

You’ll need an ISP programmer, either a dedicated USBasp/USBtinyISP, or another Arduino board running the “ArduinoISP” example sketch.

Hello World: blink an LED

The microcontroller equivalent of “Hello World”: PB0 toggles once a second. Wire an LED (with a resistor) to physical pin 5 (PB0), Arduino pin 0 in ATTinyCore’s standard numbering.

#include <avr/io.h>
#include <util/delay.h>

int main(void)
{
    DDRB |= (1 << PB0);   // PB0 as output
    while (1) {
        PORTB |= (1 << PB0);   // on        _delay_ms(1000);
        PORTB &= ~(1 << PB0); // off        _delay_ms(1000);
    }
}

#define LED_PIN 0 // PB0, physical pin 5
void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(1000);
  digitalWrite(LED_PIN, LOW);
  delay(1000);
}

AVR-GCC: build with avr-gcc and flash with avrdude over ISP. Arduino IDE: select “Upload Using Programmer”, see “Getting started” above.

Specifications

Official specifications for the ATtiny85.

Pinout diagram

The DIP-8 pinout with every alternate function per pin.

Pin reference

Programming (ISP)

The 6-pin ISP header maps to these ATtiny85 pins.

Safety notes