Guide

ATtiny 0/1/2-Series Pinout

The complete pin reference for Microchip’s modern ATtiny 0/1/2-series: true USART, SPI and I2C peripherals, and single-wire UPDI programming instead of classic ISP.

AVRxt core, up to 20 MHz
UPDI programming
2–32 KB flash
1.8V – 5.5V

Overview

The ATtiny 0-, 1- and 2-series are Microchip’s modern successors to the classic ATtiny85: a faster AVRxt core, real USART/SPI/I2C peripherals instead of a shared USI, and single-wire UPDI programming instead of the 4-wire ISP the ATtiny85 uses. This guide uses the 14-pin SOIC package (the “x04/x14/x24” members, e.g. ATtiny214/414/814) as the reference, larger parts in the family add a PORTC and extra PORTB pins.

One wire to program UPDI needs just one data pin (PA0) plus power and ground, instead of ISP’s four signal lines.

A real DAC on some models PA6 outputs true analog voltage on parts that include a DAC, the ATtiny85 has no DAC at all.

Runs down to 1.8V A wider voltage range than the ATtiny85’s 2.7V floor, useful for low-voltage battery projects.

Getting started

You’ll need a UPDI programmer, either a dedicated one, or a cheap USB-to-serial adapter wired as a “SerialUPDI” programmer (a single resistor between TX and RX does the trick).

1. What you need A UPDI programmer (or a USB-to-serial adapter wired as SerialUPDI), 3 jumper wires, and a breadboard.

2. Install the software Install the free Arduino IDE, then add megaTinyCore via Boards Manager (by Spence Konde), it covers the whole 0/1/2-series.

3. Upload your first sketch Select your exact chip under megaTinyCore, pick “SerialUPDI” (or your programmer) as the upload method, then Upload.

How it compares to the ATtiny85

Feature	ATtiny85 (classic)	ATtiny 0/1/2-series (modern)
CPU core	Classic AVR	AVRxt (faster, more efficient)
Flash	8 KB	2–32 KB
SRAM	512 B	128 B – 2 KB
ADC	10-bit	10- or 12-bit
DAC	No	Yes (some models)
Timers	2	3+ (advanced)
Peripherals	USI (SPI/I2C)	True USART, SPI, I2C
Programming	ISP (4-wire)	UPDI (1-wire)
Power range	2.7V – 5.5V	1.8V – 5.5V

Pin reference (14-pin SOIC)

Pin count and some peripherals vary across the family, this table and diagram use the 14-pin SOIC package shared by the ATtiny214/414/814.

ATtiny x04/x14/x24 14-pin SOIC package, dimensioned front view with the 14-pin, 1.27 mm pitch header called out — Source: Microchip ATtiny214/414/814 datasheet, Section 4.1 “14-pin SOIC”.

Pin	Name	Functions
1	VDD	Power supply (1.8 – 5.5V)
2	PA4	Analog (AIN4), PTC X0/Y0, digital I/O
3	PA5	Analog (AIN5), PTC X1/Y1, digital I/O
4	PA6	Analog (AIN6), PTC X2/Y2, digital I/O
5	PA7	Analog (AIN7), PTC X3/Y3, digital I/O
6	PB3	TOSC1 (timer oscillator), digital I/O
7	PB2	TOSC2, EVOUT1, digital I/O
8	PB1	Analog (AIN10), PTC X4/Y4, TWI SDA (alt), USART XCK (alt), digital I/O
9	PB0	Analog (AIN11), PTC X5/Y5, TWI SCL (alt), USART XDIR (alt), digital I/O
10	PA0	nRESET, UPDI, analog (AIN0), digital I/O
11	PA1	Analog (AIN1), BREAK, USART TXD (alt), SPI MOSI, TWI SDA
12	PA2	Analog (AIN2), EVOUT0, USART RXD (alt), SPI MISO, TWI SCL
13	PA3	EXTCLK, analog (AIN3), USART XCK, SPI SCK
14	GND	Ground

Programming (UPDI)

A single pin handles programming here, no separate MOSI/MISO/SCK like the ATtiny85’s ISP header.

Function	Pin	Description
UPDI	PA0	Also the reset pin, single-wire programming and debugging
VCC	Pin 1	Power the chip while programming
GND	Pin 14	Common ground with the programmer

Safety notes

Before you wire anything up

PA0 doubles as UPDI and reset, avoid tying it directly to ground or a strong pull-down if you want to reprogram the chip later.
Check your exact chip’s datasheet before assuming a pin has a DAC or a second ADC, these vary across the 0/1/2-series.
This family runs from 1.8V to 5.5V, but not every peripheral (like the DAC) works across the full range, check the datasheet’s electrical characteristics.

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