How to program ATtiny85 with Arduino UNO Easy way


Hello and welcome to this tutorial on How to program ATtiny85 with Arduino UNO Easy way. If you’re on the lookout for a cost-effective yet powerful microcontroller, the ATtiny85 is an excellent choice. In this guide, we’ll walk through the process step by step, using two examples to illustrate the programming procedure. Let’s dive in!

Hardware Required

You will require the following Hardware Components for How to program ATtiny85 with Arduino UNO Easy way.

Components#Buy From Amazon
Arduino UNO1Buy Link
ATtiny85 Microcontroller1Buy Link
LED 5mm5Buy Link
Resistors 180Ω5Buy Link
Capacitor 10uF1Buy Link
Jumper WiresFewBuy Link
Breadboard1Buy Link
5v Battery1Buy Link

What is ATtiny85?

The ATtiny85 is a powerful yet compact microcontroller that opens up a world of possibilities for your DIY projects. Despite its small size, it packs quite a punch, making it a popular choice among hobbyists and professionals alike.



Pin Configuration of Attiny85

It is an 8-pin IC as shown in the Atiny85 pin diagram shown above. Most I/O pins of the chip have more than one function and the description for each pin is given below.

Pin no.Pin NameDescriptionSecondary Function
1PB5 (PCINT5/ADC0/dW)Pin5 of  PORTBPCINT5: Pin Change Interrupt 0, Source5
RESET : Reset Pin
ADC0: ADC Input Channel 0
dW : debug WIRE I/O
2PB3 (PCINT3/XTAL1/CLKI/ADC3)Pin3 of  PORTB PCINT3: Pin Change Interrupt 0, Source3
XTAL1 : Crystal Oscillator Pin1
CLKI: External Clock Input
OC1B : Complementary Timer/Counter1 Compare Match B Output
ADC3: ADC Input Channel 3
3PB4 (PCINT4/XTAL2/CLKO/OC1B/ADC2)Pin4 of  PORTBPCINT3: Pin Change Interrupt 0, Source3
XTAL1 : Crystal Oscillator Pin1
CLKI: External Clock Input
OC1B : Complementary Timer/Counter1 Compare Match B Output
ADC3: ADC Input Channel 3
4GND Connected to Ground
5PB0(MOSI/DI/SDA/AIN0/OC0A/AREF/ PCINT0)Pin0 of  PORTBMOSI: SPI Master Data Output / Slave Data Input
DI: USI Data Input (Three Wire Mode)
SDA: USI Data Input (Two Wire Mode)
AIN0: Analog Comparator, Positive Input
OC0A : Timer/Counter0 Compare Match A output
: Complementary Timer/Counter1 Compare Match A Output
AREF: External Analog Reference
PCINT0: Pin Change Interrupt 0, Source 0
6PB1(MISO/D0/AIN1/OC0B/OC1A/ PCINT1)Pin1 of  PORTBPCINT4 : Pin Change Interrupt 0, Source 4
XTAL2 : Crystal Oscillator Pin 2
CLKO : System Clock Output
OC1B: Timer/Counter1 Compare Match B Output
ADC2: ADC Input Channel 2
7PB2(SCK/USCK/SCL/ADC1/T0/INT0/ PCINT2)Pin2 of  PORTBMISO: SPI Master Data Input / Slave Data Output
DO : USI Data Output (Three Wire Mode)
AIN1: Analog Comparator, Negative Input
OC0B : Timer/Counter0 Compare Match B Output
OC1A: Timer/Counter1 Compare Match A Output
PCINT1: Pin Change Interrupt 0, Source 1
8VCC SCK: Serial Clock Input
USCK : USI Clock (Three Wire Mode)
SCL : USI Clock (Two Wire Mode)
ADC1 : ADC Input Channel 1
T0 : Timer/Counter0 Clock Source
INT0: External Interrupt 0 Input
PCINT2: Pin Change Interrupt 0, Source 2

Features and Electrical Characteristics

CPU8 bit
Number of  Pins8
Number of  Programmable I/O pins6
Operating Voltage+1.8 V to +5.5V (ATTINY85V)+2.7 V to +5.5V (ATTINY85)(+6.0V  being absolute maximum supply voltage)
Maximum DC Current per I/O Pin40 mA
Maximum DC Current through VCC and GND Pins200 mA
Operating Temperature-55ºC to +125ºC
Communication InterfaceMaster/Slave SPI Serial Interface(5,6,7  PINS) [Can be used for programming this controller]I2C or Two-wire Serial Interface(5,7  PINS)[Can be used to connect peripheral devices and sensors]Universal Serial Interface (5,6,7 PINS) [Can be used for communicating with other controllers]
UART InterfaceNot available
ADC Feature4channels, 10-bit resolution ADC
Analog Comparators1
Timer ModuleTwo 8-bit counter
PWM outputs4
External Oscillator0-10MHz for ATTINY85V0-20MHz for ATTINY85
Internal Oscillator0-8MHz  Calibrated Internal R-C Oscillator
CPU Speed1 MIPS@1MHz
Program Memory or Flash memory size8Kbytes[10000 write/erase cycles]
RAM size512Bytes on Internal SRAM
EEPROM size512Bytes of In-System Programmable EEPROM
Program LockAvailable
Watchdog TimerAvailable
Power Save ModesThree Modes[Idle, ADC Noise Reduction, Power-down]

Circuit Diagram

The following circuit shows you the connection of How to program ATtiny85 with Arduino UNO Easy way Please make the connection carefully


Working Explanation

The ATtiny85 communicates with the Arduino UNO through a process called “Arduino as ISP” (In-System Programmer). This essentially turns your Arduino UNO into a programmer for the ATtiny85. By uploading a specific sketch to your Arduino UNO, you can then transfer your code to the ATtiny85 microcontroller, allowing it to perform various tasks.

Installing Arduino IDE Software

First, you will require to Download the updated version of Arduino IDE Software and Install it on your PC or laptop. if you Learn How to install the Arduino step-by-step guide then click on how to install Arduino Button given Blow


//For more Projects:

void setup() {
  pinMode(0, OUTPUT);

void loop() {
  digitalWrite(0, HIGH);
  digitalWrite(0, LOW);

Let’s Test the Circuit



  1. LED Blinking Patterns: Utilize the GPIO pins to create captivating LED blinking patterns. The compact size of the ATtiny85 makes it perfect for crafting small, attention-grabbing displays.
  2. Sensor Node for IoT: Leverage its ADC channels to turn the ATtiny85 into a sensor node for your Internet of Things (IoT) projects. Monitor environmental variables and send data to your central system.
  3. Sound and Music Projects: With PWM channels, you can create musical tunes or sound effects in your projects. Perfect for adding an auditory dimension to your creations.
  4. Low-Power Applications: The ATtiny85’s low power consumption makes it ideal for battery-operated projects. Design energy-efficient gadgets without compromising on functionality.
  5. Miniature Robotics: Drive small motors and control basic robotic movements using the GPIO pins. Build your own pocket-sized robots that can navigate through simple tasks.


Programming the ATtiny85 with your Arduino UNO opens up a world of possibilities, allowing you to create compact yet powerful projects. Experiment with the applications mentioned or let your imagination run wild to explore the full potential of this tiny but mighty microcontroller.

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