ATtiny85 Arduino Getting Started Tutorial, The Smallest Arduino

Attiny85 Arduino:

ATtiny85 Arduino

ATtiny85 Arduino Getting Started Tutorial, The Smallest Arduino- I am sure you already know about Arduino Uno and Arduino Nano as these are the most commonly used Arduino boards. And I am sure the majority of you guys might also know about other Arduino boards, like Arduino Mega, Arduino Pro Mini, and Arduino Leonardo, etc; there is a long list of the Arduino boards. There are so many other Arduino boards that are not available in the Arduino boards list like the Seeeduino Xiao which is considered to be the smallest Arduino.

ATtiny85 Arduino vs seeduino xiao

And here is my designed Arduino Pro Micro.

ATtiny85 Arduino

Well I could make it much smaller than the Seeeduino Xiao but, I had to make it slightly bigger for you guys, so that you could easily make it at your home.

ATtiny85 Arduino

Anyway, I want the smallest Arduino even smaller than the Seeeduino Xiao and Arduino Pro Micro. So, I decided to use the ATtiny85 CMOS 8-bit microcontroller as the smallest Arduino. You can clearly see the size difference. We don’t need to add external capacitors, resistors, and a crystal. And it’s going to be the cheapest micro version of the Arduino.

By looking at its size, you might have an idea that it has fewer IO pins, lower speed, less memory, and no USB interface. So, let me tell you beforehand that you cannot create every project with ATtiny85 that you can create using Arduino Uno, Arduino Nano, or Arduino Pro Micro. However, you can still create thousands of projects using ATtiny85.

There are many projects in which you only need to connect 1 or 2 sensors along with a display. Or you may want to control certain loads using an IR remote, an RFID module, or other similar devices. ATtiny85 has digital pins, analog pins, PWM pins, SPI pins, and more. Therefore, you can use the ATtiny85 microcontroller board in more than a million different ways. So, without any further delay let’s get started!!!

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ATtiny85 Controller

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ATtiny85 Technical Specifications:

ATtiny85 Arduino technical specifications

The ATtiny85 is a low-power, high-performance CMOS 8-bit AVR Microcontroller chip developed by Atmel Corporation, and is often used in small and low-power embedded systems. Let’s go through some of its technical specifications.

Key Parameters

Architecture: AVR(Advanced Virtual RISC)

Power Supply voltage: 2.7V to 5.5V

CPU Speed: Up to 20 Mhz

Flash Memory: 8 Kbytes

EEPROM: 512 Bytes

GPIO Pins: 6

Analog Pins: 4

PWM Channels: 2

Interface: USI (Universal Serial Interface)

Operating Temperature Range: -40C to +85C

USB interface: No

The Architecture is AVR (Advanced Virtual RISC). The power supply voltage is from 2.7V to 5.5V. CPU Speed is up to 20 Mhz. Flash Memory is 8 Kbytes. EEPROM is 512 Bytes. GPIO pins are 6. Analog pins are 4. PWM pins are basically two located on pins 0 and 1. But pin 4 can also be used as PWM pin. So, technically you can say it has 3 PWM pins. The interface type is USI (Universal Serial Interface) which can be configured to perform SPI or I2C communications. The temperature Range is from -40C to +85C. And it has no USB interface.

The ATtiny25/45/85 provides the following features: 2/4/8K byte of In-System Programmable Flash, 128/256/512 bytes EEPROM, 128/256/256 bytes SRAM, 6 general purpose I/O lines, 32general purpose working registers, one 8-bit Timer/Counter with compare modes, one 8-bit high speed Timer/Counter, Universal Serial Interface, Internal and External Interrupts, a 4-channel,10-bit ADC, a programmable Watchdog Timer with internal Oscillator, and three software select-able power saving modes. The Idle mode stops the CPU while allowing the SRAM, Timer/Counter, ADC, Analog Comparator, and Interrupt system to continue functioning. The Power-down mode saves the register contents, disabling all chip functions until the next Interrupt or Hardware Reset. The ADC Noise Reduction mode stops the CPU and all I/O modules except ADC, to minimize switching noise during ADC conversions. The device is manufactured using Atmel’s high density non-volatile memory technology. The On-chip ISP Flash allows the Program memory to be re-programmed In-System through an SPI serial interface, by a conventional non-volatile memory programmer or by an On-chip boot code running on the AVR core.

ATtiny85 Pinout:

You can follow these Pinout diagrams.

ATtiny85 Arduino pinout

Now, we are going to get it ready; So that we can program it using the Arduino IDE. And for this, we will have to Burn the Bootloader. So, let’s go ahead and do it.

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ATtiny85 Bootloader Setup:

To burn the Bootloader on the ATtiny85 microcontroller you will need to follow these connections.

ATtiny85 Arduino bootloader circuit

  • Connect pin 1 of the ATtiny85 which is also the reset pin to pin 10 of the Arduino which is the SS (Slave Select).
  • Connect pin 4 which is the ground pin to the Ground pin of the Arduino.
  • Connect pin 5 which is the MOSI pin to pin 11 of the Arduino which is the MOSI (Master-out, Slave In).
  • Connect pin 6 which is the MISO pin to pin 12 of the Arduino which is the MISO (Maser-In, Slave Out).
  • Connect pin 7 which is the SCK pin to pin 13 of the Arduino which is the SCK (Serial Clock).
  • Connect pin 8 of the ATtiny85 which is the VCC pin to the Arduino 5V pin.
  • Finally, connect a 10uF capacitor between the Reset and GND pins of the Arduino. Make sure you connect the +Ve leg of the capacitor with the Reset pin and the other leg of the capacitor with the GND. So, that’s all about the connections.

ATtiny85 Arduino

Now, let’s go ahead and start with the Arduino IDE.

ATtiny85 in Arduino IDE:

The ATtiny85 microcontroller is not pre-installed in the Arduino IDE and you can confirm this by going to the Tools Menu and then to board, you will see a long list of the Arduino boards, but you won’t find ATtiny85. So, this means you will have to manually install the ATtiny85 as a board in the Arduino IDE.

For this, copy the board manager URL link given below.

Then come back to the Arduino IDE, go to the File Menu, and then to Preferences, and paste the link in the Additional Boards Manager URLs.

ATtiny85 Arduino manager url link

Put a comma if you have added other boards otherwise you can directly paste the board URL link and then click on the OK button.

Go to the Tools Menu, then to board, and click on the Boards Manager. Search for the ATtiny and install it.

ATtiny85 Arduino board download

You can see the ATtiny85 is included in this boards Package. Anyway, you can see I have already installed this board.

Now, to confirm that the ATtiny85 Microcontroller is added, go to the Tools Menu, then to Board and you can see the ATtinny Microcontrollers.

ATtiny85 Arduino in ide

You can see different variants of the ATtiny microcontrollers. So, let’s go ahead and select the ATtiny85 controller. So, our setup on the Arduino IDE is completed.

Next, we are going to connect Arduino Uno with the Laptop. While the Arduino IDE is open, go to the File Menu, then to Examples, and open the ArduinoISP.

ATtiny85 Arduino isp library

Next, select the communication port. Next, select the Programmer “Arduino as ISP”. Finally, click on the Burn Bootloader.

ATtiny85 Arduino burn bootloader

During the Bootloader burning, you will see flashing Leds on the Arduino Uno. The Bootloader burning process is going to take a few seconds. Once the Bootloader burning process is completed, the flashing Leds on the Arduino Uno will stop, and you will also see a message in the Arduino IDE. If it doesn’t make any sense to you, then you can watch my video tutorial given at the end of this article.

So, the Bootloader burning process is completed and now we are going to check if we can program the smallest Arduino “ATtiny85” using the Arduino IDE. So, let’s go ahead and control an LED.

Note: While burning the bootloader if it gives you an error, no need to panic, you can retry by clicking on the Burn Bootloader.

LED with ATtiny85:

ATtiny85 Arduino simple led project

Connect your power source voltage and GND wires with the VCC and GND pins of the ATtiny85 microcontroller. The voltage should be from 2.7V to 5.5 volts. In the circuit diagram you can see two batteries. But you can use a 3.7V lipo battery or any other 5V regulated power supply.

Connect the Anode leg of the Led to pin 5(physical pin number) which is the digital pin 0. So, In the programming, we will refer to the physical pin 5 as pin 0. I am sure you got my point. Anyway, don’t forget to add a current limiting resistor of 330 ohms. And connect the Cathode leg of the LED with the GND.

ATtiny85 Arduino led blinking example

Now, let’s go ahead and take a look at the LED blinking program.

LED Blinking ATtiny85 Arduino Code:

This is the most basic LED blinking code. You can see, I have used the Digital pin 0 as the output to control an LED. And in the loop() function, you can see I am just turning ON and turn OFF the LED at a delay of 1 second. So, let’s go ahead and upload this program.

ATtiny85 Arduino

Right, now you can see the LED is not connected. And these are the same exact connections that I used for burning the Bootloader. So, we are going to use the Arduino Uno for uploading the program. So, to upload the program, I simply click on the Upload button. After uploading the code, next, I removed all the wires.

ATtiny85 Arduino project for beginners

I connected my 2.5V LED with the ATtiny85 as per the circuit diagram. And I am going to use my designed 5V and 3A power supply. This power supply takes up to 28 volts input and on the output it gives regulated 5 volts. So, with this power supply we can power up the ATtiny85 controller using Solar panels, Batteries, and other DC adaptors. You can watch my video on how to make this amazing 5V and 3A power supply. So, let’s go ahead and power up the smallest Arduino based on the ATtiny85 microcontroller.

ATtiny85 Arduino led blinking project

You can see the LED is blinking which means we have done everything correctly. In my upcoming videos, I will use the ATtiny85 controller in intermediate and advanced level projects. So, that’s all for now.

Watch Video Tutorial:


Engr Fahad

My name is Shahzada Fahad and I am an Electrical Engineer. I have been doing Job in UAE as a site engineer in an Electrical Construction Company. Currently, I am running my own YouTube channel "Electronic Clinic", and managing this Website. My Hobbies are * Watching Movies * Music * Martial Arts * Photography * Travelling * Make Sketches and so on...

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