attiny85 tutorials

Understanding the IO Pins of ATtiny85: Digital, Analog and PWM Pins


When it comes to working with microcontrollers, understanding the input/output (IO) pins is essential. These pins allow you to communicate with the outside world by receiving and sending signals. In this article, we will explore the IO pins of the ATtiny85 microcontroller and how they can be used in various applications.

What is ATtiny85?

The ATtiny85 is a popular microcontroller from the AVR family, designed by Atmel. It is a low-power, high-performance chip that is widely used in various electronic projects. Despite its small size, the ATtiny85 packs a punch with its 8-bit RISC architecture and a range of features.

One of the standout features of the ATtiny85 is its versatility. It can be programmed using the Arduino IDE, making it accessible to both beginners and experienced developers. Whether you’re looking to build a simple LED project or a more complex automation system, the ATtiny85 has got you covered.

Another remarkable aspect of the ATtiny85 is its low power consumption. This makes it ideal for battery-powered applications, where energy efficiency is crucial. With its sleep modes and power-down functionality, the ATtiny85 can significantly extend the battery life of your projects.

Despite its small size, the ATtiny85 offers a range of input and output options, including digital and analog pins. This allows you to connect various sensors, actuators, and other peripherals to bring your ideas to life.

Understanding the IO Pins

IO Pins of ATtiny85

The ATtiny85 has a total of 6 IO pins, labeled as PB0 to PB5. These pins can be configured as either inputs or outputs, allowing you to read data from external sources or control external devices.

Each IO pin of the ATtiny85 has multiple functions depending on its configuration. It can be used as a digital input, digital output, or even an analog input. This flexibility makes the ATtiny85 a versatile microcontroller for a wide range of applications.

Digital Input Pins

Digital input pins are a fundamental component of any microcontroller. They allow the microcontroller to read the state of external digital signals, which can be either high (logic 1) or low (logic 0). In the case of ATtiny85, it has a total of six digital input pins, labeled as PB0 to PB5.

These pins can be used to interface with a wide range of external devices, such as buttons, switches, sensors, and more. By reading the state of these pins, you can determine whether a button is pressed, a switch is on or off, or if a sensor is detecting an input.

Configuring Digital Input Pins

Configuring the digital input pins of ATtiny85 is a straightforward process. First, you need to set the corresponding pin as an input using the pinMode() function. For example, if you want to use PB2 as a digital input pin, you would write:

Once the pin is set as an input, you can read its state using the digitalRead() function. This function returns either HIGH or LOW, which corresponds to the logic level of the input pin. Here’s an example:

It’s important to note that the digital input pins of ATtiny85 are not 5V tolerant. This means that if you are using a higher voltage signal, you need to use a voltage divider or a level shifter to bring the signal down to the operating voltage of the microcontroller.

Digital Output Pins

On the other hand, when configured as a digital output, an IO pin can drive an external device or actuator. It can turn on an LED, control a motor, or send signals to other digital circuits. The ATtiny85 can source or sink up to 20mA of current per IO pin, which is sufficient for most low-power applications. The ATtiny85 microcontroller has a total of 6 digital output pins, labeled as PB0, PB1, PB2, PB3, PB4 and PB5.

Setting Up Digital Output Pins

Before we can start using the digital output pins of the ATtiny85, we need to set them up as outputs. This can be done using the pinMode() function in the Arduino IDE or by directly manipulating the registers in the ATtiny85.

Here’s an example of how to set up a digital output pin in the Arduino IDE:

Alternatively, you can use direct register manipulation to achieve the same result:

Once the digital output pins are set up, we can control their states by writing either HIGH or LOW to them. The digitalWrite() function in the Arduino IDE makes this task easy:

Similarly, we can achieve the same result using direct register manipulation:

Analog Input

In addition to digital IO, the ATtiny85 also supports analog inputs. This means that an IO pin can read analog voltages from 0V to the reference voltage. The ATtiny85 has a built-in 10-bit analog-to-digital converter (ADC) that can convert analog signals into digital values. This feature allows you to interface with analog sensors or read values from potentiometers.

Analog input is crucial for applications that involve sensors, such as temperature sensors, light sensors, or even potentiometers. These sensors provide voltage output that varies based on the physical quantity they are measuring. The ATtiny85’s analog input pins allow us to connect these sensors and read their voltage values.

ATtiny85 Analog Input Pins

IO Pins of ATtiny85

The ATtiny85 has a total of 4 pins that can be used for analog input: pin7 PB2 (ADC1), pin2 PB3 (ADC3), pin3 PB4 (ADC2), pin5 PB0 (ADC0). These pins are multiplexed with other digital I/O pins, so we need to configure them properly to use them as analog inputs.

To enable analog input on a specific pin, we need to set the corresponding bit in the ADCSRA (ADC Control and Status Register A) register. Additionally, we need to set the reference voltage for the ADC (Analog-to-Digital Converter) using the ADMUX (ADC Multiplexer Selection Register) register.

PWM Output

IO Pins of ATtiny85

Another interesting feature of the ATtiny85 is its ability to generate pulse-width modulation (PWM) signals. PWM is a technique used to control the average voltage applied to a device by rapidly switching it on and off. This can be used to control the brightness of an LED, the speed of a motor, or the position of a servo motor.

The Attiny85 has three PWM capable pins:  PB0 (pin 5), PB1 (pin 6), and PB4 (pin 3). These pins can generate PWM signals with a resolution of 8 bits, meaning they can produce 256 different levels of output.


Understanding the IO pins of the ATtiny85 is crucial for any project involving this microcontroller. Whether you need to read digital or analog signals, control external devices, or generate PWM signals, the IO pins provide the necessary functionality. With its compact size and versatile IO capabilities, the ATtiny85 is a popular choice for hobbyists and professionals alike.

So, next time you embark on a project using the ATtiny85, make sure to leverage the power of its IO pins to bring your ideas to life!

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button