What Is an ATmega328P Microcontroller?

Created by Atmel, the ATmega328P is a single-chip microcontroller based on an 8-bit RISC processor core. This small microcontroller is low-powered and affordable, making it an excellent choice for various applications, including the DIY projects you want to make.

The ATmega328P chip has been featured as a prominent part of the Arduino for many years. The Arduino Uno uses this microcontroller, along with the Arduino Pro Mini and Arduino Nano boards. This makes it extremely common in the DIY electronics space, and it is worth learning about its capabilities if you plan to use these boards.

Arduino Boards Using the ATmega328P Microcontroller

The ATmega328P is found on the Arduino Uno and Arduino Nano microcontroller boards, two of the most popular products from Arduino. You can also buy this chip as a standalone product if you would like to test it out without a microcontroller board, though this will be a challenging way to get started. You can use our handy guide to learn about the different types of Arduino microcontroller boards.

ATmega328P Datasheet Specifications

The ATmega328P has a surprisingly dense datasheet for such a small chip. There are a number of specifications to be aware of before you start writing code for your microcontroller. We’ve broken these down to make it easier to understand the limitations and restrictions of this chip. Let’s start with the basic specs to give you an idea of how the ATmega328P shapes up.

CPU: 8-bit AVR with a maximum speed of 20MHz Flash Memory: 32kB on-board flash SRAM: 2kB EEPROM: 1kB Pin Count: 28 or 32 (depending on the package type) Capacitive Touch Channels: 16 Maximum I/O Pins: 23 External Interrupts: 2

Each of these different specifications plays its own role in making the ATmega328P so well-suited to use with development boards like an Arduino. But what does any of it actually mean?

CPU: The CPU on the ATmega328P chip is an 8-bit AVR RISC-based CPU. RISC stands for “reduced instruction set computer” and is a type of processor designed to simplify the individual tasks a computer performs. By contrast, your PC’s Intel or AMD CPU is likely a CISC (complex instruction set computer) processor. Flash Memory: Flash is a type of non-volatile memory that is used for permanent storage. The ATmega328P is equipped with just 32kB of flash memory, though this is enough for plenty of code. You can learn about the differences between volatile and non-volatile memory on the MUO website. SRAM: SRAM stands for “static random access memory”. This memory plays the same role as the RAM in your PC, providing the ATmega328P chip with temporary memory to store data and variables as it runs through code. EEPROM: This is a type of byte erasable memory used to store small amounts of data. Unlike SRAM, EEPROM is non-volatile and will retain its data when the ATmega328P chip isn’t powered.

ATmega328P Pinout Diagram

The ATmega328P pinout diagram above shows the different pins on the ATmega328P DIP chip and the pins on an Arduino Uno board. This should give you a good idea of how this chip and the popular microcontroller board work together.

The ATmega328P is a versatile chip with a variety of applications. As such, a number of different packages are available for this chip, all in different shapes and with varying types of lead. TQFP (quad-flat package), MLF/VQFN (micro leadframe or quad-flat no-leads), and DIP (dual in-line package) are the most common of these packages.

Genuine Arduino Uno boards use the DIP variant of the ATmega328P chip (aka the ATmega328P-PU), and this means that the chip can be removed and replaced (unlike the ATmega328P-AU). Other types of Arduino boards use different ATmega chips of the quad-flat package type and these cannot be removed.

ATmega328P and Arduino Uno Limitations

As with any microcontroller chip, the ATmega328P comes with certain limitations that have to be considered before you decide to work with it. These limitations also apply to the Arduino boards that use these chips.

Low SRAM Budget

The ATmega328P chip comes with 2kB of SRAM, and this is plenty for most projects. For those who want to use multiple libraries and code with a lot of variables, though, it can be easy to run out of SRAM, causing your program to fail.

Programmers working with Arduino boards have a lot of control over memory management thanks to the use of C++. Text, images, and other pre-made assets can be stored in flash memory as a way to free up additional memory for the programs you are running, improving your SRAM budget.

Limited Processing Power

The 20Hz CPU found on the ATmega328P chip is great for running simple code, but it offers limited processing power for complex applications. This means that it isn’t suitable for things like speech recognition, deep learning, or other common microcontroller tasks.

Solving this problem isn’t possible with the ATmega328P. If you need more power, you will need to look for a more suitable microcontroller board for the task you would like to perform, but there are plenty of options on the market to give you access to what you need.

ATmega328P and Arduino Uno Advantages

Alongside the limitations of the ATmega328P, there are also advantages that come with using a chip like this. These will often outweigh the limitations of the microcontroller for simple projects, especially if you are new to working with microcontrollers.

Affordability: The ATmega328P chip is affordable and easy to find, making it ideal for low-cost DIY projects. Thanks to the great value of this chip, the Arduino Uno is also a very affordable board. Ease of Use: Made with consumers in mind, the ATmega328P is easy to use compared with other microcontroller chips, making it ideal for those getting started with their own DIY projects. Stand-Alone Chip: The ATmega328P chip can be used on its own or with a microcontroller board like the Arduino Uno.

Learning About the ATmega328P and Arduino Uno

There are plenty of resources around the web that are designed to help you to get started with the Arduino Uno and the ATmega328P it uses. It’s well worth spending time learning about this hardware before you start your next microcontroller project, giving yourself an idea of the limitations and challenges you might face along the way.