Introduction to Atmega328 Microcontrollers

The Atmega328 is a popular 8-bit microcontroller from Microchip (formerly Atmel). It is widely used in Arduino boards and other embedded systems due to its low cost, ease of use, and versatile features.

There are two main variants of the Atmega328 microcontroller:
– Atmega328
– Atmega328p

While they share many similarities, there are some key differences between the Atmega328 and Atmega328p to be aware of when selecting a microcontroller for your project. In this article, we’ll take an in-depth look at the features, differences, and similarities of the Atmega328 vs Atmega328p.

Key Features of Atmega328 Microcontrollers

Here are some of the main features and specifications that the Atmega328 and Atmega328p have in common:

Feature	Specification
CPU	8-bit AVR
Max. Operating Frequency	20 MHz
Flash Memory	32KB
SRAM	2KB
EEPROM	1KB
I/O Pins	23
Timers	Two 8-bit timers, One 16-bit timer
Analog Inputs	6 channels 10-bit ADC
PWM Channels	6
USART	1
SPI	1
I2C	1
Operating Voltage Range	1.8-5.5V

Some key features to highlight:

Flash Memory

Both the Atmega328 and 328p contain 32KB of flash memory for storing the program code. This is a decent amount of space for many embedded applications.

SRAM and EEPROM

In addition to flash, there is 2KB of SRAM for runtime data and variables, and 1KB of EEPROM for non-volatile storage of settings and parameters.

I/O Pins

23 general purpose I/O pins allow interfacing the microcontroller with sensors, displays, buttons, and other external components. Some special function pins include hardware SPI, I2C, USART, and PWM.

Timers

Two 8-bit timers and one 16-bit timer enable a variety of timing-related functions like counting events, measuring intervals, generating PWM signals, etc.

Analog-to-Digital Converter

The Atmega328 has a 6 channel 10-bit analog-to-digital converter (ADC) for measuring analog voltages from sensors.

Low Power Consumption

Atmega328 MCUs are designed for low power applications. They have multiple sleep modes and clock scaling options to reduce power draw.

Atmega328 vs Atmega328p – What’s the Difference?

While the Atmega328 and Atmega328p are very similar overall, there are a few notable differences between them:

PicoPower Technology

The biggest difference is that the Atmega328p features Microchip’s picoPower technology, while the Atmega328 does not.

PicoPower is a set of enhancements that allow the microcontroller to operate with extremely low power consumption in sleep modes. This includes:

• Lower sleep currents
• Ability to run peripherals like ADC, Analog Comparator, and I2C in sleep modes
• Faster wake-up times
• Wider voltage range down to 1.8V

So in summary, the 328p is better optimized for low power applications compared to the standard 328, especially when using sleep modes heavily. The 328p can achieve sleep currents as low as 100nA.

Packaging and Pinout

Another difference is that the Atmega328 was only available in PDIP and TQFP packages, while the 328p is also offered in the smaller MLF package. The pinout and dimensions are the same between respective PDIP and TQFP versions.

Here are the package options for each:

Package	Atmega328	Atmega328p
28-pin PDIP	Yes	Yes
32-pin TQFP	Yes	Yes
28-pad MLF	No	Yes

Automotive Grade Version

The Atmega328p also has an automotive grade version available (Atmega328p-AN), while the 328 does not. The automotive version has specs more suitable for vehicular applications.

Fuses

There are a couple minor differences in the fuse bytes between the 328 and 328p, namely the CKDIV8 and CKOUT bits. But this will not matter for most use cases.

Similarities Between Atmega328 and Atmega328p

Aside from the differences noted above, the Atmega328 and 328p are functionally the same. They share the same:

• Core CPU architecture and performance
• Memory sizes (flash, SRAM, EEPROM)
• Hardware peripherals (I/O pins, ADC, timers, interfaces, etc.)
• Instruction set
• Register set
• Interrupts
• Maximum frequency (20MHz)

This means that in general, code written for one will be compatible with the other. Existing Arduino boards and libraries support both interchangeably in most cases.

Atmega328 Comparison – Which One to Choose?

For most hobbyist and Arduino projects, both the Atmega328 and Atmega328p will work just fine and the difference won’t matter much. The 328p is newer and more commonly used nowadays, especially for new designs.

However, if your application prioritizes extremely low power consumption, uses sleep modes heavily, or needs to run at voltages below 2.7V, the Atmega328p is the better choice to take advantage of the picoPower enhancements. The automotive grade 328p is also the way to go for vehicle applications.

On the other hand, if you have legacy code or a design already made for the original Atmega328, it’s likely not worth the effort to switch to the 328p unless you need picoPower.

In terms of price, the Atmega328p does tend to cost slightly more than the older 328, but the difference is minimal. Both are under $2 in single quantities at most suppliers.

Frequently Asked Questions

Can I use an Atmega328p in place of an Atmega328?

Yes, the Atmega328p is backwards compatible with the 328 and can be used as a drop-in replacement in most cases. Just double check that any fuse bits are set appropriately.

Is the Atmega328p automotive grade?

Not by default, but Microchip does offer an automotive grade version called the Atmega328p-AN. The standard 328p is industrial grade.

What Arduino boards use the Atmega328p?

Many popular Arduino boards use the Atmega328p, including:
– Arduino Uno
– Arduino Nano
– Arduino Pro Mini
– Arduino Ethernet

How much power does the Atmega328p use in sleep mode?

The Atmega328p can go as low as 100nA in its deepest sleep mode (Power-Down mode). The exact number depends on factors like voltage, temperature, and which peripherals are enabled.

What is the maximum clock speed of the Atmega328?

Both the Atmega328 and Atmega328p have a maximum operating frequency of 20MHz. This requires a supply voltage of at least 4.5V. At lower voltages the max frequency is limited to 10MHz or less.

Conclusion

In summary, the Atmega328p is an enhanced version of the classic Atmega328 microcontroller. While they share the same core architecture and peripherals, the 328p adds picoPower technology for reducing power consumption in sleep modes. It also comes in a smaller package option and has an automotive grade version.

For most general purpose and Arduino applications, the Atmega328 and 328p are interchangeable. But for very low power designs, the 328p is the better choice.

Hopefully this article gave you a detailed understanding of the similarities and differences between the Atmega328 vs Atmega328p to help you choose the right microcontroller for your project!