It is also one of the most commonly used microcontrollers used by hobbyists and engineers and found in many electronic devices.

But, can you replace an Atmega8 with an Atmega328? Yes you can replace an Atmega8 with an Atmega328 as both microcontrollers have the same number of pins (28) and have the same operating voltages (2.7 – 5.5 volts). The Atmega8 and Atmega328 also share an almost identical set of peripherals such as the Timers, Analog to Digital Converter, and Serial Communication.

There are some slight differences however, between these two microcontrollers that might see you choosing the Atmega328 over the Atmega8. 

I will highlight these differences later in this article. 

Your reason to want to replace your existing Atmega8 with an Atmega328 could be as simple as you only have an Atmega328 lying around.

No matter what rest assured you can replace them with no problems.

Are the Atmega8 and Atmega328 part of the same microcontroller family?

In the world of microcontrollers, you have many options at your disposal.

There are many manufacturers of microcontrollers which include Atmel, Intel, Texas Instruments, National Semiconductor and Microchip.

These companies are responsible for manufacturing the majority of microcontrollers used today.

These include :

• AVR
• MSP
• PIC
• ARM
• 8051

Among these set of microcontrollers, the AVR family is the most widely used because of its low prices, availability, community and ease of use.

They were produced by Atmel who were acquired later by Microchip.

AVR is the type of architecture that these microcontrollers are built on.

The AVR family is further divided into a subset of families:

• tinyAVR
• megaAVR
• XMEGA

The Atmega8 and Atmega328 are both produced by Microchip, and are part of the megaAVR family.

Reasons you would want to replace your Atmega8 with an Atmega328

You might have been using an Atmega8 for a long time now and want to make the switch to a new microcontroller or you only have a spare Atmega328 lying around.

No matter what your reason ,the Atmega328 is a great choice as it shares many similar attributes as the Atmega8 and can be used as a direct replacement. 

It shares the same number of pins, clock speed, operating voltage, and set of peripherals.

But, there are some very slight differences that might make you want to choose the Atmega328 over the Atmega8 depending on your needs.

Reason #1: Extra PWM channels 

Pulse width Modulation (PWM) is used for many control applications that include controlling DC motors, control valves, pumps, hydraulics and other mechanical parts.

It is also used in applications to control the brightness of lights like LED’s.

Both the Atmega8 and Atmega328 have PWM channels, however, the Atmega328 has three extra PWM channels.

But, do you really need 3 more PWM channels?

Yes!  

Having extra PWM channels is definitely an advantage. The more the better.

Say your next project is robot arm, where you need to control 4 or more servos.

If you opt for the Atmega8 you only have access to three PWM channels and are limited by how many servos you can control.

Instead if your choice is the Atmega328, you have access to six PWM channels which means you will be able to add more servos giving your robot arm more movement. 

Reason #2: Memory

All microcontrollers come with in-built memory. This is the one of the many things that differentiates them from Microprocessors. 

Just like us humans rely on memory for many aspects of life, a microcontroller relies on its memory for many different facets of its operations.

It uses memory to store things that include the program, runtime constants and variables, and other important data.

A microcontroller has three main types of memory:

• Flash Memory
• Static Random Access Memory (SRAM) 
• Electrically Erasable Programmable Read Only Memory (EEPROM)

Flash Memory

This type of memory is ‘non-volatile’, which means when the power is removed from the microcontroller all data stored in Flash memory is saved and not lost.

The program that tells the microcontroller what to do is stored in Flash memory.

Static Random Access Memory (SRAM)

SRAM is a memory which is ‘volatile’.

So unlike Flash memory, when power is removed from the microcontroller, all data stored in SRAM is lost.

Variables and constants which are generated during program runtime are stored in SRAM.

Electrically Erasable Programmable Read Only Memory (EEPROM)

The last type of memory is EEPROM.

EEPROM is ‘non-volatile’ memory. 

It is used to store permanent data which can be called upon later.

Permanent data like device parameters and sensor data. 

Below is a table showing how much memory (Flash, EEPROM, SRAM) the Atmega328 has compared to the Atmega8:

As you can see, the Atmega328 beats the Atmega8 when it comes to memory space for all three types of memory. 

Having more memory is a definite advantage for many different applications as it will allow you to write bigger programs, store more data, and have more runtime constants and variables.

Reason #3: Extra Sleep Mode

While this is not a major difference, it is a difference nonetheless.

Every microcontroller has the ability to enter modes to help save power.

These are known as ‘Sleep Modes’. 

Atmega8 Sleep Modes:

• Idle
• ADC Noise Reduction
• Power-Save
• Power-Down
• Standby

Atmega328 Sleep Modes:

• Idle
• ADC Noise Reduction
• Power-Save 
• Power-Down
• Standy
• Extended Standby

The Atmega328 has one more sleep mode than the Atmega8. 

Having one more sleep might not seem like a big deal, but it gives you more options for conserving power which can be vital in prolonging battery life.

Reason #4: Price

The last difference between an Atmega328 and Atmega8 is their prices.

The prices shown below are as shown on Microchips website.

Again the Atmega328 comes away as the winner when it comes to price.

You might think that the price difference is negligible. You are only saving $0.37.

But, think about if you buy 100 Atmega328’s compared to 100 Atmega8’s.

You will be making a saving of $37 in the long run!

Can I use the same programmer and IDE to program an Atmega8 or Atmega328?

Now you know that you can replace the Atmega8 with the Atmega328, you will need a way to write code and program it. 

The great news is that, because both these microcontrollers are manufactured by the same company and are part of the same family, they can be programmed using the same programmer and Integrated Development Environment (IDE).

A list of IDE’s that you can use program the Atmega328 include

• Codevision AVR
• Atmel Studio
• WinAVR
• AVR-GCC

A list of AVR programmers you can use to burn the code onto the Atmega328 are:

• AVRISP
• AVR Dragon
• STK500
• JTAG Programmer/Debugger

Other microcontrollers that can replace an Atmega8?

When it comes to options for replacing the Atmega8, you have many choices available.

The Atmega328 isn’t the only microcontroller that is available at your disposal.

The table below is taken from the Microchip website and lists all the microcontrollers you can use to replace an Atmega8. 

The list of microcontrollers below are all capable of replacing the Atmega8. This list is taken from the Microchip website. 

• Atmega168
• Atmega168A
• Atmega168P
• Atmega168PA
• Atmega168PB
• Atmega328
• Atmega328P
• Atmega328PB
• Atmega48
• Atmega48A
• Atmega48P
• Atmega48PA
• Atmega48PB
• Atmega88
• Atmega88A
• Atmega88P
• Atmega88PA
• Atmega88PB
• Atmega8A

Final thoughts

You might be currently using the Atmega8 and wanting to make a switch to a different microcontroller, or your Atmega8 has stopped working and the only other microcontroller you have is the Atmega328.

No matter what your purpose is to replace the Atmega8 with an Atmega328, rest assured you can do so with no hindrance.

Both are interchangeable as they come from the same family of microcontrollers.

They both have the same number of pins, operate at the same voltages, and can be programmed using the same programmer in the same Integrated Development Environment.

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