The ATmega328P, RP2040 and RP2350 are all popular microcontroller choices for Arduino-compatible projects, but they represent very different generations of embedded hardware.
The ATmega328P is the classic 8-bit Arduino controller used on UNO, Nano and Pro Mini boards. The RP2040 is a modern dual-core microcontroller from Raspberry Pi, used on the Raspberry Pi Pico and many compact boards such as XIAO RP2040. The RP2350 is the newer and more powerful Raspberry Pi microcontroller generation, with more memory options, improved performance and more advanced features.
This comparison helps explain when the classic ATmega328P is still the right choice, and when RP2040 or RP2350 boards make more sense.
Three Very Different Microcontroller Generations
These three controllers can all be used for small embedded projects, but they are not in the same performance class.
- ATmega328P: classic 8-bit AVR microcontroller
- RP2040: modern dual-core Arm Cortex-M0+ microcontroller
- RP2350: newer Raspberry Pi microcontroller family with higher performance and more advanced architecture
The ATmega328P is simple and very well supported. The RP2040 and RP2350 are much more powerful and better suited for projects that need more memory, faster processing, USB, advanced timing, many interfaces or more flexible I/O.
ATmega328P: The Classic Arduino Choice
The ATmega328P is the microcontroller behind many classic Arduino boards, including the Arduino UNO, Nano and Pro Mini. It is an 8-bit controller with limited memory, but it is very easy to use and extremely well documented.
- 8-bit AVR microcontroller
- Usually used at 16 MHz on Arduino-compatible boards
- 32 KB flash memory
- 2 KB SRAM
- 1 KB EEPROM
- 5V logic on most UNO and Nano-style boards
- Very strong Arduino IDE support
The ATmega328P is still a good choice for simple projects such as reading sensors, controlling relays, blinking LEDs, driving small displays or learning basic microcontroller programming.
RP2040: Powerful, Cheap and Widely Supported
The RP2040 is the first Raspberry Pi microcontroller chip. It became popular because it offers much more performance and memory than classic 8-bit Arduino boards while remaining inexpensive and easy to use.
- Dual-core Arm Cortex-M0+ processor
- Clock speed commonly up to 133 MHz
- 264 KB SRAM
- External flash memory on the module or board
- 3.3V logic
- Native USB support
- Programmable I/O blocks, known as PIO
The RP2040 is especially interesting for projects that need accurate timing, custom digital interfaces, USB devices, more RAM or faster processing than an ATmega328P can provide.
RP2350: The Newer Raspberry Pi Microcontroller Generation
The RP2350 is a newer Raspberry Pi microcontroller family and can be seen as the more advanced successor to RP2040. It keeps the general idea of a powerful, inexpensive microcontroller but adds more performance, more memory options and newer features.
- More powerful than RP2040
- Dual-core architecture
- Higher clock speed than RP2040
- More SRAM than RP2040
- Available in different package and memory configurations
- 3.3V logic
- Native USB support
- Improved security and peripheral features compared with RP2040
RP2350-based boards are especially interesting when RP2040 is almost enough, but the project would benefit from more memory, more performance or a more future-proof platform.
Main Specification Comparison
| Feature | ATmega328P | RP2040 | RP2350 |
|---|---|---|---|
| Processor type | 8-bit AVR | Dual-core Arm Cortex-M0+ | Newer dual-core Raspberry Pi microcontroller architecture |
| Typical clock speed | 16 MHz on classic Arduino boards | Commonly 133 MHz | Higher than RP2040, depending on board and configuration |
| CPU cores | 1 | 2 | 2 |
| RAM | 2 KB SRAM | 264 KB SRAM | More than RP2040, depending on device variant |
| Program memory | 32 KB flash inside the chip | External flash on board or module | Variant-dependent; external or integrated memory options may exist depending on board |
| Logic voltage | Usually 5V on UNO/Nano boards | 3.3V | 3.3V |
| Native USB | No, usually requires USB-to-serial interface on the board | Yes | Yes |
| Arduino IDE support | Excellent and mature | Very good | Developing and improving as boards become more common |
| Best known advantage | Simplicity and classic Arduino compatibility | High performance and low cost | More modern and more capable than RP2040 |
| Best known limitation | Very limited memory and speed | 3.3V only, external flash, no built-in wireless | Newer ecosystem, board support may still vary |
Performance Difference
The performance difference between ATmega328P and RP2040 or RP2350 is very large. The ATmega328P is an 8-bit controller running at 16 MHz in most Arduino applications. The RP2040 and RP2350 are modern 32-bit microcontrollers with dual cores and much higher clock speeds.
This does not mean that an ATmega328P is obsolete. A simple relay controller, LED blinker or temperature display may not need more power. But for projects with larger software, faster timing, more data, USB, audio, graphics or custom protocols, RP2040 and RP2350 provide much more room.
- ATmega328P is enough for many simple control tasks
- RP2040 is much better for timing, USB, data handling and larger programs
- RP2350 is better when even more memory or performance headroom is useful
Memory Difference
Memory is often the first limitation users encounter on ATmega328P boards. With only 2 KB of SRAM, larger libraries and display buffers can quickly become a problem.
RP2040 and RP2350 provide far more RAM. This makes them more comfortable for projects using larger buffers, communication stacks, graphics, audio, file handling or more complex code.
| Memory Situation | ATmega328P | RP2040 | RP2350 |
|---|---|---|---|
| Small sensor sketch | Very good | More than enough | More than enough |
| Multiple libraries | Can become tight | Much more comfortable | Very comfortable |
| Display buffer | Often limited | Much better | Better again, depending on board and memory configuration |
| Audio or data buffering | Usually not ideal | Good for many projects | Better for larger projects |
| Large text menus or configuration data | Requires careful memory use | Much easier | Much easier |
Voltage Levels: 5V vs 3.3V
Voltage level is one of the most important practical differences.
Most ATmega328P Arduino UNO and Nano boards use 5V logic. RP2040 and RP2350 boards use 3.3V logic. This affects how sensors, displays, relay modules and other external parts are connected.
- ATmega328P UNO/Nano boards are usually 5V logic
- RP2040 and RP2350 boards are 3.3V logic
- Many modern sensors and displays are 3.3V devices
- Older Arduino shields and modules may expect 5V logic
- Level shifting may be needed when mixing 3.3V and 5V parts
If the project uses modern 3.3V sensors, displays and radio modules, RP2040 or RP2350 may actually be easier to integrate. If the project uses older 5V Arduino shields or 5V modules, the ATmega328P may still be more convenient.
Analog Inputs
The ATmega328P has analog inputs that are widely used in Arduino examples. RP2040 and RP2350 boards also provide analog input capability, but the exact number of exposed analog pins depends on the board.
For precision analog measurement, none of these controllers should automatically be treated as laboratory-grade measurement devices. External ADC modules such as ADS1115 are often a better choice when accuracy and resolution matter.
- ATmega328P is easy for classic Arduino analogRead examples
- RP2040 and RP2350 provide analog inputs, depending on board pinout
- Board layout and reference voltage affect analog quality
- Use an external ADC for better precision
USB Capabilities
USB is one of the major advantages of RP2040 and RP2350 over the ATmega328P.
Classic ATmega328P boards usually need a separate USB-to-serial chip for programming and serial monitor communication. The ATmega328P itself does not provide native USB. RP2040 and RP2350 provide native USB support, making them useful for custom USB devices.
- ATmega328P boards usually appear as USB serial through a separate bridge chip
- RP2040 and RP2350 can support native USB functions
- RP2040 and RP2350 are useful for keyboard, MIDI, serial and custom USB device projects
- USB support depends on firmware, board package and software libraries
Programmable I/O and Special Timing
One of the strongest RP2040 features is PIO, or Programmable I/O. PIO allows small state machines inside the chip to handle precise digital signal timing without relying entirely on the CPU.
This is useful for protocols and timing tasks that would be difficult or inefficient on a classic ATmega328P.
- Generating custom digital waveforms
- Reading or writing unusual communication protocols
- Driving LED protocols
- Handling timing-sensitive I/O
- Reducing CPU load for repetitive signal tasks
RP2350 continues this general direction with a more advanced microcontroller platform. For timing-heavy or interface-heavy projects, Raspberry Pi microcontrollers are much more flexible than classic AVR boards.
Arduino IDE and Software Support
The ATmega328P has the most mature Arduino support because it has been part of the Arduino ecosystem for many years. RP2040 support is also very strong today, with many boards supported through Arduino board packages. RP2350 support is newer and will continue to improve as more boards and libraries become common.
| Software Topic | ATmega328P | RP2040 | RP2350 |
|---|---|---|---|
| Arduino IDE beginner support | Excellent | Very good | Good, but newer |
| Classic Arduino examples | Best compatibility | Usually good for normal APIs | Usually good for normal APIs, depending on board package |
| Low-level register examples | Many older examples available | Different architecture, AVR register code does not apply | Different architecture, AVR register code does not apply |
| MicroPython / CircuitPython | Not the usual choice | Very common | Expected to be useful as ecosystem support grows |
| Best for learning basic Arduino | Excellent | Good | Good, but less classic |
Board Formats
The chip itself is only part of the decision. Board format matters just as much.
- ATmega328P is available as UNO, Nano, Pro Mini and many compatible formats
- RP2040 is available as Raspberry Pi Pico, XIAO RP2040 and many other compact boards
- RP2350 is available on newer Raspberry Pi and third-party boards
- Pinout, connector type, voltage regulator and flash size depend on the board
For breadboard work, board shape and pin spacing may matter more than raw microcontroller specifications. For finished products, mounting holes, USB connector type and power input options can become just as important as CPU speed.
When to Use ATmega328P
- Beginner Arduino learning
- Simple digital and analog I/O projects
- Projects based directly on older UNO or Nano tutorials
- 5V shield or 5V module projects
- Small programs that fit comfortably into 32 KB flash and 2 KB SRAM
- Situations where simplicity matters more than performance
The ATmega328P is still useful because it is easy to understand and very predictable. For many simple control projects, it is enough.
When to Use RP2040
- Projects needing much more RAM than ATmega328P
- USB device projects
- Timing-sensitive digital signal generation
- Projects using MicroPython or CircuitPython
- Low-cost modern 32-bit microcontroller projects
- Small boards such as Raspberry Pi Pico or XIAO RP2040
The RP2040 is often the best modern replacement when an ATmega328P feels too limited but WiFi is not required.
When to Use RP2350
- New designs that need more headroom than RP2040
- Projects needing more RAM or more advanced features
- Applications where long-term platform growth matters
- More demanding USB, control or data-handling projects
- Projects where a newer Raspberry Pi microcontroller board is preferred
The RP2350 is the more future-oriented choice. It makes sense when the project would benefit from a newer and stronger microcontroller platform, especially if board support for the chosen module is already available.
When Not to Use These Controllers
None of these microcontrollers includes WiFi or Bluetooth by itself. If wireless connectivity is required, it may be better to choose an ESP32, ESP32-C3, ESP32-C6, ESP32-C5 or nRF52-based board instead.
- Use ESP32 or ESP8266 when WiFi is required
- Use ESP32-C6 or nRF52840 for Thread, BLE or modern smart-home wireless projects
- Use external level shifting when mixing 3.3V controllers with 5V modules
- Use an external ADC when analog precision matters
- Use external drivers for motors, relays, solenoids and high-current outputs
Which One Should You Choose?
| Project Need | Best Choice | Why |
|---|---|---|
| Classic Arduino beginner project | ATmega328P | Best match for UNO, Nano and older Arduino tutorials |
| Simple 5V control project | ATmega328P | 5V logic is convenient for many older Arduino modules |
| More memory and speed, no wireless needed | RP2040 | Much more performance and RAM at low cost |
| USB device project | RP2040 or RP2350 | Native USB support is much better suited than ATmega328P |
| Custom digital timing or protocol | RP2040 or RP2350 | Programmable I/O and higher performance make timing tasks easier |
| Newest Raspberry Pi microcontroller platform | RP2350 | More modern and more capable than RP2040 |
| Maximum library compatibility with older Arduino examples | ATmega328P | Classic Arduino examples were often written for UNO-style boards |
Conclusion
The ATmega328P, RP2040 and RP2350 all have a place in Arduino-compatible projects, but they are suited to different needs.
- Choose the ATmega328P for classic Arduino simplicity, 5V logic and beginner-friendly UNO/Nano compatibility.
- Choose the RP2040 when you want a low-cost modern 32-bit microcontroller with much more memory, speed and USB flexibility.
- Choose the RP2350 when you want a newer, more capable Raspberry Pi microcontroller platform with more headroom for future projects.
For simple learning projects, the ATmega328P remains easy and practical. For most new non-wireless projects that need more performance, RP2040 is a strong modern choice. For more demanding new designs, RP2350 is the more future-oriented option.