The Feather M0 series of development boards use the SAMD21G microcontroller, and the actual microcontroller part is an ARM Cortex M0+, one of the simplest 32-bit processor designs.
The Adafruit SAMD Board Support Package defines all the usual convenience functions from the Arduino environment, like digitalWrite() and analogRead(), and if you stick to those, you shouldn’t see much difference between the M0 and an 8-bit board like the Metro 328P. The biggest differences you’ll see are faster clock speed (48MHz), more program memory, and more RAM.
The SAMD21G has all the peripheral-bus-and-multiplexer features of a standard 32-bit device though, so if you want to start digging around under the hood, you’ll have some reading to do.
That said, the SAMD21G is a good place to start learning the differences between 8-bit microcontrollers and 32-bit microcontrollers.
The Feather only uses a few of the SAMD21G’s IO pins (there are about 40 of them), so it isn’t a general purpose SAMD21G development board. It’s limited to fit into the Feather ecosystem.
The Feather M0 Adalogger has the same microcontroller and pinout as the Feather M0 Basic, but there’s a built-in slot for an SD card. As the name suggests, it’s good for applications where you want to collect data.
The SD card is connected to the SPI pins at the edge of the board, so you need to be aware of that if you want to connect other SPI devices to the MOSI/MISO/SCK pins at the side of the board.
The ItsyBitsy M0 also uses the SAMD21G, but brings more of the chip’s IO pins out to the edge of the PCB. On the other hand, it doesn’t have the Feather’s built-in LiPo charger.
This one is more suited to embedded projects where you need pins more than portability.
What can we say? The Arduino Uno footprint has become a standard, but people keep wanting to do things the Uno’s 8-bit microcontroller can’t handle.
The Metro M0 gives you the power of a SAMD21G with the breadboard-friendly footprint of the Uno.
One point to note: different chips have different pin connections, so the Metro M0’s SPI pins do not connect to digital pins 10-13 line on the Uno. They only connect to the 2x3 header near the microcontroller.
The Metro M4 is built around the SAMD51, a newer microcontroller from Atmel/Microchip.
Its core is an ARM Cortex-M4 microcontroller, a 32-bit device with a hardware floating-point math engine and a digital signal processor (single math instructions that work on a whole block of memory).
SAMD51 peripherals include Ethernet and CAN interfaces, cryptography features like a true random number generator (TRNG), AES, and public-key processing circuits, and a block of configurable logic similar to a small FPGA.
The fact that the hardware can do those things doesn't mean code support exists yet. Adafruit is working on getting the most out of the SAMD51, mainly through CircuitPython.
The Adafruit Grand Central features the Microchip ATSAMD51 with its 120MHz Cortex M4 and floating point support.
The Grand Central is the first SAMD board that has enough pins to make it in the form of the Arduino Mega - with a massive number of pins, tons of analog inputs, dual DAC output, 8 MBytes of QSPI flash, SD card socket, and a NeoPixel.
If you need a board with lots of GPIO pins, this is your ticket.
The Raspberry Pi RP2040 was released in January 2021 and is Raspberry Pi's first microcontroller (compared to their single-board computers (SBC) they have made since 2012).
They can be programmed in CircuitPython, MicroPython, Arduino, Raspberry Pi Pico SDK, and more.
Raspberry Pi markets their own microcontroller board with the RP2040 as the Raspberry Pi Pico and Raspberry Pi Pico W (with WiFi onboard).
Adafruit has also made a number of boards with the RP2040:
- Adafruit Metro RP2040
- Adafruit QT Py RP2040
- Adafruit Feather RP2040
- Adafruit Feather RP2040 with USB Type A Host
- Adafruit Feather RP2040 Adalogger - 8MB Flash with microSD Card - STEMMA QT / Qwiic
- Adafruit RP2040 Feather ThinkInk for 24-pin E-Paper Displays - STEMMA QT
- Adafruit MacroPad RP2040 Starter Kit - 3x4 Keys + Encoder + OLED - ADABOX019 Essentials
- Adafruit Feather RP2040 with RFM95 LoRa Radio - 915MHz - RadioFruit and STEMMA QT
- Adafruit Feather RP2040 RFM69 Packet Radio - 868 or 915MHz - RadioFruit and STEMMA QT
- Adafruit RP2040 CAN Bus Feather with MCP2515 CAN Controller - STEMMA QT
- Adafruit Feather RP2040 SCORPIO - 8 Channel NeoPixel Driver
- Adafruit KB2040 - RP2040 Kee Boar Driver
- Adafruit ItsyBitsy RP2040
- Adafruit Trinkey QT2040 - RP2040 USB Key with Stemma QT
The Raspberry Pi RP2350 was released in August 2024 and is Raspberry Pi's second generation microcontroller.
Raspberry Pi markets their own microcontroller board with the RP2040 as the Raspberry Pi Pico 2 and Raspberry Pi Pico 2 W (with WiFi onboard).
The chip has double the memory of the RP2040, is faster and uses M33 Arm cores and has Hazard 3 RISC-V cores. A HSTX bus provides high speed DMA processing for things like DVI video output. The RP2350B has additional GPIO pins.
They can be programmed in CircuitPython, MicroPython, Arduino, Raspberry Pi Pico SDK, and more.
Adafruit has also made a number of boards with the RP2350:
Page last edited July 23, 2025
Text editor powered by tinymce.
