Arduino has long used Atmel (now Microchip) 8-bit AVR architecture microcontrollers. The ATmega328P, ATmega32U4, and ATmega2560 have been discussed here. Arduino no longer is “in bed” with Microchip, but there are two other Microchip microcontrollers used in Arduino boards, the ATmega4809 and the SAMD21. Both of these are favorites of mine.
ATmega4809
The ATmega4809 is modernized version of the AVR microcontrollers in earlier Arduino boards. The on-board peripherals are completely redesigned and this is a superior part. It is used in the Arduino Nano Every, which has been discussed frequently on this blog. It is the lowest cost Arduino board. The microcontroller is also used in the Uno Wifi Rev 2, which has a Wifi/Bluetooth module but also has a much higher price.
SAMD21
This Arm Cortex-M0 32-bit microcontroller is found in 10 Arduino models, including all of the MKR series of boards. These boards are all 3.3 volt.
There are two “minimalist” boards, those without a radio. The Arduino Zero is in the Uno form factor, and is the only SAMD21 board with built-in debugger capability. However it is also strangely expensive. The Arduino MKR ZERO is a MKR form factor board, offers an SD card interface, and is the least expensive MKR board.
The true minimalist solution is the Seeedstudio XIAO SAMD21, https://www.seeedstudio.com/Seeeduino-XIAO-Arduino-Microcontroller-SAMD21-Cortex-M0+-p-4426.html, which consists of the microcontroller, crystal oscillator, voltage regulator, and a USB-C connector. This board is very inexpensive and is the obvious choice for a SAMD21 if a radio is not needed.
The Arduino Nano 33 IoT is a Nano form factor board with a Wifi/Bluetooth and inertial modules. It does not use a crystal oscillator, which keeps the cost down to be the least expensive Arduino SAMD21 board.
The remaining SAMD21 boards are all in the MKR series and differ in the radio provided.
- MKR Wifi 1010 — effectively a Nano 33 IoT with a battery connector and a crystal oscillator.
- MKR WAN 1300 and 1310 — LoRa radio
- MKR NB 1500 — Narrowband LTE radio
- MKR Vidor 4000 — no radio, but has an FPGA.
Some of the MKR boards are marked as End Of Life:
- MKR 1000 Wifi — uses a multichip module containing the SAMD21 and a Wifi module.
- MKR FOX 1200 — for SigFox networks in Europe.
- MKR GSM 1400 — GSM/3G radio
The MKR 1000 is basically superseded by the 1010. The MKR 1200 and 1400 are obsolete technologies. Note that while both the 1300 and 1310 are in active production, the 1310 basically replaces the 1300.