I recently heard about the Arduino Leonardo which had escaped my attention. I took a look at how it differs to the UNO R3 and also the two R4 boards in Instructables: Arduino Comparison in Detail: UNO R3, Leonardo, UNO R4 Minima and UNO R4 WiFi. There's
- A typical look at data sheet values and a rummage through the schematic to compare powering option/features.
- A look at GPIO input voltage levels (including hysteresis) and internal pull-up resistors.
- Some primitive clock testing showing how accurate the oscillator is on each board for the microcontroller.
- A bit of benchmarking: Dhrystone, a revised version of Benchmark STM32 vs ATMega328 (nano) vs SAM3X8E (due) vs MK20DX256 (teensy 3.2) and some random() testing inspired by Random function on R4 terribly slow - #6 by jremington