Choosing Hardware Platform

Here is a comparative table to help choose the processor and base hardware to build your keyboard. Note that not all features and not all hardware form factors are shown.

Feature	SAMD21	SAMD51	RP2040	nRF52840	STM32F4	ESP32-S2
Processor	Cortex M0+	Cortex M4F	Cortex M0+	Cortex M4F	Cortex M4F	Xtensa LX7
Speed	48 MhZ	120 Mhz	133MHz	64 MHz	168 MHz	240MHz
Ram	32KB	192KB	264KB	256KB	192KB	320KB + External
Base Flash	256KB	512KB	External 2MB	1MB	1MB	External
Hardware Features			2 cores, PIO	BLE		WiFi
CircuitPython Core Modules
_bleio	❌	✅	✅	✅	✅	✅
alarm:	❌	❌	✅	✅	✅	✅
analogio:	✅	✅	✅	✅	✅	✅
board:	✅	✅	✅	✅	✅	✅
digitalio:	✅	✅	✅	✅	✅	✅
displayio:	❌	✅	✅	✅	✅	✅
keypad:	❌	✅	✅	✅	✅	✅
neopixel_write:	✅	✅	✅	✅	✅	✅
pwmio:	✅	✅	✅	✅	✅	✅
rotaryio:	✅	✅	✅	✅	❌	✅
time:	✅	✅	✅	✅	✅	✅
touchio:	✅	✅	✅	✅	✅	✅
usb_hid:	✅	✅	✅	✅	✅	✅
Hardware Form Factors
Dongle Form	Trinkey SAMD21			nRF52840 Dongle
5 GPIOs	Trinket M0
11 GPIOs	QT Py, Seeeduino XIAO		QT Py RP2040
18 GPIOs			Pro Micro RP2040	BlueMicro840, Nice!Nano
21 GPIOs	Feather M0 Express	Feather M4 Express	Feather RP2040	Feather nRF52840 Express	Feather STM32F405 Express
21-23 GPIOs	ItsyBitsy M0 Express	ItsyBitsy M4 Express	ItsyBitsy RP2040	ItsyBitsy nRF52840 Express
26 GPIOs			Pi Pico
Finished Products		NeoTrellis M4	MacroPad RP2040, Keybow 2040, PyKey60, EncoderPad RP2040	M60 Mechanical Keyboard

Comments:

• STM boards do not have rotaryio implemented yet.
• Due to limited RAM and flash size, CircuitPython builds for SAMD21 boards only include the bare minimum core modules.
• Low clock speeds for nRF52840 allows for lower power usage and longer battery life for BLE applications.