for second release:
	USB serial interface
	PWM
	ADC

later:
	Write more board modules for Zerphyr's many boards.
	
	Generate board definition files from zephy's metadata (devicetree
	etc). Unfortunately does not include GPIO pins beyond the user led
	and switch for most boards.
	
	Zephyr has many libraries and capabilities, that could all be
	supported.
	
	Also see arduino-copilot's TODO list for some generic ideas that
	are also applicable here. And sketch-frp-copilot's TODO.