Waveshare RP2040-Zero board addition

[miketronic]

Board/Shield Check-list

• This board/shield is tested working on real hardware
• Definitions follow the general style of other shields/boards upstream (Reference)
• .zmk.yml metadata file added
• Proper Copyright + License headers added to applicable files (Generally, we stick to "The ZMK Contributors" for copyrights to help avoid churn when files get edited)
• General consistent formatting of DeviceTree files
• N/A Keymaps do not use deprecated key defines (Check using the upgrader tool)
• N/A &pro_micro used in favor of &pro_micro_d/a if applicable
• N/A If split, no name added for the right/peripheral half
• Kconfig.defconfig file correctly wraps all configuration in conditional on the shield symbol
• N/A .conf file has optional extra features commented out
• Keyboard/PCB is part of a shipped group buy or is generally available in stock to purchase (OSH/personal projects without general availability should create a zmk-config repo instead) -- board is available from many sources.

This PR takes off from where glebsexy left off. I attempted to make all changes that Pete mentioned in the comments of that PR (1871).

[Nick-Munnich]

Are the outer pins of the zero footprint-compatible with the xiaos? Could you define an interconnect and GPIO nexuses for the zero?

I would also say that this is a board worth attempting to upstream to Zephyr, since waveshare already has some boards defined there.

[miketronic]

Are the outer pins of the zero footprint-compatible with the xiaos? Could you define an interconnect and GPIO nexuses for the zero?

I would also say that this is a board worth attempting to upstream to Zephyr, since waveshare already has some boards defined there.

The Xiao is even smaller, shorter by two pins on both sides and none of the pins opposite the USB port that the Zero has.

[Nick-Munnich]

The Xiao is even smaller, shorter by two pins on both sides and none of the pins opposite the USB port that the Zero has.

My question is more, if you have a keyboard designed for the Xiao RP2040, could you use the Zero with it or would the width/spacing not match up

[Nick-Munnich]

As a consequence of them being compatible I think a xiao_d gpio nexus node should be added so that the zero can be used in place of the xiao on xiao shields.

[miketronic]

Deleted the old branch and renamed the new one.

[miketronic]

As a consequence of them being compatible I think a xiao_d gpio nexus node should be added so that the zero can be used in place of the xiao on xiao shields.

Looking deeper, unfortunately they are not pin compatible unless you very specifically designed the shield with a cutout in the middle for the internals and USB connector, essentially having a "U" of the connecting pins. 5v/GND/3v3 are on opposite sides of the board for both of the MCUs. You would need to flip the Zero over and have the guts through the cutout to make it work with a Xiao designed shield, or standing off with spacers, but then the boot/reset would be covered.

[petejohanson]

This is a compatible that should only be used if this matches the physical layout of a Pi Pico board, which the Zero does not. You'll need a new compatible bindings file for this.

[petejohanson]

Remove these instead of leaving commented out.

[petejohanson]

These defaults are what Zephyr recommends for their "stock board setup" but doesn't match ZMK's standards. Remove these please:

Suggested change

	# enable uart driver
	CONFIG_SERIAL=y
	CONFIG_UART_INTERRUPT_DRIVEN=y
	# enable console
	CONFIG_CONSOLE=y
	CONFIG_UART_CONSOLE=y

[petejohanson]

Should add lines to enable settings, flash, flash NVS, etc. by default, so we can store various settings, e.g. RGB state or studio keymaps.