Add rp2040 zero

[glebsexy]

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)

[petejohanson]

Thanks for the PR! A few items that need addressing. Also check out the pre-commit check failure for issues there.

[petejohanson]

For boards added to ZMK directly, we usually set the console to be the CDC ACM node added to the usb node. See https://github.com/zmkfirmware/zmk/blob/main/app/boards/arm/nice_nano/nice_nano.dtsi#L64 for an example node.

[petejohanson]

For ZMK boards, don't enable the UART, SPI, etc by default. This is a bit different from the upstream Zephyr board approach.

[petejohanson]

This .zmk.yml file format is not the same as the Zephyr format. See existing ZMK boards for examples of the metadata we use.

[petejohanson]

Suggested change

	CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=240000000
	CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=125000000

I had to fix this in our other boards recently, they had the wrong sys clock frequency set.

[xudongzheng]

@petejohanson I noticed that ZMK's Zephyr fork has quite a few custom RP2040 boards defined there https://github.com/zmkfirmware/zephyr/tree/v3.2.0%2Bzmk-fixes/boards/arm. Is there a rule of thumb for which boards should go in upstream Zephyr, the ZMK Zephyr fork, vs the ZMK boards directory?

[petejohanson]

@petejohanson I noticed that ZMK's Zephyr fork has quite a few custom RP2040 boards defined there https://github.com/zmkfirmware/zephyr/tree/v3.2.0%2Bzmk-fixes/boards/arm. Is there a rule of thumb for which boards should go in upstream Zephyr, the ZMK Zephyr fork, vs the ZMK boards directory?

Anything that I'd like to upstream, given time, I try to put in our Zephyr fork. That usually means anything more popular/general purpose.

The Zero is theoretically generic enough we could choose to put there as well.

[petejohanson]

Closing due to inactivity. Feel free to reopen whenever you're back to this.