Turning on USB logging interferes with TX/RX pins on Xiao BLE

[caksoylar]

I have this issue where turning on USB logging via CONFIG_ZMK_USB_LOGGING=y prevents the matrix pin I have at RX (D7/P1.12) from working. I am guessing this is because they are assigned to UART pins at https://github.com/zmkfirmware/zephyr/blob/v3.2.0%2Bzmk-fixes/boards/arm/seeeduino_xiao_ble/seeeduino_xiao_ble-pinctrl.dtsi#L7 and logging turns it on via https://github.com/zmkfirmware/zephyr/blob/v3.2.0%2Bzmk-fixes/boards/arm/seeeduino_xiao_ble/seeeduino_xiao_ble.dts#L17.

I see some shield configs deleting these properties, e.g. https://github.com/zmkfirmware/zmk/blob/main/app/boards/shields/hummingbird/hummingbird.overlay#L13. Should this be something that every shield does, or would it be better to solve it at the seeeduino_xiao_ble.overlay level?

[caksoylar]

Actually I didn't have any luck with enabling USB logging with those nodes deleted. The stock hummingbird shield fails building too:

> west build -p -d build/hummingbird -b seeeduino_xiao_ble -- -DSHIELD=hummingbird -DCONFIG_ZMK_USB_LOGGING=y
[...]
/home/.../zmk/zephyr/include/zephyr/device.h:104:39: error: '__device_dts_ord_DT_CHOSEN_zephyr_console_ORD' undeclared here (not in a function)
[...]

[xudongzheng]

I believe the issue is that USB logging enables UART, which causes this UART https://github.com/zmkfirmware/zephyr/blob/v3.2.0%2Bzmk-fixes/boards/arm/seeeduino_xiao_ble/seeeduino_xiao_ble.dts#L64 to be enabled internally within Zephyr.

My initial guess is UART_CONSOLE https://github.com/zmkfirmware/zmk/blob/main/app/Kconfig#L438C12-L438C24 needs to be removed.

[caksoylar]

Thanks, FWIW, removing select UART_CONSOLE gets the pins working again (but only when combined with deleting the chosen properties) and gets the hummingbird shield building. But I guess it is necessary for logging, since the COM port shows up but nothing gets logged in this case (even if the chosen properties are preserved).

[xudongzheng]

Two small observations:

• https://github.com/zmkfirmware/zmk/blob/main/app/boards/arm/nice_nano/nice_nano.dtsi#L19 may be needed for USB logging to work.
• https://github.com/zmkfirmware/zephyr/blob/v3.2.0%2Bzmk-fixes/boards/arm/seeeduino_xiao_ble/seeeduino_xiao_ble_defconfig also has CONFIG_UART_CONSOLE=y and CONFIG_SERIAL=y. It's possible that removing select UART_CONSOLE on its own wasn't actually removing it.