zephyr button w/ "static" pinctrl example for xiao_ble (seeed xiao nrf52840)

custom.conf

#  zephyr/samples/basic/button/boards/custom.conf
#
# "static" pinctrl to use external-uart breakout (AE-FT2232 / FTDI FT2232D) as /dev/ttyUSB0
# this file is to switch USB-CDC-ACM (/dev/ttyACM0) -->  external uart (/dev/ttyUSB0)

# disable USB CDC ACM
CONFIG_USB_DEVICE_STACK=n
CONFIG_USB_DEVICE_STACK_NEXT=n
CONFIG_BOARD_SERIAL_BACKEND_CDC_ACM=n

# enable UART console
CONFIG_UART_CONSOLE=y
CONFIG_CONSOLE=y

xiao_ble.overlay

// zephyr/samples/basic/button/boards/xiao_ble.overlay
//
// adopt from zephyr/boards/nordic/nrf52dk/nrf52dk_nrf52810.dts

/ {
    buttons {
        compatible = "gpio-keys";

        button0: button_0 {
            label = "Push button switch 0";
            gpios = <&gpio0 5 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;    // P0.05 XIAO #6 D5 --> push switch
            zephyr,code = <INPUT_KEY_0>;
        };
    };

    aliases {
        sw0 = &button0;
        uart-0 = &uart0;           // add this alias for the console
    };

    chosen {
        zephyr,console = &uart0;   // explicitly set UART0 as console
    };
};

// "static" pinctrl to use external-uart breakout (AE-FT2232 / FTDI FT2232D) as /dev/ttyUSB0
&pinctrl {
    uart0_default: uart0_default {
        group1 {
            psels = <NRF_PSEL(UART_TX, 1, 15)>;     // P1.15 XIAO #11 D10 TX --> AE-FT2232 #39 RXD (cross)
        };
        group2 {
            psels = <NRF_PSEL(UART_RX, 1, 14)>;     // P1.14 XIAO #10 D9 RX  --> AE-FT2232 #40 TXD (cross)
            bias-pull-up;
        };
    };

    uart0_sleep: uart0_sleep {
        group1 {
            psels = <NRF_PSEL(UART_TX, 1, 15)>,
                   <NRF_PSEL(UART_RX, 1, 14)>;
            low-power-enable;
        };
    };
};

// Enable UART0
&uart0 {
    status = "okay";
    current-speed = <115200>;
    pinctrl-0 = <&uart0_default>;
    pinctrl-1 = <&uart0_sleep>;
    pinctrl-names = "default", "sleep";
};