hidsh · August 16, 2025 06:57 · hidsh · Aug 16, 2025
diff --git a/CMakeLists.txt b/CMakeLists.txt
 # SPDX-License-Identifier: Apache-2.0

 cmake_minimum_required(VERSION 3.20.0)
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(button)

 target_sources(app PRIVATE src/main.c src/remap.c)
diff --git a/custom.conf b/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
diff --git a/Kconfig b/Kconfig
 # based on zephyr/samples/boards/nordic/dynamic_pinctrl/Kconfig
 #
 # Copyright (c) 2021 Nordic Semiconductor ASA
 # SPDX-License-Identifier: Apache-2.0

 mainmenu "Dynamic pin control sample"

 config REMAP_INIT_PRIORITY
 	int "Remap routine initialization priority"
 	default 50
 	help
 	  Initialization priority of the remap routine within the PRE_KERNEL1 level.
 	  This priority must be greater than GPIO_INIT_PRIORITY and lower than
 	  UART_INIT_PRIORITY.

 source "Kconfig.zephyr"
diff --git a/prj.conf b/prj.conf
 CONFIG_GPIO=y

 # ---------------------------------------------
 # dynamic-pinctrl
 # ---------------------------------------------
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_DYNAMIC=y
 # configure serial and console to come after remap hook
 CONFIG_SERIAL_INIT_PRIORITY=60
 CONFIG_CONSOLE_INIT_PRIORITY=70

diff --git a/src--main.c b/src--main.c
 /*
 * Copyright (c) 2016 Open-RnD Sp. z o.o.
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * NOTE: If you are looking into an implementation of button events with
 * debouncing, check out `input` subsystem and `samples/subsys/input/input_dump`
 * example instead.
 */

 #include <zephyr/kernel.h>
 #include <zephyr/device.h>
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/sys/util.h>
 #include <zephyr/sys/printk.h>
 #include <inttypes.h>

 #define SLEEP_TIME_MS	1

 /*
 * Get button configuration from the devicetree sw0 alias. This is mandatory.
 */
 #define SW0_NODE	DT_ALIAS(sw0)
 #if !DT_NODE_HAS_STATUS_OKAY(SW0_NODE)
 #error "Unsupported board: sw0 devicetree alias is not defined"
 #endif
 static const struct gpio_dt_spec button = GPIO_DT_SPEC_GET_OR(SW0_NODE, gpios,
 							      {0});

 #define SW1_NODE	DT_ALIAS(sw1)
 #if !DT_NODE_HAS_STATUS_OKAY(SW1_NODE)
 #error "Unsupported board: sw1 devicetree alias is not defined"
 #endif
 static const struct gpio_dt_spec button1 = GPIO_DT_SPEC_GET_BY_IDX_OR(SW1_NODE, gpios,
                                  0,    // idx
 							      {0});
 static struct gpio_callback button_cb_data;
 static struct gpio_callback button1_cb_data;

 /*
 * The led0 devicetree alias is optional. If present, we'll use it
 * to turn on the LED whenever the button is pressed.
 */
 static struct gpio_dt_spec led = GPIO_DT_SPEC_GET_OR(DT_ALIAS(led0), gpios,
 						     {0});

 void button_pressed(const struct device *dev, struct gpio_callback *cb,
 		    uint32_t pins)
 {
 	printk("Button pressed at %" PRIu32 " from pin %d\n", k_cycle_get_32(), pins);
 }

 int main(void)
 {
 	int ret;

 	if (!gpio_is_ready_dt(&button)) {
 		printk("Error: button device %s is not ready\n",
 		       button.port->name);
 		return 0;
 	}

 	if (!gpio_is_ready_dt(&button1)) {
 		printk("Error: button1 device %s is not ready\n",
 		       button1.port->name);
 		return 0;
 	}

 	ret = gpio_pin_configure_dt(&button, GPIO_INPUT);
 	if (ret != 0) {
 		printk("Error %d: failed to configure %s pin %d\n",
 		       ret, button.port->name, button.pin);
 		return 0;
 	}

 	ret = gpio_pin_configure_dt(&button1, GPIO_INPUT);
 	if (ret != 0) {
 		printk("Error %d: failed to configure %s pin %d\n",
 		       ret, button1.port->name, button1.pin);
 		return 0;
 	}

 	ret = gpio_pin_interrupt_configure_dt(&button,
 					      GPIO_INT_EDGE_TO_ACTIVE);
 	if (ret != 0) {
 		printk("Error %d: failed to configure interrupt on %s pin %d\n",
 			ret, button.port->name, button.pin);
 		return 0;
 	}

 	ret = gpio_pin_interrupt_configure_dt(&button1,
 					      GPIO_INT_EDGE_TO_ACTIVE);
 	if (ret != 0) {
 		printk("Error %d: failed to configure interrupt on %s pin %d\n",
 			ret, button1.port->name, button1.pin);
 		return 0;
 	}

 	gpio_init_callback(&button_cb_data, button_pressed, BIT(button.pin));
 	gpio_add_callback(button.port, &button_cb_data);
 	printk("Set up button at %s pin %d\n", button.port->name, button.pin);

 	gpio_init_callback(&button1_cb_data, button_pressed, BIT(button1.pin));
 	gpio_add_callback(button1.port, &button1_cb_data);
 	printk("Set up button at %s pin %d\n", button1.port->name, button1.pin);

 	if (led.port && !gpio_is_ready_dt(&led)) {
 		printk("Error %d: LED device %s is not ready; ignoring it\n",
 		       ret, led.port->name);
 		led.port = NULL;
 	}
 	if (led.port) {
 		ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT);
 		if (ret != 0) {
 			printk("Error %d: failed to configure LED device %s pin %d\n",
 			       ret, led.port->name, led.pin);
 			led.port = NULL;
 		} else {
 			printk("Set up LED at %s pin %d\n", led.port->name, led.pin);
 		}
 	}

 	printk("Press the button\n");
 	if (led.port) {
 		while (1) {
 			/* If we have an LED, match its state to the button's. */
 			int val = gpio_pin_get_dt(&button);

 			if (val >= 0) {
 				gpio_pin_set_dt(&led, val);
 			}
 			k_msleep(SLEEP_TIME_MS);
 		}
 	}
 	return 0;
 }
diff --git a/src__remap.c b/src__remap.c
 /*
 * Copyright (c) 2021 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */

 #include <zephyr/init.h>
 #include <zephyr/drivers/gpio.h>
 #include <zephyr/drivers/pinctrl.h>

 /* make sure devices and remap hook are initialized in the correct order */
 BUILD_ASSERT((CONFIG_GPIO_INIT_PRIORITY < CONFIG_REMAP_INIT_PRIORITY) &&
 	     (CONFIG_REMAP_INIT_PRIORITY < CONFIG_SERIAL_INIT_PRIORITY),
 	     "Device driver priorities are not set correctly");

 PINCTRL_DT_DEV_CONFIG_DECLARE(DT_NODELABEL(uart0));

 /* UART0 alternative configurations (default and sleep states) */
 PINCTRL_DT_STATE_PINS_DEFINE(DT_PATH(zephyr_user), uart0_alt_default);
 #ifdef CONFIG_PM_DEVICE
 PINCTRL_DT_STATE_PINS_DEFINE(DT_PATH(zephyr_user), uart0_alt_sleep);
 #endif

 static const struct pinctrl_state uart0_alt[] = {
 	PINCTRL_DT_STATE_INIT(uart0_alt_default, PINCTRL_STATE_DEFAULT),
 #ifdef CONFIG_PM_DEVICE
 	PINCTRL_DT_STATE_INIT(uart0_alt_sleep, PINCTRL_STATE_SLEEP),
 #endif
 };

 #include <zephyr/kernel.h>  // printk

 static int remap_pins(void)
 {
 	int ret;
    printk("-- enter: remap_pins()\n");

 	const struct gpio_dt_spec button = GPIO_DT_SPEC_GET_OR(DT_ALIAS(sw1),
 							       gpios, {0});


 	if (!gpio_is_ready_dt(&button)) {
 		return -ENODEV;
 	}

 	ret = gpio_pin_configure_dt(&button, GPIO_INPUT);
 	if (ret < 0) {
 		return ret;
 	}

 	/* remap UART0 pins if button is pressed */
 	if (gpio_pin_get_dt(&button)) {
 		struct pinctrl_dev_config *uart0_config =
 			PINCTRL_DT_DEV_CONFIG_GET(DT_NODELABEL(uart0));

 		return pinctrl_update_states(uart0_config, uart0_alt,
 					     ARRAY_SIZE(uart0_alt));

 	}

    printk("-- exit: remap_pins()\n");
 	return 0;
 }


 SYS_INIT(remap_pins, PRE_KERNEL_1, CONFIG_REMAP_INIT_PRIORITY);
diff --git a/xiao_ble.overlay b/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>;
        };

        sw1: sw1 {
            gpios = <&gpio0 4 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;     // sw1: P0.04 (XIAO #5 D4)
            label = "Select ttyUSB0/1";
            // zephyr,code = <INPUT_KEY_1>; // optional, for input subsystem
        };
    };

    aliases {
        sw0 = &button0;
        sw1 = &sw1;
        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";
 };

 // ---------------------------------------------
 // for dynamic-pinctl (to swap pins for uart0)
 // ---------------------------------------------
 #include <zephyr/dt-bindings/input/input-event-codes.h> // `zephyr,code`

 / {
 	zephyr,user {
 		uart0_alt_default = <&uart0_alt_default>;
 		uart0_alt_sleep = <&uart0_alt_sleep>;
 	};
 };

 // "dynamic" pinctrl to use external-uart breakout (AE-FT2232 / FTDI FT2232D) as /dev/ttyUSB1
 // when pressed sw1
 &pinctrl {
 	/* Alternative pin configuration for UART0 */
 	uart0_alt_default: uart0_alt_default {
 		group1 {
 			// psels = <NRF_PSEL(UART_TX, 0, 26)>;  // TXD: P0.26 (XIAO led0:red)
 			psels = <NRF_PSEL(UART_TX, 1, 13)>;  // TXD: P1.13 (XIAO #9 D8)
 		};
 		group2 {
 			psels = <NRF_PSEL(UART_RX, 1, 12)>;  // RXD: P1.12 (XIAO #8 D7)
 			bias-pull-up;
 		};
 	};

 	uart0_alt_sleep: uart0_alt_sleep {
 		group1 {
 			psels = <NRF_PSEL(UART_TX, 1, 13)>,  // TXD: P1.13 (XIAO #9 D8)
 				<NRF_PSEL(UART_RX, 1, 12)>;      // RXD: P1.12 (XIAO #8 D7)
 			low-power-enable;
 		};
 	};
 };

 / {
    // sw0: sw0 {
    //     compatible = "gpio-key";
    //     gpios = <&gpio0 5 GPIO_ACTIVE_LOW>;     // sw0: P0.05 (XIAO #6 D5)
    //     label = "Push Switch";
    //     zephyr,code = <INPUT_KEY_0>; // optional, for input subsystem
    // };

    // sw1: sw1 {
    //     compatible = "gpio-key";
    //     gpios = <&gpio0 4 GPIO_ACTIVE_LOW>;     // sw1: P0.04 (XIAO #5 D4)
    //     label = "Select ttyUSB0/1";
    //     zephyr,code = <INPUT_KEY_1>; // optional, for input subsystem
    // };

    // aliases {
    //     // sw0 = &sw0;
    //     sw1 = &sw1;
    // };
 };
	# SPDX-License-Identifier: Apache-2.0

	cmake_minimum_required(VERSION 3.20.0)
	find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
	project(button)

	target_sources(app PRIVATE src/main.c src/remap.c)
	# 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
	# based on zephyr/samples/boards/nordic/dynamic_pinctrl/Kconfig
	#
	# Copyright (c) 2021 Nordic Semiconductor ASA
	# SPDX-License-Identifier: Apache-2.0

	mainmenu "Dynamic pin control sample"

	config REMAP_INIT_PRIORITY
	int "Remap routine initialization priority"
	default 50
	help
	Initialization priority of the remap routine within the PRE_KERNEL1 level.
	This priority must be greater than GPIO_INIT_PRIORITY and lower than
	UART_INIT_PRIORITY.

	source "Kconfig.zephyr"
	CONFIG_GPIO=y

	# ---------------------------------------------
	# dynamic-pinctrl
	# ---------------------------------------------
	CONFIG_PINCTRL=y
	CONFIG_PINCTRL_DYNAMIC=y
	# configure serial and console to come after remap hook
	CONFIG_SERIAL_INIT_PRIORITY=60
	CONFIG_CONSOLE_INIT_PRIORITY=70
	/*
	* Copyright (c) 2016 Open-RnD Sp. z o.o.
	* Copyright (c) 2020 Nordic Semiconductor ASA
	*
	* SPDX-License-Identifier: Apache-2.0
	*
	* NOTE: If you are looking into an implementation of button events with
	* debouncing, check out `input` subsystem and `samples/subsys/input/input_dump`
	* example instead.
	*/

	#include <zephyr/kernel.h>
	#include <zephyr/device.h>
	#include <zephyr/drivers/gpio.h>
	#include <zephyr/sys/util.h>
	#include <zephyr/sys/printk.h>
	#include <inttypes.h>

	#define SLEEP_TIME_MS 1

	/*
	* Get button configuration from the devicetree sw0 alias. This is mandatory.
	*/
	#define SW0_NODE DT_ALIAS(sw0)
	#if !DT_NODE_HAS_STATUS_OKAY(SW0_NODE)
	#error "Unsupported board: sw0 devicetree alias is not defined"
	#endif
	static const struct gpio_dt_spec button = GPIO_DT_SPEC_GET_OR(SW0_NODE, gpios,
	{0});

	#define SW1_NODE DT_ALIAS(sw1)
	#if !DT_NODE_HAS_STATUS_OKAY(SW1_NODE)
	#error "Unsupported board: sw1 devicetree alias is not defined"
	#endif
	static const struct gpio_dt_spec button1 = GPIO_DT_SPEC_GET_BY_IDX_OR(SW1_NODE, gpios,
	0, // idx
	{0});
	static struct gpio_callback button_cb_data;
	static struct gpio_callback button1_cb_data;

	/*
	* The led0 devicetree alias is optional. If present, we'll use it
	* to turn on the LED whenever the button is pressed.
	*/
	static struct gpio_dt_spec led = GPIO_DT_SPEC_GET_OR(DT_ALIAS(led0), gpios,
	{0});

	void button_pressed(const struct device dev, struct gpio_callback cb,
	uint32_t pins)
	{
	printk("Button pressed at %" PRIu32 " from pin %d\n", k_cycle_get_32(), pins);
	}

	int main(void)
	{
	int ret;

	if (!gpio_is_ready_dt(&button)) {
	printk("Error: button device %s is not ready\n",
	button.port->name);
	return 0;
	}

	if (!gpio_is_ready_dt(&button1)) {
	printk("Error: button1 device %s is not ready\n",
	button1.port->name);
	return 0;
	}

	ret = gpio_pin_configure_dt(&button, GPIO_INPUT);
	if (ret != 0) {
	printk("Error %d: failed to configure %s pin %d\n",
	ret, button.port->name, button.pin);
	return 0;
	}

	ret = gpio_pin_configure_dt(&button1, GPIO_INPUT);
	if (ret != 0) {
	printk("Error %d: failed to configure %s pin %d\n",
	ret, button1.port->name, button1.pin);
	return 0;
	}

	ret = gpio_pin_interrupt_configure_dt(&button,
	GPIO_INT_EDGE_TO_ACTIVE);
	if (ret != 0) {
	printk("Error %d: failed to configure interrupt on %s pin %d\n",
	ret, button.port->name, button.pin);
	return 0;
	}

	ret = gpio_pin_interrupt_configure_dt(&button1,
	GPIO_INT_EDGE_TO_ACTIVE);
	if (ret != 0) {
	printk("Error %d: failed to configure interrupt on %s pin %d\n",
	ret, button1.port->name, button1.pin);
	return 0;
	}

	gpio_init_callback(&button_cb_data, button_pressed, BIT(button.pin));
	gpio_add_callback(button.port, &button_cb_data);
	printk("Set up button at %s pin %d\n", button.port->name, button.pin);

	gpio_init_callback(&button1_cb_data, button_pressed, BIT(button1.pin));
	gpio_add_callback(button1.port, &button1_cb_data);
	printk("Set up button at %s pin %d\n", button1.port->name, button1.pin);

	if (led.port && !gpio_is_ready_dt(&led)) {
	printk("Error %d: LED device %s is not ready; ignoring it\n",
	ret, led.port->name);
	led.port = NULL;
	}
	if (led.port) {
	ret = gpio_pin_configure_dt(&led, GPIO_OUTPUT);
	if (ret != 0) {
	printk("Error %d: failed to configure LED device %s pin %d\n",
	ret, led.port->name, led.pin);
	led.port = NULL;
	} else {
	printk("Set up LED at %s pin %d\n", led.port->name, led.pin);
	}
	}

	printk("Press the button\n");
	if (led.port) {
	while (1) {
	/* If we have an LED, match its state to the button's. */
	int val = gpio_pin_get_dt(&button);

	if (val >= 0) {
	gpio_pin_set_dt(&led, val);
	}
	k_msleep(SLEEP_TIME_MS);
	}
	}
	return 0;
	}
	/*
	* Copyright (c) 2021 Nordic Semiconductor ASA
	*
	* SPDX-License-Identifier: Apache-2.0
	*/

	#include <zephyr/init.h>
	#include <zephyr/drivers/gpio.h>
	#include <zephyr/drivers/pinctrl.h>

	/* make sure devices and remap hook are initialized in the correct order */
	BUILD_ASSERT((CONFIG_GPIO_INIT_PRIORITY < CONFIG_REMAP_INIT_PRIORITY) &&
	(CONFIG_REMAP_INIT_PRIORITY < CONFIG_SERIAL_INIT_PRIORITY),
	"Device driver priorities are not set correctly");

	PINCTRL_DT_DEV_CONFIG_DECLARE(DT_NODELABEL(uart0));

	/* UART0 alternative configurations (default and sleep states) */
	PINCTRL_DT_STATE_PINS_DEFINE(DT_PATH(zephyr_user), uart0_alt_default);
	#ifdef CONFIG_PM_DEVICE
	PINCTRL_DT_STATE_PINS_DEFINE(DT_PATH(zephyr_user), uart0_alt_sleep);
	#endif

	static const struct pinctrl_state uart0_alt[] = {
	PINCTRL_DT_STATE_INIT(uart0_alt_default, PINCTRL_STATE_DEFAULT),
	#ifdef CONFIG_PM_DEVICE
	PINCTRL_DT_STATE_INIT(uart0_alt_sleep, PINCTRL_STATE_SLEEP),
	#endif
	};

	#include <zephyr/kernel.h> // printk

	static int remap_pins(void)
	{
	int ret;
	printk("-- enter: remap_pins()\n");

	const struct gpio_dt_spec button = GPIO_DT_SPEC_GET_OR(DT_ALIAS(sw1),
	gpios, {0});


	if (!gpio_is_ready_dt(&button)) {
	return -ENODEV;
	}

	ret = gpio_pin_configure_dt(&button, GPIO_INPUT);
	if (ret < 0) {
	return ret;
	}

	/* remap UART0 pins if button is pressed */
	if (gpio_pin_get_dt(&button)) {
	struct pinctrl_dev_config *uart0_config =
	PINCTRL_DT_DEV_CONFIG_GET(DT_NODELABEL(uart0));

	return pinctrl_update_states(uart0_config, uart0_alt,
	ARRAY_SIZE(uart0_alt));

	}

	printk("-- exit: remap_pins()\n");
	return 0;
	}


	SYS_INIT(remap_pins, PRE_KERNEL_1, CONFIG_REMAP_INIT_PRIORITY);
	// 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>;
	};

	sw1: sw1 {
	gpios = <&gpio0 4 (GPIO_PULL_UP \| GPIO_ACTIVE_LOW)>; // sw1: P0.04 (XIAO #5 D4)
	label = "Select ttyUSB0/1";
	// zephyr,code = <INPUT_KEY_1>; // optional, for input subsystem
	};
	};

	aliases {
	sw0 = &button0;
	sw1 = &sw1;
	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";
	};

	// ---------------------------------------------
	// for dynamic-pinctl (to swap pins for uart0)
	// ---------------------------------------------
	#include <zephyr/dt-bindings/input/input-event-codes.h> // `zephyr,code`

	/ {
	zephyr,user {
	uart0_alt_default = <&uart0_alt_default>;
	uart0_alt_sleep = <&uart0_alt_sleep>;
	};
	};

	// "dynamic" pinctrl to use external-uart breakout (AE-FT2232 / FTDI FT2232D) as /dev/ttyUSB1
	// when pressed sw1
	&pinctrl {
	/* Alternative pin configuration for UART0 */
	uart0_alt_default: uart0_alt_default {
	group1 {
	// psels = <NRF_PSEL(UART_TX, 0, 26)>; // TXD: P0.26 (XIAO led0:red)
	psels = <NRF_PSEL(UART_TX, 1, 13)>; // TXD: P1.13 (XIAO #9 D8)
	};
	group2 {
	psels = <NRF_PSEL(UART_RX, 1, 12)>; // RXD: P1.12 (XIAO #8 D7)
	bias-pull-up;
	};
	};

	uart0_alt_sleep: uart0_alt_sleep {
	group1 {
	psels = <NRF_PSEL(UART_TX, 1, 13)>, // TXD: P1.13 (XIAO #9 D8)
	<NRF_PSEL(UART_RX, 1, 12)>; // RXD: P1.12 (XIAO #8 D7)
	low-power-enable;
	};
	};
	};

	/ {
	// sw0: sw0 {
	// compatible = "gpio-key";
	// gpios = <&gpio0 5 GPIO_ACTIVE_LOW>; // sw0: P0.05 (XIAO #6 D5)
	// label = "Push Switch";
	// zephyr,code = <INPUT_KEY_0>; // optional, for input subsystem
	// };

	// sw1: sw1 {
	// compatible = "gpio-key";
	// gpios = <&gpio0 4 GPIO_ACTIVE_LOW>; // sw1: P0.04 (XIAO #5 D4)
	// label = "Select ttyUSB0/1";
	// zephyr,code = <INPUT_KEY_1>; // optional, for input subsystem
	// };

	// aliases {
	// // sw0 = &sw0;
	// sw1 = &sw1;
	// };
	};