boards/seeedstudio-xiao-esp32c3: add support

Port the Seeed Studio Xiao ESP32C3 to RIOT.

boards/seeedstudio-xiao-esp32c3/Kconfig

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+# Copyright (c) 2025 David Picard
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+config BOARD
+    default "seeedstudio-xiao-esp32c3" if BOARD_SEEEDSTUDIO_XIAO_ESP32C3
+
+config BOARD_SEEEDSTUDIO_XIAO_ESP32C3
+    bool
+    default y
+    select BOARD_COMMON_ESP32C3
+    select CPU_MODEL_ESP32C3_FH4
+
+source "$(RIOTBOARD)/common/esp32c3/Kconfig"

boards/seeedstudio-xiao-esp32c3/Makefile

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+MODULE = board
+
+DIRS = $(RIOTBOARD)/common/esp32c3
+
+include $(RIOTBASE)/Makefile.base

boards/seeedstudio-xiao-esp32c3/Makefile.dep

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+ifeq (,$(filter stdio_% slipdev_stdio,$(USEMODULE)))
+  USEMODULE += stdio_usb_serial_jtag
+endif
+
+ifneq (,$(filter saul_default,$(USEMODULE)))
+  USEMODULE += saul_gpio
+endif
+
+include $(RIOTBOARD)/common/esp32c3/Makefile.dep

boards/seeedstudio-xiao-esp32c3/Makefile.features

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+CPU_MODEL = esp32c3_fh4
+
+# common board and CPU features
+include $(RIOTBOARD)/common/esp32c3/Makefile.features
+
+# additional features provided by the board
+FEATURES_PROVIDED += periph_adc
+FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_pwm
+FEATURES_PROVIDED += periph_spi
+
+# unique features provided by the board
+FEATURES_PROVIDED += esp_jtag
+
+FEATURES_PROVIDED += arduino_pins

boards/seeedstudio-xiao-esp32c3/Makefile.include

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+PORT_LINUX ?= /dev/ttyACM0
+
+include $(RIOTBOARD)/common/esp32c3/Makefile.include

boards/seeedstudio-xiao-esp32c3/doc.md

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+<!--
+Copyright (C) 2025 David Picard
+
+This file is subject to the terms and conditions of the GNU Lesser
+General Public License v2.1. See the file LICENSE in the top level
+directory for more details.
+-->
+
+@defgroup    boards_seeedstudio-xiao-esp32c3 Seeed Studio Xiao ESP32C3
+@ingroup     boards_esp32c3
+@brief       Support for the Seeed Studio Xiao ESP32-C3 board
+@author      David Picard
+
+\section seeedstudio-xiao-esp32c3 Seeed Studio Xiao ESP32C3
+
+## Table of Contents {#seeedstudio-xiao-esp32c3_toc}
+
+1. [Overview](#seeedstudio-xiao-esp32c3_overview)
+2. [Hardware](#seeedstudio-xiao-esp32c3_hardware)
+    1. [MCU](#seeedstudio-xiao-esp32c3_mcu)
+    2. [Board Configuration](#seeedstudio-xiao-esp32c3_board_configuration)
+    3. [Board Pinout](#seeedstudio-xiao-esp32c3_pinout)
+    4. [Board documentation](#seeedstudio-xiao-esp32c3_documentation)
+3. [Flashing the Device](#seeedstudio-xiao-esp32c3_flashing)
+
+## Overview {#seeedstudio-xiao-esp32c3_overview}
+
+Seeed Studio Xiao ESP32C3 is an IoT mini development board based on the Espressif ESP32-C3
+WiFi/Bluetooth dual-mode chip, featuring a single ­core 32-bit RISC-V CPU that operates at up to 160 MHz.
+
+- Wi-Fi
+- Bluetooth
+- Battery charging chip: Supports lithium battery charge and discharge management
+- Memory: 400KB of SRAM, and 4MB of on-board flash memory
+- Small size: 21 x 17.8mm
+- Ultra-Low Power: Deep sleep power consumption is about 43μA
+- Battery charge indicator red LED
+
+@image html https://files.seeedstudio.com/wiki/XIAO_WiFi/board-pic.png "Seeed Studio EPS32-C3 Xiao" width=200pix
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)
+
+## Hardware {#seeedstudio-xiao-esp32c3_hardware}
+
+This section describes
+
+- the [MCU](#seeedstudio-xiao-esp32c3_mcu),
+- the default [board configuration](#seeedstudio-xiao-esp32c3_board_configuration),
+- the [board pinout](#seeedstudio-xiao-esp32c3_pinout).
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)
+
+### MCU {#seeedstudio-xiao-esp32c3_mcu}
+
+Most features of the board are provided by the ESP32-C3 SoC. For detailed
+information about the ESP32-C3 variant (family) and ESP32x SoCs,
+see section \ref esp32_mcu_esp32 "ESP32 SoC Series".
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)
+
+### Board Configuration {#seeedstudio-xiao-esp32c3_board_configuration}
+
+The Seeed Studio EPS32-C3 Xiao board has a reset button and a bootloader button,
+but no LED.
+After reset, the bootloader button may be used by the application.
+
+To select the board, add the following to the make command line:
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+BOARD=seeedstudio-xiao-esp32c3 make ...
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Almost all GPIOs are broken out and can be used for different peripherals:
+
+- 3 x ADC channels at maximum
+- 1 x SPI
+- 1 x I2C
+- 1 x UART
+- 11 x PWM channels (only 4 defined by default)
+
+The purpose for which a GPIO is used depends on which module
+or function is used first. For example, if module `periph_spi` is not used,
+the GPIOs listed in SPI configuration can be used for other purposes.
+
+The following table shows the default board configuration.
+This configuration can be overridden by \ref esp32_application_specific_configurations
+"application-specific configurations".
+
+<center>
+Function        | Pin                   | Configuration
+:---------------|:----------------------|:-------------
+BUTTON0         | GPIO9                 | GPIO9 is a [strapping pin](https://docs.espressif.com/projects/esptool/en/latest/esp32c3/advanced-topics/boot-mode-selection.html)
+ADC             | GPIO2, GPIO3, GPIO4   | \ref esp32_adc_channels "ADC Channels"
+I2C_DEV(0):SCL  | GPIO7                 | \ref esp32_i2c_interfaces "I2C Interfaces"
+I2C_DEV(0):SDA  | GPIO6                 | \ref esp32_i2c_interfaces "I2C Interfaces"
+PWM_DEV(0)      | GPIO2, GPIO3, GPIO4, GPIO5 | \ref esp32_pwm_channels "PWM Channels"
+SPI_DEV(0):SCK  | GPIO8                 | \ref esp32_spi_interfaces "SPI Interfaces"
+SPI_DEV(0):MISO | GPIO9                 | \ref esp32_spi_interfaces "SPI Interfaces"
+SPI_DEV(0):MOSI | GPIO10                | \ref esp32_spi_interfaces "SPI Interfaces"
+SPI_DEV(0):CS0  | GPIO5                 | \ref esp32_spi_interfaces "SPI Interfaces"
+UART_DEV(0):TxD | GPIO21                | \ref esp32_uart_interfaces "UART interfaces"
+UART_DEV(0):RxD | GPIO20                | \ref esp32_uart_interfaces "UART interfaces"
+</center>
+\n
+@note The configuration of ADC channels contains all ESP32-C3 GPIOs that could
+      be used as ADC channels.
+
+For detailed information about the peripheral configurations of ESP32-C3
+boards, see section \ref esp32_peripherals "Common Peripherals".
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)
+
+### Board Pinout {#seeedstudio-xiao-esp32c3_pinout}
+
+The following figures show the pinouts as configured by default board
+definition.
+
+@image html https://files.seeedstudio.com/wiki/XIAO_WiFi/pin_map-2.png "Seeed Studio EPS32-C3 Xiao Pinout" width=800
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)
+
+### Board documentation {#seeedstudio-xiao-esp32c3_documentation}
+
+- [schematic](https://files.seeedstudio.com/wiki/XIAO_WiFi/Resources/Seeeduino-XIAO-ESP32C3-SCH.pdf) (PDF)
+- [pinout](https://files.seeedstudio.com/wiki/XIAO_WiFi/Resources/XIAO-ESP32C3-pinout_sheet.xlsx) (XLSX)
+- [ESP32-C3 datasheet](https://files.seeedstudio.com/wiki/Seeed-Studio-XIAO-ESP32/esp32-c3_datasheet.pdf) (PDF)
+- [power consumption report](https://files.seeedstudio.com/wiki/Seeed-Studio-XIAO-ESP32/Low_Power_Consumption.pdf) (PDF)
+- [product page](https://www.seeedstudio.com/Seeed-XIAO-ESP32C3-p-5431.html?qid=eyJjX3NlYXJjaF9xdWVyeSI6InhpYW8gZXNwMzJjMyIsImNfc2VhcmNoX3Jlc3VsdF9wb3MiOjQsImNfdG90YWxfcmVzdWx0cyI6ODcsImNfc2VhcmNoX3Jlc3VsdF90eXBlIjoiUHJvZHVjdCIsImNfc2VhcmNoX2ZpbHRlcnMiOiJzdG9yZUNvZGU6W3JldGFpbGVyXSJ9)
+- [wiki page](https://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/)
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)
+
+## Flashing the Device {#seeedstudio-xiao-esp32c3_flashing}
+
+The USB-C connector of the board is directly connected to the USB Serial/JTAG
+interface of the ESP32-C3 SoC. It can be used to program the board and to debug
+the application. Just connect the board to your host computer and use the
+following command:
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+make flash BOARD=seeedstudio-xiao-esp32c3 ...
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The make utility will normally restart the board in download mode in order
+to flash it.
+But, on occasion, this reset doesn't work.
+The programmer can't connect to the board and the flashing operation is
+aborted with a timeout error:
+```
+Serial port /dev/ttyACM0
+Connecting...
+...
+serial.serialutil.SerialTimeoutException: Write timeout
+```
+In this situation, restart the board manually in download mode:
+1. hold down the BOOT button
+2. press and release the RESET button
+3. release the BOOT button.
+
+After flashing the board, it will still be in download mode. You have to press
+the RESET button to start your application.
+
+For detailed information about ESP32-C3 as well as configuring and compiling
+RIOT for ESP32-C3 boards, see \ref esp32_riot.
+
+[Back to table of contents](#seeedstudio-xiao-esp32c3_toc)

boards/seeedstudio-xiao-esp32c3/include/arduino_iomap.h

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+/*
+ * Copyright (C)  2025 David Picard
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_seeedstudio-xiao-esp32c3
+ * @{
+ *
+ * @file
+ * @brief       Mapping from MCU pins to Arduino pins
+ *
+ * @author      David Picard
+ */
+
+#ifndef ARDUINO_IOMAP_H
+#define ARDUINO_IOMAP_H
+
+#include "periph/gpio.h"
+#include "periph/adc.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name   Mapping of MCU pins to Arduino pins
+ * @{
+ */
+#define ARDUINO_PIN_0       GPIO2       /**< Arduino pin 0 */
+#define ARDUINO_PIN_1       GPIO3       /**< Arduino pin 1 */
+#define ARDUINO_PIN_2       GPIO4       /**< Arduino pin 2 */
+#define ARDUINO_PIN_3       GPIO5       /**< Arduino pin 3 */
+#define ARDUINO_PIN_4       GPIO6       /**< Arduino pin 4 (I2C SDA) */
+#define ARDUINO_PIN_5       GPIO7       /**< Arduino pin 5 (I2C SCL) */
+#define ARDUINO_PIN_6       GPIO21      /**< Arduino pin 1 (TxD) */
+#define ARDUINO_PIN_7       GPIO20      /**< Arduino pin 0 (RxD) */
+#define ARDUINO_PIN_8       GPIO8       /**< Arduino pin 8 (SPI SCK) */
+#define ARDUINO_PIN_9       GPIO9       /**< Arduino pin 0 (SPI MISO)*/
+#define ARDUINO_PIN_10      GPIO10      /**< Arduino pin 0 (SPI MOSI) */
+
+#define ARDUINO_PIN_LAST    10
+/** @} */
+
+/**
+ * @name    Aliases for analog pins
+ * @{
+ */
+#define ARDUINO_PIN_A0          ARDUINO_PIN_0
+#define ARDUINO_PIN_A1          ARDUINO_PIN_1
+#define ARDUINO_PIN_A2          ARDUINO_PIN_2
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ARDUINO_IOMAP_H */
+/** @} */

boards/seeedstudio-xiao-esp32c3/include/board.h

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+/*
+ * Copyright (C) 2025 David Picard
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_seeedstudio-xiao-esp32c3
+ * @brief       Board definitions for the Seeed Studio Xiao ESP32-C3 board
+ * @{
+ *
+ * @file        board.h
+ * @author      David Picard
+ */
+
+#ifndef BOARD_H
+#define BOARD_H
+
+#include <stdint.h>
+
+/**
+ * @name    Button pin definitions
+ * @{
+ */
+
+/**
+ * @brief   Default button GPIO pin definition
+ *
+ * The Seeed Studio Xiao ESP32-C3 board has a BOOT button connected to GPIO9, which can
+ * be used as button during normal operation. Since the GPIO9 pin is pulled up,
+ * the button signal is inverted, i.e., pressing the button will give a
+ * low signal.
+ */
+#define BTN0_PIN        GPIO9
+
+/**
+ * @brief   Default button GPIO mode definition
+ *
+ * Since the GPIO of the button is pulled up with an external resistor, the
+ * mode for the GPIO pin has to be GPIO_IN.
+ */
+#define BTN0_MODE       GPIO_IN_PU
+
+/**
+ * @brief   Default interrupt flank definition for the button GPIO
+ */
+#ifndef BTN0_INT_FLANK
+#define BTN0_INT_FLANK  GPIO_FALLING
+#endif
+
+/**
+ * @brief   Definition for compatibility with previous versions
+ */
+#define BUTTON0_PIN     BTN0_PIN
+
+/** @} */
+
+/* include common board definitions as last step */
+#include "board_common.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+} /* end extern "C" */
+#endif
+
+#endif /* BOARD_H */
+/** @} */

boards/seeedstudio-xiao-esp32c3/include/gpio_params.h

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+/*
+ * Copyright (C) 2025 David Picard
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+#ifndef GPIO_PARAMS_H
+#define GPIO_PARAMS_H
+
+/**
+ * @ingroup     boards_seeedstudio-xiao-esp32c3
+ * @brief       Board specific configuration of direct mapped GPIOs
+ * @file
+ * @author      David Picard
+ * @{
+ */
+
+#include "board.h"
+#include "saul/periph.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   LED and Button configuration
+ */
+static const  saul_gpio_params_t saul_gpio_params[] =
+{
+    {
+        .name = "BOOT",
+        .pin = BTN0_PIN,
+        .mode = BTN0_MODE,
+        .flags = SAUL_GPIO_INVERTED
+    },
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* GPIO_PARAMS_H */
+/** @} */