boards/common: Introduce Atmel xmega common

Add atxmega common board definitions.  This works is a port from @josar
with few modifications.

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>

boards/common/atxmega/Makefile

@@ -0,0 +1,3 @@
+MODULE = boards_common_atxmega
+
+include $(RIOTBASE)/Makefile.base

boards/common/atxmega/Makefile.features

@@ -0,0 +1 @@
+CPU = atxmega

boards/common/atxmega/Makefile.include

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+INCLUDES += -I$(RIOTBOARD)/common/atxmega/include
+
+# Use JTAG as default protocol for debugging
+DEBUGPROTO ?= -x
+FLASHFILE ?= $(ELFFILE)
+
+# Use avrdude programmer with Atmel ICE as default flash/debug system
+PROGRAMMER ?= avrdude
+AVRDUDE_PROGRAMMER ?= atmelice
+
+ifneq (,$(filter flash%,$(MAKECMDGOALS)))
+  FFLAGS_EXTRA ?= -e
+endif
+
+# If avrdude specific programmer is not set, set it based on the bootloader used
+ifeq (,$(AVRDUDE_PROGRAMMER))
+  FLASHFILE ?= $(BINFILE)
+
+  ifeq (stk500v2,$(BOOTLOADER))
+    AVRDUDE_PROGRAMMER = stk500v2
+    BOOTLOADER_SIZE ?= 4K
+    # Disable auto erase; erasing the flash is done implicitly by the bootloader
+    # and explicit erase is not supported
+    FFLAGS_EXTRA += -D
+  endif
+
+  ifeq (avr109,$(BOOTLOADER))
+    AVRDUDE_PROGRAMMER = avr109
+    BOOTLOADER_SIZE ?= 4K
+  endif
+
+  ifneq (,$(BOOTLOADER_BAUD))
+    FFLAGS_EXTRA += -b $(BOOTLOADER_BAUD)
+  endif
+endif
+
+BOOTLOADER_SIZE ?= 0
+ROM_RESERVED ?= $(BOOTLOADER_SIZE)

boards/common/atxmega/board.c

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+/*
+ * Copyright (C) 2021 Gerson Fernando Budke <nandojve@gmail.com>
+ *
+ * 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_common
+ * @{
+ *
+ * @file
+ * @brief       Common implementations for ATxmega boards
+ *
+ * @author      Gerson Fernando Budke <nandojve@gmail.com>
+ *
+ * @}
+ */
+
+#include "board.h"
+#include "cpu.h"
+
+#ifdef LED_PORT
+void __attribute__((weak)) led_init(void)
+{
+    LED_PORT.DIR = LED_PORT_MASK;
+    LED_PORT.OUT = LED_PORT_MASK;
+}
+#endif
+
+void __attribute__((weak)) board_init(void)
+{
+    cpu_init();
+#ifdef LED_PORT
+    led_init();
+#endif
+}

boards/common/atxmega/doc.txt

@@ -0,0 +1,5 @@
+/**
+@defgroup    boards_common_atxmega ATxmega common
+@ingroup     boards
+@brief       Shared files and configuration for ATxmega-based boards
+ */

boards/common/atxmega/include/periph_conf_common.h

@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2021 Gerson Fernando Budke <nandojve@gmail.com>
+ *
+ * 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_common_atxmega
+ * @{
+ *
+ * @file
+ * @brief       Common configuration of MCU periphery for ATxmega boards
+ *
+ * @author      Gerson Fernando Budke <nandojve@gmail.com>
+ */
+
+#ifndef PERIPH_CONF_COMMON_H
+#define PERIPH_CONF_COMMON_H
+
+#include "periph_cpu.h"
+#include "macros/units.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    Clock configuration
+ * @{
+ */
+#ifndef CLOCK_CORECLOCK
+#define CLOCK_CORECLOCK     MHZ(32)
+#endif /* CLOCK_CORECLOCK */
+/** @} */
+
+/**
+ * @name ADC Configuration
+ *
+ * @{
+ */
+#ifndef ADC_NUMOF
+#define ADC_NUMOF           (0U)
+#endif /* ADC_NUMOF */
+/** @} */
+
+/**
+ * @name    I2C configuration
+ * @{
+ */
+#ifndef I2C_NUMOF
+#define I2C_NUMOF           (0U)
+#endif /* I2C_NUMOF */
+/** @} */
+
+/**
+ * @name   PWM configuration
+ *
+ * @{
+ */
+#ifndef PWM_NUMOF
+#define PWM_NUMOF           (0U)
+#endif /* PWM_NUMOF */
+/** @} */
+
+/**
+ * @name    SPI configuration
+ *
+ * The SS pin must be configured as output for the SPI device to work as
+ * master correctly, though we do not use it for now (as we handle the chip
+ * select externally for now)
+ *
+ * @{
+ */
+#ifndef SPI_NUMOF
+#define SPI_NUMOF           (0U)
+#endif /* SPI_NUMOF */
+/** @} */
+
+/**
+ * @name    UART configuration
+ *
+ * The UART devices have fixed pin mappings, so all we need to do, is to specify
+ * which devices we would like to use and their corresponding RX interrupts. See
+ * the reference manual for the fixed pin mapping.
+ *
+ * @{
+ */
+#ifndef UART_NUMOF
+#define UART_NUMOF          (0U)
+#endif /* UART_NUMOF */
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_CONF_COMMON_H */
+/** @} */