target: add initial russian woodpecker port

Signed-off-by: Rafael Silva <perigoso@riseup.net>

config/linker/russian-woodpecker/russian-woodpecker.ld

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+
+INCLUDE sam3u/sam3u2.ld

config/targets/russian-woodpecker.toml

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+family = 'sam3u'
+has-config = true

src/targets/russian-woodpecker/config/russian-woodpecker.h

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+/*
+ * SPDX-License-Identifier: MIT
+ * SPDX-FileCopyrightText: 2021 Rafael Silva <perigoso@riseup.net>
+ */
+
+/* clang-format off */
+
+/* General Config */
+
+#define __SAM3U2C__
+
+/* Clock Config */
+#define EXTERNAL_CLOCK_VALUE 12000000UL

src/targets/russian-woodpecker/main.c

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+/*
+ * SPDX-License-Identifier: MIT
+ * SPDX-FileCopyrightText: 2022 Rafael Silva <perigoso@riseup.net>
+ */
+
+#include "util/data.h"
+#include "util/types.h"
+
+#include "platform/sam3u/eefc.h"
+#include "platform/sam3u/pmc.h"
+#include "platform/sam3u/wdt.h"
+
+void main()
+{
+	pmc_init(EXTERNAL_CLOCK_VALUE, 0UL);
+	pmc_update_clock_tree();
+
+	wdt_disable();
+
+	// systick_init();
+
+	for (;;) {
+	}
+}

src/targets/russian-woodpecker/tusb_config.h

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+/*
+ * SPDX-License-Identifier: MIT
+ * SPDX-FileCopyrightText: 2021 Rafael Silva <perigoso@riseup.net>
+ */
+
+/* Common Configuration */
+
+#define CFG_TUSB_MCU OPT_MCU_SAM3U
+
+#define CFG_TUSB_OS OPT_OS_NONE
+
+#define CFG_TUSB_RHPORT0_MODE (OPT_MODE_DEVICE | OPT_MODE_HIGH_SPEED)
+
+/*
+ * USB DMA on some MCUs can only access a specific SRAM region with restriction on alignment.
+ * Tinyusb use follows macros to declare transferring memory so that they can be put
+ * into those specific section.
+ * e.g
+ * - CFG_TUSB_MEM SECTION : __attribute__ (( section(".usb_ram") ))
+ * - CFG_TUSB_MEM_ALIGN   : __attribute__ ((aligned(4)))
+ */
+#ifndef CFG_TUSB_MEM_SECTION
+#define CFG_TUSB_MEM_SECTION
+#endif
+
+#ifndef CFG_TUSB_MEM_ALIGN
+#define CFG_TUSB_MEM_ALIGN __attribute__((aligned(4)))
+#endif
+
+/* Device Configuration */
+
+#define CFG_TUD_ENDPOINT0_SIZE 64
+
+/* Class */
+#define CFG_TUD_HID    3
+#define CFG_TUD_CDC    0
+#define CFG_TUD_MSC    0
+#define CFG_TUD_MIDI   0
+#define CFG_TUD_VENDOR 0
+
+/* HID buffer size Should be sufficient to hold ID (if any) + Data */
+#define CFG_TUD_HID_BUFSIZE 64