sam3x8e: Add initial support for Arduino Due boards

This adds basic support for running on the Atmel SAM3x8e
micro-controllers that are found in the Arudino Due boards.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/sam3x8e/Makefile

@@ -0,0 +1,28 @@
+# Additional sam3x8e build rules
+
+# Setup the toolchain
+CROSS_PREFIX=arm-none-eabi-
+
+dirs-y += src/sam3x8e src/generic
+dirs-y += lib/cmsis-sam3x8e/source lib/cmsis-sam3x8e/source/gcc
+
+CFLAGS-y += -mthumb -mcpu=cortex-m3
+CFLAGS-y += -Ilib/cmsis-sam3x8e/include -Ilib/cmsis-sam3x8e/cmsis-include
+CFLAGS-y += -D__SAM3X8E__
+
+LDFLAGS-y += -Llib/cmsis-sam3x8e/source/gcc
+LDFLAGS-y += -T lib/cmsis-sam3x8e/source/gcc/sam3x8e_flash.ld
+LDFLAGS-y += --specs=nano.specs --specs=nosys.specs
+
+# Add source files
+src-y += sam3x8e/main.c sam3x8e/timer.c sam3x8e/gpio.c generic/crc16_ccitt.c
+src-y += ../lib/cmsis-sam3x8e/source/system_sam3xa.c
+src-y += ../lib/cmsis-sam3x8e/source/gcc/startup_sam3xa.c
+src-$(CONFIG_SERIAL) += sam3x8e/serial.c
+
+# Build the additional hex output file
+target-y += $(OUT)klipper.bin
+
+$(OUT)klipper.bin: $(OUT)klipper.elf
+	@echo "  Creating hex file $@"
+	$(Q)$(OBJCOPY) -O binary $< $@