Add example firmware

Author: zapb-0

.gitmodules

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+[submodule "firmware/libopencm3"]
+	path = firmware/libopencm3
+	url = https://github.com/libopencm3/libopencm3
+	branch = 78c23ba5

firmware/.gitignore

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+firmware.*
+*.o

firmware/Makefile

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+##
+## Copyright (C) 2020 Marc Schink <[email protected]>
+##
+## This program is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+PREFIX ?= arm-none-eabi-
+CC = $(PREFIX)gcc
+OBJCOPY = $(PREFIX)objcopy
+
+OPENOCD ?= openocd
+
+FP_FLAGS = -msoft-float
+ARCH_FLAGS = -mcpu=cortex-m3 -mthumb $(FP_FLAGS)
+
+LD_SCRIPT = libopencm3/lib/stm32/f1/stm32f100xb.ld
+
+LDFLAGS = -L./libopencm3/lib
+LDFLAGS += --static -nostartfiles
+LDFLAGS += -T$(LD_SCRIPT)
+
+CFLAGS = $(ARCH_FLAGS)
+CFLAGS += -std=c11 -g3 -O0
+CFLAGS += -I./libopencm3/include
+CFLAGS += -fno-common -ffunction-sections -fdata-sections
+CFLAGS += -DSTM32F1
+
+LDLIBS = -Wl,--start-group -lc -lgcc -lnosys -Wl,--end-group
+LDLIBS += -lopencm3_stm32f1
+
+FIRMWARE_ELF = firmware.elf
+FIRMWARE_BIN = firmware.bin
+FIRMWARE_HEX = firmware.hex
+
+all: $(FIRMWARE_ELF) $(FIRMWARE_BIN) $(FIRMWARE_HEX)
+
+$(FIRMWARE_ELF): main.c libopencm3/lib/libopencm3_stm32f1.a
+	$(CC) $(CFLAGS) $(LDFLAGS) main.c $(LDLIBS) -o firmware.elf
+
+libopencm3/Makefile:
+	git submodule update --init
+
+libopencm3/lib/libopencm3_%.a: libopencm3/Makefile
+	$(MAKE) -C libopencm3 TARGETS=stm32/f1
+
+$(FIRMWARE_BIN): $(FIRMWARE_ELF)
+	$(OBJCOPY) -O binary $< $@
+
+$(FIRMWARE_HEX): $(FIRMWARE_ELF)
+	$(OBJCOPY) -O ihex $< $@
+
+flash: $(FIRMWARE_ELF)
+	$(OPENOCD) -f interface/jlink.cfg -c "transport select swd" -f target/stm32f1x.cfg -c "program $(FIRMWARE_ELF) verify reset exit"
+
+clean:
+	$(RM) $(FIRMWARE_ELF) $(FIRMWARE_BIN) $(FIRMWARE_HEX)
+
+distclean: clean
+	$(MAKE) -C libopencm3 clean
+
+.PHONY: all flash clean distclean

firmware/libopencm3

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+/*
+ * Copyright (C) 2020 Marc Schink <[email protected]>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+
+#define LED2_GPIO	GPIOA
+#define LED2_PIN	GPIO5
+
+char *text = "This is some secret data stored in the flash memory together with the firmware. Exception(al) failure...!";
+
+int main(void)
+{
+	rcc_periph_clock_enable(RCC_GPIOA);
+
+	gpio_set_mode(LED2_GPIO, GPIO_MODE_OUTPUT_2_MHZ,
+		GPIO_CNF_OUTPUT_PUSHPULL, LED2_PIN);
+	gpio_clear(LED2_GPIO, LED2_PIN);
+
+	while (true) {
+		for (uint32_t i = 0; i < (1 << 18); i++) {
+			__asm__("nop");
+		}
+
+		gpio_toggle(LED2_GPIO, LED2_PIN);
+	}
+}