tbm: initial commit

Makefile

@@ -0,0 +1,13 @@
+BINARY = tbm
+
+LDSCRIPT = support/stm32f0-discovery.ld
+
+OPENCM3_DIR = libopencm3
+
+OBJS += main.o
+OBJS += shell.o
+OBJS += spi_flash.o
+OBJS += usart.o
+
+include support/libopencm3.target.mk
+include support/libopencm3.rules.mk

flash.scr

@@ -0,0 +1,2 @@
+load
+run

main.c

@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+#include "shell.h"
+#include "spi_flash.h"
+#include "usart.h"
+
+int main(void)
+{
+	FILE *fp;
+
+	init_spi();
+	fp = init_usart(USART1);
+	cmd_loop(fp, "tbm # ");
+
+	return 0;
+}

shell.c

@@ -0,0 +1,269 @@
+#define _GNU_SOURCE
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/spi.h>
+#include <libopencm3/stm32/usart.h>
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stddef.h>
+#include <limits.h>
+#include <sys/types.h>
+
+#include "shell.h"
+#include "spi_flash.h"
+#include "usart.h"
+
+static void do_probe(FILE *fp, const char *s);
+static void do_read(FILE *fp, const char *s);
+static void do_write(FILE *fp, const char *s);
+static void do_erase(FILE *fp, const char *s);
+
+struct cmd cmds[] = {
+	{ "probe", do_probe },
+	{ "read", do_read },
+	{ "write", do_write },
+	{ "erase", do_erase },
+	{ NULL, NULL },
+};
+
+/* TODO: implement a parser for hex arrays that is more user-friendly.
+ * Also implement dry runs for programmers. */
+static void parse_hex(FILE *fp, char *buf, size_t len)
+{
+	size_t i;
+	char s[3];
+
+	for (i = 0; i < len; ++i) {
+		memset(s, '\0', 3);
+
+		while ((s[0] = fgetc(fp)) && !isxdigit(s[0]))
+			fputc(s[0], fp);
+
+		fputc(s[0], fp);
+
+		while ((s[1] = fgetc(fp)) && !isxdigit(s[1]))
+			fputc(s[1], fp);
+
+		fputc(s[1], fp);
+
+		*buf++ = strtoul(s, NULL, 16);
+	}
+}
+
+static void print_hex_ascii(FILE *fp, const char *buf, size_t len)
+{
+	size_t i, j;
+	char c;
+
+	for (j = 0; j < len; j += 16, buf += 16) {
+		for (i = 0; i < 16; ++i) {
+			fprintf(fp, "%02x", buf[i]);
+		}
+
+		fprintf(fp, " ");
+
+		for (i = 0; i < 16; ++i) {
+			c = buf[i];
+			fprintf(fp, "%c", isalnum(c) ? c : '.');
+		}
+
+		fprintf(fp, "\r\n");
+	}
+}
+
+static char *prompt(FILE *fp, const char *prefix)
+{
+	char *alloc, *line, *s;
+	size_t nbytes = 0, nalloc_bytes = 16;
+	char c;
+
+	fprintf(fp, prefix);
+
+	if (!(line = malloc(nalloc_bytes)))
+		return NULL;
+
+	s = line;
+
+	while ((c = fgetc(fp)) && c != '\r') {
+		fputc(c, fp);
+
+		if (nbytes + 1 >= nalloc_bytes) {
+			nalloc_bytes *= 2;
+
+			if (!(alloc = realloc(line, nalloc_bytes)))
+				goto err_free_line;
+
+			line = alloc;
+		}
+
+		*s++ = c;
+		nbytes++;
+	}
+
+	fprintf(fp, "\r\n");
+	*s = '\0';
+
+	return line;
+
+err_free_line:
+	free(line);
+	return NULL;
+}
+
+
+
+static void do_probe(FILE *fp, const char *s)
+{
+	char cmd[1] = { CMD_READ_ID };
+	char buf[6];
+
+	(void)s;
+
+	spi_send_cmd(SPI1, cmd, 1, buf, 6);
+	fprintf(fp, "JEDEC ID: %02x%02x%02x\r\n", buf[0], buf[1], buf[2]);
+}
+
+static void do_read(FILE *fp, const char *s)
+{
+	char buf[256], *end = NULL;
+	size_t addr, len, nbytes;
+
+	if (strncmp(s, "0x", 2) == 0)
+		s += 2;
+
+	addr = strtoull(s, &end, 16);
+	s = end;
+
+	if (errno == EINVAL || errno == ERANGE)
+		return;
+
+	s += strspn(s, " \r\n");
+
+	if (strncmp(s, "0x", 2) == 0)
+		s += 2;
+
+	len = strtoull(s, &end, 16);
+	s = end;
+
+	if (errno == EINVAL || errno == ERANGE)
+		return;
+
+	if (!len)
+		return;
+
+	while (len) {
+		nbytes = (len > 256) ? 256 : len;
+		spi_flash_read(SPI1, addr, buf, nbytes);
+		print_hex_ascii(fp, buf, nbytes);
+
+		addr += nbytes;
+		len -= nbytes;
+	}
+}
+
+static void do_write(FILE *fp, const char *s)
+{
+	char buf[256], *end = NULL;
+	size_t addr, len, nbytes;
+
+	if (strncmp(s, "0x", 2) == 0)
+		s += 2;
+
+	addr = strtoull(s, &end, 16);
+	s = end;
+
+	if (errno == EINVAL || errno == ERANGE)
+		return;
+
+	s += strspn(s, " \r\n");
+
+	if (strncmp(s, "0x", 2) == 0)
+		s += 2;
+
+	len = strtoull(s, &end, 16);
+	s = end;
+
+	if (errno == EINVAL || errno == ERANGE)
+		return;
+
+	if (!len)
+		return;
+
+	while (len) {
+		nbytes = (len > 256) ? 256 : len;
+		parse_hex(fp, buf, nbytes);
+		fprintf(fp, "\r\n");
+		print_hex_ascii(fp, buf, nbytes);
+		spi_flash_write(SPI1, addr, buf, nbytes);
+
+		addr += nbytes;
+		len -= nbytes;
+	}
+}
+
+static void do_erase(FILE *fp, const char *s)
+{
+	char *end = NULL;
+	size_t addr, len;
+
+	(void)fp;
+
+	if (strncmp(s, "0x", 2) == 0)
+		s += 2;
+
+	addr = strtoull(s, &end, 16);
+	s = end;
+
+	if (errno == EINVAL || errno == ERANGE)
+		return;
+
+	s += strspn(s, " \r\n");
+
+	if (strncmp(s, "0x", 2) == 0)
+		s += 2;
+
+	len = strtoull(s, &end, 16);
+	s = end;
+
+	if (errno == EINVAL || errno == ERANGE)
+		return;
+
+	if (!len)
+		return;
+
+	spi_flash_erase(fp, SPI1, addr, len);
+}
+
+static void parse_cmd(FILE *fp, const char *s)
+{
+	struct cmd *cmd;
+	const char *args;
+	char *key;
+	size_t n;
+
+	n = strcspn(s, " \r\n");
+	key = strndup(s, n);
+
+	args = s + n;
+	args += strspn(args, " \r\n");
+
+	for (cmd = cmds; cmd->key; cmd++) {
+		if (strcmp(cmd->key, key) == 0)
+			cmd->exec(fp, args);
+	}
+}
+
+void cmd_loop(FILE *fp, const char *show)
+{
+	char *line;
+
+	while (1) {
+		line = prompt(fp, show);
+		parse_cmd(fp, line);
+		free(line);
+	}
+}

shell.h

@@ -0,0 +1,8 @@
+#pragma once
+
+struct cmd {
+	const char *key;
+	void (* exec)(FILE *fp, const char *s);
+};
+
+void cmd_loop(FILE *fp, const char *s);

spi_flash.c

@@ -0,0 +1,154 @@
+#define _GNU_SOURCE
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/spi.h>
+#include <libopencm3/stm32/usart.h>
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stddef.h>
+#include <limits.h>
+#include <sys/types.h>
+
+#include "spi_flash.h"
+
+void init_spi(void)
+{
+	/* Set up clocks for SPI 1 */
+	rcc_clock_setup_in_hsi_out_48mhz();
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_SPI1);
+
+	/* Set up GPIOs for SPI 1 */
+	gpio_mode_setup(GPIOA, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, GPIO4);
+	gpio_set(GPIOA, GPIO4);
+	gpio_mode_setup(GPIOB, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO3 | GPIO4 | GPIO5);
+	gpio_set_af(GPIOB, GPIO_AF0, GPIO3 | GPIO4 | GPIO5);
+
+	spi_set_master_mode(SPI1);
+	spi_set_baudrate_prescaler(SPI1, SPI_CR1_BR_FPCLK_DIV_64);
+	spi_set_clock_polarity_0(SPI1);
+	spi_set_clock_phase_0(SPI1);
+	spi_set_full_duplex_mode(SPI1);
+	spi_set_unidirectional_mode(SPI1); /* bidirectional but in 3-wire */
+	spi_set_data_size(SPI1, SPI_CR2_DS_8BIT);
+	spi_enable_software_slave_management(SPI1);
+	spi_send_msb_first(SPI1);
+	spi_set_nss_high(SPI1);
+	spi_fifo_reception_threshold_8bit(SPI1);
+	SPI_I2SCFGR(SPI1) &= ~SPI_I2SCFGR_I2SMOD;
+	spi_enable(SPI1);
+}
+
+void spi_send_cmd(uint32_t dev, const char *cmd, size_t cmd_len,
+	char *data, size_t data_len)
+{
+	size_t i;
+
+	gpio_clear(GPIOA, GPIO4);
+
+	for (i = 0; i < cmd_len; ++i) {
+		spi_send8(dev, *cmd++);
+		(void)spi_read8(dev);
+	}
+
+	for (i = 0; i < data_len; ++i) {
+		spi_send8(dev, 0);
+		*data++ = spi_read8(dev);
+	}
+
+	gpio_set(GPIOA, GPIO4);
+}
+
+static void spi_flash_addr(char *cmd, uint32_t addr)
+{
+	cmd[1] = addr >> 16;
+	cmd[2] = addr >> 8;
+	cmd[3] = addr;
+}
+
+static void spi_enable_write(uint32_t dev)
+{
+	char cmd[1] = { CMD_WRITE_ENABLE };
+
+	spi_send_cmd(dev, cmd, 1, NULL, 0);
+}
+
+static void spi_disable_write(uint32_t dev)
+{
+	char cmd[1] = { CMD_WRITE_DISABLE };
+
+	spi_send_cmd(dev, cmd, 1, NULL, 0);
+}
+
+void spi_flash_read(uint32_t dev, uint32_t addr, char *data, size_t len)
+{
+	char cmd[4] = { CMD_READ_ARRAY_SLOW };
+
+	spi_flash_addr(cmd, addr);
+	spi_send_cmd(dev, cmd, 4, data, len);
+}
+
+void spi_flash_write(uint32_t dev, uint32_t addr, char *data, size_t len)
+{
+	char cmd[4] = { CMD_PAGE_PROGRAM };
+	size_t i;
+
+	spi_enable_write(dev);
+	spi_flash_addr(cmd, addr);
+
+	gpio_clear(GPIOA, GPIO4);
+
+	for (i = 0; i < 4; ++i) {
+		spi_send8(dev, cmd[i]);
+		(void)spi_read8(dev);
+	}
+
+	for (i = 0; i < len; ++i) {
+		spi_send8(dev, data[i]);
+		(void)spi_read8(dev);
+	}
+
+	gpio_set(GPIOA, GPIO4);
+
+	spi_disable_write(dev);
+}
+
+void spi_flash_erase(FILE *fp, uint32_t dev, uint32_t addr, size_t len)
+{
+	char cmd[4];
+	size_t size;
+
+	spi_enable_write(dev);
+
+	addr = ROUND_UP(addr, 4 * KIB);
+
+	for (; len; addr += size, len -= size) {
+		if (IS_ROUND(addr, 64 * KIB) && IS_ROUND(len, 64 * KIB))
+			size = 64 * KIB;
+		else if (IS_ROUND(addr, 32 * KIB) && IS_ROUND(len, 32 * KIB))
+			size = 32 * KIB;
+		else if (IS_ROUND(addr, 4 * KIB) && IS_ROUND(len, 4 * KIB))
+			size = 4 * KIB;
+		else
+			size = 0;
+
+		switch (size) {
+		case 64 * KIB: cmd[0] = CMD_ERASE_64K; break;
+		case 32 * KIB: cmd[0] = CMD_ERASE_32K; break;
+		case 4 * KIB: cmd[0] = CMD_ERASE_4K; break;
+		default: goto err_disable_write;
+		};
+
+		fprintf(fp, "addr: %lx; size: %u\n", addr, size);
+		spi_flash_addr(cmd, addr);
+		spi_send_cmd(dev, cmd, 4, NULL, 0);
+	}
+
+err_disable_write:
+	spi_disable_write(dev);
+}

spi_flash.h

@@ -0,0 +1,33 @@
+#pragma once
+
+/* Human-readable sizes */
+#define KIB 1024
+#define MIB (1024 * KIB)
+#define GIB (1024 * GIB)
+
+/* Read commands */
+#define CMD_READ_ARRAY_SLOW		0x03
+#define CMD_READ_ID				0x9f
+
+/* Write commands */
+#define CMD_PAGE_PROGRAM		0x02
+#define CMD_WRITE_DISABLE		0x04
+#define CMD_WRITE_ENABLE		0x06
+
+/* Erase commands */
+#define CMD_ERASE_4K			0x20
+#define CMD_ERASE_32K			0x52
+#define CMD_ERASE_64K			0xD8
+#define CMD_ERASE_CHIP			0x60
+
+/* Rounding */
+#define IS_ROUND(x, k) (!((x) & ((k) - 1)))
+#define ROUND_DOWN(x, k) ((x) & ~((k) - 1))
+#define ROUND_UP(x, k) (((x) + (k) - 1) & ~((k) - 1))
+
+void init_spi(void);
+void spi_send_cmd(uint32_t dev, const char *cmd, size_t cmd_len,
+	char *data, size_t data_len);
+void spi_flash_read(uint32_t dev, uint32_t addr, char *data, size_t len);
+void spi_flash_write(uint32_t dev, uint32_t addr, char *data, size_t len);
+void spi_flash_erase(FILE *fp, uint32_t dev, uint32_t addr, size_t len);

support/libopencm3.rules.mk

@@ -0,0 +1,183 @@
+##
+## This file is part of the libopencm3 project.
+##
+## Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+## Copyright (C) 2010 Piotr Esden-Tempski <piotr@esden.net>
+## Copyright (C) 2013 Frantisek Burian <BuFran@seznam.cz>
+##
+## This library is free software: you can redistribute it and/or modify
+## it under the terms of the GNU Lesser General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This library 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 Lesser General Public License for more details.
+##
+## You should have received a copy of the GNU Lesser General Public License
+## along with this library.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+# Be silent per default, but 'make V=1' will show all compiler calls.
+ifneq ($(V),1)
+Q		:= @
+NULL		:= 2>/dev/null
+endif
+
+###############################################################################
+# Executables
+
+PREFIX		?= arm-none-eabi
+
+CC		:= $(PREFIX)-gcc
+LD		:= $(PREFIX)-gcc
+AR		:= $(PREFIX)-ar
+AS		:= $(PREFIX)-as
+OBJCOPY		:= $(PREFIX)-objcopy
+OBJDUMP		:= $(PREFIX)-objdump
+GDB		:= $(PREFIX)-gdb
+STFLASH		= $(shell which st-flash)
+STYLECHECK	:= /checkpatch.pl
+STYLECHECKFLAGS	:= --no-tree -f --terse --mailback
+STYLECHECKFILES	:= $(shell find . -name '*.[ch]')
+
+
+###############################################################################
+# Source files
+
+LDSCRIPT	?= $(BINARY).ld
+
+ifeq ($(strip $(OPENCM3_DIR)),)
+# user has not specified the library path, so we try to detect it
+
+# where we search for the library
+LIBPATHS := ./libopencm3 ../../../../libopencm3 ../../../../../libopencm3
+
+OPENCM3_DIR := $(wildcard $(LIBPATHS:=/locm3.sublime-project))
+OPENCM3_DIR := $(firstword $(dir $(OPENCM3_DIR)))
+
+ifeq ($(strip $(OPENCM3_DIR)),)
+$(warning Cannot find libopencm3 library in the standard search paths.)
+$(error Please specify it through OPENCM3_DIR variable!)
+endif
+endif
+
+ifeq ($(V),1)
+$(info Using $(OPENCM3_DIR) path to library)
+endif
+
+INCLUDE_DIR	= $(OPENCM3_DIR)/include
+LIB_DIR		= $(OPENCM3_DIR)/lib
+SCRIPT_DIR	= $(OPENCM3_DIR)/scripts
+
+###############################################################################
+# C flags
+
+CFLAGS		+= -Os -g
+CFLAGS		+= -Wextra -Wshadow -Wimplicit-function-declaration
+CFLAGS		+= -Wredundant-decls -Wmissing-prototypes -Wstrict-prototypes
+CFLAGS		+= -fno-common -ffunction-sections -fdata-sections
+
+CPPFLAGS	+= -MD
+CPPFLAGS	+= -Wall -Wundef
+CPPFLAGS	+= -I$(INCLUDE_DIR) $(DEFS)
+
+###############################################################################
+# Linker flags
+
+LDFLAGS		+= --static -nostartfiles
+LDFLAGS		+= -L$(LIB_DIR)
+LDFLAGS		+= -T$(LDSCRIPT)
+LDFLAGS		+= -Wl,-Map=$(*).map
+LDFLAGS		+= -Wl,--gc-sections
+ifeq ($(V),99)
+LDFLAGS		+= -Wl,--print-gc-sections
+endif
+
+###############################################################################
+# Used libraries
+
+LDLIBS		+= -l$(LIBNAME)
+LDLIBS		+= -Wl,--start-group -lc -lgcc -lnosys -Wl,--end-group
+
+###############################################################################
+###############################################################################
+###############################################################################
+
+.SUFFIXES: .elf .bin .hex .srec .list .map .images
+.SECONDEXPANSION:
+.SECONDARY:
+
+all: elf
+
+elf: $(BINARY).elf
+bin: $(BINARY).bin
+hex: $(BINARY).hex
+srec: $(BINARY).srec
+list: $(BINARY).list
+
+images: $(BINARY).images
+flash: $(BINARY).flash
+
+$(LDSCRIPT):
+    ifeq (,$(wildcard $(LDSCRIPT)))
+        $(error Unable to find specified linker script: $(LDSCRIPT))
+    endif
+
+%.images: %.bin %.hex %.srec %.list %.map
+	@#printf "*** $* images generated ***\n"
+
+%.bin: %.elf
+	@#printf "  OBJCOPY $(*).bin\n"
+	$(Q)$(OBJCOPY) -Obinary $(*).elf $(*).bin
+
+%.hex: %.elf
+	@#printf "  OBJCOPY $(*).hex\n"
+	$(Q)$(OBJCOPY) -Oihex $(*).elf $(*).hex
+
+%.srec: %.elf
+	@#printf "  OBJCOPY $(*).srec\n"
+	$(Q)$(OBJCOPY) -Osrec $(*).elf $(*).srec
+
+%.list: %.elf
+	@#printf "  OBJDUMP $(*).list\n"
+	$(Q)$(OBJDUMP) -S $(*).elf > $(*).list
+
+%.elf %.map: $(OBJS) $(LDSCRIPT) $(LIB_DIR)/lib$(LIBNAME).a
+	@#printf "  LD      $(*).elf\n"
+	$(Q)$(LD) $(LDFLAGS) $(ARCH_FLAGS) $(OBJS) $(LDLIBS) -o $(*).elf
+
+%.o: %.c
+	@#printf "  CC      $(*).c\n"
+	$(Q)$(CC) $(CFLAGS) $(CPPFLAGS) $(ARCH_FLAGS) -o $(*).o -c $(*).c
+
+clean:
+	@#printf "  CLEAN\n"
+	$(Q)$(RM) *.o *.d *.elf *.bin *.hex *.srec *.list *.map
+
+stylecheck: $(STYLECHECKFILES:=.stylecheck)
+styleclean: $(STYLECHECKFILES:=.styleclean)
+
+# the cat is due to multithreaded nature - we like to have consistent chunks of text on the output
+%.stylecheck: %
+	$(Q)$(SCRIPT_DIR)$(STYLECHECK) $(STYLECHECKFLAGS) $* > $*.stylecheck; \
+		if [ -s $*.stylecheck ]; then \
+			cat $*.stylecheck; \
+		else \
+			rm -f $*.stylecheck; \
+		fi;
+
+%.styleclean:
+	$(Q)rm -f $*.stylecheck;
+
+%.flash: %.elf
+	@printf "  GDB   $(*).elf (flash)\n"
+	$(Q)$(GDB) --batch \
+		   -ex 'target extended-remote $(STLINK_PORT)' \
+		   -x flash.scr \
+		   $(*).elf
+
+.PHONY: images clean stylecheck styleclean elf bin hex srec list
+
+-include $(OBJS:.o=.d)

support/libopencm3.target.mk

@@ -0,0 +1,6 @@
+LIBNAME		= opencm3_stm32f0
+DEFS		+= -DSTM32F0
+FP_FLAGS	?= -msoft-float
+ARCH_FLAGS	= -mthumb -mcpu=cortex-m0 $(FP_FLAGS)
+STLINK_PORT	?= :4242
+

support/stm32f0-discovery.ld

@@ -0,0 +1,32 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+ * Copyright (C) 2011 Stephen Caudle <scaudle@doceme.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Linker script for ST STM32F0DISCOVERY (STM32F051R8T6, 64K flash, 8K RAM). */
+
+/* Define memory regions. */
+MEMORY
+{
+	rom (rx) : ORIGIN = 0x08000000, LENGTH = 64K
+	ram (rwx) : ORIGIN = 0x20000000, LENGTH = 8K
+}
+
+/* Include the common ld script. */
+INCLUDE libopencm3_stm32f0.ld
+

support/stm32f042.ld

@@ -0,0 +1,649 @@
+
+
+
+
+
+
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+
+
+
+  <link crossorigin="anonymous" href="https://assets-cdn.github.com/assets/frameworks-d876e21057f406b37686f3dc7b9666f5957cda4847a48ec11e040df065624617.css" media="all" rel="stylesheet" />
+  <link crossorigin="anonymous" href="https://assets-cdn.github.com/assets/github-05196ad2eeaad9504e7bb3adc33d4d19adc2bad851a35ed9b9b0f73702c554f5.css" media="all" rel="stylesheet" />
+  
+  
+  <link crossorigin="anonymous" href="https://assets-cdn.github.com/assets/site-dd6d43570c14503704e8983a7dd8e62484a668da1ce4ce997929ae2f367584c0.css" media="all" rel="stylesheet" />
+  
+
+  <meta name="viewport" content="width=device-width">
+  
+  <title>stm32f0_libopencm3_template/stm32f042.ld at master · hexagon5un/stm32f0_libopencm3_template · GitHub</title>
+  <link rel="search" type="application/opensearchdescription+xml" href="/opensearch.xml" title="GitHub">
+  <link rel="fluid-icon" href="https://github.com/fluidicon.png" title="GitHub">
+  <meta property="fb:app_id" content="1401488693436528">
+
+
+  <link rel="assets" href="https://assets-cdn.github.com/">
+  
+  <meta name="pjax-timeout" content="1000">
+  
+  <meta name="request-id" content="BB5E:386B:99A8F1:F9FC95:58B02434" data-pjax-transient>
+  
+
+  <meta name="selected-link" value="repo_source" data-pjax-transient>
+
+  <meta name="google-site-verification" content="KT5gs8h0wvaagLKAVWq8bbeNwnZZK1r1XQysX3xurLU">
+<meta name="google-site-verification" content="ZzhVyEFwb7w3e0-uOTltm8Jsck2F5StVihD0exw2fsA">
+    <meta name="google-analytics" content="UA-3769691-2">
+
+<meta content="collector.githubapp.com" name="octolytics-host" /><meta content="github" name="octolytics-app-id" /><meta content="https://collector.githubapp.com/github-external/browser_event" name="octolytics-event-url" /><meta content="BB5E:386B:99A8F1:F9FC95:58B02434" name="octolytics-dimension-request_id" />
+<meta content="/&lt;user-name&gt;/&lt;repo-name&gt;/blob/show" data-pjax-transient="true" name="analytics-location" />
+
+
+
+  <meta class="js-ga-set" name="dimension1" content="Logged Out">
+
+
+
+      <meta name="hostname" content="github.com">
+  <meta name="user-login" content="">
+
+      <meta name="expected-hostname" content="github.com">
+    <meta name="js-proxy-site-detection-payload" content="MDRiN2ZjODAzOTc3OGE3MjRlZTdiMDEyZjFlZDViZWI0ZTA2NGVkYmE0ZDJmZjQ1OGNiZWQ2ODNiOTllODViM3x7InJlbW90ZV9hZGRyZXNzIjoiMTQ1LjEwOS42Mi4yNDciLCJyZXF1ZXN0X2lkIjoiQkI1RTozODZCOjk5QThGMTpGOUZDOTU6NThCMDI0MzQiLCJ0aW1lc3RhbXAiOjE0ODc5Mzg2MTIsImhvc3QiOiJnaXRodWIuY29tIn0=">
+
+
+  <meta name="html-safe-nonce" content="fb19cedee2c0b12accfe12d68383502249b0e148">
+
+  <meta http-equiv="x-pjax-version" content="d315960581ecedf86906f3f215b9732a">
+  
+
+    
+  <meta name="description" content="stm32f0_libopencm3_template - The simplest possible working OpenCM3 application for the STM32f0 chips.">
+  <meta name="go-import" content="github.com/hexagon5un/stm32f0_libopencm3_template git https://github.com/hexagon5un/stm32f0_libopencm3_template.git">
+
+  <meta content="1560700" name="octolytics-dimension-user_id" /><meta content="hexagon5un" name="octolytics-dimension-user_login" /><meta content="54214757" name="octolytics-dimension-repository_id" /><meta content="hexagon5un/stm32f0_libopencm3_template" name="octolytics-dimension-repository_nwo" /><meta content="true" name="octolytics-dimension-repository_public" /><meta content="false" name="octolytics-dimension-repository_is_fork" /><meta content="54214757" name="octolytics-dimension-repository_network_root_id" /><meta content="hexagon5un/stm32f0_libopencm3_template" name="octolytics-dimension-repository_network_root_nwo" />
+  <link href="https://github.com/hexagon5un/stm32f0_libopencm3_template/commits/master.atom" rel="alternate" title="Recent Commits to stm32f0_libopencm3_template:master" type="application/atom+xml">
+
+
+    <link rel="canonical" href="https://github.com/hexagon5un/stm32f0_libopencm3_template/blob/master/support/stm32f042.ld" data-pjax-transient>
+
+
+  <meta name="browser-stats-url" content="https://api.github.com/_private/browser/stats">
+
+  <meta name="browser-errors-url" content="https://api.github.com/_private/browser/errors">
+
+  <link rel="mask-icon" href="https://assets-cdn.github.com/pinned-octocat.svg" color="#000000">
+  <link rel="icon" type="image/x-icon" href="https://assets-cdn.github.com/favicon.ico">
+
+<meta name="theme-color" content="#1e2327">
+
+
+
+  </head>
+
+  <body class="logged-out env-production vis-public page-blob">
+    
+
+  <div class="position-relative js-header-wrapper ">
+    <a href="#start-of-content" tabindex="1" class="accessibility-aid js-skip-to-content">Skip to content</a>
+    <div id="js-pjax-loader-bar" class="pjax-loader-bar"><div class="progress"></div></div>
+
+    
+    
+    
+
+
+
+          <header class="site-header js-details-container Details" role="banner">
+  <div class="container-responsive">
+    <a class="header-logo-invertocat" href="https://github.com/" aria-label="Homepage" data-ga-click="(Logged out) Header, go to homepage, icon:logo-wordmark">
+      <svg aria-hidden="true" class="octicon octicon-mark-github" height="32" version="1.1" viewBox="0 0 16 16" width="32"><path fill-rule="evenodd" d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z"/></svg>
+    </a>
+
+    <button class="btn-link float-right site-header-toggle js-details-target" type="button" aria-label="Toggle navigation">
+      <svg aria-hidden="true" class="octicon octicon-three-bars" height="24" version="1.1" viewBox="0 0 12 16" width="18"><path fill-rule="evenodd" d="M11.41 9H.59C0 9 0 8.59 0 8c0-.59 0-1 .59-1H11.4c.59 0 .59.41.59 1 0 .59 0 1-.59 1h.01zm0-4H.59C0 5 0 4.59 0 4c0-.59 0-1 .59-1H11.4c.59 0 .59.41.59 1 0 .59 0 1-.59 1h.01zM.59 11H11.4c.59 0 .59.41.59 1 0 .59 0 1-.59 1H.59C0 13 0 12.59 0 12c0-.59 0-1 .59-1z"/></svg>
+    </button>
+
+    <div class="site-header-menu">
+      <nav class="site-header-nav">
+        <a href="/personal" class="js-selected-navigation-item nav-item" data-ga-click="Header, click, Nav menu - item:personal" data-selected-links="/personal /personal">
+          Personal
+</a>        <a href="/open-source" class="js-selected-navigation-item nav-item" data-ga-click="Header, click, Nav menu - item:opensource" data-selected-links="/open-source /open-source/stories /open-source">
+          Open source
+</a>        <a href="/business" class="js-selected-navigation-item nav-item" data-ga-click="Header, click, Nav menu - item:business" data-selected-links="/business /business/partners /business/features /business/customers /business/why-github-for-work /business/security /business">
+          Business
+</a>        <a href="/explore" class="js-selected-navigation-item nav-item" data-ga-click="Header, click, Nav menu - item:explore" data-selected-links="/explore /trending /trending/developers /integrations /integrations/feature/code /integrations/feature/collaborate /integrations/feature/ship /showcases /explore">
+          Explore
+</a>        <a href="/pricing" class="js-selected-navigation-item nav-item" data-ga-click="Header, click, Nav menu - item:pricing" data-selected-links="/pricing /pricing">
+          Pricing
+</a>      </nav>
+
+      <div class="site-header-actions">
+          <div class="header-search scoped-search site-scoped-search js-site-search" role="search">
+  <!-- '"` --><!-- </textarea></xmp> --></option></form><form accept-charset="UTF-8" action="/hexagon5un/stm32f0_libopencm3_template/search" class="js-site-search-form" data-scoped-search-url="/hexagon5un/stm32f0_libopencm3_template/search" data-unscoped-search-url="/search" method="get"><div style="margin:0;padding:0;display:inline"><input name="utf8" type="hidden" value="&#x2713;" /></div>
+    <label class="form-control header-search-wrapper js-chromeless-input-container">
+      <div class="header-search-scope">This repository</div>
+      <input type="text"
+        class="form-control header-search-input js-site-search-focus js-site-search-field is-clearable"
+        data-hotkey="s"
+        name="q"
+        placeholder="Search"
+        aria-label="Search this repository"
+        data-unscoped-placeholder="Search GitHub"
+        data-scoped-placeholder="Search"
+        autocapitalize="off">
+    </label>
+</form></div>
+
+
+          <a class="text-bold" href="/login?return_to=%2Fhexagon5un%2Fstm32f0_libopencm3_template%2Fblob%2Fmaster%2Fsupport%2Fstm32f042.ld" data-ga-click="(Logged out) Header, clicked Sign in, text:sign-in">Sign in</a>
+            <span class="text-gray">or</span>
+            <a class="text-bold" href="/join?source=header-repo" data-ga-click="(Logged out) Header, clicked Sign up, text:sign-up">Sign up</a>
+      </div>
+    </div>
+  </div>
+</header>
+
+
+  </div>
+
+  <div id="start-of-content" class="accessibility-aid"></div>
+
+    <div id="js-flash-container">
+</div>
+
+
+
+  <div role="main">
+      <div itemscope itemtype="http://schema.org/SoftwareSourceCode">
+    <div id="js-repo-pjax-container" data-pjax-container>
+      
+
+
+<div class="pagehead repohead instapaper_ignore readability-menu experiment-repo-nav">
+  <div class="container repohead-details-container">
+
+    
+
+<ul class="pagehead-actions">
+
+  <li>
+      <a href="/login?return_to=%2Fhexagon5un%2Fstm32f0_libopencm3_template"
+    class="btn btn-sm btn-with-count tooltipped tooltipped-n"
+    aria-label="You must be signed in to watch a repository" rel="nofollow">
+    <svg aria-hidden="true" class="octicon octicon-eye" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M8.06 2C3 2 0 8 0 8s3 6 8.06 6C13 14 16 8 16 8s-3-6-7.94-6zM8 12c-2.2 0-4-1.78-4-4 0-2.2 1.8-4 4-4 2.22 0 4 1.8 4 4 0 2.22-1.78 4-4 4zm2-4c0 1.11-.89 2-2 2-1.11 0-2-.89-2-2 0-1.11.89-2 2-2 1.11 0 2 .89 2 2z"/></svg>
+    Watch
+  </a>
+  <a class="social-count" href="/hexagon5un/stm32f0_libopencm3_template/watchers"
+     aria-label="2 users are watching this repository">
+    2
+  </a>
+
+  </li>
+
+  <li>
+      <a href="/login?return_to=%2Fhexagon5un%2Fstm32f0_libopencm3_template"
+    class="btn btn-sm btn-with-count tooltipped tooltipped-n"
+    aria-label="You must be signed in to star a repository" rel="nofollow">
+    <svg aria-hidden="true" class="octicon octicon-star" height="16" version="1.1" viewBox="0 0 14 16" width="14"><path fill-rule="evenodd" d="M14 6l-4.9-.64L7 1 4.9 5.36 0 6l3.6 3.26L2.67 14 7 11.67 11.33 14l-.93-4.74z"/></svg>
+    Star
+  </a>
+
+    <a class="social-count js-social-count" href="/hexagon5un/stm32f0_libopencm3_template/stargazers"
+      aria-label="1 user starred this repository">
+      1
+    </a>
+
+  </li>
+
+  <li>
+      <a href="/login?return_to=%2Fhexagon5un%2Fstm32f0_libopencm3_template"
+        class="btn btn-sm btn-with-count tooltipped tooltipped-n"
+        aria-label="You must be signed in to fork a repository" rel="nofollow">
+        <svg aria-hidden="true" class="octicon octicon-repo-forked" height="16" version="1.1" viewBox="0 0 10 16" width="10"><path fill-rule="evenodd" d="M8 1a1.993 1.993 0 0 0-1 3.72V6L5 8 3 6V4.72A1.993 1.993 0 0 0 2 1a1.993 1.993 0 0 0-1 3.72V6.5l3 3v1.78A1.993 1.993 0 0 0 5 15a1.993 1.993 0 0 0 1-3.72V9.5l3-3V4.72A1.993 1.993 0 0 0 8 1zM2 4.2C1.34 4.2.8 3.65.8 3c0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2zm3 10c-.66 0-1.2-.55-1.2-1.2 0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2zm3-10c-.66 0-1.2-.55-1.2-1.2 0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2z"/></svg>
+        Fork
+      </a>
+
+    <a href="/hexagon5un/stm32f0_libopencm3_template/network" class="social-count"
+       aria-label="1 user forked this repository">
+      1
+    </a>
+  </li>
+</ul>
+
+    <h1 class="public ">
+  <svg aria-hidden="true" class="octicon octicon-repo" height="16" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M4 9H3V8h1v1zm0-3H3v1h1V6zm0-2H3v1h1V4zm0-2H3v1h1V2zm8-1v12c0 .55-.45 1-1 1H6v2l-1.5-1.5L3 16v-2H1c-.55 0-1-.45-1-1V1c0-.55.45-1 1-1h10c.55 0 1 .45 1 1zm-1 10H1v2h2v-1h3v1h5v-2zm0-10H2v9h9V1z"/></svg>
+  <span class="author" itemprop="author"><a href="/hexagon5un" class="url fn" rel="author">hexagon5un</a></span><!--
+--><span class="path-divider">/</span><!--
+--><strong itemprop="name"><a href="/hexagon5un/stm32f0_libopencm3_template" data-pjax="#js-repo-pjax-container">stm32f0_libopencm3_template</a></strong>
+
+</h1>
+
+  </div>
+  <div class="container">
+    
+<nav class="reponav js-repo-nav js-sidenav-container-pjax"
+     itemscope
+     itemtype="http://schema.org/BreadcrumbList"
+     role="navigation"
+     data-pjax="#js-repo-pjax-container">
+
+  <span itemscope itemtype="http://schema.org/ListItem" itemprop="itemListElement">
+    <a href="/hexagon5un/stm32f0_libopencm3_template" class="js-selected-navigation-item selected reponav-item" data-hotkey="g c" data-selected-links="repo_source repo_downloads repo_commits repo_releases repo_tags repo_branches /hexagon5un/stm32f0_libopencm3_template" itemprop="url">
+      <svg aria-hidden="true" class="octicon octicon-code" height="16" version="1.1" viewBox="0 0 14 16" width="14"><path fill-rule="evenodd" d="M9.5 3L8 4.5 11.5 8 8 11.5 9.5 13 14 8 9.5 3zm-5 0L0 8l4.5 5L6 11.5 2.5 8 6 4.5 4.5 3z"/></svg>
+      <span itemprop="name">Code</span>
+      <meta itemprop="position" content="1">
+</a>  </span>
+
+    <span itemscope itemtype="http://schema.org/ListItem" itemprop="itemListElement">
+      <a href="/hexagon5un/stm32f0_libopencm3_template/issues" class="js-selected-navigation-item reponav-item" data-hotkey="g i" data-selected-links="repo_issues repo_labels repo_milestones /hexagon5un/stm32f0_libopencm3_template/issues" itemprop="url">
+        <svg aria-hidden="true" class="octicon octicon-issue-opened" height="16" version="1.1" viewBox="0 0 14 16" width="14"><path fill-rule="evenodd" d="M7 2.3c3.14 0 5.7 2.56 5.7 5.7s-2.56 5.7-5.7 5.7A5.71 5.71 0 0 1 1.3 8c0-3.14 2.56-5.7 5.7-5.7zM7 1C3.14 1 0 4.14 0 8s3.14 7 7 7 7-3.14 7-7-3.14-7-7-7zm1 3H6v5h2V4zm0 6H6v2h2v-2z"/></svg>
+        <span itemprop="name">Issues</span>
+        <span class="counter">0</span>
+        <meta itemprop="position" content="2">
+</a>    </span>
+
+  <span itemscope itemtype="http://schema.org/ListItem" itemprop="itemListElement">
+    <a href="/hexagon5un/stm32f0_libopencm3_template/pulls" class="js-selected-navigation-item reponav-item" data-hotkey="g p" data-selected-links="repo_pulls /hexagon5un/stm32f0_libopencm3_template/pulls" itemprop="url">
+      <svg aria-hidden="true" class="octicon octicon-git-pull-request" height="16" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M11 11.28V5c-.03-.78-.34-1.47-.94-2.06C9.46 2.35 8.78 2.03 8 2H7V0L4 3l3 3V4h1c.27.02.48.11.69.31.21.2.3.42.31.69v6.28A1.993 1.993 0 0 0 10 15a1.993 1.993 0 0 0 1-3.72zm-1 2.92c-.66 0-1.2-.55-1.2-1.2 0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2zM4 3c0-1.11-.89-2-2-2a1.993 1.993 0 0 0-1 3.72v6.56A1.993 1.993 0 0 0 2 15a1.993 1.993 0 0 0 1-3.72V4.72c.59-.34 1-.98 1-1.72zm-.8 10c0 .66-.55 1.2-1.2 1.2-.65 0-1.2-.55-1.2-1.2 0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2zM2 4.2C1.34 4.2.8 3.65.8 3c0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2z"/></svg>
+      <span itemprop="name">Pull requests</span>
+      <span class="counter">0</span>
+      <meta itemprop="position" content="3">
+</a>  </span>
+
+  <a href="/hexagon5un/stm32f0_libopencm3_template/projects" class="js-selected-navigation-item reponav-item" data-selected-links="repo_projects new_repo_project repo_project /hexagon5un/stm32f0_libopencm3_template/projects">
+    <svg aria-hidden="true" class="octicon octicon-project" height="16" version="1.1" viewBox="0 0 15 16" width="15"><path fill-rule="evenodd" d="M10 12h3V2h-3v10zm-4-2h3V2H6v8zm-4 4h3V2H2v12zm-1 1h13V1H1v14zM14 0H1a1 1 0 0 0-1 1v14a1 1 0 0 0 1 1h13a1 1 0 0 0 1-1V1a1 1 0 0 0-1-1z"/></svg>
+    Projects
+    <span class="counter">0</span>
+</a>
+
+
+  <a href="/hexagon5un/stm32f0_libopencm3_template/pulse" class="js-selected-navigation-item reponav-item" data-selected-links="pulse /hexagon5un/stm32f0_libopencm3_template/pulse">
+    <svg aria-hidden="true" class="octicon octicon-pulse" height="16" version="1.1" viewBox="0 0 14 16" width="14"><path fill-rule="evenodd" d="M11.5 8L8.8 5.4 6.6 8.5 5.5 1.6 2.38 8H0v2h3.6l.9-1.8.9 5.4L9 8.5l1.6 1.5H14V8z"/></svg>
+    Pulse
+</a>
+  <a href="/hexagon5un/stm32f0_libopencm3_template/graphs" class="js-selected-navigation-item reponav-item" data-selected-links="repo_graphs repo_contributors /hexagon5un/stm32f0_libopencm3_template/graphs">
+    <svg aria-hidden="true" class="octicon octicon-graph" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M16 14v1H0V0h1v14h15zM5 13H3V8h2v5zm4 0H7V3h2v10zm4 0h-2V6h2v7z"/></svg>
+    Graphs
+</a>
+
+</nav>
+
+  </div>
+</div>
+
+<div class="container new-discussion-timeline experiment-repo-nav">
+  <div class="repository-content">
+
+    
+
+<a href="/hexagon5un/stm32f0_libopencm3_template/blob/c74b2a199ef51b73a1e019aefb8ea10453810f0b/support/stm32f042.ld" class="d-none js-permalink-shortcut" data-hotkey="y">Permalink</a>
+
+<!-- blob contrib key: blob_contributors:v21:927ed12541fefdabe9e6ba3c92db5ece -->
+
+<div class="file-navigation js-zeroclipboard-container">
+  
+<div class="select-menu branch-select-menu js-menu-container js-select-menu float-left">
+  <button class="btn btn-sm select-menu-button js-menu-target css-truncate" data-hotkey="w"
+    
+    type="button" aria-label="Switch branches or tags" tabindex="0" aria-haspopup="true">
+    <i>Branch:</i>
+    <span class="js-select-button css-truncate-target">master</span>
+  </button>
+
+  <div class="select-menu-modal-holder js-menu-content js-navigation-container" data-pjax aria-hidden="true">
+
+    <div class="select-menu-modal">
+      <div class="select-menu-header">
+        <svg aria-label="Close" class="octicon octicon-x js-menu-close" height="16" role="img" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M7.48 8l3.75 3.75-1.48 1.48L6 9.48l-3.75 3.75-1.48-1.48L4.52 8 .77 4.25l1.48-1.48L6 6.52l3.75-3.75 1.48 1.48z"/></svg>
+        <span class="select-menu-title">Switch branches/tags</span>
+      </div>
+
+      <div class="select-menu-filters">
+        <div class="select-menu-text-filter">
+          <input type="text" aria-label="Filter branches/tags" id="context-commitish-filter-field" class="form-control js-filterable-field js-navigation-enable" placeholder="Filter branches/tags">
+        </div>
+        <div class="select-menu-tabs">
+          <ul>
+            <li class="select-menu-tab">
+              <a href="#" data-tab-filter="branches" data-filter-placeholder="Filter branches/tags" class="js-select-menu-tab" role="tab">Branches</a>
+            </li>
+            <li class="select-menu-tab">
+              <a href="#" data-tab-filter="tags" data-filter-placeholder="Find a tag…" class="js-select-menu-tab" role="tab">Tags</a>
+            </li>
+          </ul>
+        </div>
+      </div>
+
+      <div class="select-menu-list select-menu-tab-bucket js-select-menu-tab-bucket" data-tab-filter="branches" role="menu">
+
+        <div data-filterable-for="context-commitish-filter-field" data-filterable-type="substring">
+
+
+            <a class="select-menu-item js-navigation-item js-navigation-open selected"
+               href="/hexagon5un/stm32f0_libopencm3_template/blob/master/support/stm32f042.ld"
+               data-name="master"
+               data-skip-pjax="true"
+               rel="nofollow">
+              <svg aria-hidden="true" class="octicon octicon-check select-menu-item-icon" height="16" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M12 5l-8 8-4-4 1.5-1.5L4 10l6.5-6.5z"/></svg>
+              <span class="select-menu-item-text css-truncate-target js-select-menu-filter-text">
+                master
+              </span>
+            </a>
+        </div>
+
+          <div class="select-menu-no-results">Nothing to show</div>
+      </div>
+
+      <div class="select-menu-list select-menu-tab-bucket js-select-menu-tab-bucket" data-tab-filter="tags">
+        <div data-filterable-for="context-commitish-filter-field" data-filterable-type="substring">
+
+
+        </div>
+
+        <div class="select-menu-no-results">Nothing to show</div>
+      </div>
+
+    </div>
+  </div>
+</div>
+
+  <div class="BtnGroup float-right">
+    <a href="/hexagon5un/stm32f0_libopencm3_template/find/master"
+          class="js-pjax-capture-input btn btn-sm BtnGroup-item"
+          data-pjax
+          data-hotkey="t">
+      Find file
+    </a>
+    <button aria-label="Copy file path to clipboard" class="js-zeroclipboard btn btn-sm BtnGroup-item tooltipped tooltipped-s" data-copied-hint="Copied!" type="button">Copy path</button>
+  </div>
+  <div class="breadcrumb js-zeroclipboard-target">
+    <span class="repo-root js-repo-root"><span class="js-path-segment"><a href="/hexagon5un/stm32f0_libopencm3_template"><span>stm32f0_libopencm3_template</span></a></span></span><span class="separator">/</span><span class="js-path-segment"><a href="/hexagon5un/stm32f0_libopencm3_template/tree/master/support"><span>support</span></a></span><span class="separator">/</span><strong class="final-path">stm32f042.ld</strong>
+  </div>
+</div>
+
+
+  <div class="commit-tease">
+      <span class="float-right">
+        <a class="commit-tease-sha" href="/hexagon5un/stm32f0_libopencm3_template/commit/8bb1e121c5c2dcaecd3fe21bb451533ac673a522" data-pjax>
+          8bb1e12
+        </a>
+        <relative-time datetime="2016-03-19T19:15:36Z">Mar 19, 2016</relative-time>
+      </span>
+      <div>
+        <img alt="" class="avatar" data-canonical-src="https://1.gravatar.com/avatar/a8edc34b75970fefe210fd3d4ef93a10?d=https%3A%2F%2Fassets-cdn.github.com%2Fimages%2Fgravatars%2Fgravatar-user-420.png&amp;r=x&amp;s=140" height="20" src="https://camo.githubusercontent.com/a790acf3dfbefac38fd3f439c026f1575f3df4de/68747470733a2f2f312e67726176617461722e636f6d2f6176617461722f61386564633334623735393730666566653231306664336434656639336131303f643d68747470732533412532462532466173736574732d63646e2e6769746875622e636f6d253246696d6167657325324667726176617461727325324667726176617461722d757365722d3432302e706e6726723d7826733d313430" width="20" />
+        <span class="user-mention">Elliot Williams</span>
+          <a href="/hexagon5un/stm32f0_libopencm3_template/commit/8bb1e121c5c2dcaecd3fe21bb451533ac673a522" class="message" data-pjax="true" title="Added a linker file for STM32F042">Added a linker file for STM32F042</a>
+      </div>
+
+    <div class="commit-tease-contributors">
+      <button type="button" class="btn-link muted-link contributors-toggle" data-facebox="#blob_contributors_box">
+        <strong>0</strong>
+         contributors
+      </button>
+      
+    </div>
+
+    <div id="blob_contributors_box" style="display:none">
+      <h2 class="facebox-header" data-facebox-id="facebox-header">Users who have contributed to this file</h2>
+      <ul class="facebox-user-list" data-facebox-id="facebox-description">
+      </ul>
+    </div>
+  </div>
+
+
+<div class="file">
+  <div class="file-header">
+  <div class="file-actions">
+
+    <div class="BtnGroup">
+      <a href="/hexagon5un/stm32f0_libopencm3_template/raw/master/support/stm32f042.ld" class="btn btn-sm BtnGroup-item" id="raw-url">Raw</a>
+        <a href="/hexagon5un/stm32f0_libopencm3_template/blame/master/support/stm32f042.ld" class="btn btn-sm js-update-url-with-hash BtnGroup-item" data-hotkey="b">Blame</a>
+      <a href="/hexagon5un/stm32f0_libopencm3_template/commits/master/support/stm32f042.ld" class="btn btn-sm BtnGroup-item" rel="nofollow">History</a>
+    </div>
+
+
+        <button type="button" class="btn-octicon disabled tooltipped tooltipped-nw"
+          aria-label="You must be signed in to make or propose changes">
+          <svg aria-hidden="true" class="octicon octicon-pencil" height="16" version="1.1" viewBox="0 0 14 16" width="14"><path fill-rule="evenodd" d="M0 12v3h3l8-8-3-3-8 8zm3 2H1v-2h1v1h1v1zm10.3-9.3L12 6 9 3l1.3-1.3a.996.996 0 0 1 1.41 0l1.59 1.59c.39.39.39 1.02 0 1.41z"/></svg>
+        </button>
+        <button type="button" class="btn-octicon btn-octicon-danger disabled tooltipped tooltipped-nw"
+          aria-label="You must be signed in to make or propose changes">
+          <svg aria-hidden="true" class="octicon octicon-trashcan" height="16" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M11 2H9c0-.55-.45-1-1-1H5c-.55 0-1 .45-1 1H2c-.55 0-1 .45-1 1v1c0 .55.45 1 1 1v9c0 .55.45 1 1 1h7c.55 0 1-.45 1-1V5c.55 0 1-.45 1-1V3c0-.55-.45-1-1-1zm-1 12H3V5h1v8h1V5h1v8h1V5h1v8h1V5h1v9zm1-10H2V3h9v1z"/></svg>
+        </button>
+  </div>
+
+  <div class="file-info">
+      33 lines (28 sloc)
+      <span class="file-info-divider"></span>
+    1.1 KB
+  </div>
+</div>
+
+  
+
+  <div itemprop="text" class="blob-wrapper data type-linker-script">
+      <table class="highlight tab-size js-file-line-container" data-tab-size="8">
+      <tr>
+        <td id="L1" class="blob-num js-line-number" data-line-number="1"></td>
+        <td id="LC1" class="blob-code blob-code-inner js-file-line">/*</td>
+      </tr>
+      <tr>
+        <td id="L2" class="blob-num js-line-number" data-line-number="2"></td>
+        <td id="LC2" class="blob-code blob-code-inner js-file-line"> * This file is part of the libopencm3 project.</td>
+      </tr>
+      <tr>
+        <td id="L3" class="blob-num js-line-number" data-line-number="3"></td>
+        <td id="LC3" class="blob-code blob-code-inner js-file-line"> *</td>
+      </tr>
+      <tr>
+        <td id="L4" class="blob-num js-line-number" data-line-number="4"></td>
+        <td id="LC4" class="blob-code blob-code-inner js-file-line"> * Copyright (C) 2009 Uwe Hermann &lt;uwe@hermann-uwe.de&gt;</td>
+      </tr>
+      <tr>
+        <td id="L5" class="blob-num js-line-number" data-line-number="5"></td>
+        <td id="LC5" class="blob-code blob-code-inner js-file-line"> * Copyright (C) 2011 Stephen Caudle &lt;scaudle@doceme.com&gt;</td>
+      </tr>
+      <tr>
+        <td id="L6" class="blob-num js-line-number" data-line-number="6"></td>
+        <td id="LC6" class="blob-code blob-code-inner js-file-line"> *</td>
+      </tr>
+      <tr>
+        <td id="L7" class="blob-num js-line-number" data-line-number="7"></td>
+        <td id="LC7" class="blob-code blob-code-inner js-file-line"> * This library is free software: you can redistribute it and/or modify</td>
+      </tr>
+      <tr>
+        <td id="L8" class="blob-num js-line-number" data-line-number="8"></td>
+        <td id="LC8" class="blob-code blob-code-inner js-file-line"> * it under the terms of the GNU Lesser General Public License as published by</td>
+      </tr>
+      <tr>
+        <td id="L9" class="blob-num js-line-number" data-line-number="9"></td>
+        <td id="LC9" class="blob-code blob-code-inner js-file-line"> * the Free Software Foundation, either version 3 of the License, or</td>
+      </tr>
+      <tr>
+        <td id="L10" class="blob-num js-line-number" data-line-number="10"></td>
+        <td id="LC10" class="blob-code blob-code-inner js-file-line"> * (at your option) any later version.</td>
+      </tr>
+      <tr>
+        <td id="L11" class="blob-num js-line-number" data-line-number="11"></td>
+        <td id="LC11" class="blob-code blob-code-inner js-file-line"> *</td>
+      </tr>
+      <tr>
+        <td id="L12" class="blob-num js-line-number" data-line-number="12"></td>
+        <td id="LC12" class="blob-code blob-code-inner js-file-line"> * This library is distributed in the hope that it will be useful,</td>
+      </tr>
+      <tr>
+        <td id="L13" class="blob-num js-line-number" data-line-number="13"></td>
+        <td id="LC13" class="blob-code blob-code-inner js-file-line"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</td>
+      </tr>
+      <tr>
+        <td id="L14" class="blob-num js-line-number" data-line-number="14"></td>
+        <td id="LC14" class="blob-code blob-code-inner js-file-line"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the</td>
+      </tr>
+      <tr>
+        <td id="L15" class="blob-num js-line-number" data-line-number="15"></td>
+        <td id="LC15" class="blob-code blob-code-inner js-file-line"> * GNU Lesser General Public License for more details.</td>
+      </tr>
+      <tr>
+        <td id="L16" class="blob-num js-line-number" data-line-number="16"></td>
+        <td id="LC16" class="blob-code blob-code-inner js-file-line"> *</td>
+      </tr>
+      <tr>
+        <td id="L17" class="blob-num js-line-number" data-line-number="17"></td>
+        <td id="LC17" class="blob-code blob-code-inner js-file-line"> * You should have received a copy of the GNU Lesser General Public License</td>
+      </tr>
+      <tr>
+        <td id="L18" class="blob-num js-line-number" data-line-number="18"></td>
+        <td id="LC18" class="blob-code blob-code-inner js-file-line"> * along with this library.  If not, see &lt;http://www.gnu.org/licenses/&gt;.</td>
+      </tr>
+      <tr>
+        <td id="L19" class="blob-num js-line-number" data-line-number="19"></td>
+        <td id="LC19" class="blob-code blob-code-inner js-file-line"> */</td>
+      </tr>
+      <tr>
+        <td id="L20" class="blob-num js-line-number" data-line-number="20"></td>
+        <td id="LC20" class="blob-code blob-code-inner js-file-line">
+</td>
+      </tr>
+      <tr>
+        <td id="L21" class="blob-num js-line-number" data-line-number="21"></td>
+        <td id="LC21" class="blob-code blob-code-inner js-file-line">/* Linker script for ST STM32F0DISCOVERY (STM32F051R8T6, 64K flash, 8K RAM). */</td>
+      </tr>
+      <tr>
+        <td id="L22" class="blob-num js-line-number" data-line-number="22"></td>
+        <td id="LC22" class="blob-code blob-code-inner js-file-line">
+</td>
+      </tr>
+      <tr>
+        <td id="L23" class="blob-num js-line-number" data-line-number="23"></td>
+        <td id="LC23" class="blob-code blob-code-inner js-file-line">/* Define memory regions. */</td>
+      </tr>
+      <tr>
+        <td id="L24" class="blob-num js-line-number" data-line-number="24"></td>
+        <td id="LC24" class="blob-code blob-code-inner js-file-line">MEMORY</td>
+      </tr>
+      <tr>
+        <td id="L25" class="blob-num js-line-number" data-line-number="25"></td>
+        <td id="LC25" class="blob-code blob-code-inner js-file-line">{</td>
+      </tr>
+      <tr>
+        <td id="L26" class="blob-num js-line-number" data-line-number="26"></td>
+        <td id="LC26" class="blob-code blob-code-inner js-file-line">	rom (rx) : ORIGIN = 0x08000000, LENGTH = 0x8000</td>
+      </tr>
+      <tr>
+        <td id="L27" class="blob-num js-line-number" data-line-number="27"></td>
+        <td id="LC27" class="blob-code blob-code-inner js-file-line">	ram (rwx) : ORIGIN = 0x20000000, LENGTH = 0x1800</td>
+      </tr>
+      <tr>
+        <td id="L28" class="blob-num js-line-number" data-line-number="28"></td>
+        <td id="LC28" class="blob-code blob-code-inner js-file-line">}</td>
+      </tr>
+      <tr>
+        <td id="L29" class="blob-num js-line-number" data-line-number="29"></td>
+        <td id="LC29" class="blob-code blob-code-inner js-file-line">
+</td>
+      </tr>
+      <tr>
+        <td id="L30" class="blob-num js-line-number" data-line-number="30"></td>
+        <td id="LC30" class="blob-code blob-code-inner js-file-line">/* Include the common ld script. */</td>
+      </tr>
+      <tr>
+        <td id="L31" class="blob-num js-line-number" data-line-number="31"></td>
+        <td id="LC31" class="blob-code blob-code-inner js-file-line">INCLUDE libopencm3_stm32f0.ld</td>
+      </tr>
+      <tr>
+        <td id="L32" class="blob-num js-line-number" data-line-number="32"></td>
+        <td id="LC32" class="blob-code blob-code-inner js-file-line">
+</td>
+      </tr>
+</table>
+
+  </div>
+
+</div>
+
+<button type="button" data-facebox="#jump-to-line" data-facebox-class="linejump" data-hotkey="l" class="d-none">Jump to Line</button>
+<div id="jump-to-line" style="display:none">
+  <!-- '"` --><!-- </textarea></xmp> --></option></form><form accept-charset="UTF-8" action="" class="js-jump-to-line-form" method="get"><div style="margin:0;padding:0;display:inline"><input name="utf8" type="hidden" value="&#x2713;" /></div>
+    <input class="form-control linejump-input js-jump-to-line-field" type="text" placeholder="Jump to line&hellip;" aria-label="Jump to line" autofocus>
+    <button type="submit" class="btn">Go</button>
+</form></div>
+
+  </div>
+  <div class="modal-backdrop js-touch-events"></div>
+</div>
+
+
+    </div>
+  </div>
+
+  </div>
+
+      <div class="container site-footer-container">
+  <div class="site-footer" role="contentinfo">
+    <ul class="site-footer-links float-right">
+        <li><a href="https://github.com/contact" data-ga-click="Footer, go to contact, text:contact">Contact GitHub</a></li>
+      <li><a href="https://developer.github.com" data-ga-click="Footer, go to api, text:api">API</a></li>
+      <li><a href="https://training.github.com" data-ga-click="Footer, go to training, text:training">Training</a></li>
+      <li><a href="https://shop.github.com" data-ga-click="Footer, go to shop, text:shop">Shop</a></li>
+        <li><a href="https://github.com/blog" data-ga-click="Footer, go to blog, text:blog">Blog</a></li>
+        <li><a href="https://github.com/about" data-ga-click="Footer, go to about, text:about">About</a></li>
+
+    </ul>
+
+    <a href="https://github.com" aria-label="Homepage" class="site-footer-mark" title="GitHub">
+      <svg aria-hidden="true" class="octicon octicon-mark-github" height="24" version="1.1" viewBox="0 0 16 16" width="24"><path fill-rule="evenodd" d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0 0 16 8c0-4.42-3.58-8-8-8z"/></svg>
+</a>
+    <ul class="site-footer-links">
+      <li>&copy; 2017 <span title="0.09905s from github-fe126-cp1-prd.iad.github.net">GitHub</span>, Inc.</li>
+        <li><a href="https://github.com/site/terms" data-ga-click="Footer, go to terms, text:terms">Terms</a></li>
+        <li><a href="https://github.com/site/privacy" data-ga-click="Footer, go to privacy, text:privacy">Privacy</a></li>
+        <li><a href="https://github.com/security" data-ga-click="Footer, go to security, text:security">Security</a></li>
+        <li><a href="https://status.github.com/" data-ga-click="Footer, go to status, text:status">Status</a></li>
+        <li><a href="https://help.github.com" data-ga-click="Footer, go to help, text:help">Help</a></li>
+    </ul>
+  </div>
+</div>
+
+
+
+  
+
+  <div id="ajax-error-message" class="ajax-error-message flash flash-error">
+    <svg aria-hidden="true" class="octicon octicon-alert" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M8.865 1.52c-.18-.31-.51-.5-.87-.5s-.69.19-.87.5L.275 13.5c-.18.31-.18.69 0 1 .19.31.52.5.87.5h13.7c.36 0 .69-.19.86-.5.17-.31.18-.69.01-1L8.865 1.52zM8.995 13h-2v-2h2v2zm0-3h-2V6h2v4z"/></svg>
+    <button type="button" class="flash-close js-flash-close js-ajax-error-dismiss" aria-label="Dismiss error">
+      <svg aria-hidden="true" class="octicon octicon-x" height="16" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M7.48 8l3.75 3.75-1.48 1.48L6 9.48l-3.75 3.75-1.48-1.48L4.52 8 .77 4.25l1.48-1.48L6 6.52l3.75-3.75 1.48 1.48z"/></svg>
+    </button>
+    You can't perform that action at this time.
+  </div>
+
+
+    <script crossorigin="anonymous" src="https://assets-cdn.github.com/assets/compat-8e19569aacd39e737a14c8515582825f3c90d1794c0e5539f9b525b8eb8b5a8e.js"></script>
+    <script crossorigin="anonymous" src="https://assets-cdn.github.com/assets/frameworks-506169cb2fe76254b921e8c944dd406e5cab2d719e657eace8ada98486231472.js"></script>
+    <script async="async" crossorigin="anonymous" src="https://assets-cdn.github.com/assets/github-ca0d7593e02f66f0e077e6af00e2777dbc4e8928d61b88078131e9344d065f32.js"></script>
+    
+    
+    
+    
+  <div class="js-stale-session-flash stale-session-flash flash flash-warn flash-banner d-none">
+    <svg aria-hidden="true" class="octicon octicon-alert" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M8.865 1.52c-.18-.31-.51-.5-.87-.5s-.69.19-.87.5L.275 13.5c-.18.31-.18.69 0 1 .19.31.52.5.87.5h13.7c.36 0 .69-.19.86-.5.17-.31.18-.69.01-1L8.865 1.52zM8.995 13h-2v-2h2v2zm0-3h-2V6h2v4z"/></svg>
+    <span class="signed-in-tab-flash">You signed in with another tab or window. <a href="">Reload</a> to refresh your session.</span>
+    <span class="signed-out-tab-flash">You signed out in another tab or window. <a href="">Reload</a> to refresh your session.</span>
+  </div>
+  <div class="facebox" id="facebox" style="display:none;">
+  <div class="facebox-popup">
+    <div class="facebox-content" role="dialog" aria-labelledby="facebox-header" aria-describedby="facebox-description">
+    </div>
+    <button type="button" class="facebox-close js-facebox-close" aria-label="Close modal">
+      <svg aria-hidden="true" class="octicon octicon-x" height="16" version="1.1" viewBox="0 0 12 16" width="12"><path fill-rule="evenodd" d="M7.48 8l3.75 3.75-1.48 1.48L6 9.48l-3.75 3.75-1.48-1.48L4.52 8 .77 4.25l1.48-1.48L6 6.52l3.75-3.75 1.48 1.48z"/></svg>
+    </button>
+  </div>
+</div>
+
+
+  </body>
+</html>
+

usart.c

@@ -0,0 +1,69 @@
+#define _GNU_SOURCE
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/usart.h>
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stddef.h>
+#include <limits.h>
+#include <sys/types.h>
+
+#include "usart.h"
+
+static ssize_t usart_read(void *cookie, char *buf, size_t n)
+{
+	uint32_t dev = (uint32_t)cookie;
+	size_t nbytes = 0;
+
+	while (n-- > 0) {
+		*buf++ = (char)usart_recv_blocking(dev);
+		nbytes++;
+	}
+
+	return nbytes;
+}
+
+static ssize_t usart_write(void *cookie, const char *buf, size_t n)
+{
+	uint32_t dev = (uint32_t)cookie;
+	size_t nbytes = 0;
+
+	while (n-- > 0) {
+		usart_send_blocking(dev, *buf++);
+		nbytes++;
+	};
+
+	return nbytes;
+}
+
+FILE *init_usart(uint32_t dev)
+{
+	cookie_io_functions_t stub = { usart_read, usart_write, NULL, NULL };
+	FILE *fp;
+
+	/* Set up clocks for USART 1 */
+	rcc_periph_clock_enable(RCC_GPIOA);
+	rcc_periph_clock_enable(RCC_USART1);
+
+	/* Set up GPIOs for USART 1 */
+	gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO9 | GPIO10);
+	gpio_set_af(GPIOA, GPIO_AF1, GPIO9 | GPIO10);
+	gpio_set_af(GPIOA, GPIO_AF1, GPIO10);
+
+	usart_set_baudrate(dev, 115200);
+	usart_set_databits(dev, 8);
+	usart_set_parity(dev, USART_PARITY_NONE);
+	usart_set_stopbits(dev, USART_CR2_STOP_1_0BIT);
+	usart_set_mode(dev, USART_MODE_TX_RX);
+	usart_set_flow_control(dev, USART_FLOWCONTROL_NONE);
+
+	usart_enable(dev);
+
+	fp = fopencookie((void *)dev, "rw+", stub);
+	setvbuf(fp, NULL, _IONBF, 0);
+	return fp;
+}

usart.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <libopencm3/stm32/usart.h>
+
+#include <stdint.h>
+#include <stdio.h>
+
+FILE *init_usart(uint32_t dev);