From e946d0ce3d85caa0e350eee7c818c72fc495331e Mon Sep 17 00:00:00 2001
From: "S.J.R. van Schaik" <stephan@whiteboxsystems.nl>
Date: Mon, 27 Feb 2017 14:48:38 +0000
Subject: [PATCH] tbm: initial commit

---
 Makefile                     |  13 +
 debug.c                      |   0
 flash.scr                    |   2 +
 main.c                       |  16 ++
 shell.c                      | 269 ++++++++++++++++++
 shell.h                      |   8 +
 spi_flash.c                  | 154 ++++++++++
 spi_flash.h                  |  33 +++
 support/libopencm3.rules.mk  | 183 ++++++++++++
 support/libopencm3.target.mk |   6 +
 support/stm32f0-discovery.ld |  32 +++
 support/stm32f042.ld         | 649 +++++++++++++++++++++++++++++++++++++++++++
 usart.c                      |  69 +++++
 usart.h                      |   8 +
 14 files changed, 1442 insertions(+)
 create mode 100644 Makefile
 create mode 100644 debug.c
 create mode 100644 flash.scr
 create mode 100644 main.c
 create mode 100644 shell.c
 create mode 100644 shell.h
 create mode 100644 spi_flash.c
 create mode 100644 spi_flash.h
 create mode 100644 support/libopencm3.rules.mk
 create mode 100644 support/libopencm3.target.mk
 create mode 100644 support/stm32f0-discovery.ld
 create mode 100644 support/stm32f042.ld
 create mode 100644 usart.c
 create mode 100644 usart.h

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..d340002
--- /dev/null
+++ b/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
diff --git a/debug.c b/debug.c
new file mode 100644
index 0000000..e69de29
diff --git a/flash.scr b/flash.scr
new file mode 100644
index 0000000..444d30f
--- /dev/null
+++ b/flash.scr
@@ -0,0 +1,2 @@
+load
+run
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..1f94f13
--- /dev/null
+++ b/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;
+}
diff --git a/shell.c b/shell.c
new file mode 100644
index 0000000..1397911
--- /dev/null
+++ b/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);
+	}
+}
diff --git a/shell.h b/shell.h
new file mode 100644
index 0000000..14c60af
--- /dev/null
+++ b/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);
diff --git a/spi_flash.c b/spi_flash.c
new file mode 100644
index 0000000..b392d5f
--- /dev/null
+++ b/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);
+}
diff --git a/spi_flash.h b/spi_flash.h
new file mode 100644
index 0000000..d44e289
--- /dev/null
+++ b/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);
diff --git a/support/libopencm3.rules.mk b/support/libopencm3.rules.mk
new file mode 100644
index 0000000..5d87b94
--- /dev/null
+++ b/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)
diff --git a/support/libopencm3.target.mk b/support/libopencm3.target.mk
new file mode 100644
index 0000000..dafdb2a
--- /dev/null
+++ b/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
+
diff --git a/support/stm32f0-discovery.ld b/support/stm32f0-discovery.ld
new file mode 100644
index 0000000..7e54e84
--- /dev/null
+++ b/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
+
diff --git a/support/stm32f042.ld b/support/stm32f042.ld
new file mode 100644
index 0000000..e4ffde3
--- /dev/null
+++ b/support/stm32f042.ld
@@ -0,0 +1,649 @@
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+        <span class="user-mention">Elliot Williams</span>
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+    1.1 KB
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+
+  
+
+  <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>
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+      <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">
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+      <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">
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diff --git a/usart.c b/usart.c
new file mode 100644
index 0000000..eaa426f
--- /dev/null
+++ b/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;
+}
diff --git a/usart.h b/usart.h
new file mode 100644
index 0000000..5ac6f1c
--- /dev/null
+++ b/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);