Proper building for Flash

INSTALL.txt

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+- Download a toolchain from https://launchpad.net/gcc-arm-embedded/+download
+- Install openocd (tested with 0.8.0)

Makefile

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+CC=arm-none-eabi-gcc
+LD=arm-none-eabi-ld.bfd
+GDB=arm-none-eabi-gdb
+OBJCOPY=arm-none-eabi-objcopy
+CFLAGS=-march=armv7e-m -mcpu=cortex-m4 -mthumb -std=c99 -g
+
+objs := boot/crt0.o src/blinky.o
+
+run: boot.elf
+	$(GDB) -x gdb_script.gdb boot.elf
+
+boot.hex: boot.elf
+	@echo "OBJCOPY $@"
+	@$(OBJCOPY) -O ihex boot.elf boot.hex
+
+boot.bin: boot.elf
+	@echo "OBJCOPY $@"
+	@$(OBJCOPY) -O binary boot.elf boot.bin
+
+boot.elf: $(objs)
+	@echo "LD      $@"
+	@$(LD) -T boot/stm32f429_flash.ld $(objs) -o $@
+
+%.o: %.c
+	@echo "CC      $@"
+	@$(CC) $(CFLAGS) -c $< -o $@
+
+clean:
+	@echo "CLEAN"
+	@rm -f $(objs) boot.elf boot.bin boot.hex

boot/crt0.c

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+typedef long uint32_t;
+
+extern const void * _data_segment_start_flash;
+extern const void * _data_segment_start_ram;
+extern const void * _data_segment_end_ram;
+
+void reset(void);
+
+/* Interrupt Service Routines are void->void functions */
+typedef void(*ISR)(void);
+
+/* Notice: The Cortex-M4 expects all jumps to be made at an odd address when
+ * jumping to Thumb code. For example, if you want to execute Thumb code at
+ * address 0x100, you'll have to jump to 0x101. Luckily, this idiosyncrasy is
+ * properly handled by the C compiler that will generate proper addresses when
+ * using function pointers. */
+
+#define INITIALISATION_VECTOR_SIZE 0x6B
+
+ISR InitialisationVector[INITIALISATION_VECTOR_SIZE]
+  __attribute__((section(".isr_vector_table")))
+  = {
+  0x20010000, //FIXME: This is the stack pointer!
+  reset,
+  0,
+  0,
+  0
+};
+
+void blink(void);
+
+void reset(void) {
+  // This is where execution start after reset.
+  // Many things are not initialized yet so the code here has to pay attention.
+
+  /* Copy data segment to RAM
+   * The data segment is R/W but its initialization value matters. It's stored
+   * in Flash, but linked as if it were in RAM. Now's our opportunity to copy
+   * it. Note that until then the data segment (e.g. global variables) contains
+   * garbage values and should not be used. */
+//  int dataSegmentSize = &_data_segment_end_ram - &_data_segment_start_ram;
+  uint32_t * ramPointer = (uint32_t *)&_data_segment_start_ram;
+  uint32_t * flashPointer = (uint32_t *)&_data_segment_start_flash;
+  while (ramPointer < (uint32_t *)&_data_segment_end_ram) {
+    *ramPointer++ = *flashPointer++;
+  }
+
+  blink();
+}
+/*
+void _start(void) {
+}*/

boot/stm32f429_flash.ld

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+MEMORY {
+  FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 2048K
+  RAM (rwx)  : ORIGIN = 0x20000000, LENGTH = 192K
+  CCM (rwx)  : ORIGIN = 0x10000000, LENGTH = 64K
+}
+
+SECTIONS {
+  .isr_vector_table ORIGIN(FLASH) : {
+    /* We're explicitly asking for the ISR vector table to be at the beginning
+     * of the Flash memory. This is what the STM32F42xx expects when booting.
+     * See ST/RM0090/p70 */
+    *(.isr_vector_table)
+    /*LONG(0x20010000);*/ /* Stack pointer */
+    /*LONG(0x00000201);*/ /* Reset vector */
+    /* CAUTION: The least significant bit of the reset
+     * vector should be set to indicate Thumb code */
+  } >FLASH
+
+  .text : {
+    . = ALIGN(4);
+    *(.text)
+  } >FLASH
+
+  .rodata : {
+    . = ALIGN(4);
+    *(.rodata)
+  } >FLASH
+
+  .data : {
+    /* The data section is written to Flash but linked as if it were in RAM.
+     * This is required because its initial value matters (so it has to be in
+     * persistant memory in the first place), but it is a R/W area of memory
+     * so it will have to live in RAM upon execution (in linker lingo, that
+     * translate to the data segment having a LMA in Flash and a VMA in RAM).
+     * This means we'll have to copy it from Flash to RAM on initialization.
+     * To do this, we'll need to know the source location of the data segment
+     * (in Flash), the target location (in RAM), and the size of the segment.
+     * That's why we're defining three symbols that we'll use in the initial-
+     * -ization routine. */
+    . = ALIGN(4);
+    _data_segment_start_flash = LOADADDR(.data);
+    _data_segment_start_ram = .;
+    *(.data)
+    _data_segment_end_ram = .;
+  } >RAM AT> FLASH
+  /*. = 0x8000000;
+  .data : { *(.data) }
+  .bss : { *(.bss) }*/
+}

gdb_script.gdb

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+# Let's connect to OpenOCD
+target remote localhost:3333
+
+# Load our executable
+load boot.elf
+
+# Tell OpenOCD to reset and halt
+monitor reset halt

openocd.cfg

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+source [find board/stm32f429discovery.cfg]