06. Module1_ToolchainOverview

PART 5: Toolchain Overview: From Code to Microcontroller

Bare-metal programming requires a toolchain that transforms your C/C++ source code into machine code and deploys it to your microcontroller. This section gives a structured overview of each part in the pipeline.

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What Is a Toolchain?

A toolchain is a set of programs that work together to:

• Compile code (.c / .cpp → .o)
• Link object files and libraries into an executable (.elf)
• Convert the executable into a binary (.bin / .hex)
• Flash the binary to your microcontroller
• Debug the program in real-time

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Components of a Typical Toolchain

1. Compiler

Converts human-readable code into machine instructions.

Popular choices:

• GCC (GNU Arm Embedded Toolchain): Free, widely supported
• Keil MDK (ARMCC): Commercial, powerful IDE
• IAR Embedded Workbench: High-performance commercial compiler

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2. Linker

Merges multiple object files (.o) and resolves addresses and memory layout using a linker script.

Example Linker Script (STM32):

MEMORY  
{  
	FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 64K  
	RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 20K  
}

SECTIONS  
{  
	.text : { _(.text_) } > FLASH  
	.data : { _(.data_) } > RAM  
}

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3. Startup Code

Before main() runs, the MCU executes startup code that:

• Initializes stack and heap
• Sets up interrupt vector table
• Initializes global/static variables

Example: startup_stm32f1xx.s (Assembly)

Reset_Handler:  
LDR R0, =_estack  
MOV SP, R0  
BL SystemInit  
BL main

Startup Sequence:

Power-on/Reset
   ↓
Sample BOOT0/BOOT1 pins
   ↓
Select boot memory (Flash, system memory, SRAM)
   ↓
Fetch Stack Pointer and Reset Handler from vector table
   ↓
Run startup code (initialize memory, hardware)
   ↓
Call main()

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4. Flashing Tools

Once you’ve compiled your program, you need to flash it to your microcontroller.

Tool	Description
ST-Link Utility / STM32CubeProgrammer	Official ST flashing tools
OpenOCD	Open-source flashing/debug tool
dfu-util	For USB bootloaders (DFU mode)
pyocd	Python-based flasher/debugger

Example (using OpenOCD + ST-Link):

openocd -f interface/stlink.cfg -f target/stm32f1x.cfg

Then, in a separate terminal:

telnet localhost 4444

> reset halt  
> flash write_image erase myprogram.elf  
> reset run

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5. Debugger

This lets you pause execution, inspect registers, set breakpoints, and step through your code.

Popular options:

• GDB (via OpenOCD or pyocd)
• Segger Ozone (for J-Link)
• Keil / IAR IDEs with GUI debuggers

Example: Running GDB:

arm-none-eabi-gdb myprogram.elf  
target remote localhost:3333  
monitor reset halt  
break main  
continue

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IDEs and Build Systems

You can either use:

Bare Toolchain + Makefile/CMake

Pros: Total control, transparency

Tools: VS Code + Makefile, CMake, custom scripts

Example Makefile:

CC=arm-none-eabi-gcc  
CFLAGS=-mcpu=cortex-m3 -mthumb -Wall

all: main.elf

main.elf: main.o startup.o  
$(CC) $(CFLAGS) -T linker.ld -o $@ $^

Smart IDEs

IDE	Features
STM32CubeIDE	One-stop IDE with ST tools built-in
Keil uVision	Commercial, mature, GUI debugging
PlatformIO	Cross-platform embedded dev in VS Code
Segger Embedded Studio	Lightweight IDE for J-Link users

**In the upcoming sections, we will stick with the STM32CubeIDE.

Summary

Component	Role
Compiler	Converts source to machine code
Linker	Combines files & maps memory
Startup Code	Prepares the system for main()
Flash Tool	Uploads your binary to the MCU
Debugger	Lets you inspect and test code
IDE/Build System	Automates the workflow

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