STM32 Firmware Development #7: Boot Process & Vector Table | How Startup Code Works

Welcome to Episode 7 of STM32 Firmware Development: From HAL to Bare-Metal! In this episode, we explore one of the most fundamental parts of every STM32 microcontroller: the booting process and the vector table. Before your firmware runs anything, the Cortex-M core performs a carefully defined startup sequence—and understanding this flow is crucial for writing reliable, low-level embedded code. We break down how the processor initializes, how the vector table guides execution, and how the reset handler leads into your application. By the end of this episode, you’ll have a clear picture of what happens between power-on and main()—knowledge that becomes essential as you move toward bare-metal development, custom bootloaders, or advanced startup configurations. ⚙️ What You’ll Learn: How the Cortex-M boot process works from reset to user code The purpose and structure of the STM32 vector table How initial stack pointer and reset handler are loaded during startup The role of startup files and how they define exception/IRQ handlers How execution transitions from low-level initialization to your main() function Why understanding the boot sequence is critical for debugging early firmware failures 🚀 What’s Next? In Episode 8, we’ll take this theory into practice, customizing startup code, modifying the vector table, and exploring how to tailor the boot sequence to fit your application needs—whether bare-metal, RTOS-based, or bootloader-enabled. Let’s dive into the foundation of every STM32 program and demystify the journey from power-on to your first instruction!