Reduce STM32 Firmware Size Using GCC -Os Optimization for Memory Constraints

Reducing STM32 Firmware Size Using GCC Optimization Flags -Os for Memory-Constrained Applications

When developing applications for STM32 microcontrollers, firmware size can be a critical concern, especially in memory-constrained environments. This tutorial will guide you through using GCC optimization flags to reduce the firmware size effectively while maintaining performance.

Prerequisites

• Basic understanding of C/C++ programming.
• STM32 development environment set up (e.g., STM32CubeIDE, Keil, or PlatformIO).
• GCC toolchain installed and configured for STM32.
• Access to an STM32 development board for testing.

Parts/Tools

• Computer with GCC toolchain installed.
• STM32 development board (e.g., Nucleo, Discovery).
• USB cable for programming the STM32 board.
• STM32CubeMX (optional, for code generation).

Steps

1. Open Your Project

   Launch your development environment and open the STM32 project you want to optimize.

2. Locate Compiler Settings

   Find the settings for your compiler. In STM32CubeIDE, this can be done by:

   1. Right-click on your project in the Project Explorer.
   2. Select Properties.
   3. Navigate to C/C++ Build > Settings.
3. Modify Optimization Level

   In the compiler settings, locate the Optimization Level dropdown. Set the optimization level to -Os.

   This flag optimizes for size, which is ideal for memory-constrained applications.

4. Update Additional Compiler Flags

   Consider adding other flags that can help reduce the firmware size:

   -fdata-sections -ffunction-sections

   Enabling these flags will allow the linker to discard unused sections, further reducing size.

5. Rebuild Your Project

   After making the changes, rebuild your project:

   1. Select Project > Build Project.
   2. Wait for the build process to complete.
6. Check the Firmware Size

   Once the build is complete, check the size of the generated firmware:

   1. Navigate to the Debug or Release folder in your project directory.
   2. Locate the .bin or .hex file.
   3. Right-click and select Properties to view the file size.
7. Test the Firmware

   Upload the firmware to your STM32 board and test to ensure functionality is maintained:

   1. Connect your STM32 board to the computer using the USB cable.
   2. Use the programming tool (e.g., ST-Link) to flash the firmware.
   3. Verify that the application runs correctly.

Troubleshooting

• Firmware Fails to Build

  If you encounter build errors, double-check your compiler flags for typos or invalid settings.

• Application Crashes or Behavior is Unexpected

  Ensure that your code does not rely on unused functions or variables. Use -Wl,–gc-sections to help with garbage collection during linking.

• Firmware Size Not Reduced

  Review your code for large libraries or unnecessary dependencies that can be optimized or removed.

Conclusion

By using the GCC optimization flag -Os and adjusting your compiler settings, you can significantly reduce the firmware size of your STM32 applications. Always ensure thorough testing after optimizations to maintain functionality. This approach helps you fit your applications into memory-constrained environments effectively.