Add beginner-friendly GPIO LED blink example with register explanations

[MrAbhi19]

This PR introduces a simple demo in /Src/examples/stm32f4xx_hal_led.c that toggles an LED using STM32F4 HAL functions. The example is designed for beginners and includes clear comments explaining the underlying register-level operations (RCC_AHB1ENR, GPIOx_MODER, GPIOx_ODR, etc.).

Details:

• Added new source file: /Src/examples/stm32f4xx_hal_led.c
• Updated README.md with a section highlighting the example
• Example assumes LED on GPIOD Pin 12 (STM32F4 Discovery board), but can be adapted to other pins/boards
• Comments connect HAL abstractions with hardware registers for educational clarity

Motivation:
The goal is to make the repository more accessible to students and first-time contributors by providing a reproducible, beginner-friendly demo. This contribution aligns with the repo’s mission of offering HAL drivers and examples that bridge abstraction with hardware logic.

Impact:

• Helps newcomers understand how HAL functions map to registers
• Provides a ready-to-run LED blink demo for testing setup
• Strengthens educational value of the STM32F4 HAL driver repo

[MrAbhi19]

Thanks for reviewing this PR!
I’ve added a beginner-friendly GPIO LED blink example in /Src/examples with clear register-level notes.
The goal is to help students connect HAL functions with the underlying hardware logic.
Looking forward to your feedback!

[ALABSTM]

Hello @MrAbhi19,

Thank you for this proposal. However, we already provide such a beginner-friendly example, like this, running on a STM32F410 Nucleo board. As you can see from the code snippet below, it toggles an LED using a while(1) loop and a delay function.

  /*##-3- Toggle PA05 IO in an infinite loop #################################*/  
  while (1)
  {
    HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
    
    /* Insert a 100ms delay */
    HAL_Delay(100);
  }

Moreover, this repository is solely dedicated to host the drivers. Examples are rather hosted in the firmware repository under the Projects folder here.

With regards,

[ALABSTM]

Hello @MrAbhi19,

Please allow me to close this pull request. Thank you for your understanding and thank you again for this proposal.

With regards,