STM32 HAL vs LL: Which One Should You Use?

When you start programming STM32 microcontrollers in STM32CubeIDE, you will see two main driver options: HAL (Hardware Abstraction Layer) and LL (Low Layer). Beginners often get confused and don’t know which one to pick. Some tutorials use HAL, while others rely on LL, making it even more confusing.

This guide explains STM32 HAL vs LL, compares their features, and helps you decide which one is best for your project.

What is STM32 HAL?

HAL stands for Hardware Abstraction Layer. It is a high-level driver library provided by STMicroelectronics.

Features of HAL

• Easy to use with simple functions.

• Abstracts hardware details into ready-made APIs.

• Widely supported in STM32CubeIDE auto-generated code.

• Portable across different STM32 families.

Example: HAL GPIO Toggle

HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_13);
HAL_Delay(1000);

This code toggles an LED with just two lines.

What is STM32 LL?

LL stands for Low Layer. It is a lightweight driver library that gives more direct access to STM32 registers.

Features of LL

• Closer to hardware, faster execution.

• Lightweight, minimal overhead.

• Provides more control than HAL.

• Best for time-critical applications.

Example: LL GPIO Toggle

LL_GPIO_TogglePin(GPIOC, LL_GPIO_PIN_13);
LL_mDelay(1000);

Looks similar to HAL, but functions are more direct and faster.

STM32 HAL vs LL: Key Differences

When to Use STM32 HAL

HAL is a great choice if you:

• Are a beginner starting with STM32.

• Want quick results with less coding.

• Need portable code across multiple STM32 families.

• Are building applications where performance is not extremely critical.

Examples:

• LED blinking, sensor interfacing, UART communication, simple IoT projects.

When to Use STM32 LL

LL is best if you:

• Need high performance and minimal overhead.

• Want precise control of registers.

• Are building real-time or time-sensitive applications.

• Want smaller code size and faster execution.

Examples:

• Motor control, real-time signal processing, communication at high baud rates.

Can You Mix HAL and LL?

Yes, one of the best things about STM32CubeIDE is that you can mix HAL and LL in the same project.

For example:

• Use HAL for initialization and configuration.

• Use LL for critical functions that require speed.

This approach is often used in professional projects where both ease of development and performance are important.

STM32 HAL Example: UART Transmit

char msg[] = "Hello via HAL UART\r\n";
HAL_UART_Transmit(&huart2, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);

STM32 LL Example: UART Transmit

while(!LL_USART_IsActiveFlag_TXE(USART2));
LL_USART_TransmitData8(USART2, 'H');

HAL makes it easier but slower, while LL requires more coding but gives better control.

Pros and Cons of STM32 HAL vs LL

HAL Pros

• Beginner-friendly.

• Portable across families.

• Fast development.

HAL Cons

• More code size.

• Slower execution.

LL Pros

• High performance.

• Minimal code size.

• Direct hardware control.

LL Cons

• More complex.

• Less portable.

FAQ on STM32 HAL vs LL

What is STM32 HAL used for?
It is used for high-level programming of STM32, making development easier with ready APIs.

What is STM32 LL used for?
It is used for low-level programming with more speed and control.

Which is better: HAL or LL?
HAL is better for beginners, while LL is better for performance-critical applications.

Can I use HAL and LL together?
Yes, you can mix both in the same project.

Is LL faster than HAL?
Yes, LL has less overhead and is closer to registers.

Does HAL work on all STM32 series?
Yes, HAL is designed to be portable across STM32 families.

Does LL work on all STM32 series?
No, LL is chip-specific and less portable.

Which is easier to learn: HAL or LL?
HAL is easier for beginners, LL requires more hardware knowledge.

Do professionals use HAL or LL?
Many professional projects use a mix of both.

Should I start with HAL or LL as a beginner?
Start with HAL, then move to LL for advanced performance needs.

Conclusion

Both STM32 HAL and LL have their own strengths. HAL makes programming easy and portable, while LL gives speed and control. For beginners and quick prototypes, HAL is the right choice. For performance-driven applications, LL is better.

In practice, many developers use a combination of HAL and LL to get the best of both worlds.

If you want step-by-step STM32 projects with HAL and LL examples, check ControllersTech for detailed tutorials.