Embedded Systems

Generating PWM with STM32

May 21, 2026 2 min read

This day and age operate on minuscule chunks of extremely engineered silicon: microcontrollers. They govern almost everything electrical around us, utilizing control techniques for purposes as simple as temperature sensing, digital noise cancellation, or the speed control of traction motors in electric trains.

While platforms like Arduino (often based on 8-bit microcontrollers) are popular for simple prototyping, 8-bit architectures frequently become bottlenecks for heavy data processing or high-frequency control loops. This is where the 32-bit STM32 series excels. With features like 12-bit ADCs with 1 μs sampling times, inbuilt DACs, and varied hardware interfaces, it is an absolute industry standard for robust embedded development.

View the complete source code and project on GitHub

The Development Ecosystem

To generate precise PWM signals on the STM32 architecture (e.g. STM32F103x8), the toolchain is critical:

  • Software: STM32CubeMX provides a GUI for hardware initialisation and pin muxing, generating the boiler-plate code so you can focus on the application logic. Keil uVision serves as the IDE for actual C/C++ development.
  • Hardware: An ST-Link v2 is used for real-time programming and Serial-Wire Debugging (SWD).
  • Libraries: While ST’s Hardware Abstraction Layer (HAL) library provides human-readable code and rapid deployment, understanding the underlying hardware registers is paramount for high-reliability systems.

The Physical Layer of PWM

When configuring bare-metal PWM, you are essentially setting up a hardware timer to count up to an Auto-Reload Register (ARR) value. A separate Capture/Compare Register (CCR) sets the duty cycle.

// Example Bare-Metal Timer Configuration
TIM2->PSC = 79;        // Prescaler (e.g., for 80MHz clock, sets tick to 1us)
TIM2->ARR = 999;       // Auto-reload value (Period = 1ms -> 1kHz frequency)
TIM2->CCR1 = 499;      // Duty Cycle = ~50%
TIM2->CCMR1 |= TIM_CCMR1_OC1M_1 | TIM_CCMR1_OC1M_2; // PWM Mode 1
TIM2->CCER |= TIM_CCER_CC1E; // Enable Output
TIM2->CR1 |= TIM_CR1_CEN;    // Start Timer

Why It Matters in Power Electronics

In power electronics, the precision of your timer dictates the granularity of your control loops. If you’re designing a grid-tied inverter or a digital SMPS, knowing exactly when the registers update (shadow registers vs active registers) is critical to avoiding shoot-through in half-bridge configurations.