Lecture Notes: STM32 Timers and Microcontrollers

Introduction

• Importance of timers in modern microcontrollers:
  • Counting clock pulses
  • Creating delays
  • Generating periodic interrupts
  • Measuring time between events
  • Setting up pulse width modulation signals

Understanding Timers in STM32

• Main CPU Clock (HClock):

  • Connects to prescalers to divide the clock
  • Example with Nucleo board at 80 MHz:
    • Prescaler set to divide by 80 results in 1 MHz clock signal

• Timer Operations:

  • Timers count from zero to a set maximum value
  • Increment once per microsecond with 1 MHz clock
  • STM32 microcontrollers often have multiple timers
  • Example microcontroller: STM32L476RG

STM32L476RG Timers and Configuration

• Datasheet Overview:

  • General-purpose timers (e.g., Timers 16 and 17)
  • Special-purpose timers like watchdog timers
  • HAL API uses SysTick for delays (important for real-time systems)

• Clock Tree and Timer Connections:

  • Timer 16 connected to clock multiplier, APB2 prescaler
  • Prescalers affect how timers operate (e.g., APB2 set to 8, timer prescaler to 4)

CubeMX and IDE Setup

• Project Setup:

  • Naming and configuration in STM32 Cube IDE
  • Clock configuration and prescaler settings
  • Default settings: 80 MHz CPU clock, prescaler adjustments

• Timer Activation:

  • Using CubeMX to activate timer 16
  • Timer functionalities (Input Capture, Output Compare, PWM)
  • Prescaler setting: 80 (enter 79 due to zero-indexing)
  • Auto Reload Register set for 16-bit max value (65535)

Timer Example Applications

• Simple Timer Application:

  • Using HAL APIs to read CNT register and measure elapsed time
  • Serial terminal output for debugging
  • Limitations: Maximum measurement duration of ~65 milliseconds

• Blinky Example with Timer:

  • Adjust prescaler for 1 tick every 100 microseconds
  • LED toggling without blocking CPU cycles
  • Non-blocking code execution

Advanced Use: Timer Interrupts

• Interrupts for Timer Events:

  • Timer value increments and triggers interrupts on reset
  • Timer Period Elapsed Callback for handling interrupts

• CubeMX Configuration for Interrupts:

  • Set timer period and enable NVIC settings
  • Use HAL functions for starting timers in interrupt mode
  • Implement callback function for LED toggling

Conclusion

• Recap of using timers in STM32 microcontrollers
• Encouragement to explore further and use provided resources
• Link to demo code and encouragement to subscribe for more content

Note: The lecture included practical examples and demonstrations using the STM32 Cube IDE and HAL APIs to configure and utilize timers effectively in an embedded system.