4.1.6.2. STM32F411

An overview of the STM32F411 microcontroller, focusing on its core features, GPIO functionality, clock initialization, USART configuration, and PWM/timer usage.

4.1.6.2.1. Features

  • Core: ARM Cortex-M4 running at 100 MHz, with an FPU and ART accelerator for fast memory access.

  • Memory: 512 KB of Flash memory, 128 KB of SRAM.

  • Power Consumption: - Run: 100 μA/MHz. - Stop: 42 μA/MHz (fast wake-up), 9 μA/MHz (deep power-down). - Standby: 1.8 μA.

  • Voltage Range: 1.7V to 3.6V.

  • Analog: 12-bit ADC with 16 channels.

  • Timers: 11 timers, including a watchdog and SysTick timer.

  • Communication Interfaces: I2C, USART, SPI, USB, and more.

4.1.6.2.2. GPIO (General-Purpose Input/Output)

  • Purpose: Interface between the microcontroller and external devices.

  • Key Registers: - MODER: Configures the pin mode (input, output, analog). - PUPDR: Configures pull-up/pull-down resistors for inputs. - OTYPER: Sets output type (e.g., push-pull). - OSPEEDR: Configures output speed. - AFR: Specifies alternate functions. - IDR/ODR: Used for reading and writing pin states. - BSSR: Allows setting and resetting individual pins.

  • Modes: - Input (signal reading) - Output (device control) - Analog (ADC/DAC)

  • Applications: Digital control, signal monitoring, communication, PWM.

  • Importance: Proper configuration ensures efficient system performance.

4.1.6.2.3. Clock Initialization

  • RCC (Reset and Clock Control): Manages system clocks and resets.

  • Key Registers: - CR (Control Register): Manages clock sources. - APB1ENR: Enables or disables the peripheral clock for the APB1 bus. - PLLCFGR: Configures the PLL (adjusts multipliers and dividers for frequency).

  • Clock Sources: - HSI: 8 MHz internal clock. - HSE: External high-speed clock. - LSI: Low-speed internal clock.

  • PLL Configuration: - PLLM: Main clock multiplier. - PLLN: PLL multiplier. - PLLP: PLL divider for main clock output.

  • Flash Configuration: - FLASH_ACR_LATENCY: Sets wait states for flash memory.

  • Power Control: - VOS: Voltage scaling to balance performance and power.

  • Importance: - Accuracy: Crucial for timing-sensitive tasks. - Performance: Ensures optimal microcontroller speed. - Power Efficiency: Reduces power usage in low-power modes.

  • Proper clock initialization is essential for accurate, efficient, and optimized operations.

4.1.6.2.4. USART (Universal Synchronous/Asynchronous Receiver-Transmitter)

  • Overview: Supports both asynchronous (with start/stop bits) and synchronous (data with clock) communication.

  • Oversampling: Default 16x for better accuracy.

  • Baud Rate: Determines data transmission speed.

  • Configuration Steps: 1. Enable the clock in RCC. 2. Configure GPIO for TX/RX in alternate function mode. 3. Set the baud rate using Baud Rate = Fck / (Baudrate * 2) and write it to the BRR register. 4. Enable USART by setting relevant bits in CR1 (UE, TE, RE).

  • Transmission: Check the TXE flag, then write data to DR.

  • Key Registers: - CR1: Configures USART, enabling TX/RX. - BRR: Sets baud rate. - DR: Holds data for transmission. - SR: Indicates the transmission status.

  • Proper configuration ensures reliable serial communication.

4.1.6.2.5. Timer and PWM (Pulse Width Modulation)

  • Overview: Each STM32 timer can be used for PWM outputs.

  • Configuration Steps: 1. Enable the timer’s clock through the RCC registers. 2. Configure the GPIO pin for PWM output. 3. Set the PWM mode using the timer’s Capture/Compare Registers and enable output using the CCER.

  • Modes: - Edge-Aligned: Timer counts from 0 to ARR. - Center-Aligned: Timer counts up and down for symmetrical output.

  • Applications: PWM can be used to control power to motors, LEDs, etc.

  • Importance: Proper PWM configuration allows for adjustable frequency and duty cycles for effective power management.

4.1.6.2.6. Overview of Register Importance

Registers in STM32 microcontrollers provide direct control over hardware. Proper register management is vital for setting up peripherals, controlling GPIO pins, and configuring timers, enabling efficient and precise hardware programming.