stm32f4滴答定时器

### STM32F4 SysTick Timer Usage and Examples For the STM32F4 series microcontrollers, both SysTick and TIM can serve as system tick timers to provide a time base for applications. However, when using SysTick specifically: The SysTick timer is an essential component of the Cortex-M core[^1]. It provides a simple down-counter that decrements from a reload value until it reaches zero, generating interrupts at regular intervals which are useful for implementing delays or periodic activities. To configure the SysTick timer on STM32F4 devices, one typically initializes HAL (Hardware Abstraction Layer) with predefined settings through CubeMX or manually sets up parameters such as clock source frequency and interrupt priority level within application code. Below demonstrates how to set up and use the SysTick timer in C language for creating delay functions without relying on external libraries like `delay()` provided by some development environments: ```c #include "stm32f4xx_hal.h" void SystemClock_Config(void); static void MX_GPIO_Init(void); int main(void){ HAL_Init(); SystemClock_Config(); MX_GPIO_Init(); /* Configure the SysTick handler */ if(HAL_SYSTICK_Config(SystemCoreClock / 1000U) != HAL_OK){ // Set systick period to generate 1ms interval. while(1); // If configuration fails enter infinite loop. } } // Example function utilizing SysTick for timing purposes __weak void HAL_IncTick(void){ static uint32_t TimingDelay; if((TimingDelay != 0x00)){ if(TimingDelay < HAL_GetTick()){ TimingDelay = 0; }else{ TimingDelay--; } } } ``` In this example, after configuring the system clock and initializing GPIOs, the SysTick timer gets configured via `HAL_SYSTICK_Config()`, setting its period so that every millisecond generates an interrupt request. The weak implementation of `HAL_IncTick` shows handling timed events based on elapsed ticks counted since startup.