Nucleo-F411RE （STM32F411）LL库体验 5 - 通用定时器TIM2的使用

1、简述

设定TIM2，计数周期为10KHZ，即计时1s需要10000次，通过shell命令动态修改reload值，来更改定时器的频率。
假定设定TIM2 counter clock = 10K,那么TIM2 prescaler = (SystemCoreClock /10 KHz) - 1，代码中通过
__LL_TIM_CALC_PSC(SystemCoreClock, 10000)来计算得到。
假定 100ms进入一次中断，即freq=10HZ，那么tim2的autoreload的值通过下面的函数得到。
InitialAutoreload = __LL_TIM_CALC_ARR(SystemCoreClock, LL_TIM_GetPrescaler(TIM2), 10);
（InitialAutoreload即是hal库的period值）

2、TIM2的初始化

a、时钟初始化

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b、TIM初始化

// 初始化TIM2 控制LED灯的闪烁，默认100ms一次
static void BOARD_Tim2Init(void)
{
	uint32_t InitialAutoreload = 0;
	/* Set counter mode */
	/* Reset value is LL_TIM_COUNTERMODE_UP */
	//LL_TIM_SetCounterMode(TIM2, LL_TIM_COUNTERMODE_UP);

	/* Set the pre-scaler value to have TIM2 counter clock equal to 10 kHz      */
	/*
		In this example TIM2 input clock (TIM2CLK)  is set to APB1 clock (PCLK1),
		since APB1 prescaler is equal to 1.
		TIM2CLK = PCLK1
		PCLK1 = HCLK
		=> TIM2CLK = HCLK = SystemCoreClock
		To get TIM2 counter clock at 10 KHz, the Prescaler is computed as following:
		Prescaler = (TIM2CLK / TIM2 counter clock) - 1
		Prescaler = (SystemCoreClock /10 KHz) - 1
		设置TIM2 counter clock at 10 KHz，即1s需要10000次，那么100ms需要计数1000次。
		所以autoReload=1000-1时，100ms进中断一次。
	*/
	LL_TIM_SetPrescaler(TIM2, __LL_TIM_CALC_PSC(SystemCoreClock, 10000));
	
	/* Set the auto-reload value to have an initial update event frequency of 10 Hz */
		/* TIM2CLK = SystemCoreClock / (APB prescaler & multiplier)                 */
	
	InitialAutoreload = __LL_TIM_CALC_ARR(SystemCoreClock, LL_TIM_GetPrescaler(TIM2), 10);
	
	LL_TIM_SetAutoReload(TIM2, InitialAutoreload);
	
	/* Enable the update interrupt */
	LL_TIM_EnableIT_UPDATE(TIM2);
	
	/* Configure the NVIC to handle TIM2 update interrupt */
	NVIC_SetPriority(TIM2_IRQn, 0);
	NVIC_EnableIRQ(TIM2_IRQn);
	
	/* Enable counter */
	LL_TIM_EnableCounter(TIM2);
	
	/* Force update generation */
	LL_TIM_GenerateEvent_UPDATE(TIM2);
}

c、中断处理函数

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3、shell的调试

a、shell命令添加

volatile static uint32_t InitialAutoreload = 0;
volatile static uint32_t Freq = 10;

int Tim_Control(int argc,char *argv[])
{
	if (argc == 2)
	{
		if (!strncmp(argv[1],"On",2))
		{	
			LL_TIM_EnableCounter(TIM2);
		}
		else if (!strncmp(argv[1],"Off",3))
		{	
			LL_TIM_DisableCounter(TIM2);
		}
		else
		{
			printf("error,please use / TIM On/TIM Off\r\n");
			return -1;
		}
	}
	else if (argc == 3)
	{
		if (!strncmp(argv[1],"Freq",4))
		{	
			Freq = strtol(argv[2],NULL,10);
			if (Freq > 0)
			{
				LL_TIM_DisableCounter(TIM2);
				InitialAutoreload = __LL_TIM_CALC_ARR(SystemCoreClock, LL_TIM_GetPrescaler(TIM2), Freq);
				LL_TIM_SetAutoReload(TIM2, InitialAutoreload);
				LL_TIM_EnableCounter(TIM2);
				LL_TIM_GenerateEvent_UPDATE(TIM2);
			}
			else
			{
				printf("please use TIM Freq 10 \r\n");
				LL_TIM_DisableCounter(TIM2);
				return -1;
			}
		}
		else
		{
			printf("error,please use / TIM On/TIM Off\r\n");
		}
	}
	else
	{
		printf("error,please use / TIM On/TIM Off\r\n");
		return -1;
	}
    return 0;
}

SHELL_EXPORT_CMD(SHELL_CMD_PERMISSION(0)|SHELL_CMD_TYPE(SHELL_TYPE_CMD_MAIN), TIM, Tim_Control, Tim_Control);

TIM On 打开定时器
TIM Off 关闭定时器
TIM Freq xx 更改定时器的频率，1-10K之间.
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