问题描述

通用定时器预分频问题

MCU是stm32f103zet6,采用TIM2，向上计数器模式，外部晶振8MHZ，RCC APB1=36MHZ,预分频：36000-1，目标是想得到在计数时，计数器每增加一，耗时是1ms
但是怎么都实现不了，时间增加0.1us，计数器增加一个远远大于1的不确定值。
void RCC_Configuration(void)
{
ErrorStatus HSEStartUpStatus;

/* RCC system reset(for debug purpose) */
RCC_DeInit();

/* Enable HSE */
RCC_HSEConfig(RCC_HSE_ON);

/* Wait till HSE is ready */
HSEStartUpStatus = RCC_WaitForHSEStartUp();

if (HSEStartUpStatus == SUCCESS)
{
/* Enable Prefetch Buffer */
//FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

/* Flash 2 wait state */
//FLASH_SetLatency(FLASH_Latency_2);

/* HCLK = SYSCLK */
RCC_HCLKConfig(RCC_SYSCLK_Div1); 

/* PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1); 

/* PCLK1 = HCLK/2 */
RCC_PCLK1Config(RCC_HCLK_Div2);

/* PLLCLK = 8MHz * 9 = 72 MHz */
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);

/* Enable PLL */
RCC_PLLCmd(ENABLE);

/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET) {}

/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08) {}

}

/* Enable GPIOC clock */
//RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);

/* Enable TIM2 clock */
//RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

}
void Timer_Config(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
/* Enable TIM2 clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
TIM_DeInit(TIM2);
TIM_InternalClockConfig(TIM2);

TIM_TimeBaseStructure.TIM_Period=40000;
TIM_TimeBaseStructure.TIM_Prescaler = 36000 - 1;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);
TIM_ClearFlag(TIM2,TIM_FLAG_Update);
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);

TIM_ClearFlag(TIM2, TIM_FLAG_Update);
//TIM_ARRPreloadConfig(TIM2, DISABLE); //????????????????????
TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
TIM_Cmd(TIM2,ENABLE);

}

解决方案

0.1uS 你怎么测的呢？
如果我做，大概会每次定时中断反转一个I/O，然后用示波器看波形时间，调整计数分频