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我使用的是STM32的HAL库，STM32F103ZET6，主频为72MHz。这里使用的定时器是TIM3。定时器的预分频系数我设置为了72，即定时器以1MHz运作，即计一个数要用1us。在使用定时器实现微秒延时函数时，我在调试时发现，我想延时1000us时，实际上延时了7000us左右，为什么会这样呢？
- //TIM3初始化
- TIM_HandleTypeDef htim3;
- void MX_TIM3_Init(void){
- TIM_ClockConfigTypeDef sClockSourceConfig = {0};
- TIM_MasterConfigTypeDef sMasterConfig = {0};
-
- htim3.Instance = TIM3;
- htim3.Init.Prescaler = 71;
- htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
- htim3.Init.Period = 65535;
- htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
- htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
-
- if (HAL_TIM_Base_Init(&htim3) != HAL_OK){
- Error_Handler();
- }
- sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
- if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK){
- Error_Handler();
- }
- sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
- sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
- if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK){
- Error_Handler();
- }
- }
-
- //TIM3 msp初始化
- void HAL_TIM_Base_MspInit(TIM_HandleTypeDef* tim_baseHandle){
- GPIO_InitTypeDef GPIO_InitStruct = {0};
- if(tim_baseHandle->Instance == TIM3){
- __HAL_RCC_TIM3_CLK_ENABLE();
- __HAL_RCC_GPIOA_CLK_ENABLE();
-
- GPIO_InitStruct.Pin = GPIO_PIN_7;
- GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
- GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
- HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
-
- HAL_NVIC_SetPriority(TIM3_IRQn, 2, 0);
- HAL_NVIC_EnableIRQ(TIM3_IRQn);
- }
- }
-
- //微秒延时函数
- void HAL_Delay_us(uint16_t us){
- __HAL_TIM_SET_COUNTER(&htim3, 0); //设置计数器的值为0
- __HAL_TIM_ENABLE(&htim3); //使能TIM3
- while (__HAL_TIM_GET_COUNTER(&htim3) < us);
- __HAL_TIM_DISABLE(&htim3); //失能TIM3
- }
-
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