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定时器是我们在嵌入式单片机里应用最广泛的外设。使用定时器的水平高低也决定着整个项目实施的水平高低。本次版主给大家带了使用TIM3定时器产生不同频率的示例。例程主要使用TIM3来产生不同频率的方波，占空比为50%，按键按下时，频率增加。

实例还是比较简单的，版主就不再多多叙述，大家直接看源代码吧！

源代码：

/** * @brief tim3 base 1KHz * @param * @retval * @date 2015-03-31 * @note */ void TIM3Freq(void) { TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; NVIC_InitTypeDef NVIC_InitStructure; GPIO_InitTypeDef GPIO_InitStructure; TIM_OCInitTypeDef TIM_OCInitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE); /* GPIOA Configuration: TIM3 CH4 (PB1) */ GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ; GPIO_Init(GPIOB, &GPIO_InitStructure); GPIO_PinAFConfig(GPIOB, GPIO_PinSource1, GPIO_AF_1); /* Enable the TIM3 gloabal Interrupt */ NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn; NVIC_InitStructure.NVIC_IRQChannelPriority = 0; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); TIM_TimeBaseStructure.TIM_Period = 0xFFFF; TIM_TimeBaseStructure.TIM_Prescaler = 23; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle; TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; TIM_OCInitStructure.TIM_Pulse = gCCR4_Val; TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; TIM_OC4Init(TIM3, &TIM_OCInitStructure); TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Disable); TIM_ITConfig(TIM3, TIM_IT_CC4, ENABLE); TIM_Cmd(TIM3, ENABLE); } /** * @brief TIM3_IRQHandler的中断入口函数 * @param * @retval * @date 2015-03-30 * @note */ void TIM3_IRQHandler(void) { uint16_t capture; /* TIM3_CH4 toggling with frequency = 4687.5 Hz */ if (TIM_GetITStatus(TIM3, TIM_IT_CC4) != RESET) { TIM_ClearITPendingBit(TIM3, TIM_IT_CC4); capture = TIM_GetCapture4(TIM3); TIM_SetCompare4(TIM3, capture + gCCR4_Val); } }

工程文件：

exp07_TIM3Frequence.zip