自动重装载值和预分频系数是怎么算出来的？如果知道频率的话

七月de · 发表于 2019-5-4 09:24:00

如果知道频率是100hz，自动重装载值和预分频系数是怎么算出来的呢？

void TIM6_Configuration(unsigned int TIM_Period,unsigned int TIM_Prescaler)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStruct;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);

TIM_TimeBaseStruct.TIM_Period=1799;//初值
TIM_TimeBaseStruct.TIM_Prescaler=9;//预分频
TIM_TimeBaseStruct.TIM_ClockDivision=0;
TIM_TimeBaseStruct.TIM_CounterMode=TIM_CounterMode_Up;//向上

TIM_TimeBaseInit(TIM6,&TIM_TimeBaseStruct);
// TIM_ClearFlag(TIM6,TIM_IT_Update);
TIM_ITConfig(TIM6,TIM_IT_Update,ENABLE);

// TIM_Cmd(TIM6,ENABLE);
}

void NVIC_Tim6_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

NVIC_InitStructure.NVIC_IRQChannel = TIM6_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}

DongInker · 发表于 2019-5-4 09:24:01

/*
* Input Clk 72MHz
*/
GLOBAL void AdcTIM1Init(u32 freq)
{
u32 Period,Prescaler;

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef       TIM_OCInitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
Prescaler = 72;
Period = 72000000l/Prescaler/freq;

/* Time Base configuration */
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = Period - 1;
TIM_TimeBaseStructure.TIM_Prescaler = Prescaler - 1;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x00;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

/* TIM1 channel1 configuration in PWM mode */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = Period/2;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);

TIM_CtrlPWMOutputs(TIM1, ENABLE);
TIM_Cmd(TIM1, DISABLE);
}
这是我使用定时中断触发AD采集的定时器配置

假设你的主时钟为72MHz 要得到100Hz的频率
可以配置为
TIM_TimeBaseStruct.TIM_Period= 10000 -1;//初值
TIM_TimeBaseStruct.TIM_Prescaler=72 - 1;//预分频

100 = 72000000L/72/10000;

七月de · 发表于 2019-5-4 09:31:19

或者知道自动重装载值和预分频系数，怎么算出频率是100hz呢?

七月de · 发表于 2019-5-4 09:53:07

DongInker 发表于 2019-5-4 09:45
/*
* Input Clk 72MHz
*/

按照我上面的程序，如果知道自动重装载值和预分频系数，怎么算出频率是100hz呢?，假设主时钟是72MHz

ZTO13 · 发表于 2019-5-4 09:54:13

这个看你定时器时钟来源？假如定时器时钟来源频率为36MHZ，定时器为4分频那就是9MHZ，定时器预装载值是5536的话，如果是向上计数，16位计数寄存器最大值就是2^16=65536,中断时间就是（65536-5536）*（1/9）=XX(us),
同样16位如果是向下计数就是5536 *(1/9)=xx(us)。1HZ对应1s,这个换算不知道百度下。