频率(HZ)是频率的基本单位1HZ是1s的倒数
STM32F103C8T6一般情况给定时器的内部时钟都是72MHz(系统主频率)
TIM基本构成
计数器、预分频器、自动化重装 // 都是16位
其中计数器、自动化重装,都是16位换算成10进制范围为[0, 655536]
时间 = 1 / [(1 + 自动化重装) * (1 + 预分频器) / 72M ]
其中自动分频器取值为[0, 65535]
分频 = 自动分频器取值 + 1
例如:
自动化重装为72、预分频器取值为2^16 - 1、计数器为2^16 - 1
那么计数器完成计数所耗费的时间为:
1/[65536 * 65536 / 72M] = 59.65s
定时器基本结构
朴素的讲计数器计数达到自动重装值就会申请NVIC中断,此过程耗费的时间就是我们想要的时间
代码:
#include "stm32f10x.h" // Device header
#include "Delay.h"
#include "OLED.h"
uint16_t num = 0;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
/*初始化通用定时器TIM2*/
void Timer_Init(void){
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);//APB1外设开启
TIM_InternalClockConfig(TIM2);//选择内部时钟
/*初始化时基单元*/
TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;//向上计数
TIM_TimeBaseInitStructure.TIM_Period = 10000 - 1;//ARR自动重装
TIM_TimeBaseInitStructure.TIM_Prescaler = 7200 - 1;//psc预分频器
TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;//高级计时器内容直接给零
//记录1s
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStructure);//刚初始化完就会进中断
TIM_ClearFlag(TIM2, TIM_FLAG_Update);//消除中断标志位
//使能更新中断
TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
/*配置中断*/
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);//选择组2
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;//定时器2在NVIC内的通道
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_Init(&NVIC_InitStructure);
TIM_Cmd(TIM2, ENABLE);//启动定时器
}
void TIM2_IRQHandler(void){//定时器2的中断函数,名字固定
if(TIM_GetITStatus(TIM2, TIM_IT_Update) == SET){
num = num + 1;
TIM_ClearITPendingBit(TIM2, TIM_IT_Update);//清除标志位
}
}
int main(void){
OLED_Init();//初始化OLED
Timer_Init();
while(1){
OLED_ShowNum(1,1, num, OLED_GetNumLength(num));
OLED_ClearLocation(1,OLED_GetNumLength(num));
}
}
其中:
uint8_t OLED_GetNumLength(uint16_t num){
uint8_t length = 0;
if(num == 0) return (uint8_t)1;
while(num > 0){
num = num / 10;
length = length + 1;
}
return length;
}
void OLED_ClearLocation(uint8_t row, uint8_t len)
{
uint8_t i, j;
for (j = row * 2 - 2; j < row * 2; j++)
{
OLED_SetCursor(j, len * 8);
for(i = len * 8; i < 128; i++)
{
OLED_WriteData(0x00);
}
}
}
效果:
每过一秒,数字增加1