江科大STM32(3)：定时器（2）定时器的输出比较功能

1.输出比较

1.1 基本概念

• 主要用于输出PWM波形控制电机。
• OC（Output Compare）输出比较

1. 输出比较可以通过比较CNT与CCR寄存器值的关系，来对输出电平进行置1、置0或翻转的操作，用于输出一定频率和占空比的PWM波形

CNT ：计数器，CCR ：捕获比较器

2. 每个高级定时器和通用定时器都拥有4个输出比较通道

3. 高级定时器的前3个通道额外拥有死区生成和互补输出的功能

1.2 输出比较通道（通用）

• CNT计数器和CCR1第一路的捕获比较寄存器，当CNT>CCR1，或者CNT=CCR1时，就会给输出模式控制器传一个信号，然后输出模式控制器就会改变它输出OC1REF的高低电平（REF信号实际上就是指这里信号的高低电平，reference参考信号），上面的ERTF输入，是定时器的一个小功能，然后，接着这个REF信号可以前往主模式控制器，可以把这个REF映射到主模式的TRGO输出上去，通过下面一路到达极性选择，给这个寄存器写0，信号就会往上走，就是信号电平不翻转，写1就会往下走，信号通过一个非门取反，那输出的信号就是输入信号高低电平反转的信号，就是选择是不是要把高低电平反转一下，OC1引脚，就是CH1通道的引脚。

下面为输出模式控制器可配置的模式

2.PWM

2.1 PWM简介

• PWM（Pulse Width Modulation）脉冲宽度调制
• 在具有惯性的系统中，可以通过对一系列脉冲的宽度进行调制，来等效地获得所需要的模拟参量，常应用于电机控速等领域
• PWM参数：
•      频率 = 1 / T_S            占空比 = T_ON / T_S           分辨率 = 占空比变化步距

 2.2 PWM基本结构

 

参数计算

 

参数计算公式：

• PWM频率： Freq = CK_PSC / (PSC + 1) / (ARR + 1)
• PWM占空比： Duty = CCR / (ARR + 1)
• PWM分辨率： Reso = 1 / (ARR + 1)

• PWM频率： Freq = CK_PSC / (PSC + 1) / (ARR + 1) =72000000 / 720 / 100 = 1000
• PWM占空比： Duty = CCR / (ARR + 1) 50 / 100 = 50%
• PWM分辨率： Reso = 1 / (ARR + 1) 1 / 100 = 1%
• 频率为1KHz，占空比为50%，分辨率为1% 的PWM波形
• 具体步骤
• 第一步，RCC开启时钟，把我们要用的TIM外设和GPIO外设的时钟打开
• 第二步，配置时基单元，包括这前面的时钟源选择
• 第三步，配置输出比较单元，包括这个CCR的值、输出比较模式、极性选择、输出使能这些参数
• 第四步，配置GPIO，把PWM对应的GPIO口，初始化为复用推挽输出的配置
• 第五步，启动计数器，这样就能输出PWM

3.实操

TIM输出比较库函数

void TIM_OC1Init(TIM_TypeDef* TIMx, TIM_OCInitTypeDef* TIM_OCInitStruct);
void TIM_OC2Init(TIM_TypeDef* TIMx, TIM_OCInitTypeDef* TIM_OCInitStruct);
void TIM_OC3Init(TIM_TypeDef* TIMx, TIM_OCInitTypeDef* TIM_OCInitStruct);
void TIM_OC4Init(TIM_TypeDef* TIMx, TIM_OCInitTypeDef* TIM_OCInitStruct);
//配置输出比较
void TIM_OCStructInit(TIM_OCInitTypeDef* TIM_OCInitStruct);
//给输出比较结构体赋一个默认值
void TIM_CtrlPWMOutputs(TIM_TypeDef* TIMx, FunctionalState NewState);
//仅使用高级定时器输出PWM时需要调用
//否则PWM将不能正常输出
//使能主输出
void TIM_SetCompare1(TIM_TypeDef* TIMx, uint16_t Compare1);
void TIM_SetCompare2(TIM_TypeDef* TIMx, uint16_t Compare2);
void TIM_SetCompare3(TIM_TypeDef* TIMx, uint16_t Compare3);
void TIM_SetCompare4(TIM_TypeDef* TIMx, uint16_t Compare4);
//单独更改CCR寄存器值
//更改占空比
 
void TIM_OC1PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);
void TIM_OC1NPolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCNPolarity);    //互补通道
void TIM_OC2PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);
void TIM_OC2NPolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCNPolarity);
void TIM_OC3PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);
void TIM_OC3NPolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCNPolarity);
void TIM_OC4PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);      //OC4无互补通道
//单独设置输出比较极性void TIM_ForcedOC1Config(TIM_TypeDef* TIMx, uint16_t TIM_ForcedAction);
void TIM_ForcedOC2Config(TIM_TypeDef* TIMx, uint16_t TIM_ForcedAction);
void TIM_ForcedOC3Config(TIM_TypeDef* TIMx, uint16_t TIM_ForcedAction);
void TIM_ForcedOC4Config(TIM_TypeDef* TIMx, uint16_t TIM_ForcedAction);
//配置强制输出模式
void TIM_OC1PreloadConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPreload);
void TIM_OC2PreloadConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPreload);
void TIM_OC3PreloadConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPreload);
void TIM_OC4PreloadConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPreload);
//配置CCR寄存器的预装功能
//写入的值不会立即生效，会在更新事件后才会生效
void TIM_OC1FastConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCFast);
void TIM_OC2FastConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCFast);
void TIM_OC3FastConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCFast);
void TIM_OC4FastConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCFast);
//配置快速使能
void TIM_ClearOC1Ref(TIM_TypeDef* TIMx, uint16_t TIM_OCClear);
void TIM_ClearOC2Ref(TIM_TypeDef* TIMx, uint16_t TIM_OCClear);
void TIM_ClearOC3Ref(TIM_TypeDef* TIMx, uint16_t TIM_OCClear);
void TIM_ClearOC4Ref(TIM_TypeDef* TIMx, uint16_t TIM_OCClear);
//外部事件时清除REF信号
void TIM_OC1PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);
void TIM_OC1NPolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCNPolarity);    //互补通道
void TIM_OC2PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);
void TIM_OC2NPolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCNPolarity);
void TIM_OC3PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);
void TIM_OC3NPolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCNPolarity);
void TIM_OC4PolarityConfig(TIM_TypeDef* TIMx, uint16_t TIM_OCPolarity);      //OC4无互补通道
//单独设置输出比较极性
void TIM_CCxCmd(TIM_TypeDef* TIMx, uint16_t TIM_Channel, uint16_t TIM_CCx);
void TIM_CCxNCmd(TIM_TypeDef* TIMx, uint16_t TIM_Channel, uint16_t TIM_CCxN);
//单独修改输出使能参数
void TIM_SelectOCxM(TIM_TypeDef* TIMx, uint16_t TIM_Channel, uint16_t TIM_OCMode);
//单独更改输出比较模式

3.1 PWM驱动LED呼吸灯

 3.1.1 实验现象

3.1.2  代码

 PWM.c

#include "stm32f10x.h"                  // Device header

void PWM_Init(void)
{
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    
//    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
//    GPIO_PinRemapConfig(GPIO_PartialRemap1_TIM2, ENABLE);
//    GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable, ENABLE);
    
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;        //GPIO_Pin_15;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    TIM_InternalClockConfig(TIM2);
    
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
    TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStructure.TIM_Period = 100 - 1;        //ARR
    TIM_TimeBaseInitStructure.TIM_Prescaler = 720 - 1;        //PSC
    TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStructure);
    
    TIM_OCInitTypeDef TIM_OCInitStructure;
    TIM_OCStructInit(&TIM_OCInitStructure);
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;        //CCR
    TIM_OC1Init(TIM2, &TIM_OCInitStructure);
    
    TIM_Cmd(TIM2, ENABLE);
}

void PWM_SetCompare1(uint16_t Compare)
{
    TIM_SetCompare1(TIM2, Compare);
}

main.c

#include "stm32f10x.h"                  // Device header
#include "Delay.h"
#include "OLED.h"
#include "PWM.h"

uint8_t i;

int main(void)
{
    OLED_Init();
    PWM_Init();
    
    while (1)
    {
        for (i = 0; i <= 100; i++)
        {
            PWM_SetCompare1(i);
            Delay_ms(10);
        }
        for (i = 0; i <= 100; i++)
        {
            PWM_SetCompare1(100 - i);
            Delay_ms(10);
        }
    }
}

3.2 PWM驱动舵机

3.2.1 实验现象 

 

3.2.2 舵机介绍

• 舵机是一种根据输入PWM信号占空比来控制输出角度的装置
• 输入PWM信号要求：周期为20ms，高电平宽度为0.5ms~2.5ms

 

 硬件电路

3.2.3 代码

 PWM.c

#include "stm32f10x.h"                  // Device header

void PWM_Init(void)
{
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    TIM_InternalClockConfig(TIM2);
    
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
    TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStructure.TIM_Period = 20000 - 1;        //ARR
    TIM_TimeBaseInitStructure.TIM_Prescaler = 72 - 1;        //PSC
    TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStructure);
    
    TIM_OCInitTypeDef TIM_OCInitStructure;
    TIM_OCStructInit(&TIM_OCInitStructure);
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;        //CCR
    TIM_OC2Init(TIM2, &TIM_OCInitStructure);
    
    TIM_Cmd(TIM2, ENABLE);
}

void PWM_SetCompare2(uint16_t Compare)
{
    TIM_SetCompare2(TIM2, Compare);
}

servo.c

#include "stm32f10x.h"                  // Device header
#include "PWM.h"

void Servo_Init(void)
{
    PWM_Init();
}

void Servo_SetAngle(float Angle)
{
    PWM_SetCompare2(Angle / 180 * 2000 + 500);
}

main.c

#include "stm32f10x.h"                  // Device header
#include "Delay.h"
#include "OLED.h"
#include "Servo.h"
#include "Key.h"

uint8_t KeyNum;
float Angle;

int main(void)
{
    OLED_Init();
    Servo_Init();
    Key_Init();
    
    OLED_ShowString(1, 1, "Angle:");
    
    while (1)
    {
        KeyNum = Key_GetNum();
        if (KeyNum == 1)
        {
            Angle += 30;
            if (Angle > 180)
            {
                Angle = 0;
            }
        }
        Servo_SetAngle(Angle);
        OLED_ShowNum(1, 7, Angle, 3);
    }
}

3.3 PWM驱动直流电机

 3.3.1 实验现象

3.3.2 直流电机

• 直流电机是一种将电能转换为机械能的装置，有两个电极，当电极正接时，电机正转，当电极反接时，电机反转
• 直流电机属于大功率器件，GPIO口无法直接驱动，需要配合电机驱动电路来操作
• TB6612是一款双路H桥型的直流电机驱动芯片，可以驱动两个直流电机并且控制其转速和方向

 驱动模块硬件电路

3.3.3 代码

 PWM.c

#include "stm32f10x.h"                  // Device header

void PWM_Init(void)
{
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    TIM_InternalClockConfig(TIM2);
    
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
    TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInitStructure.TIM_Period = 100 - 1;        //ARR
    TIM_TimeBaseInitStructure.TIM_Prescaler = 36 - 1;        //PSC
    TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStructure);
    
    TIM_OCInitTypeDef TIM_OCInitStructure;
    TIM_OCStructInit(&TIM_OCInitStructure);
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 0;        //CCR
    TIM_OC3Init(TIM2, &TIM_OCInitStructure);
    
    TIM_Cmd(TIM2, ENABLE);
}

void PWM_SetCompare3(uint16_t Compare)
{
    TIM_SetCompare3(TIM2, Compare);
}

motor.c

#include "stm32f10x.h"                  // Device header
#include "PWM.h"

void Motor_Init(void)
{
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
    
    GPIO_InitTypeDef GPIO_InitStructure;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    
    PWM_Init();
}

void Motor_SetSpeed(int8_t Speed)
{
    if (Speed >= 0)
    {
        GPIO_SetBits(GPIOA, GPIO_Pin_4);
        GPIO_ResetBits(GPIOA, GPIO_Pin_5);
        PWM_SetCompare3(Speed);
    }
    else
    {
        GPIO_ResetBits(GPIOA, GPIO_Pin_4);
        GPIO_SetBits(GPIOA, GPIO_Pin_5);
        PWM_SetCompare3(-Speed);
    }
}

main.c

#include "stm32f10x.h"                  // Device header
#include "Delay.h"
#include "OLED.h"
#include "Motor.h"
#include "Key.h"

uint8_t KeyNum;
int8_t Speed;

int main(void)
{
    OLED_Init();
    Motor_Init();
    Key_Init();
    
    OLED_ShowString(1, 1, "Speed:");
    
    while (1)
    {
        KeyNum = Key_GetNum();
        if (KeyNum == 1)
        {
            Speed += 20;
            if (Speed > 100)
            {
                Speed = -100;
            }
        }
        Motor_SetSpeed(Speed);
        OLED_ShowSignedNum(1, 7, Speed, 3);
    }
}