上一篇文章已经介绍了如何驱动直流有刷电机转动起来，这篇文章讲解如何获取编码器的计数值，并且计算出速度信息。在实际的运行中，随着机器的重量不一样，电机受到的阻力就会不一样，给定同样的PWM在不同载重的情况下速度会不一样，要解决这个问题就需要引入反馈系统，使用PID进行调节，通过期望值和反馈值的信息动态的去调整PWM值，从而保证速度满足期望值的要求，而反馈值就是需要通过编码器来进行计算。
控制器的编码器端口如下图所示：
其中PA0是定时器5的CH1、PA1是定时器5的CH2；PA15是定时器2的CH1、PB3是定时器2的CH2，定时器的编码器模式只能接在CH1和CH2端口上，STM32定时器的编码器模式原理需要大家自行去阅读手册，博文只讲解代码实现。
初始化代码在HwConfig/hw_STM32F40x.c中：
void EncoderInit(uint8_t eName_t,uint8_t mMotorType){
GPIO_TypeDef* ENCODER_A_PORT[ENCODERn] = {STARBOT_ENCODER1_A_GPIO_PORT, STARBOT_ENCODER2_A_GPIO_PORT, STARBOT_ENCODER3_A_GPIO_PORT, STARBOT_ENCODER4_A_GPIO_PORT};
GPIO_TypeDef* ENCODER_B_PORT[ENCODERn] = {STARBOT_ENCODER1_B_GPIO_PORT, STARBOT_ENCODER2_B_GPIO_PORT, STARBOT_ENCODER3_B_GPIO_PORT, STARBOT_ENCODER4_B_GPIO_PORT};
TIM_TypeDef* ENCODER_TIM[ENCODERn] = {STARBOT_ENCODER1_TIM, STARBOT_ENCODER2_TIM, STARBOT_ENCODER3_TIM, STARBOT_ENCODER4_TIM,};
const uint16_t ENCODER_TIR[ENCODERn] = {STARBOT_ENCODER1_TIR,STARBOT_ENCODER2_TIR,STARBOT_ENCODER3_TIR,STARBOT_ENCODER4_TIR};
const uint32_t ENCODER_TIM_CLK[ENCODERn] = {STARBOT_ENCODER1_TIM_CLK, STARBOT_ENCODER2_TIM_CLK, STARBOT_ENCODER3_TIM_CLK, STARBOT_ENCODER4_TIM_CLK};
const uint16_t ENCODER_GPIO_AF_TIM[ENCODERn] = {STARBOT_ENCODER1_GPIO_AF_TIM,STARBOT_ENCODER2_GPIO_AF_TIM,STARBOT_ENCODER3_GPIO_AF_TIM,STARBOT_ENCODER4_GPIO_AF_TIM};
uint32_t ENCODER_A_PORT_CLK[ENCODERn] = {STARBOT_ENCODER1_A_GPIO_CLK, STARBOT_ENCODER2_A_GPIO_CLK, STARBOT_ENCODER3_A_GPIO_CLK, STARBOT_ENCODER4_A_GPIO_CLK,};
uint32_t ENCODER_B_PORT_CLK[ENCODERn] = {STARBOT_ENCODER1_B_GPIO_CLK,STARBOT_ENCODER2_B_GPIO_CLK,STARBOT_ENCODER3_B_GPIO_CLK,STARBOT_ENCODER4_B_GPIO_CLK};
uint16_t ENCODER_A_PIN[ENCODERn] = {STARBOT_ENCODER1_A_PIN, STARBOT_ENCODER2_A_PIN, STARBOT_ENCODER3_A_PIN, STARBOT_ENCODER4_A_PIN,};
uint16_t ENCODER_B_PIN[ENCODERn] = {STARBOT_ENCODER1_B_PIN, STARBOT_ENCODER2_B_PIN, STARBOT_ENCODER3_B_PIN, STARBOT_ENCODER4_B_PIN};
uint16_t ENCODER_A_GPIO_PinSource[ENCODERn] ={STARBOT_ENCODER1_A_GPIO_PinSource,STARBOT_ENCODER2_A_GPIO_PinSource,STARBOT_ENCODER3_A_GPIO_PinSource,STARBOT_ENCODER4_A_GPIO_PinSource};
uint16_t ENCODER_B_GPIO_PinSource[ENCODERn] ={STARBOT_ENCODER1_B_GPIO_PinSource,STARBOT_ENCODER2_B_GPIO_PinSource,STARBOT_ENCODER3_B_GPIO_PinSource,STARBOT_ENCODER4_B_GPIO_PinSource};
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_ICInitTypeDef TIM_ICInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB1PeriphClockCmd(ENCODER_TIM_CLK[eName_t], ENABLE);
RCC_AHB1PeriphClockCmd(ENCODER_A_PORT_CLK[eName_t]|ENCODER_B_PORT_CLK[eName_t], ENABLE);
GPIO_InitStructure.GPIO_Pin = ENCODER_A_PIN[eName_t];
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(ENCODER_A_PORT[eName_t], &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = ENCODER_B_PIN[eName_t];
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(ENCODER_B_PORT[eName_t], &GPIO_InitStructure);
GPIO_PinAFConfig(ENCODER_A_PORT[eName_t],ENCODER_A_GPIO_PinSource[eName_t],ENCODER_GPIO_AF_TIM[eName_t]);
GPIO_PinAFConfig(ENCODER_B_PORT[eName_t],ENCODER_B_GPIO_PinSource[eName_t],ENCODER_GPIO_AF_TIM[eName_t]);
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Prescaler = 0x0; // No prescaling //不分频
if(ENCODER1 == eName_t || ENCODER2 == eName_t){
TIM_TimeBaseStructure.TIM_Period = 0xffffffff; //设定计数器自动重装值
} else {
TIM_TimeBaseStructure.TIM_Period = 0xffff; //设定计数器自动重装值
}
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //选择时钟分频：不分频
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上计数
TIM_TimeBaseInit(ENCODER_TIM[eName_t], &TIM_TimeBaseStructure); //初始化定时器
TIM_EncoderInterfaceConfig(ENCODER_TIM[eName_t], TIM_EncoderMode_TI12, TIM_ICPolarity_Rising, TIM_ICPolarity_Rising); //使用编码器模式3
TIM_ICStructInit(&TIM_ICInitStructure);
TIM_ICInitStructure.TIM_ICFilter = 6;
TIM_ICInit(ENCODER_TIM[eName_t], &TIM_ICInitStructure);
TIM_SetCounter(ENCODER_TIM[eName_t],0);
TIM_ITConfig(ENCODER_TIM[eName_t], TIM_IT_Update, ENABLE);
TIM_ClearITPendingBit(ENCODER_TIM[eName_t], TIM_IT_Update); //清除TIM的更新标志位
TIM_ClearFlag(ENCODER_TIM[eName_t], TIM_FLAG_Update); //清除TIM的更新标志位
TIM_Cmd(ENCODER_TIM[eName_t], ENABLE);
NVIC_InitStructure.NVIC_IRQChannel=ENCODER_TIR[eName_t];
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=6;
NVIC_InitStructure.NVIC_IRQChannelSubPriority=0;
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructure);
}定时器2和定时器5是32位定时器，所以设置计数为0xFFFFFFFF，然后我们还需要在溢出中断里对溢出次数进行处理，和需要一个定时器定时去计算单位时间内编码器的增量，然后换算为速度值。
溢出处理的代码在APP/moveBase_Task.cpp中：
void TIM2_IRQHandler(void)
{
if(TIM2->SR&0X0001)//溢出中断
{
if((TIM2->CR1 & 0x10) == 0x10){
OverEnc2--;
}else{
OverEnc2++;
}
}
TIM2->SR&=~(1<<0);//清除中断标志位
}
void TIM5_IRQHandler(void)
{
if(TIM5->SR&0X0001)//溢出中断
{
if((TIM5->CR1 & 0x10) == 0x10){
OverEnc1--;
}else{
OverEnc1++;
}
}
TIM5->SR&=~(1<<0);//清除中断标志位
}需要判断是向上溢出还是向下溢出，然后对溢出次数进行处理，处理完溢出后我们还需要一个定时器来计算他的单位时间内的增量，博主使用的是定时器6。
定时器6的初始化代码在HwConfig/hw_STM32F40x.c中：
void BaseBoard_TIM6_Init(void){ //10ms
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
//84MHz
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6,ENABLE);
TIM_TimeBaseInitStructure.TIM_Period = 83;
TIM_TimeBaseInitStructure.TIM_Prescaler=9999;
TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInitStructure.TIM_ClockDivision=TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM6,&TIM_TimeBaseInitStructure);
TIM_ITConfig(TIM6,TIM_IT_Update,ENABLE);
TIM_Cmd(TIM6,ENABLE);
NVIC_InitStructure.NVIC_IRQChannel=TIM6_DAC_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0x00;
NVIC_InitStructure.NVIC_IRQChannelSubPriority=0x00;
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructure);
}这里给定定时器的周期是10ms，即100HZ，大家可以根据自己的需要进行修改，然后在定时器6的中断函数中对编码器数据进行处理。
编码器数据处理的代码在APP/moveBase_Task.cpp中：
void TIM6_DAC_IRQHandler(void)
{
if(TIM_GetITStatus(TIM6,TIM_IT_Update)==SET) {
encPIDCnt++;
if(encPIDCnt >= DELTA_CNT){ // DELTA_CNT = 10
编码器采样周期 10 x 10ms = 100ms
if(MotorType_t != M_CAN_1_2){
gCurrentEnc1 = (int64_t)(((TIM5 -> CNT)) + OverEnc1*0xffffffff);
gCurrentEnc2 = (int64_t)(((TIM2 -> CNT)) + OverEnc2*0xffffffff);
if(lastCurrentEnc1 == 0){lastCurrentEnc1 = gCurrentEnc1;}
delta_ticks_1 = gCurrentEnc1 - lastCurrentEnc1;
lastCurrentEnc1 = gCurrentEnc1;
if(lastCurrentEnc2 == 0){lastCurrentEnc2 = gCurrentEnc2;}
delta_ticks_2 = gCurrentEnc2 - lastCurrentEnc2;
lastCurrentEnc2 = gCurrentEnc2;
Motor_Rpm.MotorEncoder1 += delta_ticks_1;
Motor_Rpm.MotorEncoder2 += delta_ticks_2;
Motor_Rpm.Current_Rpm1 = (delta_ticks_1*600/Time_counts_per_rev);
Motor_Rpm.Current_Rpm2 = (delta_ticks_2*600/Time_counts_per_rev);
}
moveBase_Manage();
encPIDCnt = 1;
}
}
TIM_ClearITPendingBit(TIM6,TIM_IT_Update);
}rpm的计算公式为：分钟内编码器的增量/输出轴转一圈编码器的计数值，我们这里是100ms计算一次，因此单位时间要进行转换：1min = 60s=60000ms 所以需要乘上600就可以得到RPM值。如果文章有错误欢迎大家及时纠正，感谢大家的支持