The general counter of stm32 is used to count the pulses of the encoder

This week, I worked on the encoder module for the computer mouse. It took me a whole week.
The process was really funny. We planned to use the CH3 and CH4 channels of TIM3 to collect the PWM of the left motor to measure speed and distance, and use the CH2 and CH1 of TIM4 to measure the right motor.
When writing the code, we first worked on the left motor. It was not until Friday that we found that the CH3 and CH4 channels of the general timer could not be used for PWM input. What a mess! ! The following is one of our configurations, which I would like to share with you!
  We use GPIO_B_7, the second channel of TIMER4

 void MY_CONFIG(void)
{
   NVIC_InitTypeDef NVIC_InitStructure;  
   GPIO_InitTypeDef GPIO_InitStructure;
   TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
   /* TIM4 clock source enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
  /* Enable GPIOA, clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
 

GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_7; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; 
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz; 
GPIO_Init(GPIOB, &GPIO_InitStructure);

//TIM4 output initialization 
TIM_DeInit(TIM4);  
TIM_TimeBaseStructure.TIM_Period = 100; //Count value = 100-1 
TIM_TimeBaseStructure.TIM_Prescaler = 0; //Pre-scaling 
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //Clock division TIM_TimeBaseStructure.TIM_CounterMode 
= TIM_CounterMode_Down; //Mode 
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); //Basic initialization

TIM_SetCounter(TIM4, 100); //Set TIM4 counter register value  
 //Set TIMx auto-reload register value 
 TIM_ARRPreloadConfig(TIM4, ENABLE);
TIM_SelectInputTrigger(TIM4, TIM_TS_TI2FP2); //If it is channel 1, it is TIM_TS_TI1FP1
//TIM_SelectInputTrigger(TIM2, TIM_TS_TI1F_ED); 
TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_External1); 
//TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_Reset);

TIM_SetCompare2(TIM4, 100); //If one channel is used, then: TIM_SetComper1(TIM4,100);
TIM_Cmd(TIM4, ENABLE); //Start TIM4 
TIM_ClearFlag(TIM4, TIM_IT_CC2); //If one channel is used, then here and the following TIM_IT_CC2 are changed to TIM_IT_CC1
TIM_ITConfig(TIM4, TIM_IT_CC2, ENABLE)
//Interrupt configuration

NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQChannel;; // 
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3; //Preemption priority 0 
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; //Response priority 0 
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //Enable interrupt 
NVIC_Init(&NVIC_InitStructure); //Write settings 
}

void TIM4_IRQHandler(void) 
{

TIM_ClearFlag(TIM4, TIM_IT_CC2);

} 
It's sad, I have to redraw the board. But I learned a lot about the general timer of stm32, keep it up