使用正点原子的串口初始程序，然后tim8在pwm2模式下运行，无法输出波形，同时tim1，也在工作，正常输出，就是tim8不行，求解？代码如下
u16 TIM1_FLAG,TIM8_FLAG; void stepper_motor57or42_init_l(u32 PulseFrequency) { NVIC_InitTypeDef          NVIC_InitStructure; GPIO_InitTypeDef          GPIO_InitStructure; TIM_TimeBaseInitTypeDef   TIM_BaseInitStructure; TIM_OCInitTypeDef         TIM_OCInitStructure; u16 nPDTemp ; nPDTemp = 72000UL/PulseFrequency; RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1|RCC_APB2Periph_GPIOA, ENABLE); NVIC_InitStructure.NVIC_IRQChannel = TIM1_UP_IRQn;          /*?¨?±?÷????????*/ NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;   /*??????????0*/ NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;          /*?ì????????1*/ NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;             /*???í????*/ NVIC_Init(&NVIC_InitStructure); GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_11; GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_PP; //???ì???? GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOA, &GPIO_InitStructure); GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_12; GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_Out_PP; //???ì???? GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOA, &GPIO_InitStructure); TIM_BaseInitStructure.TIM_Period = nPDTemp-1; TIM_BaseInitStructure.TIM_Prescaler = 999; TIM_BaseInitStructure.TIM_ClockDivision = 0; TIM_BaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_BaseInitStructure.TIM_RepetitionCounter = 0;        /*?????¨?±?÷????????*/ TIM_TimeBaseInit(TIM1, &TIM_BaseInitStructure); TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  TIM_OCInitStructure.TIM_Pulse = nPDTemp>>1;//50%  TIM_OC4Init(TIM1, &TIM_OCInitStructure);  TIM_ClearFlag(TIM1, TIM_FLAG_Update); TIM_ITConfig(TIM1, TIM_IT_Update, ENABLE); TIM_Cmd(TIM1, DISABLE);  //????TIMx???è TIM_CtrlPWMOutputs(TIM1,DISABLE); } ///////////////////////////////////////////////////////////////////////////////////
void stepper_motor57or42_init_r(u32 PulseFrequency) { NVIC_InitTypeDef          NVIC_InitStructure; GPIO_InitTypeDef          GPIO_InitStructure; TIM_TimeBaseInitTypeDef   TIM_BaseInitStructure; TIM_OCInitTypeDef         TIM_OCInitStructure; u16 nPDTemp ; nPDTemp = 72000UL/PulseFrequency; RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8|RCC_APB2Periph_GPIOC, ENABLE); NVIC_InitStructure.NVIC_IRQChannel = TIM8_UP_IRQn;          /*?¨?±?÷????????*/ NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3;   /*??????????0*/ NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;          /*?ì????????1*/ NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;             /*???í????*/ NVIC_Init(&NVIC_InitStructure); GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_8; GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_PP; //???ì???? GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOC, &GPIO_InitStructure); GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_9; GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_Out_PP; //???ì???? GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOC, &GPIO_InitStructure); TIM_BaseInitStructure.TIM_Period = nPDTemp-1; TIM_BaseInitStructure.TIM_Prescaler = 999; TIM_BaseInitStructure.TIM_ClockDivision = 0; TIM_BaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_BaseInitStructure.TIM_RepetitionCounter = 0;        /*?????¨?±?÷????????*/ TIM_TimeBaseInit(TIM8, &TIM_BaseInitStructure); TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  TIM_OCInitStructure.TIM_Pulse = nPDTemp>>1;//50%  TIM_OC3Init(TIM8, &TIM_OCInitStructure);  TIM_ClearFlag(TIM8, TIM_FLAG_Update); TIM_ITConfig(TIM8, TIM_IT_Update, ENABLE); TIM_Cmd(TIM8, DISABLE);  //????TIMx???è TIM_CtrlPWMOutputs(TIM8,DISABLE); } /////////////////////////////////////////////////////////
void  TIM1_UP_IRQHandler(void) { if(TIM1_FLAG>0) { TIM1->RCR=255; TIM1_FLAG--; } else if(TIM1_FLAG==0) { TIM_Cmd(TIM1, DISABLE);  //????TIMx???è TIM_CtrlPWMOutputs(TIM1,DISABLE); } TIM_ClearITPendingBit(TIM1,  TIM_FLAG_Update);  } //////////////////////////////////////////////////////////////
void  TIM8_UP_IRQHandler(void) { 
if(TIM8_FLAG>0) { TIM8->RCR=255; TIM8_FLAG--; } else if(TIM1_FLAG==0) { TIM_Cmd(TIM8, DISABLE);   TIM_CtrlPWMOutputs(TIM8,DISABLE); } TIM_ClearITPendingBit(TIM8,  TIM_FLAG_Update);  } ////////////////////////////////////////////////////////// void revolution_l(u16 angle,u8 direction) { u8 bb; while(TIM1_FLAG); TIM1_FLAG=angle/256; bb=(angle%256)-1; cw_l=direction; TIM1->RCR=bb; TIM_Cmd(TIM1, ENABLE);  //????TIMx???è TIM_CtrlPWMOutputs(TIM1,ENABLE); }

void revolution_r(u16 angle,u8 direction) { u8 bb; while(TIM8_FLAG); TIM8_FLAG=angle/256; bb=(angle%256)-1; cw_r=direction; TIM8->RCR=bb; TIM_Cmd(TIM8, ENABLE);   TIM_CtrlPWMOutputs(TIM8,ENABLE); }
int angle(float angle) { float pulse=(float)angle*subsection/1.8; if((pulse-(int)pulse)>=0.5) { pulse+=1; return pulse; } else { return pulse; } }

///////////////////////////主函数/////////////////////////////////////////////


#include "led.h" #include "delay.h" #include "sys.h" #include "usart.h" //#include "lcd.h" #include "57or42.h"

int main(void) { SystemInit(); uart_init(9600); //LED_Init(); //LCD_Init(); //LCD_Clear(BLACK); //POINT_COLOR=WHITE; //BACK_COLOR=BLACK; stepper_motor57or42_init_l(1000); stepper_motor57or42_init_r(1000); while(1) { revolution_r(angle(50),forward); revolution_l(angle(60),forward); delay_ms(2500); } }