void TIM2_PWM_Init(u16 arr,u16 psc)

{  

GPIO_InitTypeDef GPIO_InitStructure;

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

TIM_OCInitTypeDef  TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);// 

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA , ENABLE);  

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; //TIM2_CH1

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1; //TIM2_CH2

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; //TIM2_CH3

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

TIM_TimeBaseStructure.TIM_Period = arr;

TIM_TimeBaseStructure.TIM_Prescaler =psc; 

TIM_TimeBaseStructure.TIM_ClockDivision = 0; 

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  

TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure); 

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 

TIM_OCInitStructure.TIM_Pulse = 0; 

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 

TIM_OC1Init(TIM2, &TIM_OCInitStructure);  

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 

TIM_OCInitStructure.TIM_Pulse = 0; 

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 

TIM_OC2Init(TIM2, &TIM_OCInitStructure);  

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 

TIM_OCInitStructure.TIM_Pulse = 0; 

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 

TIM_OC3Init(TIM2, &TIM_OCInitStructure);  

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 

TIM_OCInitStructure.TIM_Pulse = 0; 

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 

TIM_OC4Init(TIM2, &TIM_OCInitStructure);  

  TIM_CtrlPWMOutputs(TIM2,ENABLE);

TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);   

TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable);   

TIM_OC3PreloadConfig(TIM2, TIM_OCPreload_Enable);   

TIM_OC4PreloadConfig(TIM2, TIM_OCPreload_Enable);  

TIM_ARRPreloadConfig(TIM2, ENABLE); 

TIM_Cmd(TIM2, ENABLE);  

}